I [LIBRARY ^ UNIVERSITY OP CALIFORNIA AN DIEGO i ^ GASOLINE AUTOMOBILES \PODLJ_S_H_ER1 Of .BOOKS .F O R_/" CoalAgel v tlectflcllailway Journal Electrical World v Engineering News-Record American Machinist, v Ingenieria Internacional Engineering ^Mining Journal V Power Chemical & Metallurgical Engineering Electrical Merchandising " GASOLINE AUTOMOBILES BY JAMES A. MOYER Director of University Extension, Massachusetts Department of Education; formerly Junior Professor of Mechanical Engineering in the. University of Michigan. Member of Society of Automotive Engineers, and American Society of Mechanical Engineers; formei ly member of Standards Committee of the Society of Automobile Engineers. FIRST EDITION SECOND IMPRESSION McGRAW-HILL BOOK COMPANY, INC. NEW YORK: 370 SEVENTH AVENUE LONDON: 6 & 8 BOUVERIE ST., E. C. 4 1921 COPYRIGHT, 1921, BY THE McGRAW-HILL BOOK COMPANY, INC. PREFACE THE purpose of this book is to present clearly, briefly, and interestingly the essential principles of automobile con- struction and operation. It is expected to furnish practical help to drivers who, when faced by ordinary operating troubles, want to know how to locate the cause and apply the remedy. Ordinarily an owner wishes to know first of all the uses of the numerous parts of his automobile, so that he may anticipate repairs and, when repairs actually become neces- sary, he may know where to begin repair work, and whether, once done, such work is right and the charges therefor are reasonable. Because of the increasing cost of materials and services there is a growing tendency among owners to keep auto- mobiles for several seasons. There is, therefore, more incen- tive than formerly to keep automobiles in good repair. Auto- mobiles generally deteriorate more because of lack of care and attention than from actual use. Much of this deteriora- tion is due to ignorance and the consequent failure to pre- vent the kind of wear which, if not corrected, will lead to heavy expenses for repairs. As the cost of repairs has greatly increased of late be- cause of labor charges, automobile operators are becoming interested in finding ways of decreasing ordinary as well as extraordinary running expenses. They want to learn how to get the last unit of power from a gallon of gasoline and how to exact the greatest possible mileage from an auto- mobile before it is exchanged for a new one. vi PREFACE A book prepared with these objects in view should also be suitable for general scientific study, if, of course, the theory is accurate and carefully explained. Such a book will give information that will be most useful to students of automotive engineering, whose schooling, obviously, should not deal too much with minor details of automobile equipment. Many books on this subject are really catalogs of details, and books, if at all complete, must be of unwieldy size and include many dry and uninteresting data. The author be- lieves that there is a demand for a readable book devoted only to essentials. For example, not all types of carbureters and ignition devices will be explained, but considerable space will be devoted to the explanation of the principles underlying commonly used equipment and systems. In the description of carbureters a series of symbols has been adopted which should make it easy to understand any type mentioned after the careful study of one type. Only limited space has been given to the subject of magnetos because their use on automobiles, except on trucks, is rapidly de- creasing in favor of simple battery systems of ignition. The author is especially indebted to his brother J. C. Moyer, consulting mechanical engineer, of Philadelphia, for the preparation of portions of many chapters. Special acknowledgment is also due to J. C. Vincent, Past-President of Society of Automotive Engines and Vice-President of the Packard Motor Car Company, to Charles W. Hobbs, Herbert A. Dallas, agents of the Massachusetts Division of Univer- sity Extension, and to Arthur E. Ashworth, Miss Betsy McCausland, and Herbert S. Eames, instructors in the same Division. JAMES A. MOYER. Boston, Mass., March, 1921. CONTENTS PREFACE v CHAPTER PAQE I AUTOMOBILE TYPES AND PARTS 1-20 II AUTOMOBILE ENGINES 21- 48 III GASOLINE AND SUBSTITUTES 49- 62 IV GASOLINE CARBURETERS 63-103 V AUTOMOBILE IGNITION 104-147 VI MAGNETOS AND IGNITION TESTING 148-166 VII ELECTRIC STARTERS 167-183 VIII CLUTCHES, TRANSMISSIONS AND DIFFERENTIALS 184-222 IX LUBRICATION AND COOLING SYSTEMS 223-246 X AUTOMOBILE TROUBLES AND NOISES 247-256 INDEX . 257 GASOLINE AUTOMOBILES CHAPTER I AUTOMOBILE TYPES AND PARTS THE purpose of this book is to give such information about the construction and maintenance of automobiles that inexpert owners can make the simpler adjustments and repairs intelligently and economically. The average man is becoming more and more dependent on automobiles. Economic considerations make it necessary for him to main- tain and care for his automobile as easily and with as little expense as he used to keep his horse and carriage. Automobiles have given rise to extraordinary develop- ments in modern industry and vast changes in methods of transportation and living. Statistics of the number of registered automobiles give some idea of the extent and nature of their use. In 1900 there were less than 20,000 automobiles in the United States. In 1910 there were about 50,000. In 1921 there are over 10,000,000. At the present rate of production about 2,000,000 automobiles are manu- factured annually in the United States, a large part of these being for export to foreign countries. With this enormous growth, the problem of an adequate supply of fuel for automobiles has become increasingly difficult. At present gasoline is used more extensively than any other substance, but at times during recent years the demand has exceeded the supply. Heretofore a balance between supply and demand has been partially brought about by (1) decreasing the demand by designing the auto- mobile parts that have to do with combustion so that heavier 2 GASOLINE AUTOMOBILES and cheaper grades of gasoline may be used, (2) reducing the weight of automobiles so that the engine has less load to carry, and (3) increasing the supply by the use of new methods of distillation and the development of new oil fields. The present high price of gasoline together with the increased cost of labor for automobile repairs, has spurred the owners to cut down the cost by taking more intelligent interest in economical operation and proper care of their automobiles, with the object of (1) Eliminating the inconvenience of poorly operating machines. (2) Keducing the charges for repairs and replacement of broken and worn parts. If the efforts to decrease demand and increase supply still refuse to yield an adequate supply at a corresponding price reduction, other fuels doubtless will become important rivals of gasoline. In fact, a further increase of less than fifty per cent in the price of gasoline will make alcohol an important competitive fuel. Classification of Automobiles. The various kinds of auto- mobiles may be classified according to (1) kind of motive power; (2) kind of service. These may be tabulated as follows : 1. Kind of Motive Power: a. Steam Engine b. Electric Motor c. Gasoline or Alcohol Engine. 2. Kind of Service: a. Pleasure automobiles. b. Commercial automobiles (trucks). The following chapters will be devoted to the consideration mainly of pleasure automobiles that receive their power from gasoline engines though in the next few paragraphs the advantages and disadvantages of steam automobiles and electric automobiles will be explained. Steam Automobiles. A steam driven automobile has im- portant points of difference when compared with a gasoline AUTOMOBILE TYPES AND PARTS 3 automobile, the chief one being that the modern steam automobile has, besides an engine, a steam boiler completely equipped with pumps, water and steam gages, safety valve, condenser, etc. Thus it is a complicated apparatus, requir- ing careful attention. The steam automobile as compared with the gasoline and electric kinds has several disadvan- tages, the most important among them being that it cannot be made instantly available for service. Even with the most modern types of quick-firing portable steam boilers it takes several minutes to heat water sufficiently to generate enough steam to start the engine. Other disadvantages are (1) that large quantities of water are needed for making steam so that a considerable weight of water must be carried ; (2) that if there is no provision for condensing the steam and using the water over again in the boiler, the distance that can be traveled between refillings is very limited; (3) that the cloud of steam discharged from such an engine especially in cold weather is annoying to the -drivers of other con- veyances; (4) that both the open flame which furnishes heat to the boiler and the high steam pressure which is necessary are objectionable because of the danger of fire and destructive explosions. There are, however, advantages in steam-driven vehicles, of which the most obvious is the simplicity of speed control. Merely by adjusting an ordinary throttling valve the pres- sure of the steam admitted to the engine can be closely regulated and thereby also the speed of the automobile. The shifting of gears is never necessary on hilly roads or in starting or reversing since a simple movement of links controlling the steam valves gives all necessary control of speed, power, and forward and backward movement. Electric Automobiles. For simplicity and easy control electric automobiles approach the ideal. By merely moving a small lever-switch, all the operations of changing speed, reversing and maximum power are positively controlled. An electric automobile involves, however, the inconveniences of carrying a very heavy electric battery made mostly of 4 GASOLINE AUTOMOBILES lead in order to furnish the power necessary for a high speed and travelling in hilly country, and of having the bat- tery recharged at a properly equipped place, every hundred miles or less. Gasoline Automobiles. Gasoline automobiles are the real subject of these chapters, and all the following pages will be devoted to the detailed descriptions of their parts. In construction and methods of operation, when compared with the steam and electric kinds, gasoline automobiles have the disadvantage of having a type of engine which cannot be started without special and expensive auxiliary equipment. Furthermore, this type of engine in order to avoid "stalling" if overloaded at normal engine speed, requires a system of speed-change gearing between the engine and the wheels on the driving axle. Various mechanical and electrical devices however have been applied to the modern gasoline automobile, so that in spite of the disadvantages named, it has practically a non- competitive field for general touring, pleasure, and business services. The great advantage in its favor is that it can carry a sufficient supply of gasoline for fuel, oil for lubrica- tion and water for cooling the engine, to run from two hundred to four hundred miles without refilling. As the result of very careful and thoughtful designing, it can be run day after day with little attention, and, if carefully and intelligently operated, with only small charges for repairs and replacement of parts. Types of Automobile Bodies. Automobiles are given various names according to the style or type of the body, which is generally taken to mean all that part above the wheels to the rear of the sheet metal hood over the engine. The touring-car body (Fig. 1) is the one most generally used on pleasure cars. It has always front and rear seats and some- times additional folding seats, and is made with a folding top. The roadster (Fig. 2) resembles a touring car in general lines but has only one seat. The coupe (Fig. 3) has only one seat and is made with an enclosed body and glass windows. AUTOMOBILE TYPES AND PARTS The cabriolet (Fig. 4) is a semi-closed roadster with folding top. The sedan (Fig. 5) has an entirely enclosed body, and differs from the coupe in having more than one seat. The limousine (Fig. 6) has a driver's seat in front, which is usually open at the sides and separated by a partition from the passenger seats behind. The touring-car, roadster, and cabriolet have tops which can be let down and folded at the rear; but as a rule such automobiles are now not operated as much as formerly with FIG. 1. Touring Car. FIG. 2. Roadster. FIG. 3. Coupe. FIG. 4. Cabriolet. FIG. 5. Sedan. FIG. 6. Limousine. the top down and folded, except on a tour in unusually picturesque country where a standing top shuts off the view. The important principles of present body design are (1) Giving a low appearance to the automobile by the use of low wheels, a high back on the rear seat of touring cars, and a low angle steering column, and (2) Accentuating the length by the use of stream lines, that is, body lines which blend continuously from the hood to the rear seat. 6 GASOLINE AUTOMOBILES Eecent automobile designers favor a low-hung body, most of the latest models having the floor of the body from three to five inches nearer the ground than in the automobiles made several years ago. The automobile with the low body and low top has a pleasing appearance, but it is not so easy riding as the high-hung body type, and is not so con- veniently arranged for getting in and out. The latest body designs are intended to give soft, straight-line effects without necessarily sacrificing the beau- tiful results obtained by the use of moderately rounded corners. With too many curves there seems to be no char- acter to the body, while with too many straight lines there is harshness. A suitable combination of the two is required to make a pleasing design. The present tendency is for the roofs of enclosed bodies to be straight and nearly flat with straight lines for the doors, because distinctly rounded corners at the window openings and at the doors give the impression of greater weight than straight-line corners, and lightness in appearance is an important matter in present body designs. The weight of the body is a principal factor in determin- ing the necessary strength in the automobile frame and the engine power, and since an automobile for everyday use does not usually require room enough for seven, and since a shortage of the gasoline supply is quite possible, designers of automobiles are now giving more and more attention to the requirement of lightness. Many hoods on automobiles have more louvres as the vertical slots in the side of the hood are called than are necessary. There are cases where the ventilating fan fo.r cooling the engine draws nearly as much air through the front louvres as it discharges through the rear ones. For proper and efficient operation, the cooling air should enter only from the front of the automobile and only the dis- charged heated air pass through the louvres of the hood. Air circulation through the hood can be easily tested by placing a piece of tissue paper so as to cover some of the AUTOMOBILE TYPES AND PARTS 7 front louvres and observing whether the draft is outward, as it should be. For winter service, demountable tops for making enclosed bodies on touring cars and roadsters are being sold with the object of making them all-year automobiles, but because of the difficulty of making the tops with pleasing body lines and neat fittings, there is not much demand for them; the coupe, sedan, and limousine still being the favorites for all- year service. The sedan has been coming into more general use of late and has to a certain extent replaced the limousine. It gained favor during the war when chauffeurs went into army and navy service in large numbers, and driving had to be done by the owner or by a member of his family. The sedan made it possible for all members of the family to sit together, without one of their number being shut off by a glass partition, as would be the case in a limousine, and gave protection to the driver in stormy weather. The driver of a sedan, it is true, is at a disadvantage as compared with the driver of a limousine, because he cannot hear or see so readily as when sitting in the open; but except for this disadvantage, the sedan is almost ideal as an all-year transportation automobile. It gives satisfactory ventilation and a fairly unobstructed view for the passengers in prac- tically all conditions of winter and summer service even when touring, and certainly for winter service it is at least far more satisfactory and comfortable than the touring car with its top up and its dilapitated side curtains. A coupe with a roomy body is well adapted for summer and winter touring because suit-cases, traveling bags, and boxes may be left in it with safety in a public garage since the windows and doors of the car can be locked. Flow of Power. Before explaining the details of auto- mobile construction and operation it will be helpful to trace the flow of power from its source in the engine to the rear wheels which drive the car. Power in a gasoline engine originates in successive 8 GASOLINE AUTOMOBILES explosions in a series of cylinders. The force of each explo- sion is communicated through a set of pistons moving up and down in the cylinders to a crankshaft which is con- nected to a flywheel. The momentum of the flywheel makes the flow of power steady and smooth. A shaft extending to the rear from the center of the flywheel transmits the power through the friction clutch and speed-change gears to the axle drive shaft. At its rear end the central drive shaft engages a set of gears called the differential. The differential gears are connected to two rear axle shafts Emergency Brake Lever Speeckhange Shifting U 'V Gasoline Engint WfndShield /Cylinder RearSpriny , \ UniversalJoint \ Axle Dri've Shaft ' Differential and Rear Axle I flynhettahd \ Friction Ctufch Speed^hancje dears or Transmission Starting Crank FIG. 7. Side View (Section) of Automobile. which extend to right and left and in turning communicate the power to the rear wheels at their hubs. Parts of Gasoline Automobiles. The engine with its radiator, the automobile frame, wheels, steering gear, axles, springs, friction clutch, speed-change gears, and body* are the essential parts of a modern gasoline automobile. These and some other parts of minor importance are shown and labelled in Figs. 7 and 8, the first of these shows the side * All the parts of a gasoline automobile, excluding the body and hood are called the chassis (from a French word meaning to chase or run). Some automobile engineers also exclude the engine from the chassis. The chassis corresponds to the running gear of a wagon. AUTOMOBILE TYPES AND PARTS 9 view of an automobile with a touring car body as if cut through the middle, and the second shows the same auto- mobile (without body and hood) as seen when looking down from the top. These figures give a good idea of the position and relation of the essential parts. The radiator shown at the front of the automobile in Fig. 7 is really an essential part of the engine (sometimes called the motor), which, by burning or "exploding" gasoline in its enclosed cylinders, like C in the figure, turns the crank- shaft or drive shaft. This shaft is connected at the front end of the automobile to the starting crank for use when an engine is started by hand, and at the other end is connected to the friction clutch, which has a central shaft entering the FIG. 8. Top View of Automobile Chassis. speed-change gear box. Strong, interlocking, or meshing, gear wheels in this gear box are on short shafts which can be connected up in several ways through a universal joint to the axle drive shaft connected to another set of gears (called the differential) in the enlarged middle portion of the rear axle. The gears in the rear axle are rigidly attached on each side to enclosed rods which, when rotated, drive the rear wheels. Power from the engine is thus transmitted to the rear wheels, which by their gripping on the ground move the automobile forward or backward as desired. The engine, friction clutch, and speed-change gear box are supported on the automobile frame, which is itself supported flexibly on the front and rear axles by means of springs. 10 GASOLINE AUTOMOBILES Brakes (Fig. 8) for stopping the automobile usually have inside and outside bands with a mechanism to tighten them against a drum on each rear wheel in order to provide the necessary friction. Steel rods and links connect these bands to the brake pedal and to the emergency brake lever in front of the driver's seat. The muffler is in nearly all automobiles a drum or cylinder into which the exhaust pipe carries the exhaust gases. It is used to stifle the noise of rapid explosions, which would otherwise be deafening. The purpose of the tires is to absorb road shocks and make riding easy, as well as to keep the automobile from jolt- ing to pieces. Differential Gears. A means must be provided in auto- mobiles to make it possible to drive the rear wheels so that one wheel can turn faster than the other in going around a corner. The rear axle is made, therefore, in two separate pieces or separate axles, and each piece is connected at the middle of the rear axle to differential gears. This gearing device permits the two rear wheels to turn at different speeds as necessary in driving along a curved road or in making a sharp turn. If differential gears were not provided and the two rear wheels had to move at the same speed, when going around a curve the wheel on the inside would have to slip on the road bed without much turning motion. It would be possible to get around a curve with an automobile with such a single-piece axle, if it were not going fast, but one can easily see that an automobile made with a one-piece axle would be difficult to steer on a rough road and would soon wear out its rear tires and wheel rims. When the rear end of an automobile is jacked up and both hind wheels are off the ground if the engine is started the wheels may be seen to turn at different rates of speed. One wheel may not even turn at all. This behavior is perfectly normal and is due to the nature of the differential. When an automobile is started with one rear wheel on firm ground and the other on ice or thin mud, the wheel AUTOMOBILE TYPES AND PARTS 11 on slippery ground will often spin while the other does not move at all. This is only another illustration of the peculiar working of the differential gears and divided axle shaft. The special tendency of automobile wheels to spin, slip, and skid is offset to a considerable extent by the use of chains and other friction devices which give the wheels a fairly firm grip on slippery ground. A common type of rear axle, divided in the middle and turned by the differential gears is shown in Fig. 9. The figure shows that, though the rear axle carries the power for moving the wheels it does not have to bear the weight of the body. This burden is borne by the heavy casing or housing, usually made of steel, in which the axle shafts and differential gearing are enclosed. At A Differential Gears Axle Casing or Housing FIG. 9. Example of Bear Axle. and B in the figure there are plates or lugs on the housing. To these are attached the rear springs on which the body frame is supported. When properly made and put together the rear axle housing is sufficiently tight to keep out road dust and to keep in the heavy oils which are used for the purpose of lubricating the moving parts and deadening their noise. Sometimes a rear axle which has been taken apart and reassembled, sputters oil over the wheels, brakes, or other parts. When this is the case, the parts have not been put together tightly. Ordinarily differential gears cause very little trouble if their housing is kept well filled with oil of good lubricating value and of proper thickness to prevent leakage. Friction Clutch. The power from the engine is trans- mitted from the flywheel on the engine crankshaft to the 12 GASOLINE AUTOMOBILES other parts of the automobile power plant by a friction device which can be made to engage or disengage with the inside surface of the flywheel. This friction device is called the clutch. (Marked in Figs. 7 and 8.) By the use of the clutch it is possible to start or stop an automobile with a gradual change of speed. Without a clutch, starting or stop- ping would be jerky and uncomfortable in the extreme. A skillful operator will let his clutch in so slowly and gently when starting that the automobile picks up speed gradually and smoothly. The ability to make a good stop is an important matter in driving. There are three ways to stop an automobile: (1) by disengaging the clutch and letting the automobile glide along until it stops; (2) by disengaging the clutch and at the same time applying the foot brake; (3) by disengaging the clutch and applying the foot brake and also the hand emergency brake. At critical times inexperienced operators sometimes forget momentarily how to stop quickly. Most automobiles, except the Ford, will be stopped for emergencies by pushing both feet forward upon the clutch and foot-brake pedals and pulling on the emergency brake lever. If all operators were well drilled in these movements as a single operation there would be very few collision accidents; pro- vided, of course, the brakes are kept in good adjustment. The method of stopping by running into a stone wall or other obstruction need only be mentioned, although in case the brakes and speed-change gears fail to control the auto- mobile when it is going down a steep curved mountain road, there may be occasion to use it. Speed-change Gears. Provision must be made in all automobiles driven by gasoline engines for a system of gears or a similar device to permit both changing the speed of the automobile without changing that of the engine, and reversing or running the automobile backward, as a gasoline engine itself can run in only one direction. Changing gears is often called "shifting gears." Speed-change gears may be set in such a position as to be entirely disconnected from AUTOMOBILE TYPES AND PARTS 13 the axle drive shaft. They are then said to be "in neutral." The gears should always be in neutral when the engine is being started, or when "idling"; that is, running while the automobile stands still. The reasons for "shifting" gears are (1) to get more pulling force on hilly and rough roads; (2) to get very low automobile speed without reducing the engine speed so as to risk its stopping by getting "stalled"; (3) to "reverse" or to run the automobile backward. Speed-change gears are also called the transmission. The differential gears, the friction clutch, and the speed- change gears have been referred to here in only a general way so as to give an idea of the operation of the various essential parts of an automobile. In later chapters these parts will be described with detailed explanations and illus- trations. Universal Joints. A little study of Fig. 7 will show that the engine, clutch, and speed-change gears are rigidly mounted on the frame and form a unit with it, while the rear axle and rear wheels form another unit which rests upon the ground and supports the frame by means of the springs. The axle drive shaft, which connects these two units, must be free to move somewhat in any direction, to be adjustable when the car swerves slightly or when the rear axle moves up and down as the wheels pass over rough places in the road. The axle drive shaft is therefore provided with a joint which allows flexible rotary motion between the speed-change gears and the rear axle. This kind of joint is called a universal joint. Fig. 10 shows a typical universal joint for an axle drive shaft. Steering Gears. The steering wheel which is used in guiding the automobile is connected as shown in Fig. 11 by rods, levers, and gears (all called the steering gear) to the ends of the front axle near each of the front wheels. Turning the steering wheel in clockwise direction draws in the right-hand front wheel toward the body and swings out- ward the left-hand front wheel so that the automobile is 14 GASOLINE AUTOMOBILES guided to move toward the right-hand side. Anti-clockwise movement of the steering wheel guides in the opposite direc- tion. Nearly all automobiles now made in America use the left-hand drive, that is, the steering wheel is on the left-hand FIG. 10. Universal Joint. side of the automobile so that the driver sits on the left- hand seat. The front axle of most automobiles is made of a solid steel forging. It does not turn on a "fifth wheel" as on Steering Wheel ffiah-f- Yoke and Knuckle -,. Automobile Frame ' SfaerirrgLeverAnn *7 L,nk Front Axle /^ y ^ gndKnuekle Fie. 11. Example of Steering Gear. a wagon or carriage, but is attached by means of flexible springs to the body frame work. The wheels are on short horizontal spindles which are movable for steering. Frame and Springs. The automobile frame is a frame- AUTOMOBILE TYPES AND PARTS 15 work made usually of steel but sometimes of wood, to support the engine, radiator, friction clutch, speed-change gear box, engine drive shaft, and all other parts not attached directly to the axles. It is claimed that a wooden frame transmits less vibration and is easier riding than a steel frame, but actually there is little difference between frames of steel and of wood when they are equally well designed. The frame is supported on springs as shown in the figures. A long frame FIG. 12. Spring Leaves. makes possible a long wheel base, which is the distance measured between the centers of the front and rear axles. This is considered desirable since an automobile with a long wheel base usually rides more comfortably than one with a short wheel base. Automobile springs are made in exactly the same way that springs have been made for a hundred years for use in horse- drawn carriages. The usual kind of springs used for attach- FIG. 13. Spring Leaves Assembled. ing the automobile frame to the axles is made oT~a number of flat steel plates called leaves (Fig. 12), which are tapered at the ends and bent into curved shapes as shown in Fig. 13, each leaf being given a little greater curvature than the next longer one. The leaves for a complete spring are pressed together and fastened with clamps. In addition to the clamp- ing, the leaves are sometimes put together more permanently with a bolt passing through the middle of each leaf (Fig. 14). Although all automobile body springs are made by the 16 GASOLINE AUTOMOBILES same general method, there are several types or arrangements in use. Full Elliptic Springs. A spring made by fastening to- gether with hinged ends two sets of leaves as shown in Fig. 15 is called a full elliptic spring. It gives very easy riding and in this respect is most satisfactory, but it is not generally FIG. 14. Bolted Automobile Spring. FlG. 15. Full Elliptic Spring. used for automobiles because it takes up too much room to be adaptable to low-hung automobile bodies. It is attached to an automobile by fastening the middle of the top part to the automobile frame and the middle of the lower part to the axle. FIG. 16. Three-quarters Elliptic Spring. Three-quarters Elliptic Spring. Fig. 16 shows a kind of automobile spring made with a set of leaves at the bottom which are hinged to half of a similar set at the top. This type is called a three-quarters elliptic spring. It is attached to the automobile frame at the end of the short top part at A while the free end of the longer bottom part is fastened AUTOMOBILE TYPES AND PARTS 17 to a pin bolted to the side of the frame at B. The two ends of the spring are joined by a pin at C. The axle is fastened to the middle of the lower part. Semi-Elliptic Springs. Fig. 17 consists simply of a set of spring leaves like those shown in Fig. 13 but in an inverted FlG. 17. Semi-Elliptic Spring. position. This type is shown as commonly attached to front axles. It is usually attached by fastening one end with a hinged connection by means of a pin to the front end of the automobile frame at A, the middle part to the axle as at B, and the other end is hung by means of a link suspended from TIG. 18. Cantilever Spring. a pin attached to- the side of the automobile frame. When used as a rear spring the method of attachment is essentially the same. Cantilever Spring. Fig. 18 illustrates a cantilever spring which is a single set of spring leaves flexibly attached to the 18 GASOLINE AUTOMOBILES side of the automobile frame at one end and at the middle, while the other end is rigidly fastened to the rear axle. As shown in the figure the spring is clamped securely at the FIG. 19. Platform Springs. middle to a block B, which is itself supported and turns on a pin P bolted to the side of the frame. Platform Spring. Fig. 19 consists of two semi-elliptic springs each attached at one end by links to the side of the FlO. 20. Inverted Semi-Elliptic Spring (Ford Type Front Spring). frame, at the middle to the rear axle, and at the other ends by means of links to a third spring, fastened at the middle to an extension of the frame. Inverted Semi-Elliptic Springs. Figs. 20 and 21 are used FIG. 21. Inverted Semi-Elliptic Spring (Ford Type Bear Spring). on some light weight automobiles because of simplicity and cheapness in construction. Only one spring is used at the front (Fig. 20) and only one at the rear (Fig. 21). AUTOMOBILE TYPES AND PARTS 19 In each case the spring is attached at the middle to the frame with its length parallel to the axle, and the two ends are fastened by links to the axle near the wheels. Lubrication of Springs. The first automobiles were built without provision for reducing the friction of the springs. Neither the bolts used nor the holes in the springs into which they fitted were carefully made to give smooth working surfaces, and there was continuous squeaking. The springs of modern automobiles, however, are provided at all pin connections or other flexible attachments with oil or grease cups for lubrication. Some types of springs are made with small depressions which are filled with a mixture of graphite and lubricating grease, in order to eliminate friction between the leaves. These provisions for lubrication together with carefully made and low-friction linings or bushings for the bolt holes have made squeaking at the spring joints easily avoidable. Automobile Engines. The engine of a gasoline auto- mobile furnishes the driving power. It is usually made with a number of cylinders in which occurs the burning or exploding of a highly combustible mixture of gasoline vapor and air, which furnishes the power. As a rule the larger the number of cylinders the more even and steady the propelling power will be. The "explosions" in a one- cylinder engine for instance, are strong, few, and far be- tween, making this kind of engine unusually noisy. Two- cylinder engines are not much used on automobiles, and three-cylinder engines practically never. Four-cylinder engines are used more than any others, since with this number of cylinders it is possible to make the individual cylinders so small that none of the " explosions" will be noisy and a sufficiently uniform turning movement is secured on the driving shaft to give easy and steady running quali- ties. In a four-cylinder engine there is a power impulse every half revolution, in a six-cylinder engine every one- third revolution, in an eight-cylinder engine every one- quarter revolution, and in a twelve-cylinder engine every 20 GASOLINE AUTOMOBILES one-sixth revolution. The reasons for this are not explained here but will be fully discussed in the next chapter. It should be clear, however, from this statement that with increased number of cylinders in an automobile engine there is greater so-called " flexibility " with smoother running, easier starting, and less vibration. Eight-cylinder and twelve-cylinder engines because of the uniformity of the "flow of power" can be operated at very slow speed with- out using speed-change gears, except for starting and for exceptionally heavy pulling and are able to "pick up" speed much more rapidly than the automobile having a four-cylinder engine. CHAPTER II AUTOMOBILE ENGINES The detailed study of gasoline automobiles begins naturally with the most important part, the engine, or the "motor" as it is commonly called in the automobile industry. In the following pages, however, the name engine will be used exclusively to avoid confusion in later chapters when the name "motor" will be used in referring to the electric motor of starting systems. Good understanding of the prin- Intafa Valve I Open, Valve E Closed ^ WATER JACKET FlG. 22. Cylinder of Gasoline Engine. ciples of operation and of the important details of the automobile engine should be a part of the education of every automobile operator or driver. Knowing how to cor- rect faulty adjustments in the engine and in its auxiliary equipment as soon as they occur is the best insurance against nerve-racking annoyances and large expenses for repairs. Gasoline Engine Operation. The power of a gasoline engine comes from the explosion of a mixture of gasoline vapor and air in a confined space, usually in a closed cylinder. Fig. 22 shows the cylinder of a simple type of gasoline engine. The explosive mixture enters through the opening opposite 21 22 GASOLINE AUTOMOBILES the valve disk I. If after taking in a quantity of explosive mixture, this opening is closed and the mixture is exploded, the movable plunger, or piston P of the engine will be forced by the explosion toward the right-hand end of the cylinder, just as a ball is driven from the free end of a cannon by the explosion of the powder behind it (Fig. 23). An explosion is really nothing more than the practically instantaneous burning of a highly inflammable material. In a gasoline engine the explosion results from the very rapid burning of gasoline vapor mixed with air. Such a mixture when put into an engine cylinder must have proper proportions. It is possible to use so much gasoline that the mixture is too "rich" to explode effectively. On the other hand, with too FIG. 23. Explosive Force in a Cannon. little gasoline in the mixture the explosion is too weak. Be- tween the mixtures that are too "rich" and those that are too weak, or "lean," there is a wide range of mixtures which are highly explosive. The proper explosive mixture of gaso- line vapor and air is of fundamental importance. In the following chapters there will be frequent references to this subject. Fig. 24 represents diagrammatically a gasoline engine divided through the center in cross-section, showing the cylinder C with its plunger, or piston. On the left-hand side is the intake pipe through which the explosive mixture enters the cylinder. On the right-hand side is the exhaust pdpe through which the burned mixture called exhaust gases escapes from the cylinder. A most important device called a carbureter is attached to the end of the intake pipe. This AUTOMOBILE ENGINES 23 device, when properly adjusted, mixes automatically the right proportions of gasoline and air for the explosive mix- ture. The parts of a carbureter are delicate and can be adjusted so that the proportions of the mixture may be changed to suit the varying conditions of engine operations in summer and winter, in high and low altitudes. When the force caused by the explosion of the mixture in the engine cylinder drives the piston (Fig. 24) downward this motion is transmitted through the connecting rod R to give rotary motion to the crank shaft 8, which revolves and on each explosion stroke receives enough force to move the piston up and down during the return stroke as well as also during the other strokes when no power is developed. A heavy wheel on the crank shaft, called a flywheel, is used as a means of storing up energy during the explosion stroke to be used later in turning over the engine during the other three strokes when there are no power impulses. From the engine crank shaft the power is transmitted by means to be fully described later, to the rear wheels, and the automobile thus gets its driving power. The steel casing which surrounds the crank shaft and lower part of the connecting rods is called the crank case. Engine Types. There are two principal kinds of gasoline engines, named according to the number of up and down movements, or strokes of the piston occurring between one explosion or power stroke and the next power stroke. The kind used almost exclusively for automobiles has one ex- plosion in every four strokes of the piston. In this kind of engine, the explosion stroke together with the other three strokes (until the next explosion) are called its cycle; and because there are four strokes in its cycle it is called a four- stroke or four-cycle engine. Another kind of engine not often used on automobiles but much used for marine purposes has only one stroke between an explosion stroke and the next. It has, therefore, only two strokes in a cycle and is called a two-stroke or two-cycle engine. In every piston engine one stroke of the piston occurs every half revolution or 24 GASOLINE AUTOMOBILES half turn of the crank shaft. Briefly then a standard type of automobile engine has four strokes or two complete revolu- tions of the crank shaft in its cycle. Intake Pipe ,Spark PIug-K FIG. 24. Automobile Engine. Intake Position. FIG. 25. Automobile Engine. Compression Position. FIG. 26. Explosion Position. FIG. 27. Exhaust Position. Four-stroke Automobile Engine. Figs. 24, 25, 26, 27, show the positions of the engine piston in the four strokes in a four-stroke cycle; that is, from the beginning say of an explosion stroke till the piston is back again in position AUTOMOBILE ENGINES 25 for the next explosion. For simplicity of explanation, the description of what takes place during the four strokes of such a cycle will begin with the intake or suction stroke, as shown in Fig. 24 when the piston is moving downward in the direction of the arrow to draw the mixture of gasoline vapor and air from the intake pipe into the cylinder. During this stroke the engine must suck in the explosive mixture just as an air-pump sucks in air before compressing it, or as the ordinary wooden pump draws water by suction from a well. After the explosive mixture of gasoline vapor and air is in the cylinder the intake valve I closes, making an air tight chamber. After this the piston rises as shown in Fig. 25 and compresses the imprisoned mixture. This compression of the explosive mixture is an important part of the cycle, as it causes an explosion pressure from three to five times greater than would be possible without compression. Com- pression also serves to mix more evenly the gasoline vapor with the air and at the same time raises the temperature so that good ignition is made easier. Anyone who has operated an automobile engine in both winter and summer knows how much more easily good ignition is secured with warm air than with cold air. Just at the beginning of the next downward stroke (Fig. 26) the explosive mixture is ignited by an electric spark from a device, called a spark plug K, located in the top of the engine cylinder. The combustion resulting from this ignition raises, almost instantly, the pressure due to the compression stroke, which is from 50 to 75 pounds per square inch to about 300 pounds per square inch. On this explosion stroke the piston is driven downward with great force between 2000 and 3000 pounds in each cylinder according to the surface of the piston, and by means of the connecting rod this force is transmitted to the crank shaft of the engine. In order to make the explosions in an engine cylinder as strong as possible, the ignition of the explosive mixture should occur a trifle before the point of greatest compression. Ignition should take place, therefore, just before the end of 26 GASOLINE AUTOMOBILES the compression stroke. The faster the engine is running the earlier in this stroke the ignition should occur. This is what is meant when one says the "spark" or ignition should be "advanced," that is, occur earlier at high than at low speed. Valve Operation. For controlling the order of the strokes of a gasoline engine there are usually two valves for each cylinder. One controls the suction or admission of the mix- ture of gasoline vapor and air into the cylinder and is called the intake valve marked / in the preceding figures (Figs. 24-27). Another controls the discharge of the burned or exhaust gases and is called the exhaust valve E. The valves of gasoline automobile engines are opened and closed by mechanical means similar to that shown in Fig. 24. Both intake and exhaust valves have vertical rods attached cen- trally to the valve disks which extend downward toward the crank case on each side of the cylinder. These rods are called valve stems. The one on the intake valve is marked IS (for intake Valve /Stem) and the one on the exhaust valve E8 (for Exhaust Valve /Stem). The valve disks are normally held in the closed position by the force of strong spiral springs (not shown in the figures). The intake valve / is opened by being pushed upward by the "tooth" T on the cam shaft at the left-hand side of the engine. When the engine is in motion this cam shaft revolves constantly at half the engine speed, and opens the valve when the "tooth" T is pointed vertically upward. If this fact about cam shaft speed is kept in mind it will be easy to understand the valve operation of any four-stroke automobile engine. Every time the "tooth" T on the left-hand cam shaft comes around in a revolution it raises upward the intake valve stem IS and valve / against the force of a spring which tends to hold it down. There is also another cam shaft on the right-hand side of this engine which moves the exhaust valve. This cam shaft has also a "tooth" for opening the valve but its position is different from that of the "tooth" T during each of the AUTOMOBILE ENGINES 27 engine strokes just described. The exhaust valve is kept tightly closed during the intake stroke. During the com- pression (Fig. 25) both valves remain closed during the whole stroke so that the explosive mixture is " trapped" within the cylinder and none of it can escape. Both valves are closed also during the explosion or power stroke. When the piston is at the bottom of the explosion stroke and is about to begin the next upward stroke, called the exhaust stroke, the "tooth" on the right-hand cam shaft comes into contact with the valve stem E8 and pushes open the exhaust valve E. On this stroke, as the piston goes up, the space in the cylinder above the piston becomes continually smaller, and with the exhaust valve open, the burned mixture is driven out through the exhaust pipe into the atmosphere, clearing the cylinder to receive the next fresh explosive mixture. Summary of Four-stroke Engine Operation. By drawing down the engine piston during the suction stroke a vacuum is created in the upper part of the cylinder. At the right moment the intake valve is opened and a mixture of gasoline vapor and air is sucked in. Then the intake valve closes and the rising piston compresses this charge. When the piston reaches its highest point an electric spark is introduced through the spark plug. The explosion stroke gives enough power to carry the crank over the strokes which have no power impulses. There are four strokes, or up and down movements, of the piston in each cycle of a four-stroke engine. The first which draws in the mixture is called the suction stroke; the next is the compression stroke, the third is the explosion or power stroke, and the fourth is the exhaust stroke, when the burned gases are expelled from the engine cylinder. During these four strokes there are two complete revolutions of the crank shaft. The explosion or power stroke does all the useful work in turning the engine crank shaft, which moves the automobile. The suction and the compression strokes serve only to take in the explosive mixture and get it ready for 28 GASOLINE AUTOMOBILE^ efficient explosive burning. The exhaust stroke serves only for cleaning out the cylinder. Engine Flywheels. For every four strokes of a four- stroke engine there are three "idle" strokes during which no power is developed. During these "idle" strokes the pistpn must be driven from the crank shaft, and in most engines the power to keep the crank shaft moving during these "idle" strokes must come from "stored energy" or momentum in a flywheel. Flywheels as provided on auto- mobile engines are usually a part of the friction clutch. (See Chapter 1, page 9.) A flywheel is made extra heavy because it is difficult to stop a heavy wheel when revolving at high speed. A flywheel of proper weight when once started will keep an engine running for some time. A well designed automobile engine of six or more cylinders once started will, however, keep itself going without a flywheel if all its cylinders are operating. Valve and Cylinder Arrangements. The typical engine shown in Figs. 24, 25, 26, 27, has the intake valves on one side of the engine cylinder and the exhaust valves on the other side. This is called a T-head cylinder because the top of the cylinder resembles the letter T. It is shown diagram- matically also in Fig. 28. This arrangement is used on many of the larger makes of automobiles as it allows room for valves of wide diameter. As such valves have to be lifted but slightly off their seats to admit sufficient mixture and to carry off exhaust gas, they make little noise in operation. Most automobile engines, however, are constructed with a more compact valve arrangement called an L-Jiead cylinder in which both the intake and exhaust valves are on the same side of the cylinder as shown in Fig. 29. It is a well known fact that the larger the surface of the cylinder, including the valve spaces in which the explosive mixture is ignited and exploded, the greater will be the losses due to wasted heat by cooling. On this account an engine with an L-head cylinder and with other parts the same, will be more economical in the use of gasoline than one with a T-head cylinder. AUTOMOBILE ENGINES 29 Fig. 30 shows a valve and cylinder arrangement called valve-in-the-head. The valves are in the center of the top of the engine cylinder and open downward. This affords a very short passage for the explosive mixture into the cylinder, and a very small surface around the valves exposed to cooling. This is sometimes called an I-head cylinder. "Valves-in-the- head" have, therefore, special advantages as regards power and economy, but they are likely to be more noisy than other types. Though most automobile engines are at present made with the L-head construction, there is an increasing number being built with the ''valve-in-the-head" arrangement. FIG. 28. T-Head Engine Cylinder. FIG. 29. L-Head Engine Cylinder. FIG. 30. Valve-in-the- Head Engine Cylinder. Slide Valve Engines. The elimination of noise in auto- mobile engines has always been an important consideration. It is well known that a great deal of the noise in engine operation is due to the valves. In any engine in which the ordinary so-called poppet valves are used there is necessarily some noise from the valves, especially after repairing, if the lengths of the push rods are not carefully adjusted. On the other hand, slide valves are almost noiseless and their use on all kinds of engines is not new. In fact, the first gas engines ever built were made with slide valves ; but on account of the high temperature in such engines there was excessive wear and warping and it was difficult to keep the exhaust valves tight enough to hold the compression pressure. 30 GASOLINE AUTOMOBILES Knight Slide Valves. In recent years a type of engine has been developed in which poppet valves are successfully replaced by slide valves. These slide valves have a relatively gradual motion, and slide over the intake and the exhaust openings in the cylinder, instead of being snapped into their Intake Stroke Intake Ports Open Exhaust Ports Closed Compression Stroke All Ports Closed and Sealed by Ring La Cylinder Power Stroke All Ports Closed and Protected by Ring in Cylinder Exhaust Stroke Intake Ports Closed Exhaust Ports Open FIG. 31. Knight Slide Valves and Engine Cylinder. seats by a strong spring, as is the case with poppet valves. There is, however, another advantage besides the elimination of noise, as a slide valve engine develops more power for its size, because larger intake and exhaust valve openings can be used. Figs. 31 and 32 show plainly the position of the piston and Knight slide valves on the suction, compression, AUTOMOBILE ENGINES 31 explosion, and exhaust strokes. The thickness of the valves is purposely exaggerated to show the details more clearly. The difference between the operation of poppet valves and Knight slide valves can be readily understood when one considers that the ordinary poppet valve has its maximum opening during the time that the valve stem roller rides on the point of the cam. This roller follows accurately the Exhaust Valve Opening FIG. 32. Details of Knight Valves. irregular surface of the cam only at low and moderate speeds. At high speeds the cam will throw the valve stem instead of lifting it so that the action cannot be the same at high speeds as at low. On the other hand, in a Knight slide valve engine the intake and exhaust passages are opened and closed at exactly the proper time, and these passages can be made large enough so that the power of the engine is increased in proportion to the increase in speed. Another advantage claimed for slide-valves is that there are no projecting par- 32 GASOLINE AUTOMOBILES tides of metal or of carbon on the valves to remain hot after the discharge of the exhaust gases to cause premature explo- sions of the incoming fresh mixture. Pistons and Piston Rings. Formerly all gasoline engine pistons were made of gray cast iron. Recently a number of manufacturers of automobile engines have been using pistons made of aluminum alloys. Aluminum pistons are much lighter than those made of cast iron and therefore reduce the weight to be supported by the engine crank shaft. Reducing the weight on the crank shaft reduces also the vibration of the shaft and makes an engine quieter in operation. Aluminum is a better conductor of heat than iron. The use of this metal makes it easier to keep the pistons cool. Engine pistons are never made to fit tightly in the cylinders. The pistons must be made a trifle smaller than the inside of the cylinders to make provision for: 1. A film of oil between the curved part of the piston and the walls of the cylinder. 2. The greater expansion of the piston than of tha cylinder, because of the greater heating of the piston. Aluminum expands more than cast iron, therefore aluminum pistons must be made to fit more loosely in the cylinders than those of cast iron. It is not economical to allow the explosive mixture to escape between the pistons and the cylinder walls into the crank case during the compression stroke. To prevent such leakage, the pistons are fitted with elastic cast-iron rings, called piston rings, placed in grooves around the body of each piston. As a rule, three rings are placed in each piston as shown in Fig. 33. The most satisfactory piston rings are of the concentric type in which the thickness is uniform all around the ring. The varying degree of elasticity which is required in the ring in order that it should tend to expand in a circle and fill the cylinder bore is attained by certain peening methods. The butting ends of the ring are generally finished AUTOMOBILE ENGINES 33 to form a lapped joint at forty-five degrees. There has been much misrepresentation in the matter of specially designed piston-rings which attempt to form a more perfect seal than is afforded by the lapped joint. The fact is that the per- centage of leakage past the joint is such a small part or the whole that any improvement in this regard yields result., FlG. 33. Engine Piston. too small to measure. On the other hand, the simple rugged- ness of the plain ring, as contrasted with the complicated construction associated with the majority of special piston- ring designs, has everything to recommend it for ordinary service. The kind of piston rings most used are shown in Figs. FIG. 34. Typical FIG. 35. Peened Piston King. Piston Eing. 34 and 35. Many pistons are now made with a groove below the lower piston ring shown in Fig. 33, with five or six holes drilled in the groove through the piston. The piston ring then scrapes the oil from the cylinder wall into the groove and it drains back into the crank case through the holes in the piston walls. This is intended to prevent oil from working up the cylinder walls and burning in the 34 GASOLINE A UTOMOBILES combustion chamber. In some cases another groove is made near the bottom of the piston into which a " wiper" piston ring is fitted. This "wiper" ring is used to prevent oil from getting started on the way to the explosion space in the cylinder. Piston rings are subjected to considerable wear. When badly worn, the rings do not function properly and let oil pass into the combustion chamber. The oil only partially burns during the explosions and leaves a black, greasy deposit on the spark plugs and piston heads. This deposit is commonly called carbon and unless removed befouls the engine to such an extent as to lower its efficiency very per- ceptibly. Worn piston rings also permit gasoline to work back into the crank case and mix with the oil. As gasoline destroys the lubricating quality of the oil, the bearings are subjected to undue wear. When an engine smokes badly and consumes unusual quantities of oil loose piston rings are likely to be the cause. Despite the fact that it is economical from every standpoint to keep piston rings tight, a great many automobiles are run with worn rings. Crank Shafts. The crank shaft of an automobile engine must be made very strong; because it must support the weight of the pistons and connecting rods and resist stresses and vibrations produced by the irregular arrangement of the connecting rods on the shaft. In a four-cylinder engine there are usually three bearings or "rests" for the crank shaft as shown in Fig. 36. A six-cylinder engine has usually four bearings as shown in Fig. 37, although some six-cylinder engines are made with only three bearings. On the other hand some four-cylinder engines have five bearings, that is, each of the connecting rods is between two bearings. There is a similar arrangement for some six-cylinder engines which have seven bearings. These examples are given to show that there is great variation in the number of bearings which are provided for the engine crank shaft in different makes of engines. Obviously in an engine with a larger number of bearings there will be less vibration of the crank AUTOMOBILE ENGINES 35 shaft than in an engine with fewer bearings. On the other hand, a larger number of bearings add materially to the expense of making an engine. Fig. 36, illustrating the crank shaft of a four-cylinder Ftywheet FIG. 36. Crank Shaft for Four-Cylinder Engine. engine with three bearings, shows the conventional arrange- ment of pistons corresponding to the firing order, No. 1, No. 2, No. 4, No. 3. These numbers are consecutive on the engine for the cylinders numbered from the front of the Connecting Rod 'Piston Ring ..--CrankShaft Bearing Flywheel / \ ^Piston / ..- Connecting Rod Bearing ,.,-CrarT( Shaft '.. CranffShaff ' 6ear .... Starting Nut FIG. 37. Crank Shaft for Six-Cylinder Engine. automobile. The pistons in the two middle cylinders move up and down together and the pistons in the two end cylinders similarly move together. This means that when the No. 1 piston is on the compression stroke, No. 4 is on 36 GASOLINE AUTOMOBILES the exhaust stroke and Xos. 2 and 3 are respectively on the suction and explosion strokes. Engine Speeds. The maximum speed of a four-cylinder engine is about eighteen hundred revolutions of the crank shaft per minute. The highest speed of six-cylinder engines is from two thousand to twenty-five hundred revolutions per minute, and eight- and twelve-cylinder engines are usually designed for a maximum speed of three thousand to thirty-five hundred revolutions per minute. Arrangement of Cylinders in Automobile Engines. Early automobile engines were made with one or two horizontal cylinders. With the introduction of engines with four ver- tical cylinders came an era of great improvement in auto- mobile construction. This kind of engine is compact, accessible, and can be built in units giving reasonably high horsepower ; also, the distribution of explosive mixture from a single carbureter presents no difficulties. The useful power range of a four-cylinder automobile engine may be con- sidered to lie between four hundred and eighteen hundred revolutions per minute, which corresponds to an automobile speed of from twelve to sixty miles per hour. For the low speed requirements of congested automobile traffic the speed-change gears of a four-cylinder engine must be shifted frequently. The next improvement in automobile engines was to increase the number of cylinders from four to six, or eight. These engines with more frequent power strokes met in- stantly the demand for more power, more flexibility, more smoothness, and less noisy operation. A six-cylinder auto- mobile engine will doubtless be a standard type for many years as it has many advantages over a four-cylinder engine, and avoids much of the complication and excessive upkeep expense of eight-cylinder and twelve-cylinder engines. There are, however, certain structural difficulties which limit the general application of such engines in cheaply constructed automobiles. The crank shaft of a six-cylinder engine is relatively long, and in some designs weight limitations do not AUTOMOBILE ENGINES 37 permit making it as stout as might be desired. Because of this slenderness there is a certain amount of twisting which causes considerable vibration of the crank shaft in every revolution. At some speeds (called "critical") these vibra T tions become excessive and disagreeable to passengers. They are, of course, more noticeable in a large engine of high power with a slender crank shaft than in small ones. The next step in the development of automobile engines was the introduction of eight- and twelve-cylinder engines. Four-cylinder engines and six-cylinder engines are always made with the cylinders in a row. Eight-cylinder engines and twelve-cylinder engines as usually made should be con- sidered as two four-cylinder engines or two six-cylinder engines built up with the same crank shaft and crank case for the attachment of two rows of cylinders. It is easy to see that to some extent at least, an eight-cylinder engine must have the disadvantages of a four-cylinder engine, and that a twelve-cylinder engine will correspondingly have the disadvantages of a six-cylinder engine. For the same horsepower, the individual cylinders of an eight-cylinder engine are considerably smaller than those of a four-cylinder engine of the same horsepower, and, because the moving parts of individual cylinders are lighter in weight there is less vibration than in a four-cylinder engine. The objection to some six-cylinder engines because of vibration of a slender crank shaft applies, of course, equally to a twelve-cylinder engine, except that the method of con- struction with two rows of small cylinders permits the use of a crank shaft actually shorter than would be installed in a six-cylinder engine. The best authorities agree that there is little likelihood that practical automobile engines will be built with more than twelve cylinders. Compared with the simplicity of construction of the standard four-cylinder and six-cylinder engines there are many practical difficulties in the construction of an auto- mobile engine with eight cylinders in a single row. Even 38 GASOLINE AUTOMOBILES a six-cylinder engine has the disadvantage of having a relatively long crank shaft. This difficulty is obviously much increased with eight cylinders in a row. There is also the further disadvantage that with eight cylinders in a row the hood of the automobile is excessively long. Eight- cylinder engines are, therefore, made as a rule in two rows of four cylinders each, with the cylinders placed in most makes so that each row is at an angle of forty -five degrees from the vertical center line of the engine ; in other words, the two rows of cylinders are made with an angle of ninety degrees between them. The advantages of eight cylinders over four other than the increased power are as follows : (1) more even turning power; (2) greater flexibility; (3) less vibration. Practically continuous power is obtained in an eight-cylinder engine because one of its cylinders gives a power stroke every quarter revolution of the engine crank shaft and each one of these power impulses lasts about three-quarters of the stroke, which is the same as saying that the power impulse is effective for each of the cylinders for three-eighths of a revolution. It is obvious, therefore, that the power strokes aided by the momentum of the fly- wheel, will overlap and give almost perfectly constant power. This explanation should make it clear that an eight-cylinder engine with its four power strokes per revolution should give more uniform power than a six-cylinder engine with three explosions per revolution, and that it will be twice as smoothly running as a four-cylinder engine with only two explosions per revolution. Fig. 38 shows the relative con- tinuity or "flow" of power in engines having one, two, four, six, and eight cylinders. From the foregoing, it is easy to understand that there is the same increase in smooth running and of steady power application in a twelve-cylinder engine when compared with a six-cylinder or an eight-cylinder engine. It was just explained that with an eight-cylinder engine there were four explosions per revolution of the crank shaft. In a AUTOMOBILE ENGINES 39 twelve-cylinder engine there are six explosions per revolu- tion and the overlapping of power strokes is still more pronounced. Typical Automobile Engines. One-, two-, and three- cylinder automobile engines are now so infrequently used that no space need be given to their description. In essen- tial parts they are not very different from the modern types of automobile engines with more cylinders. Fig. 39 shows Legend Excess Energy abore Useful Energy negative Work Six Cylinder Engine jfisft .JLAAAJ Eight Cylinder Engine FIG. 38. Relative Flow of Power. a typical four-cylinder engine and may be considered repre- sentative of standard usage. The four cylinders are arranged with their connecting rods attached to the same crank shaft operating in a single enclosed crank case. A section of the crank case and two of the cylinders are shown broken away to make clear the attachment of the connecting rods to the crank shaft. The first cylinder from the left is cut in two through the middle to show the construction of the piston, connecting rod and wrist pin. The next cylinder shows only the cylindrical section cut-away with the piston 40 GASOLINE AUTOMOBILES and connecting rod uncut. The third cylinder from the left is sectioned to show the arrangement of the valves. A typical six-cylinder engine is shown in Figs. 40 and 41. Water Jacket. ....Water Pipe ....-Engine Block -Coo I ing Fan ..Starting Crank .-Crank Case Crank Shaft v - Connecting Rod FlG. 39. Typical Four-Cylinder Automobile Engine. Generator \Ignit/bn Coif, .' .ShrttrtqCrank- ^ Oil Pump \ Crank Case Pump FIG. 40. Typical Six-Cylinder Engine, Showing Water Pump. Vacuum Tank Water Outte^ ; ..-Manifold .Carbureter Clutch Release Shaft- FIG. 41. Typical Six-Cylinder Engine, Showing Intake Manifold and Carbureter. AUTOMOBILE ENGINES 41 Figs. 42 and 43 show typical eight-cylinder and twelve- cylinder engines with their accompanying equipment. Note that in the eight-cylinder engine there is an angle of ninety degrees between the two rows of cylinders whereas twelve- cylinder engines are made with an angle of only sixty degrees between the rows. Although the valves are arranged as in the usual L-head cylinder construction, they are more FlG. 42. Typical Eight-Cylinder Automobile Engine. accessible than in eight-cylinder engines because of the reduction of width made possible by placing the two rows of cylinders with angle of only sixty degrees between them. By this saving in width of the engine, the electric generator, the starting motor, the air pump, and the other attachments can be mounted at the side of the crank case as in most four-cylinder and six-cylinder engines. One method of attaching connecting rods to the crank shaft in eight and twelve-cylinder engines is shown in Fig. 44. 42 GASOLINE AUTOMOBILES The Intake Manifold. In an automobile engine the intake pipe is made with as many "branches" as there are Cylinder y 'arburerer Water Jacketed Intake Manifold Cylinder Camshaft Connecting Rod ^-Crankshaft FIG. 43. Typical Twelve-Cylinder Automobile Engine. Oil Wiper King Connecting Bod-Blade Type meeting Bod- Fork Type FIG. 44. Connecting Kods for Eight and Twelve-Cylinder Engines. AUTOMOBILE ENGINES 43 cylinders. These "branches" of the intake pipe are called the intake manifold. In some recent engines the "branches" of the manifold going to the intake valves are cast in the sides of the cylinders. The advantage of this construction is that the manifold can be kept warm by the heat of the engine and the carbureter can be placed high and close to the cylinders. Power Plant Suspension. In nearly all recently designed FlG. 45. Four-point Suspension. FIG. 46. Three-point Suspension. automobile engines the clutch and speed-change gears are combined with the engine in practically a continuous casing in such a way as to form what we call a single power plant unit. This "unit construction" has the advantage of retain- ing positively the alignment of the shafts in the speed-change gears, under most conditions of operation. This method of setting up the engine, clutch, and speed-change gears makes it also easy to apply what is called the three-point suspension. 44 GASOLINE AUTOMOBILES In some automobiles the engine and speed-change gear case are attached to the automobile frame at four points two in the front and two near the middle of the frame as in Fig. 45. This method has the disadvantage that in case of distortion of the frame caused by operation over very rough roads, or by a collision, it is difficult to adjust the alignment of the engine crank shaft, the clutch and the shafts of the speed- change gears, so that there would not be excessive wear on the several parts. Because of these difficulties the three-point suspension was introduced. This method of suspension means that the power plant unit is supported as in Fig. 46 on two Rear Supports on Side Brackets Front Power Plant Support FIG. 47. Three-point Suspension Applied to Dodge Engine. points in front and one point near the speed-change gears. In the Dodge automobile (Fig. 47) the three-point suspen- sion is reversed. There is one point of suspension in front and two other supports on brackets at the rear end of the crank case. It should be evident that with the three-point suspension there can be considerable distortion of the frame without interfereing with the correct alignment of any parts of the unit power plant. Engine Cylinders. Most four-cylinder and six-cylinder engines are made with all the cylinders in a single casting. This is called block cylinder construction. It makes the engine AUTOMOBILE ENGINES 45 considerably shorter, more rigid, and lighter than if there is a separate casting for each cylinder. In separate cylinder construction the expense for renewal of a cylinder is less in case it is broken or otherwise damaged. The inside diameter of an engine cylinder is often called the bore. Many automobile engines are made with detachable cylinder heads as shown in Fig. 48. This construction is more costly than "solid" cylinder heads, but the advantages are so apparent that it is coming into more general use. It is particularly desirable in multiple cylinder engines, like eight- cylinder and twelve-cylinder engines in which there are a number of cylinders to be cleaned. Worn Cylinders. In much used engines the cylinder may Removable Head FIG. 48. Detachable Cylinder Head on Block Cylinders. be worn oval, so that the piston and its rings do not fit tightly. When the cylinder is oval, compression is weak and the piston will not suck in the mixture properly. Furthermore, when the explosion occurs much of the burned gas will be forced past the pistons down into the crank case. Improper lubrication is a common cause of worn cylinders. Firing Order. In conventional four-cylinder engines the relative positions of pistons, connecting rods, and crank shaft, are arranged as shown in Fig. 49. In this figure the main bearings and the connecting rod bearings are in the same vertical plane and the latter are marked from right to left with the numbers 1, 2, 3, and 4. Connecting-rod bearings 1 and 4 are 180 degrees from bearings 2 and 3 ; so that the pis- 46 GASOLINE AUTOMOBILES tons 1 and 4 are always in the same up or down position in the cylinders at any instant, but for different services. Thus, if No. 1 piston is on the compression stroke, No. 4 piston will be on the exhaust stroke. At the same time No. 2 FIG. 49. Crank Shaft for Four-Cylinder Engine. piston will be on the suction stroke and No. 3 piston will be on the explosion, or power, stroke. The order "of firing" or sequence or explosions in the cylinders is in this case 1, 2, G FIG. 49A. Typical Crank Shafts FIG. 49B. Typical Crank Shafts for Four-Cylinder Engines. for Six-Cylinder Engines. 4, 3. In a four-cylinder engine the firing order is sometimes 1, 3, 4, 2. The cranks of a six-cylinder engine are placed 120 degrees apart as shown in Fig. 50. Cranks 1 and 6, 2 and 5, 3 and 4 move together in pairs. The firing order is usually AUTOMOBILE ENGINES 47 1, 5, 3, 6, 2, 4 for the first shaft shown and 1, 4, 2, 6, 3, 5 for the other. Horsepower of Automobile Engines. The usual method of calculating the horsepower of automobile engines is by the use of the 8. A. E. formula (Society of Automotive En- gineers). This formula is intended to determine only approxi- mately the useful, or brake horsepower (b.h.p.) of a high speed gasoline engine. Briefly, bore in inches X b re in inches X number cylinders horsepower = _ . =st r i ring < I-4-2-6-3 1 ! TlG. 50. Firing Orders in Six-Cylinder Engines. If D represents the diameter, or bore, of the engine cylinders in inches, and N represents the number of cylinders in the engine, this formula is stated as follows: D 2 N ' ' P ' = 2lT =0 ' For instance, if an automobile has 6 cylinders and the bore is 4 inches, the horsepower is, 4 V 4 V fi =38.4 horsepower. 48 GASOLINE AUTOMOBILES In abbreviated form the formula may be used as follows: For 4 cylinder engines, b.h.p. = 1.6JD* " 6 " " " =2.41)* "8 " " " =3.2D* " 12 " " " This formula gives ratings much too low for modern high-speed automobile engines, but gives with some degree of accuracy the maximum horsepower of the most common makes of four-cylinder engines, which are not intended to run at more than about 1800 revolutions per minute. Modern eight- and twelve-cylinder engines are intended to operate at least fifty percent higher piston speeds than the above formula was intended to cover.* * Piston displacement is a term sometimes used when describing the size of engine cylinders. It depends on the diameter of the cylinder and the length of the piston stroke. Literally it means the space in the cylinder swept through by the piston in going from one end of the stroke to the other. It is calculated by multiplying the area of a circle of the diameter of the inside of the cylinder in square inches by the length of the piston stroke. The displacement is in cubic inches. The clearance in an automobile engine is the space inside the top of the engine cylinder which the piston does not 'enter. CHAPTER III GASOLINE AND SUBSTITUTES Gasoline. Nearly all automobiles. use gasoline for engine fuel. The reason is that it vaporizes more easily than other similar engine fuels. It is a product of the distillation of crude oil (petroleum), which, when heated in large closed retorts or stills, gives off vapor, which rises from the oil. The vapor passes from the top of the retort into pipes or cooling coils in which it is condensed. In this process of crude oil distillation, the lighter vapors like gasoline, naphtha, benzine, etc., are collected. With ordinary atmospheric pressure in the retort, these lighter vapors will be obtained when the crude oil is heated from about one hundred to one hundred twenty-five degrees Fahrenheit. If considerable pressure above atmospheric is maintained in the retort by an air pump, the lighter vapors can be dis- tilled off (called the "cracking," "Burton," or "Rittman" process) when the temperature is very much increased above the limits for distillation at atmospheric pressure. After the lighter vapors of the gasoline variety have been collected and condensed, if heating is continued, there is further rise in temperature in the retort, and heavier vapors are collected which, when condensed, give in succes- sion, according to the vaporizing temperature, kerosene, light lubricating ("engine") oil, fuel oil (for steam boilers), paraffine, etc. No definite percentages can be stated as to the relative amounts of gasoline, kerosene, etc., from such distillation, for much depends on the kind of crude oil used. Some kinds of heavy crude oil from Middle Western and Western States give relatively little gasoline with heating at atmospheric pressure, but considerable amounts with 49 50 GASOLINE AUTOMOBILES pressure distillation. This distillation process is usually called oil refining. Kerosene and Alcohol. For the same reason that kero- sene does not vaporize readily in the distillation process, it is difficult to use it in automobile engines as a substitute for gasoline, which is easily vaporized. Alcohol is nearly as difficult to vaporize as kerosene. Neither kerosene nor alcohol can be easily vaporized without applying heat, and cannot, therefore, be used satisfactorily for starting engines. Gasoline Mixtures. A liquid fuel made up mostly of a mixture of alcohol and gasoline has some advantages as a substitute for gasoline in engines. It is a well known fact that the efficiency of combustion in an engine can be con- siderably increased by going above the present limited com- pression. When gasoline of the ordinary commercial quality is used in an engine, the compression should not much exceed seventy-five pounds per square inch (gage) pressure, be- cause, at a higher pressure, an explosive mixture of gasoline and air is likely to be decomposed by the heat due to greater compression, so that uncontrollable combustion results.* It is equally well known that, if in the same kind of engine, alcohol is used for fuel instead of gasoline, there is not the same limit to compression, which can be carried to a much higher pressure without serious disadvantages. If a mixture of gasoline and alcohol, in about equal pro- portions, is used for engine fuel, the mixture will combine the advantages of both. The gasoline portion will vaporize readily for starting the engine and the alcohol will make it possible to use much higher compression pressures, with the advantages of higher engine efficiency. Unless, however, the head of the engine piston is made thicker, so as to reduce the amount of space in the top of the engine cylinder provided * The allowable limits of compression for very high grade gasoline intended for high compression engines, such as are used for aeroplane service, is about one hundred and twenty-five pounds per square inch (gage). Ordinary compression pressures do not much exceed seventy to seventy-five pounds per square inch. GASOLINE AND SUBSTITUTES 51 for the compression of the explosive mixture, the advantages from the use of alcohol will not, of course, be obtained. To use mixtures of gasoline and alcohol efficiently the compres- sion pressure should be raised to at least double the pressure now used. A recommended gasoline and alcohol mixture consists of forty percent alcohol, forty percent gasoline, and twenty percent benzol. The benzol is added to make starting easier. When this mixture is used in automobile engines, there is practically no noticeable knocking in the engine due to the high compression. Some of the large gasoline selling stations do not furnish gasoline but instead a mixture of heavy gasoline and benzol, which is a first class engine fuel and is usually sold a little cheaper than standard gasoline. Such mixtures are easily recognized, for the odor is unmis- takable and is different from that of gasoline. For winter service not much benzol can be used in gasoline mixtures as it freezes at about fifteen degrees Fahrenheit. In very severe climates, such mixtures might freeze solid in the gasoline tank. It is claimed that when such gasoline mixtures are used, a gasoline engine runs more smoothly than when ordinary commercial gasoline alone is used. Mixtures of gasoline and benzol are commonly called "doped" gasoline. The addition of benzol to gasoline gives it a "sweet" odor. Gasoline made by the cracking process, especially if it has been stored a long while, has a disagreeable odor. The principal advantage claimed for a gasoline and alcohol mixture is that the maximum power of an engine is increased about five percent with the usual gasoline com- pression, and about fifteen percent with the compression increased to about one hundred and fifty pounds per square inch. At maximum power, the fuel consumption per brake horsepower, when a mixture of gasoline and alcohol is used and the engine is operated at high compression, is ten percent less than with gasoline at normal engine compression. Rate of Production of Gasoline. The present production of gasoline is nearly two gallons for every automobile in service per day. With between 2,000,000 and 3,000,000 new 52 GASOLINE AUTOMOBILES automobiles and tractors put on the market each year, it is likely that the amount which can be allotted for each automobile or tractor must be reduced in the near future. in the distillation of crude oil, between twenty and twenty- five percent of the product on the average is gasoline, twelve percent is kerosene, about fifty percent is fuel oil, and the rest is lubricating oil, paraffin, vaseline, carbon, etc. About thirty percent of the gasoline now produced comes from the portion that was formerly called kerosene. All the kero- sene cannot be taken to increase the gasoline supply because ninety percent of the world is still lighted with kerosene lamps, and about ninety-five percent of the world does not know what electric lights are. The kerosene market, there- fore, is still an important factor. The price of kerosene will probably soon be nearly the same as that of gasoline. Knocking Caused by Engine FueL The real problem today in automobile engineering is to eliminate the carbon and the knocking in the engine. For years engineers have been trying to find out the cause of knocking in gasoline engines when there is carbon in the cylinders. Knocking in the engine cylinders used to be called pre-ignition, by which is meant ignition of the explosive mixture near the beginning of the compression stroke, thought to be caused by red-hot particles of carbon on the inside surface of the cylinders setting the explosive mixture afire prematurely. Chemical analysis of gasoline shows that it is made up of hydrogen and carbon. Now when gasoline is imperfectly vaporized, it breaks up and bums only the hydrogen. The carbon is left behind to settle on the inside surfaces of the cylinders. Carbon is one of the best possible heat insulators. "Wool ranks first as a heat insulator, and finely divided carbon is second of the ordinary materials. As long as the temperature of combus- tion is below a certain point, the gasoline will burn normally and without noise. If the temperature of the incoming air is reduced to ten degrees below the Fahrenheit zero, an engine will run well on kerosene with compression at eighty-five pounds per square GASOLINE AND SUBSTITUTES 53 inch. The refrigerated air simply prevents the temperature of combustion from going above the critical point at which the kerosene or gasoline breaks up. The only reason a gaso- line automobile engine runs better with all the carbon removed is that the cooling system is more active and takes away heat rapidly enough at the time of highest temperature to keep the gasoline from breaking up. As soon, however, as there is a little deposit of carbon, the cooling system is not so active and the temperature gets too high.* If the temperature of combustion is kept from rising above the point at which the gasoline breaks up, perfect combustion is possible and gasoline engines will run without carbon accumulations and without knocking in the cylinders. Regulating Combustion by Additions to the Fuel. A small quantity of ordinary aniline added to the gasoline used in a gasoline engine will entirely change its operation. The addition of only one percent of aniline to the gasoline used in an automobile engine which does not travel well on steep hills and is troublesome on account of knocking will change the running of the engine to give almost perfect operation. Schroeder, when he tried to make his great altitude flights in 1919, at first reached only 32,000 feet and could go no higher with ordinary gasoline. Later, he mixed two or three percent of aniline with the gasoline and went up for a record- breaking flight, and had no trouble with the explosive mixture. The increase in gasoline supply must come from the present ''fuel" part of crude oil, which is now about fifty percent. At least eighty percent of 1 this can be refined into * This temperature change is relatively large for a slight change in cooling, because the specific heat of the gases is so low; that is, the amount of heat which is required to raise a volume of gas through a degree is so low that just a little more energy, plus or minus, means a great raising or lowering of the temperature curve, and a few heat units added to the gas will raise the temperature many degrees. When the temperature reaches the point where gasoline breaks up, the combustion is fifty or sixty times as fast as in a normal explosion, and it is the im- pact of this violent explosion that causes knocking in the engine. 54 GASOLINE AUTOMOBILES water-white oil resembling kerosene, which makes an excellent engine fuel, if used in such a way as to prevent the breaking up of the fuel. Aniline, iodine, or some other similar ingredient, when mixed with gasoline, will break up at a lower temperature than the gasoline, and by thus absorbing heat energy it keeps down the temperature of the gasoline. For example, if a mixture of water and alcohol is put on a stove, the tempera- ture of the water cannot be raised while any alcohol remains, because the alcohol will evaporate and keep the temperature down. Aniline breaks up at about one thousand or eleven hundred degrees Fahrenheit, and in the process of breaking up absorbs considerable heat. If the automobile manufacturers could get the chemical industry to increase the coal tar production of the country, so that aniline could be sold at two dollars per gallon, it would not be too expensive for general use. If the use of such gasoline and aniline mixtures became common, the com- pression of automobile engines could be safely raised to one hundred pounds per square inch, which would almost double the efficiency of normal running. Automobile engineers pre- dict that within five years gasoline engines will run inde- finitely without any carbon trouble on almost any kind of petroleum fuel. Even if the addition of antiknocking chemicals increases the cost of gasoline two or three cents per gallon, the method would be economical because of the saving of fuel and of the cost of carbon removal. Hydrometers. In order to. determine the quality of gaso- line, as to whether it is a light or a heavy grade, a sample may be conveniently tested with a small glass instrument called a hydrometer. A typical hydrometer is shown in Fig. 51, as it appears when immersed in gasoline and in kerosene. There are etched numbers on the stem, reading upward. These numbers on a hydrometer for gasoline testing are called degrees of Baume test, named for the man who introduced this method of testing. These Baume or hydrometer degrees have no relation to degrees of temperature. A hydrometer GASOLINE AND SUBSTITUTES 55 placed in a vessel containing liquid like gasoline sinks to a depth corresponding to the density of the liquid. It sinks deeper in light gasoline than in heavy oil. The reading is taken on the etched scale at the surface of the liquid. The heavier the liquid, the lower the reading will be ; thus, gaso- line testing fifty degrees is much heavier and more difficult to vaporize than that testing sixty degrees. It is easy to Fis. 51. Hydrometer. remember that 0.70 specific gravity is approximately the same at 70 degrees on the Baume scale. There is not much difference in the heating or "power" value of the different kinds of gasoline per pound; that is, a pound of gasoline will give about the same amount of heating value irrespective of the source of the crude oil from which it was distilled or of the process of distillation. But low test (heavy) gasoline has more pounds to the gallon than high test (light) gasoline, so that measured in gallons 56 GASOLINE AUTOMOBILES assuming, of course, equally good vaporization and combus- tion low test gasoline will take an automobile farther per gallon than the high test kind. Gasoline Tanks. Gasoline for use in automobile engines is usually carried in a tank holding from ten to twenty gallons, placed in most automobiles at the rear between the back springs, but there are some automobiles with high-hung bodies in which the gasoline tank is placed under the front seat, and in still others, under the dash behind the engine. In the most common system of gasoline supply, which is, in fact, used in at least eighty percent of the automobiles with rear tanks, the principle of vacuum or suction, as explained in the following paragraphs, is applied to bring the gasoline to the engine. Vacuum Gasoline Feed System. A commonly used device to draw gasoline from a tank located below the level of the carbureter is the Stewart vacuum apparatus shown in Fig. 52. The method of attachment of this system in an automo- bile is shown in Fig. 53. The auxiliary tank is placed higher than the intake pipes of the engine so that it is necessary to draw the gasoline into it from the main tank by suction. The suction of the automobile engine is used to draw the gasoline from the main tank at the rear of the automobile to the auxiliary tank, which acts really as a vacuum pump. From the auxiliary tank the gasoline flows to the engine by gravity. By this system all the advantages of a simple gravity system as explained later are obtained with a relatively simple apparatus, which is usually mounted in front of the dash, at one side of the engine. There must be a small vent hole in the filling plug of the main tank at the rear so that the pressure inside that tank will be atmospheric. The auxiliary vacuum tank is divided into two chambers ; the upper one is the filling chamber, marked F. The lower one is the emptying chamber E. The two chambers are separated by a diaphragm which has a downward projecting spout P. The upper chamber has a float L, which controls the valves D and U. The gasoline pipe 8, running to the GASOLINE AND SUBSTITUTES 57 main tank at the rear of the automobile, discharges into the upper chamber F. An air pipe T extends from the top of this chamber to the intake pipe of the engine; the engine suction for drawing the gasoline from the rear tank is exerted through this pipe. The lower chamber is used to supply FIG. 52. Vacuum Gasoline Feed Tank. gasoline to the engine by gravity, and must be, therefore, under atmospheric pressure at all times so that the flow from it through the pipe to the carbureter will be continuous. Since the bottom of this gravity chamber is located at a higher level than the carbureter on the engine, there will always be a free flow of gasoline as long as this tank is kept 58 GASOLINE AUTOMOBILES filled. The pipe A, which at its lower end enters the lower chamber, has always a free opening to atmospheric pressure. Similarly there is atmospheric pressure in the pipe B, for it is open to the air at the top of the curved end. The above explanation shows the principle; but as the auxiliary or vacuum tank is usually constructed the upper chamber sets into the lower chamber, forming an inner wall and an outer wall at the upper part of the tank. (Fig. 54.) Between these two walls is left a narrow air space, which permits air to flow, through a vent in the top of the tank, down into the lower chamber. By this method the lower chamber is kept always at atmospheric pressure without the use of such a pipe as A in Fig. 52. Intake Manifold rsruum Tank FIG. 53. Vacuum System of Gasoline Supply. In order to suck gasoline from the main tank, which is at a lower level, into the upper chamber, the suction valve U at the bottom of the pipe T must be opened, and the atmos- pheric valve D at the bottom of the pipe B must be closed. In this operation one goes up and the other goes down. Under these conditions the float L is at the bottom of the upper chamber and a vacuum is produced in this chamber by the suction of the engine, transmitted through its intake pipe T. The vacuum in the upper chamber then draws the gasoline from the main supply line. As the upper chamber fills, the float rises until it gets near the top when it closes the suction valve U, and opens the atmospheric valve D. After this movement of the float valves, there will be atmos- pheric pressure in the upper chamber as well as also in the GASOLINE AND SUBSTITUTES 59 lower chamber, and the gasoline will flow by gravity from one chamber into the other through the vertical spout P. The flat valve V is put at the bottom of the vertical spout to prevent the gasoline in the lower chamber from being sucked back into the upper one when the suction valve is open. The valve U on the suction pipe T, leading to the intake pipe of the engine, and the valve D on the air vent are controlled Air Vent., To Carbureter FIG. 54. Stewart Vacuum Tank. by levers, which are pivoted at G with their outer ends connected by coil springs, as shown. These springs are arranged so that the float L is normally held near its highest position, and will be raised only a little when the level of the liquid rises high enough to elevate it farther. It is clear, therefore, that the float cannot take an intermediate position and the action of the upper chamber as a' vacuum pump is, therefore, intermittent and not gradual and continuous. This kind of intermittent action is necessary in order that the 60 GASOLINE AUTOMOBILES upper chamber may be under atmospheric pressure part of the time, when the gasoline will flow by gravity from the upper chamber to the lower. When the level of the gasoline drops to a certain point, the float L drops slightly from its elevated position, and by its movement opens the valve U on the suction line and closes the valve D on the atmospheric line. With the valves in this position, the suction of the engine again causes a flow of gasoline from the main supply tank. As soon as the level of the gasoline rises so as to elevate the float, the valves have the opposite movement, which closes the suction pipe and opens the air vent. Sometimes it happens, if an automobile is allowed to stand for a long time with the engine shut off, that because of a leakage in the system, the vacuum tank becomes empty. But this tank can usually be filled again with enough gasoline for starting when the engine is turned over four or five revolutions with the throttle valve completely closed. A metal screen is put at the end of the gasoline supply line 8, near where it enters the vacuum tank, to prevent sediment or foreign material from entering the float chamber. An emergency filling plug Q, when unscrewed and taken out, makes it possible to pour gasoline through the hole from which the plug is taken. For this filling a small funnel should be used. At other times, this plug should be screwed tightly so that there can be no air leakage into the upper chamber, for air leakage would prevent the drawing of gasoline from the main tank by engine suction. For cold weather service, this system has the advantage that the auxiliary tank is near the engine and the gasoline going through it will be heated on the way to the carbureter; in this way, vaporization is improved. Sometimes the float L will leak and fill with gasoline. If it does the valves U and D will not operate, and there will be continuous suction, so that the two chambers will fill com- pletely with gasoline, and finally the pipe leading to the intake of the engine will be partly filled. The engine will then get a mixture much too rich in gasoline for good operation. GASOLINE AND SUBSTITUTES 61 In that case, the cover of the tank (Fig. 55) should be taken off at the top so that the float can be taken out and repaired. If this trouble with the float should occur when the automobile is "on the road," it is best to take off the cover very carefully, fill the tank with gasoline, and then replace the cover loosely. The auxiliary tank will then be used as a gravity tank. When the tank is empty, the cover can be taken off and the tank refilled. Gravity Gasoline Feed System. The gravity system of gasoline supply consists simply of a gasoline tank under one of the seats of the automobile and a pipe for carrying the gasoline by gravity or by its own weight to the car- bureter. Under the tank there is a sediment chamber. Dirt FIG. 55. Top of Stewart Tank. and water being heavier than gasoline will settle at the bottom and can be cleaned out through the pet cock. Water is apt to accumulate in the bottom of the tank, and, if it freezes in cold weather, the gasoline supply may be shut off. If this happens, it is wiser to put hot cloths on the bottom of the tank and on the gasoline pipe rather than to take the risk of using a flame for heating. Pressure Gasoline Feed System. Another system used is the pressure system. Not many automobiles use this system; but some of the most expensive automobiles are equipped this way. The tank is at the rear of the auto- mobile, as it is in the Stewart vacuum system, but with the difference that it is air tight. The Packard, Pierce, and Locomobile makes still have this system. The cap of 62 GASOLINE AUTOMOBILES the gasoline tank must be screwed on tightly because air pressure on the top of the gasoline in the tank forces the gasoline into the carbureter. A small air pump, driven by the engine, delivers air under pressure through a pipe enter- ing the top of the gasoline tank. After an automobile has been standing several hours, there will not be enough pressure in the tank to force the gasoline into the carbureter ; and then a hand pump, intended for emergency use and placed near the driver's seat, is used to provide enough pressure for starting; but it is necessary first to open a valve below this pump, so that the air can be pumped into the tank. Usually the handle of a valve on any automobile hangs down when the valve is closed. Leaks in Air Lines. If there is a slight leak in any part of an air line for pressure or vacuum, the gasoline supply to the carbureter will probably be stopped. Do not test for air leaks by holding a match to the leak. That is too dangerous around an automobile. It is best to take a little soapy water and put it on the places where there are likely to be leaks. Bubbles will then form at the leak. Chewing gum or shellac may be put over air leaks until the automobile can be taken to a repair shop. CHAPTER IV GASOLINE CARBURETERS A carbureter is a device used for (1) vaporizing gasoline and then (2) mixing the vaporized gasoline with a suitable amount of air. When the proportions of gasoline vapor and air used in a gasoline engine are in correct proportions there will be high power explosions in the engine cylinders. If there is too much gasoline in proportion to air there will be imperfect explosions, indicating incomplete combus- tion, and black smoke will be observed coming through the exhaust pipe. On the other hand, if there is too much air, there will be little power and troublesome carbureter opera- tion. Right mixture proportions give the sharpest and the most efficient explosions, because the combustion of all the gasoline takes place at the proper time and leaves no un- burned parts to be wasted. Principle of Carbureter Action. The principle of suction is fundamental in all modern carbureters for automobile engines. This principle can be simply demonstrated by put- ting one end of a small glass tube in a cup of gasoline and sucking at the other end so that gasoline is drawn up into the tube. How far up the gasoline level stands in the tube depends on the suction. The same suction effect would be observed if a mechanical apparatus for pumping air were attached to the top of the glass tube. Now consider what happens in an automobile engine cylinder when a pipe, which dips into a cup of gasoline, is attached to the intake valve of the engine. During the suction stroke when the piston is moving downward with the exhaust valve closed and the intake valve open, the necessary suction is produced to suck gasoline vapor through the pipe and the intake valve GASOLINE AUTOMOBILES into the engine cylinder. An intake pipe for this purpose might be arranged with two branches as shown in Fig. 56, one of which dips into gasoline and the other is open to the air. By means of such a device the suction of the engine piston will suck a mixture of gasoline and air into the cylinder. This device suggests one way to put an explosive 'Spark Plug Exhaust Valve -E Intake Valve-/ FIG. 56. Simple Carbureter. mixture into the engine cylinder. It is a kind of carbureter. All gasoline carbureters have similarly branched passages although not so simply arranged. Through one branch air is drawn, and through the other gasoline vapor. Unless the supply of liquid gasoline is arranged to give a practically constant level in the gasoline cup (Fig. 56), the flow of gasoline vapor into the intake pipe of the engine will be irregular. If the gasoline level is lowered, the gaso- line must be sucked- up a greater distance and the engine GASOLINE CARBURETERS 65 suction will draw less into the cylinder. On the other hand, if the level is raised, it will draw more. Spray Nozzles. In nearly all types of commercial car- bureters some kind of spraying device is used for vaporizing the gasoline. In such a device the gasoline is discharged as a spray from a nozzle located in a suitable passage where the sprayed gasoline vapor will be easily mixed with air. An upward current of air passing around a small nozzle like N in Fig. 57 has enough suction effect to draw out the gasoline even when the level of the gasoline is slightly below the top of the nozzle. The figure shows the level in the nozzle the same as in the reservoir R. FIG. 57. Simple Nozzle Carbureter. FIG. 58. Nozzle Carbureter with Pistoa Suction. Actual vaporization as accomplished with a spray nozzle carbureter will be described more in detail with the help of Fig. 58. This figure shows a spray nozzle N, an air passage A, a cylinder or mixing chamber M, and a piston P with a handhold H. The gasoline level in the nozzle is shown higher than in the reservoir R, as it would be (1) on account of the upward air current causing a slight suction over the nozzle, and (2) on account of the suction produced when the piston P is raised upward in the air-tight cylinder M as indicated by the arrow.* * With air velocity through the passage A at about the usual velocities in a commercial type of carbureter using gasoline, there may 06 GASOLINE AUTOMOBILES Float Regulator. A device for regulating the amount of gasoline going into the reservoir R in a carbureter like Fig. 58 is necessary if the gasoline is to be at constant level. For this purpose a float is connected to a small valve, called a float valve, which shuts off the flow from the gasoline supply pipe. The float device is self-adjusting and the valve con- nected to the float shuts off the flow of gasoline when the level in the reservoir rises nearly to the top of the nozzle. A carbureter could be made to operate with the float arranged to have the established level of the liquid as high as the top of the nozzle, but the float is always set to shut off at a lower level so that there will be a margin of safety in case of inaccurate or sluggish operation of the float and valve, which might cause an excessive flow of gasoline from the nozzle. Even with the best devices this sometimes happens when the float or valve "sticks" and allows the gasoline to rise in the float chamber slightly above the established level so that it overflows from the nozzle. A low gasoline level in the nozzle atso prevents dripping from the nozzle when the engine is "idle" and is not in a level position, or when excessive vibration might cause the gasoline to overflow into the air passage A. Float-Feed Carbureter. Fig. 59 shows a very simple type of carbureter in which the flow or "feed" of gasoline is regulated by a float F. The liquid fuel supply enters at G and flows through the float valve FV into the float chamber C, from which some of the gasoline flows into the tube U leading to the spray nozzle N. When the gasoline level in the float chamber rises and is only about one-sixteenth inch from the top of the spray nozzle the float closes the attached valve FV, be a considerable difference in level between the top of the nozzle and the surface of the liquid in the reservoir B before the gasoline spray ceases. It may be as much even as one and one-half inches, and with a flow of gasoline once established the spray will usually continue until the difference in level is as much as two inches. These unusual condi- tions result sometimes when the gasoline supply for an engine is nearly exhausted. GASOLINE CARBURETERS 67 and prevents the gasoline from rising higher. The air supply enters through the passage A and passes up in the direction of the arrow into the mixing chamber M , where the air mixes with the gasoline vapor discharging from the spray nozzle N. The top of the mixing chamber M is made so that there will be air tight connections to the intake pipe of the engine.* The engine piston on its suction or intake stroke produces the necessary suction to draw the explosive mixture of gasoline vapor and air from the mixing chamber into the engine cylinder. FIG. 59. Simple Carbureter with Float Feed. FIG. 60. Carbureter with Auxiliary Air Valve. In the operation of the carbureter, the removal of gasoline through the nozzle N lowers the level in the float chamber C and causes the float F to descend enough to open the float valve FV, which allows more gasoline to enter. In this way a nearly constant level can be maintained in the float chamber and also in the spray nozzle. Auxiliary Air Valve. When the speed of an engine increases, the suction produced by the piston in the intake pipe increases in proportion. Increased suction will propor- tionally increase the amount of gasoline sucked out of the spray nozzle of the carbureter. On the other hand, increased * The float chamber should not be made air tight where the rod B connecting the float with the float valve FV passes through the cover plate L. 68 GASOLINE AUTOMOBILES suction does not increase proportionally the amount of air passing through the air passage. Gasoline is a liquid and its particles "hang together," when pulled by suction; but air is an elastic and "expansive" fluid with no tendency for the particles to "hang together." Because of this difference, the amounts of air and of gasoline sucked into a carbureter are not in the same proportions at different engine speeds. For example, an average size of automobile engine will take in through the carbureter about^ fifty pounds of air and five pounds of gasoline per hour when running at a speed of five hundred revolutions per minute. If the speed is increased to one thousand revolutions per minute, the amount of gasoline will be ten pounds (increased in proportion to the speed) ; but the amount of air will be only about eighty pounds instead of one hundred pounds as it would be if the amount of air increased in proportion to the speed. If the parts of the simple form of carbureter already explained will give an efficient mixture of gasoline and air at an engine speed of five hundred revolutions, the mixture will not be right at one thousand revolutions per minute^ In other words, at the higher speeds, the mixture will be too "rich" in gaso- line. Also, if the mixture is right for high speeds it will be wrong for low speeds. All simple carbureter devices like the one shown in Fig. 59 will give the engine an explosive mixture richer in gasoline when air passes around the spray nozzle at high velocity and high suction than when at low ' velocity and low suction. ( In other words, increasing the engine speed increases also the percentage of gasoline in the explosive mixture. All kinds of spray nozzle carbureters must, therefore, use some adjusting device, which should be automatic. Such a device is called an auxiliary air valve \ of which a typical example is marked AV in Fig. 60^ This \ auxiliary air valve is provided with a spiral spring X of sufficient strength to hold it closed at low engine speeds, when there is little suction in the mixing chamber M. In- creased engine speed produces greater suction so that this valve will be opened varying amounts in proportion to the GASOLINE CARBURETERS 69' speed. It will be open a little at moderate speeds, and more at high speeds, permitting additional air flow into the mixing chamber M. This additional air supply, as the speed of the engine is increased, has the effect of reducing the suction in the air passage A in proportion to the amount of opening of the valve. A plug K at the bottom of the float chamber can be removed for cleaning out water and dirt carried in from the gasoline supply pipe G. A small cock H is at the bottom of the spray-nozzle tube which is intended for the rapid removal of any accumulation of water or for tapping small quantities of gasoline from the carbureter for engine priming, cleaning, etc. Priming a Carbureter. An explosive mixture, very rich in gasoline is usually necessary, especially in cold weather, to start a gasoline engine. Conditions for combustion are very unfavorable when the engine is cold and when it is turning over slowly for starting. One reason is that there is a leakage of the compression pressure between the inside surface of the engine cylinder and the piston during the relatively long time required for a slow speed stroke. An- other reason is that the heat developed by the compression of the explosive mixture is largely lost (dissipated) at slow speed of starting. The result is that only the most easily evaporated part of the gasoline can be vaporized at the time of starting an engine, and this easily vaporized 'part is only a small percentage of that discharged from the spray nozzle of the carbureter. It is, therefore, necessary to take a large quantity of gasoline into the engine cylinders to secure enough of the easily vaporized kind to start combustion. One way to obtain an explosive mixture very rich in gasoline is to depress the float rod R (Fig. 60) by hand, so that a small quantity of gasoline will overflow from the spray nozzle into the air passage A. Gasoline exposed in this way in the air passage will be readily vaporized and mixed with the entering air so that the engine will receive a "rich" explosive mixture at the slow speed of starting, whether the engine is turned by hand or by an electrical or mechanical starting device. 70 GASOLINE AUTOMOBILES Somewhat different devices for priming carbureters will be explained in the descriptions of other carbureters. It is dangerous to let very much gasoline discharge from the spray nozzle of a carbureter by priming when the engine is very cold, because under these conditions, a slow-burning ignition flame sometimes comes back through the intake valves into the carbureter, and if a puddle of gasoline has accumu- lated, there is danger of having a troublesome fire. There is the same danger of a fire* in the carbureter if the engine is turned over a number of times without getting an explosion in the cylinders either because the electric switch for ignition has not been turned or because the ignition device is defective. Every revolution of the engine pumps more gasoline into the cylinders and this gasoline is left condensed on the pistons and on the tops of the cylinders. The engine will probably start when the trouble with the ignition has been corrected and the accumulation of gasoline has evaporated. Sometimes when a cold engine is to be started and the usual methods of priming the carbureter are ineffective, a teaspoonful of gasoline put into each of the engine cylinders will serve to start the engine. "When the engine does not start after this "treatment" there is probably some defect in the ignition. If, however, too much gasoline is put into the cylinders for priming, the mixture will be too rich for engine operation. The need is then for more air rather than more gasoline. Regulated Nozzle Carbureters. The carbureter shown in Fig. 60 has the float valve rigidly attached to the float so that when the float is raised, the valve will be raised an equal amount. Another arrangement of the float and valve is shown in Fig. 61 in which the float valve FV is at the side of the float F, which is made of cork and is in the shape of a horseshoe. The short lever L is fastened on one side to the top of the float and at the other end is forked to fit Water should not be poured on a gasoline fire. It is best to use the spray of chemicals from a good kind of fire extinguisher. Such a fire can be smothered by throwing blankets, sand, or dirt over the GASOLINE CARBURETERS 71 around the rod or stem attached to the float valve FV. This lever is supported on a horizontal pin at /. When the left- hand end of the lever is pressed downward by the weight of the float (when the gasoline level falls) the other end of the lever, which is attached to the float valve FV is raised and permits gasoline from the supply pipe G to flow into the float chamber C. The carbureter shown in Fig. 61 has a mechanical means for regulating the flow of gasoline through the spray nozzle. The spray nozzle N extends into the middle of the mixing To Engine Cylinder FIG. 61. Regulated Nozzle Carbureter. chamber M so that it is near the center of the float chamber. This arrangement has the advantage that the flow of gasoline through the nozzle is not much affected by either endwise or sidewise tilting. The needle valve or pointed stem P in the opening in the spray nozzle N is used to regulate the amount of the gasoline going into the mixing chamber.* The main * Sometimes the needle valve or pointed stem is at such an angle that by lengthening the stem it can be extended to reach to the dash board or instrument board. It may then be fitted with a handle intended to be turned slightly when starting the engine, in order to get a mixture of gasoline and air suited to the speed of the engine. 72 GASOLINE AUTOMOBILES air supply enters through the holes shown in the bottom of the carbureter and goes into the air passage A and then past the spray nozzle into the mixing chamber M. The amount of opening of the auxiliary air valve A V is propor- tional to the engine speed. The auxiliary air current has the effect at high engine speeds mainly by reducing the suction of checking the flow of gasoline from the spray nozzle. The butterfly throttle valve, as shown to the left of M, regulates the quantity of the mixture of gasoline and air going to the engine cylinders. A throttle valve of this kind is simply a small damper similar to those in the smoke pipes of furnaces and stoves. It is connected to the throttle lever on the steering column and also to the foot pedal called the accelerator. Mov- ing the throttle lever by hand or depressing the accelerator with the foot opens this valve and allows more explosive mixture to enter the engine cylinders. The throttle valve thus regulates the speed of the engine. Symbols for Carbureters. In the following descriptions of carbureters the symbols given below will be used to designate the important parts. Keeping these in mind, it should be possible to understand the operation of any car- bureter marked with these symbols by casual examination of the figures going with the description. The following symbols are used to mark the figures in this chapter: A Air Intake. AA Auxiliary Air Intake, if without auxiliary air valve. AN Auxiliary Gasoline Nozzle. AV Auxiliary Air Valve (for high speed adjustment). C Gasoline Chamber (also called float chamber). D Dash Pot (to steady valve action). E Exhaust Gas Connection. F Float in Gasoline Chamber. FV Float Valve. G Gasoline Supply Pipe. J Gasoline Pool or "Puddle." L Lever on Throttle Valve T. M Mixing Chamber. N Gasoline Spray Nozzle. GASOLINE CARBURETERS 73 P Needle Valve (also called pointed stem). 8 Valve Seat. T Throttle Valve (also called butterfly valve). V Air Valve (also called choke valve). W Weight on Weighted Valve. X Coil Spring. Z Expanding Mixing Tube ("Venturi"). Weighted Air Valve Carbureters. A somewhat different type of carbureter shown in Fig. 62, similar to the Kingston Air To Engine Intake FV FIG. 02. Kingston Carbureter. make, is used on some Ford automobiles. The gasoline enters from the supply pipe G into the float chamber when the float valve FV is open. The opening and closing of the float valve are regulated by the cork float F which is sup- ported on a horizontal pin at /. The mixing chamber is the unique part of this carbureter and is so designed that all air entering through the main air intake A must pass over a little pool of gasoline in a sort of pit / in the bottom of the mixing chamber. The amount of gasoline supplied is 74 GASOLINE AUTOMOBILES regulated by the position of the needle valve or pointed stein P which, by adjusting the size of the opening in the submerged nozzle at controls the level of gasoline in the pool. Obviously, more gasoline will be taken up by the air when the level is high than when low. On account of having such a gasoline pool, this kind of carbureter is sometimes called a "puddle" type. At low engine speeds the suction is not great enough to raise the air valve AV as it is held down with the weights W, W; and all the air for the explo- sive mixture together with the gasoline vapor it picks up in the gasoline pool must go up through the tube U, and a very "rich" mixture is thus obtained for starting and for running at low engine speeds. With increasing speeds the weighted air valve AV opens more and more so that at about the highest engine speed, it is wide open, and gives a much diluted explosive mixture. The amount of gasoline and air mixture entering the engine intake pipe is controlled in the usual manner by a butterfly throttle valve T. At low engine .speeds, as when starting, the air cannot fail to take up the gasoline vapor no matter how low the velocity of air passing over the surface of the gasoline pool. The only adjustment on this carbureter is by means of the needle valve P. A very rich mixture for starting in cold weather is secured by partly closing the air valve or choke damper V in the main air passage. The carbureter shown in Fig. 63 has no essential parts different from those already described, except as to the kind of auxiliary air valve. The main air opening is through the nir bend A at the bottom of the carbureter. The mixing chamber M is at the top of the spray nozzle N which is flared out into a conical shape. There is an overhead needle valve or pointed stem P which extends into the top of the spray nozzle and is to be used for regulating the amount of gasoline used. The supply of auxiliary air is controlled by a series of metal balls E, B, set into tightly fitted seats 8 in a circular plate near the top of the carbureter, just under the cover plate. At high speeds, the engine suction raises these balls GASOLINE CARBURETERS 75 from their seats and air is admitted through the openings thus uncovered. Marvel Carbureter. The carbureter shown in Fig. 64 is provided with two nozzles. One nozzle N is controlled by the needle valve P. At low speeds the air from the air passage A passes into the tube surrounding the nozzle N from which it takes up the sprayed gasoline vapor. At high speeds, however, the air goes in two different directions (1) through L-, FIG. 63. Kingston Carbureter with Balls for Auxiliary Air Valves. the tube around the nozzle N, and (2) through the flat damper shaped auxiliary air valve AV which at low speeds is kept closed by a spiral spring X. There is an auxiliary or high speed gasoline nozzle AN placed close to the auxiliary air valve so that when this valve opens the air velocity will be high enough around this auxiliary gasoline nozzle to take up more gasoline. The air valve or choke damper in the air passage A is provided so that it can be closed when the engine is to be started, in order to give a rich mixture. The car- bureter has a jacket similar to the water jackets on engine 76 GASOLINE AUTOMOBILES cylinders in which hot exhaust gas from the engine exhaust pipe circulates. A damper in the pipe carrying the exhaust gas to the jacket when opened, allows some of the hot exhaust gas from the engine exhaust pipe to flow through cored pas- sages E shown in the figure. The heat from the hot gas is for making vaporization in the carbureter more rapid in cold weather. The damper regulating the flow of this hot FV- Air FlG. 64. Marvel Carbureter. exhaust gas is controlled automatically by the lever L on the throttle valve T in such a way that when the throttle valve is opened half way or more the exhaust gas damper is closed. "Plain Tube" Carbureter. Fig. 65 shows the parts of a very common type of carbureter. The gasoline from the float chamber is regulated in its flow by the high speed adjustment needle 1 from which the gasoline flows into the pool below the valve 3 or into the long "idling" tube con- trolled by the valve 2, both of which are in communication GASOLINE CARBURETERS 77 with the air bleeder valve 3 where the gasoline level is main- tained the same as in the float chamber. The air bleeder valve 3 admits a little air into the gasoline passages for the purpose of breaking up the gasoline into a mist as it dis- charges from the expanding tube Z into the mixing chamber M. By the use of this small amount of air complete vaporiza- tion in the mixing chamber is made much easier. The gaso- line pool and the passages just above it are intended to fur- nish the extra amount of gasoline needed when the throttle valve is suddenly opened. (Fig. 66.) The "idling" tube con- trolled by valve 2 is in the center of the main gasoline supply FlG. 65. Stromberg "Plain Tube ' ' Carbureter. Throttle Valve Nearly Closed. FlG. 66. Stromberg "Plain Tube" Carbureter. Throttle Valve Wide Open. passage and is intended to supply a small amount of gasoline to the engine when the throttle valve is nearly closed ; as, for example, when the automobile is standing and the engine is running or when starting the engine. (Fig. 65.) In the oper- ation of this "idling" tube some air is drawn through a restricted opening under the control of the adjustment valve 2. This air mixes with the gasoline and discharges it as a spray through the small nozzle just above this adjustment needle. When the throttle valve is more than half way open there is insufficient suction to discharge gasoline spray through the "idling" nozzle and all the gasoline spray comes from the holes opening into the expanding tube Z. 78 GASOLINE AUTOMOBILES A detail showing the operation of the air bleeder valve 3, and of the small gasoline tubes discharging into the expand- ing nozzle Z is shown in Fig. 67. Fie. 67. Stromberg Air Bleeder Valve. A somewhat simpler type of the same make of carbureter is shown in Fig. 68 which has two nozzles for the gasoline Air FIG. 68. Stromberg Double Nozzle Carbureter. supply. At low speed the nozzle N discharges gasoline vapor into the expanding tube. At high speed the additional air supply needed comes through the auxiliary air valve AV GASOLINE CARBURETERS 79 which regulates also automatically a gasoline supply through the auxiliary nozzle AN. This gasoline discharges in the direction of the air flowing through the auxiliary air valve AV. By this method there is an extra supply of gasoline for high speed and for heavy pulling. This carbureter has an air valve or choke damper V in the air inlet for starting the engine in cold weather. There is a connection from this choke air valve to the auxiliary air valve AV, so that closing the choke valve closes tightly the auxiliary valve. The choke air valve is controlled either from the dash or from the steering column, depending on the method of in- stallation. Stewart Carbureter. The unique feature of the car- bureter shown in Fig. 69 is that it has a relatively heavy air valve W surrounding the spray nozzle N. This cap- like air valve W rests on its seat S and shuts off any air flowing from the air chamber marked "Air." As soon as the engine starts, vacuum is formed in the mixing chamber M and the valve W is lifted from its seat in proportion to the amount of the engine suction. At the same time because of this suction, the gasoline will be sucked up through the spray nozzle N. The lower end of the air valve W extends down and is surrounded by the gasoline in the extension of the float chamber, and the extreme lower end has a needle valve (some- times called a metering pin) P for a central guide. The needle valve extends upward into the central tube in the valve W, so that as the suction varies, the position of the air valve W will move up and down to regulate the flow of air by the distance it rises above the seat 8, and, the amount of gasoline by the distance the central tube in the valve is above the metering pin P. This device is intended to regulate the volume of air and the amount of gasoline going into the mixing chamber so as to increase or decrease the amount of each in the same proportion. Most of the air going through the carbureter passes through the space be- tween the air valve and its seat 8, but the small amount of air necessary for starting the engine is drawn through the 80 GASOLINE AUTOMOBILES very small air passages in a circuitous path to discharge around the spray nozzle N. To prevent vibration or chatter- ing of the air valve W,- its lower end fits loosely in a dash- pot D. There is a restricted flow of gasoline from the ex- tended float chamber through the ball valves B into the dash- FIG. 69. Stewart Carbureter. pot so that the rapid movement of the air valve W is pre- vented. The only adjustment of this carbureter is by raising or lowering the needle valve P and thereby increas- ing or decreasing the amount of gasoline going into the mixing chamber M. HoUey Carbureter. Fig. 70 shows a type of carbureter GASOLINE CARBURETERS 81 which differs in many details from those already described. The main air supply enters through the passage A at the side of the carbureter and after passing around the bottom of the large central tube enters the mixing chamber M. The gasoline enters from the pipe G and when the float valve FV is opened, passes into the float chamber C. The float valve is controlled by the circular cork float F supported on a horizontal pin /. The flow of gasoline is through the hole Y into the space around the needle valve P and then upward into the cup J through the spray nozzle N. When the engine G FIG. 70. Holley Carbureter. is not running, the float regulates the level in the pool cup J so that the gasoline fills it sufficiently to nearly submerge the lower end of the small tube or auxiliary gasoline nozzle AN. When starting the engine the butterfly throttle valve T is nearly closed and the explosive mixture of gasoline and air is drawn through the tube AN with high velocity as there is then a very high suction, giving a mixture rich in gaso- line. The tube AN continues to supply the engine at small throttle openings, that is, at low speeds, but as the throttle valve is opened more and more with increased speed the level in the gasoline pool J gradually sinks so that at moder- 82 GASOLINE AUTOMOBILES ate and high speeds all the mixture is supplied through the main mixing tube M. A slight modification is shown in Fig. 71 which is intended for attachment to a horizontal intake pipe of an engine. In this case the auxiliary tube AN is bent so as to be horizontal and discharges close to the throttle valve T. Some carbureters of this type have an auxiliary air passage A A (Fig. 70) which is always open. It gives a very direct flow of air for starting. The Schebler Model L Carbureter as shown in Fig. 72 has a device for regulating the nozzle opening by means of the needle valve or metering pin P which is operated auto- Air FIG. 71. Holley Carbureter for Horizontal Intake Pipe. matically with the movement of the butterfly throttle valve T. The flow of gasoline through the nozzle can be adjusted in this type of carbureter for an intermediate speed in addition to the usual low and high speed adjustments as in most other types. Each of these three adjustments is independent of the others. The opening of the butterfly throttle valve T for high speed or a heavy pull raises the metering pin (needle valve) P and increases the supply of gasoline. The auxiliary air valve AV is shown at the left-hand side of the figure. A priming pin and lever are shown just above the cork float F. By pressing on this pin the level of gasoline in the float chamber and in the nozzle is raised to provide a very rich GASOLINE CARBURETERS 83 mixture for starting. This type of carbureter must be pro- vided with a warm air connection as shown in Fig. 73. The air taken into the main air opening goes through this special Air FIG. 72. Schebler Model L Carbureter. fitting which is attached to the engine exhaust pipe and has suitable slots around the pipe for the admission of air. A dash-control (Fig. 74) is also shown for the auxiliary FiG. 73. Hot Air or "Stove" Connection. air valve spring, which is adjusted by a lever arranged to be moved by a handle on the instrument board of the auto- mobile. When the handle is in the position marked "gas" 84 GASOLINE AUTOMOBILES the setting is for a rich mixture. As the engine warms up after running a few minutes, the handle should gradually be moved back toward the "air" position to obtain the best running conditions. As this carbureter is somewhat more complicated than most others; a brief explanation of its adjustment will be given. It is poor policy, however, to experiment with cur- bureter adjustments either for practice in making adjust- ments, or for experimentation. An experienced automobile mechanic who is accustomed to one type of engine or car- bureter, can usually get much better results from carbureter adjustment by "sound" than a person inexperienced with practical automobile work can expect to get no matter how TO CARBURETER FIG. 74. Dash Control Lever. much theoretical education he may have. The method of adjustment of this carbureter is to regulate, first the spring on the auxiliary air valve so that it rests lightly but firmly on its seat. The needle valve P should be closed by turning the adjust- ment screw toward the right. It is then turned to the left about four or five turns and the carbureter primed or flushed by pulling up the priming lever and holding it up for about five seconds. Now open the throttle valve about one-third and start the engine. After closing the throttle slightly, the throt- tle lever screw and the needle valve adjusting screw are regulated so that the engine runs with even explosions at the desired speed. This is the low-speed adjustment. After getting a good adjustment with the engine running, the needle valve P should not be changed again. The inter- GASOLINE CARBURETERS 85 mediate and high-speed adjustments are made on the dials. The pointer on the right or intermediate speed dial should be set halfway between figures 1 and 3. The spark ignition should be set for moderate speed and the throttle opened so that the roller on the track running below the dials is in line with the first dial. If the engine back-fires, with the throttle in this position, the indicator or pointer should be turned a little more toward figure 3 ; if the mixture is too rich, the indicator should be turned back, or toward figure 1, until the engine is running properly with the throttle in intermediate speed position. For high-speed adjustment the throttle is opened wide and the adjustment made for high speed on the second dial in the same manner as the adjust- ment for intermediate speed on the first dial. Rayfield Model G Carbureter. A somewhat complicated carbureter illustrated in Fig. 75 has two gasoline nozzles and two air inlets, both of which are used for the admission of auxiliary air. There are no air valve adjustments but two gasoline adjustments, one for low speed and the other for high speed. For low-speed operation air is taken into the mixing chamber through the main or "constant" opening A. In the mixing chamber M this air mixes with the gaso- line vapor which the engine suction draws from the nozzle below the valve Pj. When the speed increases, the engine suc- tion opens the upper automatic (auxiliary) air valve AV and increases the amount of air. In the automatic movement of this air valve it presses down on the metering pin P 2 just below so that at the same time additional "gasoline comes through this auxiliary nozzle. A second auxiliary air valve at the bottom of the carbureter opens and closes with the main or upper automatic air valve AV as they are con- nected together by levers and links. The effect of the lower auxiliary air valve is to give a still greater volume of air at high engine speeds. The upper automatic air valve is controlled by the tension of a spiral spring shown directly below it in the figure. A small vertical rod connects this valve to a dashpot filled with gasoline on its lower side. This 86 GASOLINE AUTOMOBILES dashpot is provided for the purpose of preventing vibration of the valve and has also the effect of forcing out the gasoline from the auxiliary valve P 2 when the throttle valve is sud- denly opened, and a quick response of the engine is desired in the amount of power to be delivered. This carbureter is heated by the circulation through its jacket of ~kot water which is taken from a pipe attached to the upper part of the water jacket on the engine where the temperature of the engine cooling water is highest. This water is discharged from the carbureter jacket through a pipe AV -M/r FIG. 75. Eayfield Carbureter. connected usually to the suction side of the cooling water pump. These pipe connections provide a constant circulation of hot water through the jackets of the carbureter. The main or ''constant" air opening A is connected by a piece of flexible tubing to the usual attachment (Fig. 73) on the ex- haust pipe for heating the air. A dash-control wire is con- nected to the valve P l in such a way that its movement opens or closes the main gasoline nozzle. The vertical tube at the left of the mixing chamber M discharges a rich mixture of gasoline vapor and air above the throttle valve for idling. GASOLINE CARBURETERS 87 Compound Nozzle Carbureter. In another type of car- bureter the gasoline is supplied from a Compound nozzle which has actually two nozzles, one inside the other as illustrated in Figs. 76 and 77. It will be noted that when the throttle valve is closed (Fig. 76) the outside nozzle is supplied by a gravity flow by the constant level maintained in the auxiliary fuel well W. This compound nozzle is satis- factory for giving a uniform explosive mixture of gasoline and air for varying suction in the engine cylinders. Other carbureters have been made to use practically the same prin- ciple by combining the two nozzles of this compound type in a single one, and have provision for suitable air bleeds FIG. 76. Compound Nozzle (Throttle Valve Closed). FIG. 77. Compound Nozzle (Throttle Valve Open). (Fig. 67) so that the amount of gasoline will be more and more weakened by excess air as the suction increases. Zenith Carbureter. The carbureter shown in Fig. 78 differs from most of the carbureters which ^have been ex- plained in that it has no auxiliary air valve. It has a com- pound nozzle (Figs. 77 and 78) consisting of an inner nozzle for which the gasoline is supplied direct from the float chamber C, and an outer nozzle for the purpose of reducing the strength of the mixture at high speeds. This provision as to the gasoline supply is possible because the amount of gasoline passing through the outside or compensating nozzle is constant at all speeds. When the speed of the engine increases the amount of air drawn in through the air passage A increases 88 GASOLINE AUTOMOBILES in proportion and makes the compensating mixture relatively weak. This device has, therefore, the same effect as the auxiliary air valve on other types. The Zenith carbureter has special provision for starting and idling without a load. There is a specially constructed gasoline tube extending from below the compound nozzle to near the top of the left-hand carbureter wall. The outlet of this side' tube is in a so-called priming hole SN at the edge of the throttle valve T, where obviously the suction is greatest FIG. 78. Zenith Carbureter. when the valve is nearly closed. The gasoline is drawn up by the suction of the engine to discharge from the priming hole where it mixes with a small amount of air passing through the throttle valve so as to give a rich explosive mixture for starting the engine. The richness of this starting mixture can be regulated by adjusting the regulating screw shown in the figure near the top of the side passage. This regulating screw admits a small amount of air to the priming hole. At high speeds when the throttle valve is wide open, the priming hole ceases to discharge, and the compound nozzle is sufficient to adjust the mixture for any intermediate engine speed. GASOLINE CARBURETERS 89 Tillotson Carbureter. The carbureter shown in Fig. 79 has a unique method of regulating the air supply. The only regulation is by means of the gasoline needle valve P. The air comes through the air opening at the top and is drawn through the V-shaped passage formed by steel reeds R. At low engine speeds the reeds bear on both sides against the main gasoline nozzle N (Fig. 80) ; but as the engine speed and the suction increase, the reeds are spread apart and make a larger opening for the passage of air. A small air supply to assist . Tillotson Carbureter. FIG. 80. Eeeds of Tillotson Carbureter. in vaporizing the gasoline enters through the air holes A A at the bottom of the needle valve P. An auxiliary gasoline nozzle AN extends upward from the float chamber and at high engine speed, the engine suction draws an additional gasoline supply from this nozzle. Johnson Carbureter. Another type of carbureter which is somewhat similar to the Stewart type described on page 79 is shown in Fig. 81. The similarity is in the application of a weighted air valve V. The outside of the valve V is a thin metal tube with notches in its lower edge which allow a smell quantity of air to pass into the mixing tube M when the 90 GASOLINE AUTOMOBILES engine is idling. Gasoline enters the float chamber through the supply pipe and discharges as a spray through the nozzle N. The gasoline discharge can be controlled by the move- ment of the needle valve P. When the air valve V is in its lowest position there will be very little flow of gasoline vapor. As soon as the engine suction increases the valve V will be lifted and there will be a flow -of air around the nozzle and a discharge of gasoline vapor from the nozzle in proportion to the amount of suction. The air enters the carbureter from the side through the passages marked A and goes downward 6aso!ine FIG. 81. Johnson Carbureter. to the lower chamber surrounding the nozzle N through a series of holes not shown in the figure. As the throttle valve T is opened more and more, the cylindrical valve V is raised and permits the entrance of additional air around the gaso- line spray nozzle N. The slots at the base of the cylindrical frame are intended to supply only enough air for a rich mix- ture when starting the engine. The ring-shaped opening and the holes connecting the annular space around the nozzle N with the space marked A, supply enough air for all oper- ating conditions. The only adjustment of the carbureter is by means of the needle valve P. The weighted valve V has radial blades or ribs attached GASOLINE CARBURETERS 91 at one end of its central shaft and at the other to the cylin- drical frame of the valve. The explosive mixture discharging against the blades of valve V is given a rotary motion by projections (not shown in the figure) on the expanding tube (Venturi) surrounding the lower end of the valve V. This rotary motion of the mixture, gives also a rotary motion to the valve. This mixture and the additional air entering through the ring-shaped opening are mixed by this motion, with the result that an unusually good mixture is delivered to the engine. It is difficult to test the rotary operation of a valve of this kind so as to know whether it is actually operating as intended. Generally, the operation of such de- vices is good when new; but usually, after a little time, they fail to operate. Schebler Carbureter Model A. Fig. 82 shows a some- what complicated carbureter of the plain tube type. The air enters through the main air passage A and passes upward through a slightly expanding or Venturi tube around a com- pound spray nozzle 12. The gasoline supply enters at G through the float valve FV. From the float chamber there are two paths for the gasoline to discharge. One path is around the "idling" needle valve 9 and through the pas- sage 7. The other path is around the main gasoline needle valve 10. When starting the engine, especially in cold weather, if the choke valve V is closed the air supply will be very much restricted and there will be a strong suction to draw gasoline through the irregular passage 7 to discharge through the auxiliary gasoline nozzle AN, just above the partly closed posi- tion of the throttle valve T. With the throttle valve in this position, some gasoline will also be drawn from three holes marked 13 and the "lip" marked 6. This gives a rich mix- ture which makes starting easy. When the engine is running idle and the throttle valve T is nearly closed there will be only a small amount of air passing through the expanding tube into the mixing chamber M and its velocity will not be sufficient to draw gasoline from the holes 13 and the "lip" 6. But there will be a 92 GASOLINE AUTOMOBILES considerable suction in the passage 7 and some of the air entering through the main air passage will pass under the edge of the expanding tube and through the passage 11 from which it will discharge to mix with the gasoline from the passage 7. The mixture of gasoline and air thus obtained will be discharged from the auxiliary nozzle AN just above the throttle valve T. When the throttle valve is opened more and more the engine suction will draw increasing amounts of air through the expanding tube and will draw gasoline vapor through the holes 13 in the nozzle 12. This 1. 2, 34 5 6 78J FIG. 82. Schebler Model A Carbureter. incoming air will strike the projecting "lip" 6 on the nozzle and some of it will enter the hole on its lower side. The pressure of this air will force down the gasoline in the nozzle 12 so that the level in the passage connected to the opening 6 will be lowered sufficiently to uncover holes between this passage and the passage 4. When these holes are uncovered the air will pass through them and mix with gasoline in the passage 4. Because of this combined flow of gasoline and air through the passages of the nozzle there will be a discharge of explosive mixture of gasoline and air from the holes 13 into the mixing chamber M. At the same time there will be some discharge from the idling jet or auxiliary gasoline GASOLINE CARBURETERS 93 nozzle AN until the throttle valve is about half way opened ; but when wide open the flow through AN ceases. When the throttle valve T is wide open, as it would be for high engine speed, there is unrestricted flow of air through the expanding tube and also a maximum amount of suction at the holes 13 in the nozzle. This large flow of air exerts increased pressure on the "lip" 6 causing the air to enter still farther into the passage connected to the opening under the "lip" and lowers the gasoline level by the same amount that the air enters. This permits more air to be drawn through the connecting holes between this passage and the passage 4. Thus the proportion of air and gasoline delivered to the mixing cham- ber M is kept constant because of the varying amount of gaso- line discharged from the holes 13. After starting and warming up the engine, it is neces- sary to close the choke air valve V until the parts of the engine are sufficiently heated to give good air temperature. An engine equipped with this carbureter will start readily with the choke air valve closed one-half to three-quarters of the way. When the weather is very cold it is sometimes necessary to close this valve entirely, but this should be done only for an instant as it cuts off practically all the air and delivers a mixture much too rich in gasoline for operating the engine. Cadillac Carbureter. Several novel features are found on the Cadillac carbureter, Fig. 83. The gasoline supply is through a nozzle N placed at the throat of an expanding or so-called Venturi tube Z. The main or primary air supply is taken in through an opening on the side of the carbureter as shown. The auxiliary air valve AV is a shutter type which has a counter weight. This valve is controlled by a coil spring X. A throttle pump shown in the figure is regulated by the movement of the throttle valve T. Its purpose is to force gasoline through the spray nozzle N when the throttle is opened suddenly and the engine speed is to be increased quickly. When the throttle is opened slowly, the throttle 94 GASOLINE AUTOMOBILES pump has little or no effect upon the flow of the gasoline through the spray nozzle. Packard Carbureter. This carbureter as shown at the left-hand side of Fig. 85, page 99, is of the usual auxiliary air valve type. The main air supply at the left of the *arbu- reter furnishes all the air at low speeds. This air current picks up the gasoline from the stand pipe nozzle N. "When the engine speed and the suction are increased, the auxiliary air valve opens and supplies the additional air needed. The opening and closing of this valve are regulated by the ten- CaM.BffSi'n, DrainPfpe] FIG. 83. Cadillac Carbureter. sion on its two springs, one inside the other. This tension is adjusted by two cams under the springs. Connections to these cams are made to the control board on the dash so that the adjustment can be made from the driver's seat. This is the only adjustment to be made. It will be noticed that the carbureters used on the Packard and Cadillac auto- mobiles are relatively simple in the arrangements for adjust- ment. Intake Manifolds. The best practice is to place the car- bureter close to the engine cylinders so that the heat from them will assist in securing good vaporization of the gasoline. GASOLINE CARBURETERS 95 There is always a tendency for the gasoline vapor from the carbureter to condense in the branched pipe called the intake manifold through which it goes to the engine cylinders. Automobile designers have, therefore, carefully studied the effect of shape and location of this manifold on the condition of the explosive mixture. A short straight manifold has obvious advantages over a longer one with curved parts be- cause it gives less opportunity for the gasoline in the explo- sive mixture to condense and accumulate in drops on the walls. It is also important to have the distance approximately the same from the carbureter to each of the engine cylinders as there will then be about the same amount of explosive mix- ture going to each cylinder. In some engines which have block cylinders the manifold is made as a part of the casting including the cylinders. The intake manifold is then merely a hollow passage in the side of the cylinder block. This method has the advantage of providing a very short intake manifold and because of its being a part of the cylinder block is in an excellent position to receive heat from the engine cylinders. When this method is used the carbureter can be attached directly to the cylinder block. Another method of applying heat for the improvement of vaporization in the intake manifold is to make the mani- fold with a sort of jacket surrounding it either for its whole length or for only a part. Connecting pipes are provided on this jacket to provide for the circulation of some of the ex- haust gases from the engine exhaust pipe through it. When such an exhaust gas jacket is placed around only a small part of the intake manifold, the jacket is called a ''hot spot," meaning localized heating of the explosive mixture. Recently there has been considerable discussion as to the best location of these exhaust jackets or "hot spots." Obviously, the prin- cipal object of a device of this kind is to prevent the conden- sation of gasoline and also to re-evaporate accumulated drops. Such re-evap*oration is likely to be greatest where there is a change of direction of the flow of the explosive mixture, as, for example, where the pipe from the carbureter enters the 96 GASOLINE AUTOMOBILES manifold and the stream divides to flow to the branches. Fig. 84 shows one method of applying an exhaust jacket where the carbureter pipe enters the manifold. In some other designs, the exhaust jacket is made large enough to surround the pipe from the carbureter and also the manifold itself for a short distance from the place where it branches. It is claimed, however, that practically all the condensation, at least of that part which accumulates in drops, is on the wall of the manifold directly opposite the opening of the pipe from the carbureter into the intake manifold. It is for this reason that it is claimed the device shown in Fig. 84 is more Exhaust Manifofcl ThroWe FIG. 84. Hot-spot Manifold. effective in general service than devices covering a greater portion of the manifold with an exhaust jacket. For very good reasons, the best method of preventing gasoline accu- mulation in drops in the intake manifold is by heating it on its bottom side by the exhaust pipe placed closely ~below the intake manifold. There is, of course, always the disadvantage that if there is too much heated surface without regula- tion, the temperature of the explosive mixture may be- come much too high in warm weather for efficient engine operation. Hot-air Attachment. Except in very hot weather the operation of a carbureter is improved by supplying heated GASOLINE CARBURETERS 97 air as it improves vaporization of gasoline. A great many carbureters are provided with an attachment for heat- ing the air which goes into the air intake of the car- bureter. This is usually done by taking it through a pipe attachment which takes to the carbureter, air which has been heated by contact with the hot exhaust pipe of the engine. Fig. 73 shows an attachment of this kind. Hot- water Attachment. For the same reason that hot- air attachments are used on carbureters, some carbureters are provided with a water jacket as shown on the Rayfield carbureter in Fig. 75. Hot water from the supply used to cool the cylinders of the engine is passed through this jacket which warms the air before and as it passes the carbureter nozzle. Disadvantages of Hot-air and Hot-water Carbureter Attachments. In order to avoid the difficulties arising from the presence of unburned gasoline in the cylinder, provision must be made for supplying it to the engine cylinders in 'a dry or completely vaporized condition. The simplest method of obtaining complete vaporization is by making provision for heating the carbureter either by using the hot water from the engine water jacket or hot gases from the engine exhaust pipe. Neither of these methods is, however, alto- gether satisfactory because there is difficulty in regulating the amount of heat to the requirements. When the engine is operating with a wide open throttle valve for the condi- tions of either high speed or heavy load, either of these methods will give a great deal too much heat to the car- bureter if the amount is adjusted to give the right amount for light load operation. There are two objectionable fea- tures of this kind of carbureter heating when the throttle valve is more than half way open: (1) the added heat increases the volume of the explosive mixture and conse- quently reduces the weight of explosive mixture used to such an extent that the speed of the engine is appreciably reduced; (2) the heating the carbureter raises the tempera- 98 GASOLINE AUTOMOBILES ture of the explosive mixture so high that with the further addition of heat during the compression stroke in the en- gine, and during the explosion that follows, the lighter petroleum fuels like gasoline will be broken up or "dis- sociated" into gases having hydrogen as the important con- stituent. This hydrogen when undergoing rapid combustion because of its high heat content develops a great amount of energy which is suddenly applied to the top of the engine piston and produces in the engine what we call "knocking." There is another reason why the adding of heat to the carbureter is objectionable when the throttle valve is more than half-way open, and more especially when wide open. Wide open throttle valve permits the maximum amount of explosive mixture to enter the engine cylinders while a partially opened throttle reduces the amount of mixture going to the cylinder. It is obvious, therefore, that with wide open throttle with its large amount of explosion mix- ture, the compression in the cylinders will be carried to a higher pressure, and consequently the temperature will be higher than for a partly opened throttle valve. The ideal arrangement is, obviously, to supply only enough heat to a carbureter when the throttle valve is partly opened to pro- duce a thoroughly vaporized explosive mixture with arrange- ments for reducing the amount of heat supplied to the car- bureter when the throttle valve is wide open. Packard Fuelizer. Fig. 85 shows in considerable detail the type of apparatus called the Packard fuelizer which has been developed to produce complete vaporization of the explosive mixture before it gets to the engine cylinder and has a device for cutting off the supply of heat in proportion to the amount of opening of the engine throttle valve. The principle of this device is to take advantage of the different pressures on the two sides of the butterfly throttle valve in the carbureter and cause a small amount of explosive mixture to go through an auxiliary passage which is parallel to the main intake passage. The amount of mixture going through the auxiliary passage is set on fire by contact with GASOLINE CARBURETERS 99 the sparks from a spark plug with the result that intense heat is generated in this auxiliary passage for starting and light load engine conditions. This apparatus will, therefore, tend to improve engine efficiency when using heavy gasoline under ''low throttle" and light load when an intense heat is generated in a part of the explosive mixture. On the other hand with wide open throttle conditions, but little of the explosive mixture passes through this auxiliary passage and SparkPlug To Engine Irrhke Gasoline FIG. 85. Packard Carbureter and Fuelizer. almost a negligible amount of heat is put into the engine cyl- inder. The auxiliary passage carrying explosive mixture from the mixing chamber M to the spark plug is shown at the right- hand side of the apparatus and is marked P. The actual construction is more complicated than shown in the figure but enough details are shown to indicate the method of opera- tion. It should be clear that when the throttle valve is in a nearly closed position as indicated in the figure there will be a very small flow of explosive mixture past it, and the engine suction will be effected mostly by the flow through 100 GASOLINE AUTOMOBILES the auxiliary passage P supplying mixture for combustion at the spark plug. Opposite the spark plug is the observation window of heat-resisting glass, which permits the action of the burner to be observed at all times. Instead of actually taking the explosive mixture into the auxiliary passage P from the mixing chamber immediately below the throttle valve the combustible mixture supplied to the auxiliary passage is made by taking gasoline directly from the carbureter through the small capillary tube Q and mixing it with air taken through the pipe Y from the main air passage A. In actual operation, when the engine is idling, combustion takes place in the burner silently and continuously and a bluish-green flame completely fills the combustion chamber. This flame diminishes in intensity as the throttle is opened, with the general result that for ordinary driving conditions up to about twenty-five miles per hour, a mixture temperature of 150 to 180 degrees Fahrenheit is maintained, giving per- fect distribution, excellent acceleration, absence of spark-plug fouling and elimination of dilution of the lubricant in the crankcase. At higher speeds and wider throttle opening the influence of the fuelizer gradually decreases until at wide-open throttle it is practically out of action, which is exactly the condition desired. This combination has permitted the run- ning of a twelve-cylinder engine on kerosene at moderate driving speeds with practically the same results as when using gasoline, but when using kerosene there are critical tem- peratures below which we cannot go without considerable knocking. Suggestions for Successful Carbureter Operation. It is obviously impossible to give detailed instructions which will answer for all types of carbureters, but there are certain fundamental principles which apply to the adjustment of all types. There are numerous troubles coming from an engine itself or its auxiliaries which must be remedied before any adjustment on the carbureter can be satisfactorily made. It must be ascertained (1) whether a good spark occurs in GASOLINE CARBURETERS 101 the cylinder at the proper time; (2) whether each cylinder has the proper compression; (3) whether the intake mani- fold and its connections to the carbureter are free from air leaks; (4) whether gasoline is being furnished to the carbureter in sufficient amounts; (5) whether the carbureter is free from water and dirt in the bottom of the float chamber. The engine must be warmed to normal running conditions before any adjustments are attempted. The engine should be run idle with the spark retarded and the throttle open only enough for moderate engine speed. The low-speed adjust- ment, usually on the gasoline, is made so that the engine explosions are regular, after which the spark ignition should be set for high speed and the engine speedd up. Th high- speed adjustment, usually on the auxiliary air valve, is then made. When this adjustment is correctly made, the engine should be first operated slowly and then the throttle valve should be opened quickly to test the engine for uniformity of explosions with rapid acceleration. If upon opening the throttle, the engine back-fires or "spits back," the mixture is weak and the gasoline adjustment should be made to provide more fuel. If the engine is to be run at practically constant speed there is little need of quick acceleration ; the most economical adjustment will be one which back-fires occa- sionally on rapid acceleration. "Choking" in the car- bureter with rapid acceleration indicates too rich a mixture. A rich mixture is indicated by the (1) overheating of the cylinders, (2) waste of fuel, (3) "choking" of the engine, (4) misfiring at low speeds, (5) heavy black exhaust smoke with a very disagreeable odor. A weak mixture manifests itself by (1) back-firing through the carbureter and (2) by loss of power. Back- firing or "popping back" through the carbureter is caused when a fresh charge of explosive mixture enters the cylinder and comes into contact with a slow-burning charge left in the cylinder from the preceding power stroke. Under these 102 GASOLINE AUTOMOBILES conditions, since the intake valve is open, the force of the explosion comes back through the carbureter. A weak mix- ture bums slowly and is likely to be incompletely burned when the fresh charge of explosive mixture enters the cylinder on the next suction stroke. Back-firing may be caused also by leaky intake valves in the engine cylinder. Color of Exhaust. A proper mixture will give little or no smoke at the exhaust. Blue smoke is caused by the burning of excess lubricating oil and has no relation to the quality of the mixture. Black smoke is due to the car- bureter being set for too rich a mixture. White exhaust in cold weather is due to a small amount of steam in the exhaust gases and is not objectionable. It is not "smoke." An easy test to see whether the carbureter is working right is to run several blocks with the throttle practically closed, then, when the road is clear, press sharply upon the accelerator pedal, which opens the throttle wide and should make the engine speed up and the automobile "jump" forward. If it is sluggish there is too rich a mixture, and if it sputters and perhaps backfires, it is too weak. When the engine is running slowly, air passes through the carbureter so slowly that the gasoline is not broken up into very fine particles, consequently it does not fully vaporize and is very easily condensed. It forms liquid gasoline in the intake pipe or cylinder. This is called "loading up" and is responsible for black smoke when the automobile is started. If the owner will make sure that he is not exhausting black smoke he need not worry about the price of gasoline, and a little judgment and care will eliminate many of the items of upkeep expense. Wherever there is a leak between the carbureter and the cylinder it lets in air and thins the mixture so that it is necessary to feed in more gasoline to get a mixture that will fire and that is wasteful, for a mixture made anywhere else than in the carbureter is less efficient. It takes two hundred cubic feet of air to a pint of gasoline vaporized to produce good combustion, though the air supply GASOLINE CARBURETERS 103 is usually much more than this to insure carrying off the unburned nitrogen from the air. For starting and speeding up, more gasoline is admitted to the vaporizing chamber as the rich mixture ignites more quickly, but for running, a leaner mixture produces better results. The adjustment of the carbureter should not be changed unless one is certain that it is wrong. If the automobile has been running with the carbureter working properly and no one has changed the adjustment, it may safely be assumed, in most cases, that the carbureter adjustment is correct. On a dry, warm day the gasoline vaporizes easily and the maximum charge is readily exploded in the cylinder, giving maximum power. On a wet cold day one must slightly decrease the supply of gasoline, or the cylinders will "choke" and the engine will knock. When the heavier grades of gasoline as now sold are used in an automobile engine under normal operating conditions, when about ninety per cent of the time the engine is running under a light load, the temperature in the engine cylinders is not high enough for complete vaporization so that some of the unburned part is being deposited con- tinuously on the spark plugs and on the inside of the cylinder in the form of soot. Soot deposited on the spark plugs has the effect of short circuiting the parts of the. spark plugs which should be electrically insulated from each other and makes them useless for ignition. These soot deposits are called "carbon." Some of this unburned portion of the fuel will pass the piston in the liquid condition into the engine crankcase where it mixes with the lubricating oil. It is not unusual to hear of automobile engines which after traveling a few hundred miles will have in their crankcases a mixture of gasoline and lubricating oil which gives extremely poor lubrication, 'so that continued running without its removal will result in burned out bearings, scored cylinders, and other automobile difficulties arising from improper lubrica- tion. CHAPTER V AUTOMOBILE IGNITION When the explosive mixture of gasoline vapor and air enters the cylinder of the engine, it must be ignited ; and, in automobile engines, the usual method of ignition is by means of an electric spark. Most of the devices for making and timing the electric spark are complicated. It is neces- sary, therefore, to know the basic principles because most of the serious troubles with a modern automobile, excluding the tires, are with the electrical equipment. If the "spark" does not come right or does not come at all, there is real trouble. Electricity. Very little is known regarding the "sub- stance" of electricity. In this respect it is almost as much of a mystery today as when Benjamin Franklin took a spark from the clouds with his silk kite and string. On the other hand, the laws of the behavior of electricity under almost any conditions are well established. Electrical Pressure or Voltage. Like air, or water, elec- tricity flows from a position of high pressure to one of low pressure. There must be pressure for electricity to be car- ried on wires the same as it is necessary to have pressure to force water through pipes. Electrical pressure is measured in units called volts. Thus, if at one point the electrical pressure is ten volts and at another point it is six volts, the pressure difference between the two points is four volts. Now, if a metal wire is stretched between the two points an electric current will flow from the point of high to the point of low voltage. Electricity flows through some metals, especially copper, with very little resistance; while substances like rub- ber, porcelain, glass, fiber and any kind of gas (including 104 AUTOMOBILE IGNITION 105 air) offer very high resistance and are called electric insulators. Most metals offer little resistance to the flow of electricity. Cotton, silk, or rubber coverings on wires are to insulate them from each other and from other electric conducting materials. Insulating materials are used as cover- ings for electric wires which are close together to prevent the current from flowing from one wire to the other, or to prevent short-circuiting the wires. The insulation on wires should not rub on other wires or on metal parts of an auto- mobile, as continued rubbing may wear through the insulation and cause short-circuiting. The quantity of electricity passing over a wire is called the current, and the unit of measurement of this current is an ampere. In the flow of water the quantity is expressed in gallons per hour, while in the flow of electricity the quantity is expressed in amperes per hour or, for short, ampere-hours. Flowing electric current must always have a circuit either through wires or through metal parts of an engine. If the circuit is interrupted or "broken" by a broken wire or by an open switch, the current cannot go through. Electric Batteries for automobile ignition are of two distinct kinds: (1) dry cells or batteries; and (2) storage, batteries. Dry Cells are sometimes used, especially on small auto- mobiles, as a source of electric current for ignition. Although soon worn out in the usual ignition service, they are relatively cheap and are easily replaced. Fig. 86 shows a typical dry cell as it appears when cut open through the middle (in cross section). The outside cylindrical casing is made of zinc. Inside of this casing is fitted a piece of absorbent paper saturated with zinc chemicals and plaster of Paris. In the middle of the cell is a stick of pure carbon. The space between the absorbent paper and the carbon stick is filled with powdered carbon and manganese oxide. To prevent drying out of the saturated paper, the top of the cell is sealed air-tight with a tar compound. The electric pressure, or voltage, of a good dry cell is about 1.5 volts. 106 GASOLINE AUTOMOBILES The maximum possible current on short circuit (as a dealer tests it) is from twenty to thirty-fire amperes, depending somewhat on the size of the cell. The carbon terminal is often marked with the symbol +. The zinc casing must have on the outside a covering (side and bottom) of in- sulating material. Heavy paper is a satisfactory material, if kept dry. When a dry cell is nearly exhausted its useful service can usually be extended by making a small hole in the Zinc Terminal \ Carbon Tertnfna/ Carbon Powdered Car bo none/ 1 Manganese Pasteboard Casing FIG. 86. Dry Cell. top and pouring in a little water. If a dry cell gives out suddenly on the road, this is a convenient makeshift. When running an automobile with any kind of ignition system, it is generally a convenience to have a few good dry cells stored away for emergency service. The length of time a dry cell can be used depends largely on the kind of service. For intermittent service, for which it is intended, a dry cell will usually last several months. For diagrams showing different connections of dry cells, see Figs. 92 and 93. Storage Batteries. Storage batteries differ from dry cells in having a liquid solution. A typical storage battery AUTOMOBILE IGNITION 107 as shown in Fig. 87 consists of two sets of lead plates made like gridirons placed in a container filled with a solution of weak sulphuric acid and water. One set of plates has the spaces in the grids filled with lead peroxide (brown color). The other .set of plates has the spaces filled with ' ' sponge ' ' lead (ordinary lead color). These plates are placed in the container so that the two kinds of plates alternate and are separated from each other by perforated pieces of hard rubber or of wood treated to withstand the acid. All the lead peroxide plates are connected together at the top Hare/rubber Coyer Battery Terminals --^ Plastic Sea I ing Trecrhed 'Hare/wood Case w+h Dovetviljoiirk ^"'Gridiron Plates Supports of Hard Rubber Mud Space to Hold Sediment from P/a+es FIG. 87. Storage Cell or "Battery." by a metallic lead yoke marked the (positive) terminal. The "sponge" lead plates are similarly connected by a yoke marked the (negative) terminal. The terminals of most storage batteries are marked so that if the battery is disconnected from the wiring system of an automobile and is taken out, there will be no mistake in getting the right connections when putting it back. If it is put back the wrong way, it will be discharging instead of charging when the automobile engine is running. Charging and Discharging Storage Batteries. If the -f- terminal of the storage battery is connected to the + ter- 108 GASOLINE AUTOMOBILES minal of a source of electric current, and the terminal of the battery to the terminal of the source, the electric current passing through the plates and through the acid solution will make a chemical change in the lead peroxide and will deposit it on the "sponge" lead plate. When the charging current is stopped and the storage battery is connected up for supplying electric current, as for example, for starting an automobile engine, it is said to be discharging, and the chemical change in the battery is reversed; that is, the "sponge" lead is changed chemically and deposited again on the lead peroxide plate. All the plates connected with a set of yokes, together with their container, are called a storage cell. Technically, a group of cells is called a storage battery. The container or jar must be of some good insulating material like hard rubber or glass. Charging Test. A single storage cell when fully charged by electric current gives an electric "pressure" of about two volts. Most storage batteries consist of three cells and give, therefore, six volts. The usual method of testing for com- pleteness of electric charging is to determine the specific gravity of the acid solution in the container. "When satis- factorily charged, the specific gravity (see page 111) should be between 1.27 and 1.30, ordinarily read "1270" and "1300." The discharge of electric current from a storage cell reduces the specific gravity of the acid solution and should be stopped if the specific gravity gets as low as 1.15. If the storage cells are used for electric lights as well as for ignition, at this stage of discharge the lights will not have their usual brilliancy. Refilling Battery Solution. The acid solution should always cover at least the "gridded" part of the lead plates, and it is a good rule to inspect and refill each storage cell every two weeks. There is always some loss from the solution by evaporation and spilling if roughly handled. After refill- ing, the level of the solution in the container should be about the level of the bottom of the filling tube or filling chamber. AUTOMOBILE IGNITION 109 Use only distilled water such as can be obtained at a drug store or at an artificial ice plant. Persons of ordinary experi- ence should never add any acid for refilling. In emergencies melted artificial ice or fresh rain water caught in a glass or crockery receptacle may be safely used. Ordinarily only a few spoonfuls of water are needed for refilling. If one of the cells always requires very much more distilled water for refilling than the others, it is likely there is a leak in the container or jar of the cell, and it is best to purchase a new container. The rubber plugs of the filling tubes should be screwed carefully in place after refilling. A supply of distilled water for refilling should be kept in a large glass bottle and not in a metal bucket or can. Extreme care should be observed to keep all traces of metal out of the storage cells. Water from wells, springs, or city supplies is likely to contain traces of metal ores and other substances which will rapidly impair storage cells. All automobile storage batteries have more than one cell, so that refilling at one filling tube provides for only one cell. Each cell should be inspected regularly and refilled as necessary. Transferring the lead plates from one container to an- other is not an easy matter, as the lead peroxide plates are fragile. Such work should be done by a person experienced in battery -repairing. Instruction books furnished by the manufacturers of storage batteries should be consulted in the unusual emer- gencies of making up new acid solution in case of a broken container, or of "overcharging" a cell when it is to be stored and is not to be used for several months. Storage cells will give their most satisfactory service when in moderate, continuous use, so as to be kept well charged. Most people are too careless in the use of storage batteries to get the best service. The vibration caused by fast driving over rough roads is injurious to storage batteries. Sulphating of Battery Plates. If the lead plates of a storage cell are not kept covered with the acid solution 110 GASOLINE AUTOMOBILES by regular filling, the plates become dry, and will accumu- late a whitish material (lead sulphate). When the forma- tion of this sulphate is once started it tends to accumulate rapidly and by causing deterioration of the plates reduces the capacity of the battery. When there is any considerable sulphate accumulation, it is time to think of saving the cell by taking it to the battery "service" station for repairs. Sulphating results also if a storage cell is kept in storage when not fully charged. Freezing of the acid solution in a storage cell is prevented by keeping it fully charged as the following table shows: Amount of Charge Specific Gravity Temp, of Freezing Fully charged 1.27 to 1.29 No danger of freezing Partly discharged 1.20 15 below zero Fahren- heit Not dangerously discharged... 1.15 Fahrenheit Dangerously discharged 1.12 30 Fahrenheit (about freezing temperature of water) Testing a storage battery with a hydrometer is the only simple method to determine whether it is in good condition for service. If the lights connected to a storage battery are dim or do not light up at all, but on the other hand the hydrometer test is 1200 or over, it is likely that the trouble is with the connections rather than the battery. If pulling lightly by hand on the wires connecting the battery to the switches on the instrument board makes variable brilliancy of the lights, the trouble is obviously with the wiring or with the connections. Sometimes there is a little deposit of sul- phate on the bolts and connections where the heavy wires are attached to the battery. A film of sulphate makes a very poor electrical contact and will often interrupt the current. Whenever a storage battery is removed for recharging or for winter storage, the bolts which are used to fasten the wires to the battery terminals should be cleaned and covered with a little vaseline, when the battery is replaced in the auto- AUTOMOBILE IGNITION 111 mobile and the wires are again fastened. If a little vaseline is put on the battery connections from time to time, accu- mulation of sulphate will usually be prevented. Storage Battery Hydrometers. A convenient device for determining the specific gravity of the acid solution in storage "1.300 FIG. 88. Storage Battery Hydrometer. batteries is shown in Fig. 88. It consists of a rubber-bulb syringe with a long glass chamber in which a very small hydrometer is placed. To Use this device the air is first expelled by hand pressure on the rubber bulb, and then when the narrow stem is put into the filling tube of the cell to 112 GASOLINE AUTOMOBILES be tested, the hand pressure on the bulb is released. By this operation some of the acid solution from the cell will be drawn by suction into the glass chamber. The hydrometer inside the glass chamber will float in the solution, and the reading on its scale at the surface of the liquid denotes the specific gravity. The sample of the solution should be care- fully put back into the same cell from which it was taken. This is easily done by again putting the narrow stem of the syringe into the filling tube of the cell and pressing on the rubber bulb till all the solution is forced out. Direct and Alternating Current. There are two kinds of current obtainable for electrical services: (1) direct cur- rent, and (2) alternating current. Direct current always flows continuously in one direction through its conductor, which is commonly a wire. Every kind of electric battery generates direct current. In charging and recharging storage batteries only direct current is used. Alternating current, on the other hand, is constantly reversing its direction, flow- ing first in one direction and then in the other. The changes in direction are very rapid, running into hundreds per minute. Rectifier for Alternating Current. Before alternating current may be used in charging storage batteries it is changed to direct current by a device called a rectifier. A rectifier made by the General Electric Company for connection to an electric lamp socket is shown in Fig. 89. Such rectifiers are usually designed to give a charging current of about four amperes for the three to six cells in an automobile storage battery. A small apparatus of this kind suitable for use in a small garage can be purchased for about fifteen dollars. Charging Storage Batteries with Lighting Current. Where direct current is furnished by local light and power plants* a rectifier is unnecessary in charging storage bat- teries. The voltage of the local lighting system (usually 110 volts) is ordinarily too high for charging purposes, for if * The kind of current furnished may be learned by inquiry at the electric light plant. AUTOMOBILE IGNITION 113 a storage battery is connected to the wires which supply an electric lamp, an enormously large current will go through the battery. Making wire connections under such conditions is dangerous work for the operator; besides the heavy current may ruin the battery. The use of ordinary direct current may be made fairly safe, however, by installing a row of lamps between the charging wire and the battery. This may be done by arranging a set of eight electric lamps (either 50-watt or 16-candle power carbon lamps), and con- A!ferr?at/'r?q Current 'Line Wires Regulating Switch-"' 1 ' Mercury Bulb Lamp Socket ^ Wires FIG. 89. Mercury Rectifier for Alternating Current. necting them as shown in Fig. 90 to the terminals of a storage battery. If 25-watt tungsten lamps are used instead of 50-watt lamps, there must be sixteen lamps instead of eight in order to get the same amount of charging current about four ampejes. On the other hand, it is possible to do the charging with only eight 25-watt lamps in twice the time. For the set of lamps shown in the figure it will take from 24 to 30 hours to fully charge a battery of cells which have been run down to a specific gravity of about 1.15, or from 48 to 60 hours with eight 25-watt lamps. The 114 GASOLINE AUTOMOBILES charging need not be done at one time; part of the charge may be given one day and more another day. Direction of Charging. For charging a storage battery its + terminal must be connected to the -}- wire of the lighting circuit, and its terminal to the wire. Other- wise, if it were connected to the lighting circuit + to , and to -J-, the lighting circuit would be taking current FIG. 90. Electric Lamp Device for Charging. out of the battery instead of sending current through it to make the chemical changes in the lead plates necessary for charging. The +' and - terminals of a storage battery are usually plainly marked. The + and - terminals of battery or line wires are easily determined by a simple test the principle of which is shown in Fig. 91. First remove all insulating material from the end of each wire. Scrape the exposed wire until bright. Then dip the two ends into a AUTOMOBILE IGNITION 115 cup of water to which a tablespoonful of common salt has been added. If the ends are held about one-quarter inch apart in this salt water solution, small bubbles will rise from the wire which is the (negative) terminal. This is the wire to be attached to the terminal of the battery for charging. The other wire is -j- (positive) and should be connected to the -j- terminal of the battery. When making this test if Hyd Gaa Bubblee\ FIG. 91. Testing Electric Wires. the bubbles do not appear, the wiring may be defective and an expert should be consulted. Series and Parallel Connections. As a single storage or dry cell gives too little voltage for practical purposes in auto- mobile operation, several cells must be connected together to get the necessary voltage for ignition, lighting and start- FIG. 92. Cells in Series. ing; that is, to get from six to eight volts. The way four dry cells of one and a half volts each can be connected to get a total of six volts is shown diagrammatically in Fig. 92. By this arrangement the carbon terminal (-)-) of one cell is connected to the zinc terminal ( ) of the next. This is called connecting the cells in series. By this method the volts of the individual cells are combined, or the 116 GASOLINE AUTOMOBILES total voltage is equal to the number of cells multiplied by the volts of each cell. A dry ceU is tested for amperes, by connecting its two terminals together by an instrument (ammeter). It is safe to do this with a dry cell but should never be attempted with a storage cell because the latter can give an enormous and dangerous current when short cir- cuited. If all the carbon positive ( + ) terminals are connected together and similarly all the zinc negative ( ) terminals, as in Fig. 93, the four cells are connected in parallel. In this way the amount of current is increased and the total amperes of the set is equal to the amperes of one cell multi- X^fc/ Xu/ \W^ N*^ N **.-.. FIG. 93. Cells in Parallel. plied by the number of cells. The volts are the same as of one cell. The following brief rule is easily remembered. To increase the volts or voltage, connect the cells together in a series arrangement, as in Pig. 92. To increase the amperes or amount of current, connect the cells in parallel, as in Fig. 93. Magnetism and Electricity. In order to have a clear understanding of the electrical apparatus used in auto- mobiles, one should know the relation between magnet- ism and electricity. Magnetism suggests the attraction of pieces of iron or steel to a magnet. The field of influence, called the magnetic field, of a magnet is strongest at its ends. The close relation of electricity to magnetism is easily shown by winding a wire carrying an electric current around a bar of iron and observing the magnetization of the AUTOMOBILE IGNITION 117 iron. This is illustrated in Fig. 94 where a bar of iron M is shown with a coiled wire C around it, taking current from the battery B. The current in the coil makes a magnet of the iron bar M and produces around the magnet the magnetic field shown by the light dotted lines extending from one end of the bar to the other. The iron bar with the encircling coil is called an electro-magnet to distinguish it from a permanent magnet. If any conductor of electricity, as for example, the wire loop L in Fig. 94 is moved in any part of the magnetic field, a current of electricity will be made to flow through the conductor, in this case the wire loop. Similarly, a current FIG. 94. Magnetic Field. of electricity is produced if the wire loop is held stationary and a magnet is moved back and forth near it. Also if the electric current in the coil C, wound on the bar M is alternately "broken" and "made" (by the switch at S) a momentary electric current will flow in the wire loop L when placed as shown at one end of the bar. Now, the same electrical effect observed with the loop L, when held at the end of the magnet M, can be obtained by winding a second coil of wire 8 on top of the coil C, as shown in Fig. 95. An electric current will be made to flow through the coil 8 when the current through the coil C is alternately ' ' made ' ' or ' ' broken. ' ' The voltage of the induced current, as it is called, in the coil 8 will be the same as the 118 GASOLINE AUTOMOBILES voltage in the coil C if the number of turns or rings is the same in each coil. If, however, the numbers of turns in the coil S is ten thousand times as large as the number of turns in the coil C, then the voltage in S is ten thousand times as large as that in C. A large quantity of current (aniperes) FIG. 95. Simple Induction Coil. at the high, voltage produced by such a coil would be danger- ous, but there is only a small current in any device of this kind likely to be used on an automobile, so that a shock from it will give only an uncomfortable feeling. But do not ever connect together (short circuit) the terminals of a storage FIG. 96. Winding of Wires for Inducing High- Voltage Current. battery. Fig. 96 shows very clearly the arrangement of wires inducing a high voltage current. The necessary electric spark for practically all kinds of automobile engine ignition is obtained by means of an electric current which is made to jump across the air gap between AUTOMOBILE IGNITION 119 the points of two electric wires of an ignition device called a spark plug. In order to make electricity jump across the air gap in a spark plug a high electric pressure of at least nine thousand volts is needed. Most ignition systems using batteries have three storage cells or six dry cells. Six dry cells, for example, can give when new only about nine volts, and this low voltage, therefore, must be raised to nine thou- sand volts to force an electric spark with certainty across a one thirty-second inch air gap of a spark plug. In practically all appliances using electric current from batteries for engine ignition by means of spark plugs, the necessary increase in voltage is obtained by the use of a coil like S in Fig. 95, having a large number of turns. By this method, the required nine thousand volts can be obtained from six dry cells (nine volts) by the use of a device similar to the one shown, having one thousand times as many turns on the coil S as on the coil C* For practical reasons the low voltage coil C is made of coarse wire and the high voltage coil 8 of fine wire. Spark Plugs. A spark plug has for its essential parts two wires which are thoroughly insulated electrically from each other and are close enough together at their ends to make a short air gap. Except for minor details, the construction of all kinds of spark plugs is about the same. The one shown in Fig. 97 is an example of standard construction. The wire which brings the high voltage electric current from the fine-wire winding of the induction coil S (Fig. 95) to the spark plug, is fastened to the top T, so as to make electrical contact with a wire W, made of special heat-resisting nickel steel alloy. This wire W extends down through the central por- tion or core, which is made of porcelain or mica. Outside the central core is a steel ring or "body " B with a screw thread to which is attached a curved wire V which projects inward * The electrical principles involved are general in application ; that is, the voltage in the coil -S (called the secondary) is to the voltage in the coil C (called the primary) as the number of turns in S is to the number of turns in C. 120 GASOLINE AUTOMOBILES toward the straight central wire W. The distance between the tips of these two wires, making the air gap is usually FIG. 97. Parts of a Spark Plug. about one thirty-second of an inch (the thickness of a worn dime). The porcelain or mica core insulates electrically the two wires W and V. The electrical resistance of mica FIG. 98. Two "Point" Spark Plug. breaks down in the presence of oil so that it is not much used. The metal ring or "body" is threaded so that it can be screwed into the top of an engine cylinder. A slightly dif- AUTOMOBILE IGNITION 121 ferent spark plug with two " points" or air gaps is shown in Fig. 98. A more commonly used type is shown in Fig. 99. Afr&ap.. FIG. 99. Single "Point' Spark Plug. Battery Ignition Systems. The outline drawing shown in Fig. 95 shows the essential parts of all modern battery ignition systems. It includes a battery, an induction coil with windings of coarse and fine wire, a circuit breaker or switch with movable contact points, and a spark plug with the wires for connecting these parts as they might be applied to a single cylinder engine. Practically all automobile engines, however, have four or more cylinders, and each cylinder requires a separate device for the ignition of the explosive mixture. Figs. 100 and 101 show a diagram of a typical battery ignition system for a four cylinder engine. The top view of this diagram (Fig. 100) shows the arrangement of wires carrying the high-voltage current from the device called the distributor to the individual spark plugs. The order of numbers on the distributor is not the same as the consecutive numbers on the spark plugs. There is this differ- ence in numbering because the distributor determines the fir- ing order of the cylinders. (See page 45.) Below this draw- ing of the distributor is a side view (Fig. 101) of a complete ignition device. The top of this view shows again the dis- 122 GASOLINE AUTOMOBILES tributor with its central wire carrying the high voltage cur- rent from the induction coil, and the wires from the dis- tributor to the spark plugs. Note difference in numbers of spark plugs and distributor terminals Top View FIG. 100. High-voltage Distributor. The high-voltage current is distributed to the cylinders in proper order by the rotation of the distributing arm which w To No.4 Spark Plug Distributing Arm Induction Coil ,-Lorf Vb/ftye / Res&isfance Grounded through engine ^--'Br Breaker shaft gear wheel and frame driven at one- ha If era nk- Side View shaft speed FlG. 101. Side^View of Typical Battery Ignition System. connects by means of sliding contacts the central high-voltage wire W from the induction coil, with the ends of the wires AUTOMOBILE IGNITION 123 marked 1, 2, 4, 3 in the distributor (Fig. 100), carrying the current to the individual spark plugs. The number of wires in the distributor head with which the distributing arm makes sliding contact is the same as the number of engine cylinders. The figure shows also the movable and the stationary contacts used to "make" and "break" the battery (low voltage) current, which is carried from the induction coil to the sta- tionary contact by the heavy black wire shown in the figure. The moving contact, which is really a short lever, is held in its normal position against the stationary contact by a flat spring. At the side of the contacts there is a small cam which has as many lobes or teeth as there are engine cylinders. This cam revolves at half the engine speed and when one of its lobes is opposite the moving contact the lobe pushes out this contact so as to separate slightly the contacts or breaker points and thus interrupts the battery current through the induction coil. Every time the contacts or breaker points separate there is an induced high-voltage current in the wind- ing of fine wire of this induction coil. The rotation of the cam and the distributing arm must be so timed that this induced current will make the ignition spark in each engine cylinder at just the right instant. Ignition Safety Resistance Devices. Nearly all modern ignition systems using storage batteries have a safety resistance coil to protect the battery from excessive discharge of cur- rent in case the ignition switch (shown in Fig. 101 over the battery) is not turned off when the engine is not running and the breaker points are in the position of contact. This safety coil consists of a number of turns of iron alloy wire which has the property of increasing its resistance as it is heated by electric current ; and when it is heated to a cherry red color its resistance is increased enormously, so that then very little current can go through the coil or through the rest of the battery circuit. Some ignition systems have a device for releasing auto- matically the ignition switch on the dash board or instrument board if it is left on unusually long when the engine is not 124 GASOLINE AUTOMOBILES running. The Connecticut device for this purpose is positive in its action and instead of reducing the flow of current to a safe limit as with a safety resistance coil, it actually stops the flow. The essential part of this device (Fig. 102) is a coil of high resistance wire carrying the ignition current, which is wound around a flexible rod made of two flat strips of spring brass and nickel steel which are fastened together at the ends. When the ignition current heats this resistance coil on the rod, the metal strips expand unequally as the result of the heating and the rod bends toward and, if the temperature causes sufficient expansion, touches the tip of a wire contact and thus makes another electric circuit. The Insulated Confacf Electro Magnets FlG. 102. Connecticut Automatic Switch Release. newly formed circuit carries current to an electro-magnet which has enough pulling force to release the closed ignition switch. This device can be adjusted to operate and release the ignition switch in less than a minute. In some battery systems a safety spark gap is provided to prevent the winding of fine wire on the induction coil from burning out in case a spark plug wire becomes dis- connected, while the engine is running. If the high-voltage circuit is disconnected in this way and the high-voltage current cannot complete its circuit through the points of the spark plug, provision is made so that the current can dis- charge as a spark in the air gap between two wires, one of which is connected to the distributing arm of the dis- tributor and another is grounded to the breaker shaft. This safety gap should not be set for a shorter distance between AUTOMOBILE IGNITION 125 its points than eleven thirty-seconds of an inch. Otherwise the high-voltage current may jump across the safety spark gap rather than across the air gaps of the spark plugs in the cylinders. If this occurs, imperfect ignition will result. Automatic Spark Advance. In a battery ignition system the amount of current (amperes) that can go through the various resistances does not depend on the speed of the engine. The amount of current is practically the same whether the engine speed is high or low. At low engine speeds there are few ignitions with a relatively long time between. For each ignition at low speed, therefore, a strong, high-voltage current is generated in the coil to make a "fat" spark at the spark plugs and this system gives excep- tionally good ignition sparks for starting the engine. AVith these good conditions at low speeds, ignition in the engine cylinders is almost instantaneous. At high engine speeds, however, battery systems can have little time for generating the high-voltage current for ignition, and the sparks at the spark plugs are. weak and produce slower combustion. In order, therefore, to have ignition of the explosive mixture in the cylinders practically complete at the beginning of each explosion stroke, it is desirable, when battery systems are used, to advance the spark automatically by some mechanical means; that is, to make the spark come earlier at high than at low speeds. Otherwise the engine will waste gasoline and oil and will be easily overheated. The position of the spark as to advance or retard can be controlled by shifting by hand the spark lever on the steering wheel, but this requires the constant attention of the driver. Provision is therefore made in nearly all battery ignition systems for the automatic advance and retard of the ignition spark by the use of revolving governor weights mounted on the same shaft with the breaker points and the distributing arm. A commonly used method is to fasten the governor weights to a short hollow shaft (Fig. 103) which carries also the distributing arm and the cam for moving the breaker points. These weights move toward and 126 GASOLINE AUTOMOBILES away from the center according to the engine speed. This mechanism is arranged so that as the engine speed increases the weights tend to move outward from the center against the resistance of springs, and the cam for moving the breaker points is shifted in a backward direction with respect to the direction of motion of the breaker shaft. This has the effect Contact Points Lever High Voltage W irom Coll to Distributor m Retaining Screw for Timing Adjustment Spark Adjust L Timer Drive Shaft Oil-Le.B Bearings Spiral Gear Fl6. 103. Sectional Drawing of Distributor and Circuit Breaker Device of Delco Igniter. of advancing the spark automatically to the correct position required for the engine speed. When engine speed decreases, there is less tendency for the governor weights to move outward and the spring pulls them inward and retards the spark. The breaker and distributor mechanism together with its casing is sometimes called the igniter. A UTOMOBILE IGNITION 127 Vibrating Induction Coil. Fig. 104 shows diagrammat- ically an induction coil of the vibrating type and an engine cylinder, with its spark plug. This type of coil is used on Ford automobiles. The iron magnet in the coil is marked M. The winding of heavy wire C receives the low-voltage electric current from the battery B, which produces in the winding of fine wire 8 the high voltage current needed for the spark plug P. In the operation of this apparatus the current from one end of the battery B goes through the wire C to the left-hand end of the device. From the other end High Voltage Circuit Fie. 104. Vibrating Ignition Coil. of the battery a wire goes to the circuit breaker T, and from there through the coil to the base of vibrator V. To complete the circuit the current goes from the left-hand end of battery to the screwholder H, through the screw 0, down the flexible blade of the vibrator V, and then to the right-hand end of the low voltage winding C. At the upper end of the flexible vibrator V is a small piece of soft iron. Now in the operation of this device, when the electric current goes through the winding (7, the iron bar M is magnetized and causes this small piece of iron on the vibrator V to be attracted toward it. This magnetic attraction bends the flexible blade of the vibrator and pulls it away from the end of the screw O. As soon as the current is thus broken at the contact points 128 GASOLINE AUTOMOBILES between O and T, the iron bar M loses its magnetism and its attraction for the small piece of iron, so that the flexible vibrator V returns to a vertical position. When the vibrator is vertical, it again brings together the contact points between O and V, and electric current once more flows through the winding C to magnetize the iron bar M, which by its magnetic attraction breaks the electric circuit as before. The sequence is repeated with great rapidity when the circuit breaker T is in the position so that the cam A touches the metal contact D on the wire connected to the right-hand end of the coil. The battery current does not go to the spark plugs at all. The operating principle of this coil and its vibrator is exactly the same as that of an ordinary electric door bell. The result of rapidly opening and closing the contact points between the screw and the vibrator V is to make a high-voltage induced current in the high-voltage winding 8. To accomplish this, there must always be some kind of circuit breaker in the battery circuit. The instant the points of the circuit breaker connect, there is a momentary induced current in the winding 8, and if there is a spark plug con- nected by wires to this winding, the induced current produces a spark at the "points" of the spark plug. The instant the circuit breaker starts the battery current through the winding of coarse wire C, the magnetism due to this current goes through the winding of fine wire 8, and induces the high voltage current. The ends of the winding 8 are connected to the binding posts at the top. Either of these posts may be connected by a wire to the screw cap of the spark plug P in the engine cylinder. As applied to an automobile engine, the wire from the other post is usually attached securely to the engine casting or frame or to some part of the automobile in metallic contact with the engine cylinders. A wire attached to the metal of the engine in this way is grounded. The high- voltage electric current going through this grounded wire will pass through the metal of the engine to the body of the spark plug in the top of the engine cylinder. Every time the contact is made in the circuit breaker between the cam A AUTOMOBILE IGNITION 129 and the metal contact D, a spark crosses between the points of the spark plug. Timers. A timer is a mechanically operated circuit breaker or switch intended to be used in the low-voltage circuit of an induction spark coil. For example, in Fig. 105, the timer T is connected in the circuit of the low voltage winding C. The timer shown in this figure is for an engine with four cylinders, so that there is a coil and its spark plug connected by a wire to each of the timer terminals. Each of these terminals is in metallic contact with one FlG. 105. Vibrating Ignition Coil and Timor (with Condenser). of the metal contact blocks Z), set in the inside surface of the rim. The battery B has one terminal connected by a wire to the engine casting or frame, and through its metal and the wires shown the electric current goes to the shaft carrying the roller R of the timer, which, by its rotation, makes electric contacts with the blocks D. Briefly, the timer is a device. for alternately making and breaking the low-voltage current, thus distributing the induced high-voltage current made by the vibrator action to each of the spark plugs in the engine cylinders at the right time. Hand-operated Spark Advance. Attached to the rim of the timer is an arm A for turning the rim back and forth 130 GASOLINE AUTOMOBILES on its shaft. If the rim of the tinier is turned in the direc- tion its central shaft is moving, the spark will occur later in the stroke of each of the engine cylinders, while if moved in the opposite direction the spark will occur earlier. In the former case the spark is retarded and in the latter it is advanced. On practically all automobiles this arm A on the rim is connected by a rod to a lever on the steering wheel, so that advancing or retarding the spark is under the control of the person operating the automobile. Distributors or timers for six-, eight-, or twelve-cylinder engines are similar to those explained except that they have six, eight, or twelve terminals in the rim instead of four. Condensers. In the operation of the vibrator V of a vibrating induction coil (Fig. 105), there is a tendency to draw out a long " f at " spark at the contact points betwene and V every time the current is stopped. This drawing out of the spark, if not prevented, would have the effect of wasting much current, weakening the spark at the spark plug points, and burning off the contact points of the vibrator. To reduce these ill effects a condenser shown at the bottom of the figure is provided as part of a complete induction or spark coil. It is connected by small wires "across" the air gap made at the contact points as shown. In other words, one terminal of the condenser is connected to the low-voltage wiring on one side of the contact points, and the other terminal to the other side. The condenser in its action is somewhat like a shock absorber on the body of an automobile. Condenser Construction. A condenser consists of a number of sheets of tinfoil separated from each other by sheets of oiled paper. Every alternate tinfoil sheet is con- nected to the bottom of the screw-holder H (Fig. 105), the ends of the other tinfoil sheets are connected to the bottom of the vibrator V. If a condenser is attached to an induction coil of any kind as described and the battery current going to the coil is stopped, the battery current, instead of following the vibrator points and making a long spark, spreads over the sheets of tinfoil and produces a charge of electricity which AUTOMOBILE IGNITION 131 is "stored "'to be given back to the circuit when these contact points again come together. By this quick and clean break- ing of the low-voltage current, an induced current of higher voltage is obtained than would otherwise be the case. A condenser increases the size of the spark about twenty-five times. Condensers are often made by winding together two long strips of tinfoil separated by paraffine paper. The condenser on an induction coil may be injured if the "points" of the air gap of a spark plug are too far apart. In that case there is excessive electric stress in the condenser which causes it to break down. If the condenser is defective and there are large sparks at the vibrator, there will be weak sparks at the spark plugs, but weak sparks may be also caused by a partial breaking down of the condenser, or by a loose wire at the condenser. Three-terminal Induction Spark Coil. Most of the vibrating induction coils used on automobiles have only three terminals instead of the four terminals in Figs. 104 and 105. It might have been stated in the description of the coil in Fig. 105 that one wire from the high-voltage winding and one wire from the low-voltage winding are grounded to the engine casting. These two wires might have been connected together at the induction coil and their junction connected through the timer (grounded) to the engine casting by a single wire as shown in Fig. 106. In a three-terminal coil as made for commercial use one end of the low-voltage winding is joined to one end of the high-voltage winding and the joining place of these two windings is connected directly to one of the binding posts marked "common ground to timer" as shown in Fig. 107. The other end of the low-voltage wind- ing is connected to the binding post marked "battery," and the other end of the high-voltage winding is connected to the binding post marked "plug" (for spark plug). Fig. 108 shows four vibrating spark coils similar to Fig. 107 as they would be connected to the timer and to the spark plugs of the cylinders of a Ford engine. The four separate coils for a typical four-cylinder engine are packed in a single box 132 GASOLINE AUTOMOBILES Ground* 1 FlG. 106. Wiring Diagram of Three Terminal Vibrating Coil. Adjusting Nut Vibnrtvr Corrfack Condenser FIG. 107. Three Terminal Vibrating Spark Coil. AUTOMOBILE IGNITION 133 similar to Fig. 109. The several terminals of such a set are usually plainly marked on the sides of the box. The high-voltage circuit, as shown in the figures is from the spark plug terminal, across its air gap into the engine FlG. 108. Vibrating Spark Coils for a Four-cylinder Engine. casting or frame, and back through the metal of the engine to the grounded side of the high-voltage winding. The low-voltage circuit is from the battery to the low- voltage winding and to the timer where the wiring is grounded FIG. 108. Vibrating Spark Coils for a Four-Cylinder Engine. so that the current goes back to the battery through the metal of the engine. Ford Ignition System. In the Ford system of ignition a vibrating spark coil similar to those just explained is provided for each cylinder of the engine. The four coils for the four cylinders of a Ford engine are in a box like 134 GASOLINE AUTOMOBILES Fig. 109, usually fastened to the dash board or instrument board of the automobile. Inside the box there is a strip of brass running the whole length. A small spring on the bottom of each coil makes a connection on this brass strip. This spring is one end of the low-voltage winding of each coil. The other end of the low-voltage winding of each coil comes out at the side of the box and is connected to one of the four points on the timer, which is attached to the engine behind the radiator as shown in Fig. 110. The timer No.l.Grttn - tlo.3 giue l - Ha Hid -, HoJ Black - BffraSturct ofCurnnt Lamp Wire SraunJeJ-hffaJiirhr Wire FIG. 110. Ignition System of Ford Automobile. sends sparks through one of the cylinders for each quarter of a revolution. It has a rolling contact like the timer shown in Fig. 107 and each contact bar is nearly a half inch wide, so that the roller stays in contact longer than in other circuit breakers. A good vibrator on such a coil will make two hundred sparks a second and when starting an engine this large number of sparks is an advantage. More current, however, is needed for a "shower" of sparks than for a single spark, and when the engine is running, such a large number of sparks is not needed. The vibrator should be screwed down so that it is barely touching. It is best to screw it down slowly until the cylinder to which it belongs AUTOMOBILE IGNITION 135 begins to have explosions. Sometimes the points on the vibrator must be smoothed or scraped with sand paper. If an engine misses explosions regularly in one of the cylinders it is likely one of the spark plugs is defective. If, however, the engine runs irregularly and misses an explosion only occasionally with sometimes a loud noise from an explosion in the muffler, the difficulty can often be remedied by adjust- ing the vibrator points. Master Vibrators. In the sets of vibrating induction coils described in the preceding Paragraphs there is a FlG. 111. Diagram of Wiring of Master Vibrator Coil. separate coil for each engine cylinder so that when the vibrators on the coils are not operating properly, each coil must be separately adjusted. In order to avoid the vibrator adjustments on a number of coils and to eliminate the pos- sibility of getting sparks of different intensity in the engine cylinders a master vibrator is sometimes used. The adjust- ment of this single vibrator serves for all the cylinders of an engine and when it is installed the vibrators on the individual coils can be screwed down so that they will not operate. When a master vibrator is once adjusted all cylinders will get ignition sparks of practically the same intensity. It is placed in a spark coil system between the electric battery or other source of electric current and the 136 GASOLINE AUTOMOBILES low-voltage windings of the individual spark coils as shown diagrammatically in Figs. Ill and 112. The single coarse wire winding of the master vibrator coil and the wires of its vibrator are connected in series, as shown in the figure, with the low-voltage coils of each of the individual spark coils. Ba-ffvry Ground +o Fngi'ne Fn FIG. 112. Master Vibrator Coil for Ford Engine. It is equally necessary to provide an electric condenser to be connected across the contact points of a non-vibrating coil ignition system as to provide such a device for a system with a vibrating induction coil. Fig. 113 shows the same induc- Plug Condenser FlG. 113. Non-Vibrating Induction Coil with Condenser. tion coil with low- and high-voltage wiring as in Fig. 95 except that a condenser is used to "span" the circuit breaker points. This condenser has the effect, as explained on page 130, of pre- venting rapid wearing away of the breaker points and makes much more efficient sparks at the air gaps of the spark plugs than would be obtained without it. Fig. 113 is a diagram- AUTOMOBILE IGNITION 137 matic representation of a complete non-vibrating induction coil as applied to a simple type of battery ignition system. Fig. 114 is similar to Figs. 100 and 101 as to the essential 1234 From Induction Co//. Distributor Head-. Stationary *. Contactflrtsu/crreJ) Grounded Through Engine and Automobile Frame FIG. 114. Typical Battery Ignition System with Non- Vibrating Coil and Condenser. Breaker Condenser ToSparlrfliys FIG. 115. Ignition System with Non-Vibrating Coil and Condenser for Six-Cylinder Engine. parts, except that it has a condenser which is located on the circular bracket supporting the contact points of the circuit breaker. This apparatus is for a four-cylinder engine, with 138 GASOLINE AUTOMOBILES the distributer terminals arranged for the usual timing order 1, 2, 4, 3 at the spark plugs. Fig. 115 shows diagrammatically the same device as arranged for a six cylinder engine. Typical Non-vibrating Coil Ignition Systems. All the electric current used for the ignition, the lights, and the electric horn in the Delco non-vibrating coil ignition system shown in Fig. 116 goes direct from the storage battery to a group of distributing switches on the dash board or instru- ment board. From these switches the current is distributed Dimming Resistance To Spark Plugs Ground Insulated Circuit greater Contacts -Spring Ground ', ' Induction Coil FIG. 116. Wiring Diagram for Typical Delco Ignition System. for the three services as stated. When the engine is running and is driving a small electric generator (not shown in the figure), which is a part of this system the current comes through the wire C to the distributing switch. When the storage battery is supplying the current it comes to the dis- tributing switch through the wire B. If the switch-button for the ignition circuit is pulled out, the electric current for ignition will be taken from either the generator or from the storage battery, depending on whether or not the engine is running and is driving the electric generator. AUTOMOBILE IGNITION 139 When the electric generator is giving more current than is needed for ignition, lights, etc., the excess of current goes through the wire B to the storage battery for charging it. An ammeter is connected to this wire near the distributing switches to indicate the excess current which is going into the storage battery for charging. Automobiles having large lamps in the headlights will sometimes use for lighting all the current the generator gives when the automobile is run- ning at average speed, and no current is left for charging. Such automobiles when operated much at night and little during the day will soon have very little ''charge" in the , battery. The ammeter is also connected to show the amount of current coming from the storage battery for lights when the engine and generator are not running.* The distributor and circuit breaker of this typical system are driven by gears on a vertical shaft as shown in Fig. 103. The distributor consists of a cap of insulating fiber which has one high-voltage contact in the center connected by a wire to the non-vibrating induction coil and as many similar contacts spaced equidistant about the center as there are spark plugs in the engine. The circuit breaker is below the dis- tributor and gets its motion from the same vertical shaft that drives the distributing arm. It has a screw at the center of the shaft, which when unscrewed permits turning the cir- cuit breaker cam to adjust the timing of the spark in the cylinders. Turning it clockwise advances the spark, and turning it anti-clockwise retards. The spark is made in the cylinders at the instant the breaker contacts are separated. The non-vibrating induction coil is provided for transform- ing (by the usual method already explained) the low voltage (about five to seven volts for three cells) to the high voltage of about 10,000 volts needed for spark-plug ignition. It con- sists simply of a low-voltage winding of relatively few turns of coarse wire wound around a central core of iron rods, and *The ammeter does not show current used by the electric motor for starting the engine. 140 GASOLINE AUTOMOBILES a high-voltage coil of many turns of fine wire wound over the coarse wire coil. At high speed the spark should be advanced farther than at low. In ignition systems with automatic spark control FIG. 117. Delco Igniter with Vertical Coil. Storage &#ery Imrht'on Snitch 12-Wfs } *.%r .. V cL^*"" 1 '- '*"*** Wndm&Seyeral . . LowVoltage Winding, Thousand Turns A Few Hundred Tirme. FIG. 118. Delco Ignition System with Horizontal Coil. it is usually unnecessary to make adjustments of the hand spark lever for speed changes after the engine is started and is running normally. Special types of the Delco ignition system are shown in Figs. 117 and 118. In the first of these figures the high- AUTOMOBILE IGNITION 141 voltage wire going from the induction or ''ignition" coil to the distributor is marked W 3 . The connections to the ter- Ignifion and Lighting Snitch I Ground Safety Spark Gap FIG. 119. North East Battery Ignition System. minals of the low-voltage winding on the coil are marked W\ and W 2 . Distributor Brush \ Distributor Arm \ Circuit Breaker^ Arm LowYolfage Coil Terminals v Wires to Spark Plugs Distributor Head Cocrpfmj High Voltage Coil Terminal v /_ , Spiral Gears - -Automatic Spark Advance Weights FIG. 120. Igniter of North East Ignition System. North East Battery Ignition System is used on many Dodge Automobiles. One of the differences when compared with the typical system described is that it has always a 142 GASOLINE AUTOMOBILES twelve-volt storage battery instead of the more usual six-volt battery. Fig. 119 shows a diagram of the wiring for this system. There is a safety spark gap for the protection of the high-voltage winding on the induction coil. As actually con- FIG. 121. Automatic Spark Advance Weights (North East System). structed the ignition coil and distributor head are arranged as shown in Fig. 120. Automatic spark advance weights are located at the end of the horizontal drive shaft. These weights are shown more in detail in Fig. 121. They operate by the FIG. 122. Circuit Breaker of North East Ignition System Showing Condenser. usual centrifugal method. A detail of the circuit breaker is shown in Fig. 122, which shows also the location of the con- denser and its connecting wires W\ and W 2 as joined to the two contact points A and B. The low-voltage terminals are marked T and U. AUTOMOBILE IGNITION 143 Connecticut Ignition System is shown in a perspective drawing in Fig. 123. A detail of the circuit breaker mechan- ism is shown at the left-hand side of the drawing. At the Storage Battery FIG. 123. Connecticut Ignition System. right-hand side is a small drawing with parts marked K, L, T, of the Connecticut Automatic switch release which was explained on page 124. The drawing shows the electric cur- * To Spark Plugs ^Distributor Brushes FIG. 124. Diagram of Westinghouse Igniter. rent for ignition taken either from a storage battery or from a small electric generator. Westinghouse Ignition system is shown here merely with details of the distributor and the circuit breaker. The usual 144 GASOLINE AUTOMOBILES arrangement of the distributor over the circuit breaker is shown diagrammatically in Fig. 124. A phantom view of the igniter shown in Fig. 125 shows the method of making FIG. 125. Westinghouse Igniter. contact between the distributing arm and the spark plug ter- minals on the distributor. This system is described more in FIG. 126. Atwater-Kent Battery Ignition System. detail in the explanation of the Westinghouse starting and lighting system on pages 180-182. Atwater-Kent Ignition System is shown by the diagram in Fig. 126. The principal difference between this system AUTOMOBILE IGNITION 145 and most others is that the contact points of the circuit breaker are together and touching only for an instant just Fie. 127. Detail of Distributer Arm of Atwater-Kent System. FIG. 128. Detail of Attachment of High Voltage Wires to Distributer Head. Mechanism DryCt FiQ. 129. Kemy Ignition System. preceding the moment when the spark is to be made in one of the engine cylinders. Because of this arrangement it is 146 GASOLINE AUTOMOBILES High Voltage Cable from Coll Leads for Attachment of 'Wires to Plugs Distributor Cover Spark Adjustment Lerer Drive Shaft Ground Ground 1 FlS. 130. Igniter of Kemy Battery Ignition System. FIG. 131. Eemy Igniter. FIG. 132. Bosch Igniter. AUTOMOBILE IGNITION 147 unnecessary to have a protective device to guard against over- heating in case the ignition switch should be left closed when the engine is not running. Details of the distributing arm and method of attachment of the high-voltage wires to the distributor terminals are shown in Figs. 127 and 128. Remy Ignition System is shown clearly in Figs. 129 and 130. As shown in the latter figure the igniter (distributor and circuit breaker) is mounted on a bracket which also sup- ports the induction coil. Another view is shown in Fig. 131. The igniter used in the new Bosch battery system is shown in Fig. 132. CHAPTER VI MAGNETOS AND IGNITION TESTING In the preceding paragraphs the elementary principles of the relation of electricity to magnetism were explained. Typical applications were illustrated in devices intended for the ignition of explosive mixtures of gasoline vapor and air in automobile engines. The applications of these principles will now be extended to generating electric current for igni- tion purposes without the use of batteries of dry or storage cells. Electric generators for such ignition purposes are called magnetos. A magneto as regards the essential parts is an ignition system in itself. Magneto ignition systems are not used as much as formerly on modern pleasure automobiles. When a wire loop like L in Fig. 94 is moved in a magnetic field an electric current is generated in the wire. Consider now Fig. 133 which shows a bent bar magnet and a wire loop placed between the ends of the magnet. If the loop is re- volved in the position shown an electric current will be gen- erated. Electrical pressure or voltage is generated in the loop in proportion to the speed of its rotation the faster the loop is revolved, the higher the voltage produced. By increas- ing the number of loops and the strength of the magnetic field of the magneto the amount of current (amperes) is increased. These are the fundamental principles of the dynamo, in- cluding the electric generator and the automobile magneto. A double wire loop in position for revolving in the magnetic field of a typical magneto is shown in Fig. 134. At the bottom of this figure is another double coil wound on a shuttle- shaped iron core for holding the wire loops. The iron core and its windings are called the armature of the magneto. 148 MAGNETOS 149 The magnetic fields of all kinds of magnetos are made of permanent magnets,* which remain magnetized indefi- nitely. Magnetos should always be positively driven by gear wheels from the engine shaft because the timing of the spark is FIG. 133. Bent Bar Magnet and Wire Loop. determined by the timer which is a part of the mechanism of the magneto. A belt-driven magneto would not give accurate timing of the spark. Magneto Armature Types. The armature of a magneto FIG. 134. Magneto Coils. consists of an iron frame and the wire coils in which the electric current is generated for ignition. A magneto arma- * If a permanent magnet is used for making the magnetic field the machine is called a magneto; and if electromagnets are used the machine is called an electric generator. 150 GASOLINE AUTOMOBILES ture is not necessarily a moving part; although in most designs it is of the rotating kind similar to the one shown in Fig. 134. There is another kind in which the coils of wire FIG. 135. Magneto with Stationary Wires (Armature). generating the ignition current are stationary and the rotating part consists only of iron without a winding. In the latter kind, by generating the electric current in stationary coils the usual sliding contacts on current collecting rings are avoided. (See Figs. 135 and 136.) FIG. 136. Magneto Rotor without Wires. Magneto Speed Compared to Engine Speed. Modern types of magnetos make two sparks in one revolution of the magneto shaft. A four-cylinder automobile engine, for example, has four explosion or power strokes in two revolu- tions, so that the magneto for this engine must make four sparks in every two revolutions of the engine, or two sparks in every revolution. In a four-cylinder engine, therefore, the magneto shaft and the engine crank shaft must rotate at the same speed. In a six-cylinder automobile engine there are three explosions in one revolution of the engine crank shaft, and in an eight-cylinder engine there are four explosions. The speed of the magneto shaft of six- and eight-cylinder engines must be, therefore, respectively one and a half and two times the speed of the crank shaft. MAGNETOS 151 Kinds of Magnetos. There are two kinds of magnetos: (1) high tension, meaning high voltage and (2) low tension, meaning low voltage. A high-tension magneto has two wind- ings or coils on its iron core ; one coil consists of a few turns of coarse wire, like the low-voltage coil in an induction coil and another consists of a large number of turns of very fine wire wound over the low-voltage coil. High-tension magnetos are used much more than the low-tension type for automobile ignition. A low-tension magneto differs from a high-tension in hav- ing only one winding of wire on the armature. It delivers only low-voltage current at its terminals and a voltage trans- former* must be used to step-up the magneto voltage to make its current suitable for spark-plug ignition. Sometimes a transformer is set on top of the magneto and this combination is sometimes called a high-tension magneto but it should not be given that name, as it does not give the kind of service expected of a real high-tension magneto. High-tension Magneto. The essential parts of a high- tension magneto (with the magnets omitted) are shown in Spark Plugs Ground FIG. 137. Diagrammatic View of Parts of Magneto. Fig. 137. The low-voltage coil on the armature A is repre- sented by heavy lines and the high-voltage coil by light lines. The high-voltage and the low-voltage coils are connected at X * A voltage transformer or what is commonly called an electric trans- former consists of two coils of wire wound upon each other, one of few turns of coarse wire for the low-voltage current and the other of many turns of fine wire for the high voltage. 152 GASOLINE AUTOMOBILES and from this point a wire a is "grounded" to the metal frame of the magneto. In this diagrammatic representation a circuit breaker is shown at the left-hand end of the armature which is generally operated by some kind of cam device to break the current twice in a revolution. This circuit breaker con- sists of a pivoted lever L which has a platinum point E at one end and a fiber block C at the other end. Normally, the platinum point E is held by a spring against the point F on the insulated block D, which is connected to the low-voltage winding on the armature. As a magneto is actually con- structed, the pivoted lever L and the insulated block D are mounted on the end of the armature shaft 8, and in their rotation with the armature the piece of fiber C on the lever L passes over the stationary cams C t and C z (Fig. 138) and FIG. 138. Typical Magneto Circuit Breaker. swings the lever L back and forth to break the circuit by the separation of the points E and F. At the right-hand end of the armature shaft is a copper collector ring R (Fig. 137), insulated from the shaft by a band of hard rubber. By means of this ring the high-voltage cur- rent generated in the armature of the magneto is collected by a carbon brush B, which is held down to make electrical contact on the collector ring R by the spring K. This col- lector ring is connected to the free end of the high-voltage coil on the armature so that the current from this coil passes to the ring R, and from there through the carbon brush B and the wire W to the distributing arm which distributes the high-voltage current to the spark plugs in the proper order MAGNETOS 153 of firing. The timing arm T and its attached cams C^ and C 2 are fastened to a ring r which is mounted on the magneto frame so as to permit a little back and forth movement. The timing arm is therefore a means of moving the cams slightly so as to cause the sparks at the spark plugs a little earlier or later than for the setting shown. This arm is fitted with attachments for connection to the spark control lever on the steering wheel. A "phantom" view of a typical high-tension magneto is shown in Fig 139. The current from the high-voltage wind- flag nets.. Co/lector Brush-"?) Collector Ring R Circuit Breaker Mechanism Low Voltage Winding '" High Voltage Winding FIG. 139. Phantom View of High-tension Magneto for a Four-Cylinder Engine. (Note only two of the four spark plug terminals are shown.) ing is carried by a wire passing through the right-hand end plate to the collector ring R, from which the current passes througji the collector brush B and the wire W to the dis- tributing arm at the left-hand end of the magneto. The distributing arm is driven by the gear wheels as shown at one-half the speed of the armature shaft on a four-cylinder engine ; and at one-third the armature speed on a six-cylinder engine. Two sparks are made by a magneto in every revolution 154 GASOLINE AUTOMOBILES of this armature so that the armature of a magneto for a four-cylinder engine must make two revolutions, causing four sparks, in the same time that the distributor brush makes one revolution. The gears are so arranged that when each of the sparks is produced the distributing arm is resting on the bar or segment connected to the proper spark plug. A condenser for shortening the duration of the spark at the contact points E and F (Fig. 137) in the low- voltage circuit is mounted at the end of the armature shaft. As the diagram in Fig. 137 is laid out, one terminal of the con- denser would be connected at X and the other to the wire Cotrfnct-Bngoker FIG. 140. Magneto with Condenser on Armature Shaft. shown dotted through the hollow shaft 8. Figs. 140 and 141 show the condenser as located in a magneto of a well-known make. A diagram of a high-tension magneto of the Bosch make for a four-cylinder engine is shown in Fig. 142, with the impor- tant parts marked with numbers which are explained in the table below the figure. A somewhat simpler design is shown in Fig. 143. Safety Spark Gap. If by accident the wire connecting the high-voltage coil of the armature to the collector ring R (Fig. 137) is broken or detached, the high -voltage current will have no return path and may produce a voltage which will damage the insulation of the high voltage coil on the armature. Similar damage may result from the excessive MAGNETOS 155 voltage if the platinum points E and F of the circuit breaker are too far apart or if a wire falls off one of the spark plugs when the engine is running so that the electric current cannot go through the plug. To protect the high-voltage coil a 156 GASOLINE A UTOMOBILES safety spark gap is provided as shown at the left-hand side of Fig. 141. One side is connected to the collector brush and FlG. 142. Typical High-tension Magneto. E. Collector ring. B. Carbon brush. 12. Brush holder. 13. Terminal piece for bar 14. 14. Conducting bar. 15. Distributor brush holder. Z L K 16. Distributor carbon brush. 17. Distributor cover. 18. Central distributor contact-. 20. Nut on distributor. 22. Dust cover. 170. Nut on grounding terminal. H V N L FiO. 143. Simplified Type of High-tension Magneto, the other is attached ("grounded") to the frame of the mag- MAGNETOS 157 neto. The current will pass through this air gap in case the high-voltage line is incomplete. The discharge through this spark gap should not be al- lowed to continue for a long time as it is likely to damage the magneto. One way of locking an automobile is to put a little piece of metal between the points of the safety spark gap. The engine can then be "cranked" indefinitely without making a spark in any of the cylinders. If this description of a typical high-tension magneto is understood, the reader should have little difficulty in under- standing the construction of any other magneto of similar design. Ford Low-tension Magneto. The Ford magneto is in the same case or housing which covers the speed-change Copper Wire- Magneto Coil--'' Spool 'Magnet Clamp FIG. 144. Essential Parts of Ford Low-tension Magneto. gears or transmission. Fig. 144 shows the important parts consisting of sixteen small coils of wire in a stationary round plate and sixteen magnets. Each coil has an iron core and the winding of wire around these cores is continuous. The stationary plate and the flywheel have about the same diameter. There are sixteen magnets shaped like horseshoes 158 GASOLINE AUTOMOBILES on the flywheel and the space between these magnets and the coils on the stationary plate is only about a thirty-second of an inch. The magnets on the flywheel set up a magnetic field which when rotating in front of the coils on the stationary 'Flywheel Miynefc FIG. 145. Ford Flywheel Magneto and Vibrating Induction Coils. plate generate an electric current in these coils. The magneto, timer, and vibrator spark coils are shown diagrammatically in Fig. 145. Fig. 146 is a drawing of a Ford engine showing the flywheel magneto. Graphite should not be put in the oil used in a Ford engine as it is likely to injure the coils. Sometimes the magnets become demagnetized, causing weak ignition sparks. In that case the magnets should be replaced with new ones. A Ford magneto has only one winding which generates a low-voltage current of about 18 volts, when the engine is running at normal speed. Dual and Double Ignition Systems. Since the amount of current and voltage generated by a magneto depends on its speed, it is obvious that at the low speed of starting, especially of hand cranking, it is often difficult to get good electric sparks in the engine cylinders for ignition. For this reason some automobiles are provided with some other source of current for start-ing. The auxiliary source is a battery of dry cells or of storage cells. In the dual system of igni-' tion the battery supplies the current for starting, which is MAGNETOS 159 taken through a separate circuit breaker and then through the low-voltage winding on the armature of the high-ten- sion magneto. The high-voltage current is then generated as in a non-vibrating induction coil and goes from the magneto distributor to the spark plugs. After the engine is started, by the movement of a switch, the magneto current can be 160 GASOLINE AUTOMOBILES used for engine ignition in the ordinary way. Some induction coils are provided with a ratchet device on the dash board which makes a "shower" of sparks for starting by rapidly making and breaking the ignition circuit. In the double system of ignition the engine has two spark plugs in each cylinder, one of which gets current from a battery and induction coils and the other from the magneto. In this system there are really two separate ignition outfits, and the engine can be operated on either one or both at any time. Care of Magnetos. If any moisture gets on the high- voltage coil of a magneto it may cause a short circuit so that the high-voltage current will not go to the spark plugs but will go through the insulation of the coil and conse- quently the engine will be stopped. The bearings on each end of the magneto shaft should occasionally have a few drops of oil. But this is one part of an automobile that should not be oiled too much. As regards any other part of an automobile it is best to give too much oil rather than too little. A magneto should be kept clean and dry. Repairing a magneto is work for an expert electrical mechanic and should not be attempted by amateurs. Magneto Adjustments. Timing. If a magneto is out of adjustment, the engine should be cranked until "No. 1" cylinder (the one nearest the radiator) is in the position of firing the explosive mixture. This is usually just a little past the dead center (top of stroke) if the spark is set for the usual starting position (not advanced). Next determine which one of the distributor points is wired to "No. 1" cylinder. Then rotate the armature of the magneto until the distributing arm comes into contact with the distributing points for "No. 1" cylinder,, and adjust these relative positions so that the contact points are released from each other when the distributing ring is in the position of a fully retarded spark. In this position the magneto should be carefully attached to its driving shaft. The spark con- MAGNETOS 161 trol rod going to the steering wheel should then be con- nected and adjusted so that the contact points just open when the spark lever on the steering wheel is fully retarded. This position of the lever permits advancing the ignition spark the maximum amount. The circuit breaker points of a magneto are opened about one-sixty-fourth of an inch, while on a battery system they are usually opened about twice as much. A gage is usually furnished for setting the circuit breaker points of a magneto. The carbon brushes of the distributor will collect dust and should be occasionally cleaned with a piece of clean cloth. Demagnetized Magnets. If the magnets are weak the sparks will be weak. The spark depends not only on the strength of the magnets but also on the speed of the engine. Increased engine speed gives better ignition current from a magneto with weak magnets. If an engine stalls easily when driving through crowded city streets and seems to have little power at slow speeds it is likely that the magnets are weak and the ignition current is of very low voltage. The magnets can be remag- netized in a very short time and without much expense. Magneto vs. Battery. A magneto gives a very hot spark at high speed. Magnetos are used more on trucks than on automobiles. Most modern automobiles have an electric self- starter and a storage battery system, so arranged that one can get into the seat and start without cranking the engine. A battery ignition system gives a hotter spark at low speed than a magneto system. But when running at high speed a mag- neto may give a hotter spark than a battery. There is much advertising of the merits of one of these systems of ignition over the other. The double system of ignition shows both methods under the same conditions. Careful experiments show that there is practically no differ- ence as to the effectiveness of the two methods of ignition. Testing Spark Plugs. When a spark plug has been taken out for cleaning, it should be screwed back again into the cylinder tightly so that there will be no loss of compression 162 GASOLINE AUTOMOBILES pressure by leakage and it should be put back carefully to avoid changing of the air gap distance or breaking the porcelain. It is a good precaution to take out the spark plugs and clean them before going on a long trip. If, after cleaning a spark plug, the ignition in the cylinder in which it belongs is still not as it should be, the spark plug should be put into another cylinder and if there is then difficulty with the ignition in that cylinder, it may be assumed the spark plug is defective. The easiest way to tell whether any of the cylinders of an engine are not working is to test each of the spark plugs by putting the end of a screw-driver with a wooden handle on the casting or frame of the engine and touching the side of its steel blade on the metal top of the spark plug. The current will then go from the top of the spark plug through the screw-driver to the metal of the engine cylinder, instead of going down through the spark plug and across its air gap. While the screw-driver is in this position there is no spark at the spark plug. If the engine changes its speed, when each spark plug is tested, the ignition is satisfactory. On the other hand, if the speed of the engine does not change when the screw-driver is put on one of the spark plugs,, there is a good indication that the ignition is defective. It is very difficult, however, to test six-, eight-, or twelve-cylinder engines by this method, as it is difficult to hear a momentary change of speed in an engine with a large number of cylinders. The same voltage that will make an ignition spark jump one thirty-second of an inch across the air gap of a spark plug inside an automobile engine cylinder will make the spark jump at least a quarter of an inch outside the cylinder. The difference is due to the greater resistance of the air gap of the spark plug to the passage of the spark when it must go through a compressed explosive mixture. If, there- fore, the spark jumps across one-quarter of an inch outside the engine cylinders, it is likely the ignition current is giving a good spark inside the cylinder unless, of course, the cur- MAGNETOS 163 rent is going through a crack in the porcelain of the spark plug. One of the best tests of a spark plug is to take off the wire carrying the ignition current and hold it a quarter inch away from the top of the spark plug. If there is a spark jumping across this air gap at the top of the plug it is not likely the trouble is with the spark plug. In making this test care should be taken that the current is not stopped from going through the spark plug, as stopping the high voltage current may burn out the fine wire winding of the induction coil. Moreover, if the tester gets his fingers on bare connections or on uninsulated wires when making this test, he is likely to have an unpleasant "shock." If the engine misses explosions on a hill, and runs satis- factorily on the level, there is probably some trouble with the ignition in the spark plug. Sometimes it is difficult to find the troublesome cylinder especially if it stops missing explosions at the top of the hill. If the missing occurs with regularity it is likely the air gap of one of the spark plugs is larger than it should be. If one of the air gaps is too wide, the points should be pressed together to the proper distance. Correct Length of Spark Plugs. It is not advisable to buy all kinds of spark plugs recommended by stores. Some spark plugs picked up at random will project too far into the cylinders of some engines so that the wires or "points" at the air gap of the spark plug get red hot and may ignite the explosive mixture too soon. There is often the same difficulty with spark plugs which have very thin wires or "points" at the air gap. On the other hand, if a spark plug is too short the air gap wires cannot enter the com- bustion space and are in "dead gas." It is best to use the kind of spark plug that goes with the engine. Cheap spark plugs are dear at any price, as the high-voltage current is likely to go through the porcelain. Care of Distributor. If an engine is misfiring, after finding out that there is no trouble with the spark plugs, 164 GASOLINE AUTOMOBILES the distributor should be examined. The cover can be taken off and held up so that it can be wiped off inside. Some- times there is a thin coating of dirt or of oxide on the contact or other parts and the ignition current does not go through them at all or does not go to the right points. Because of such a coating on the distributor points, the current, in taking the easier path, may jump five or six times as far, rather than go to the right points. Under these unfavorable conditions the cylinder which is skipping ex- plosions will be the one which is on its compression stroke at the moment so that its spark plug is in highly compressed explosive mixture, and the spark goes over the coating of dirt to the distributor point of the spark plug of a cylinder which is not on the compression stroke. For cleaning the distributor, it is not necessary to remove the wires. Nearly all automobiles except the Ford make have a distributor, and in this automobile the timer must be in- spected and cleaned in very much the same way for the same reasons. Preignition. When any small piece of metal or a bit of carbon deposit in an engine cylinder becomes red hot, it will ignite the explosive mixture at the moment of contact without an ignition spark. Such "automatic" ignition generally takes place long before the spark is made by the ignition device, and thus causes a considerable loss of power. This early ignition of the mixture is called preignition. Recent investigations show that overheated valves and bits of carbon scarcely ever cause preignition but that it is fre- quently caused by' overheated "points" at the air gap of spark plugs. Preignition is simply tested by cutting off the ignition current at the switch and observing whether the engine continues to ignite the charge for a moment in one or more cylinders. If the engine has a cut-out on the muffler, its use will assist in this test. Knocking and Related Trouble. It will be noticed some- times that an engine makes unpleasant noises called knock- ing when heavily loaded. When going up a steep hill, for MAGNETOS 165 example, the throttle valve of the carbureter is opened wider than in ordinary operation so that the engine takes an un- usually large amount of explosive mixture. As a result there is higher compression in all the cylinders, which causes exceedingly rapid combustion. In other words, because of the higher compression, there is quicker combustion of the explosive mixture in the cylinders. This unpleasant noise can be avoided if the spark lever is set back a little (retarded spark) so that the ignition will be started a little later in the cylinders. Number of Spark Plugs. Two spark plugs in each engine cylinder insure more rapid ignition and increase the power of the engine for the same amount of gasoline used. Obvi- ously, the advantage of two spark plugs is greatest in cylinders of large diameter. In a test of an engine with cylinders which were five and one-half inches in diameter, four per cent more power was developed with two spark plugs than with a single spark plug. Engines of smaller diameter would similarly give more power with two spark plugs but the percentage increase would be less. Using four spark plugs instead of one in a single large engine cylinder will increase the power more than ten per cent without increas- ing the amount of gasoline used. Reasons for Spark Advance. It takes some time for the combustible mixture to be completely ignited, and obviously ignition should be complete, when the piston in an automobile engine cylinder begins its explosion or power stroke.* When starting an engine, even with a self-starter, the piston moves so slowly that if the explosive mixture is ignited before the piston gets to the top of its stroke the engine may start backward. If an engine is being started by hand cranking, it is not unusual for the quick, reverse movement of the * The result is that during all the time required for ignition, the pressure is building up rapidly in the cylinder and is causing a back- ward pressure on the piston which is not useful as "compression" pressure. Journal of Society of Automotive Engineers, November, 1920, page 475. 166 GASOLINE AUTOMOBILES starting crank to break an arm or a collar bone of the person using it. It takes a fraction of a second after the mixture is ignited before there is an explosion. The ignition spark must, therefore, be set to occur at a different piston position for starting than for regular operation. When an engine is at normal speed and the piston is moving rapidly it is necessary to start the combustion of the explosive mixture earlier than when the engine is being started. This early ignition is called the spark advance. After the engine has been started and is gaining speed the spark control lever on the steering wheel should be gradually advanced till it is in the position for usual running conditions. It should not be advanced so far that the pistons make a thumping or "pounding" noise in the cylinders. The amount of the advance of ignition depends on the three following conditions in the engine cylinders: (1) If the combustible mixture is ignited on all sides and in the center simultaneously it will cause the charge to burn more rapidly just as when, in burning a pile of brush, it burns faster if the torch is applied on all sides instead of at one point only. One way to accomplish this is to use more than one spark-plug per cylinder. (2) If the combustible mixture were agitated within the cylinder or rotated fast enough so that most of it passed the spark while the crank moved only a little, the effect would be the same as if the spark-plug ran around the edge of the cylinder igniting the gas on all sides almost simultane- ously. (3) If higher compression pressures were used, the flame would travel through the charge much faster and would at the same time, make possible the use of smaller combustion-chambers. This means that the flame would not be required to travel so far. The objection to using high com- pression is that it causes knocking. CHAPTER VII ELECTRIC STARTERS Starters in General. Although a modern gasoline engine for automobile or aeroplane services is a marvel of mechanical ingenuity furnishing power with less weight than any other kind of engine, it cannot, with all its wonder- ful improvements, start on its own power like other kinds of engines and motors. This is because there is only one power stroke to three idle strokes. Once it is started, how- ever, the power for these three "waste" strokes is supplied by a rapidly rotating flywheel. For starting, external power is needed, which may be human power as applied in "wind- ing" the engine crank or "stored" power as used in a start- ing motor. As automobiles are now equipped, nearly all the starting motors (called "self-starters") are of the electrical kind. Few mechanical starters are now used. Electric Starters. The three essential parts of an electric starter are (1) an electric motor, attached either directly to the flywheel or by intermediate gears to the crank shaft of the engine, to give the "cranking power"; (2) an electric storage battery of sufficient current capacity to drive the elec- tric motor for starting; (3) an electric generator connected by gearing or otherwise to the crank shaft of the engine to generate the electric current for charging the storage bat- tery. For simplicity of statement, it will be assumed that the current for electric lights and for cylinder ignition is also always taken from the storage battery. In some elec- tric starting systems, the electric motor and the generator are combined as will be explained later. This combination is called a starter-generator. 167 168 GASOLINE AUTOMOBILES The electric storage battery and the electric generator are not very different in construction from the usual com- mercial types. The principles underlying the operation of storage batteries have been explained (see page 107), and the general principles of electrical design of electric generators have been explained in the Chapter 011 Magnetos (see page 148). A generator differs in essential parts from a magneto only in having electro-magnets instead of permanent magnets. Permanent magnets are made of specially hardened steel and on being magnetized retain their magnetism without much diminution for many year's. A generator resembling a mag- neto would not be satisfactory for charging a storage battery as the amount of current it could give would be too small for practical use. Electro-magnets which are much stronger than permanent magnets can be made by passing a current of electricity through a coil of wire surrounding the magnet. By the use of electro-magnets, electric generators of any desired capacity can be made. A coil of wire on an iron spool, if rotated by connection to the shaft of an automobile engine in a magnetic field, will have electric current gen- erated in it just as in a magneto. The current developed in a magneto or any electric generator is, however, an alternating current, which cannot be used for charging a storage battery. In order to use electric current for storage battery service it must come from an electric machine as direct current. The device or attachment of a generator for changing the alter- nating to direct current is called a commutator. It consists of short copper bars which are insulated from each other, and each two bars diametrically opposite, are connected by a wire loop wound over the armature. As actually constructed, the commutator and armature coils are attached to the shaft and firmly bound together. Carbon brushes bear on the curved surface of the commutator to "gather" the electric current in the armature and carry it to the terminals of the storage battery, the lights, the induction coils, etc. Connected to the main wires, carrying the electric current from the armature, are small branch wires which take some of the current to the ELECTRIC STARTERS 169 electro-magnets in the frame, called the field magnets. Bearings for the shaft are on the end covers. One cover is usually made flat and the other with an extension, which when in place is the cover for the commutator. As thus assembled, the brushes for carrying away the current generated are inside the commutator cover. There is usually provision for inspection of the operation of the brushes on the commutator. The starting motor should be of sufficient power to turn the engine crank shaft between one hundred and two hundred revolutions per minute to get dependable ignition conditions; but the power is needed for only a few seconds. Because of this short duration of service, a starting motor can be made much smaller than an ordinary type of electric motor, in- tended for continuous service, without excessive heating in its coils and bearings. Large wires are needed to carry the large current, sometimes as much as two hundred amperes in the motors for large engines. The size of storage battery used with electric starting systems is not large enough to withstand the drain of so much current* for any considerable time. Starting 1 Motor Drives. After an automobile engine has been started it gains speed rapidly and gets very quickly to a speed of about one thousand revolutions per minute. Now, if no means were provided for disconnecting the electric starting motor from the engine after the engine begins run- ning itself, with increasing speed, the motor would certainly be damaged by the excessive generation of current in its coils ; for the reason that when an electric motor receives electric current at a certain voltage, it can be used to drive a machine or engine, but if the machine or engine receives power so that it goes faster than the normal speed of the motor, it will no longer take current but will act like an electric generator and make its own current. Also the low-speed *The power of a motor (kilowatts) is the product of amperes times volts divided by one thousand. In the case mentioned, it is assumed there are three storage cells giving six volts. Therefore, kilowatts of motor = 200 X 6 -r- 1000 = 1.2. 170 GASOLINE AUTOMOBILES bearings of the electric starting motor could not withstand the high speed it would have as a generator. For these reasons the starting motor must not remain in geared or in similar connection with the engine crank shaft after the engine begins running on its own power. This disconnection when the engine is running should not be left to the chance thought- fulness of the driver. The usual method is to use an automatic clutch. One method of driving the engine when starting is by means of a gear wheel on the electric starting motor which Fie. 147. Typical Delco Electric Starting Motor (and Generator). can be made to slide in and out of mesh with gear teeth on the rim of the engine flywheel. This is the method used, for example, on the Buick automobile (Fig. 147). A chain drive is used on the Ford automobile (Fig. 148). The device most commonly used to prevent driving the electric motor at too high speed when the engine starts under its own power, depends for its action on a weighted gear wheel which is automatically thrown out of mesh with the gear teeth on the flywheel when the engine gets sufficient speed. This automatic device is called the Bendix drive, and is shown in Figs. 149, 150, and 151. When the starting pedal ELECTRIC STARTERS 171 or switch closes the electric circuit of the starting motor, the armature starts to rotate its shaft, which has screw threads B at one end. Fig. 149 shows the normal position of the gear wheel A, which has internal threads to fit corresponding Motor Generator FIG. 148. Examples of Chain Drives for Electric Starters. threads on the shaft at B, and in this model is weighted on one side (eccentrically) at W. Because of this eccentric weight, and due to its inertia, the gear wheel A will not rotate immediately with the shaft, but will run forward on the FIG. 149. Bendix Drive Disconnected. FIG.- 150 Shifting Position. FIG. 151. Gears Connected. revolving screw threads B, as shown in Fig. 150, until it meshes with the teeth on the flywheel as in Fig. 151. The shaft carrying the threads B is hollow and is connected to the armature shaft by means of spring S. If the teeth of the gear wheel and those on the flywheel do not mesh when they first 172 GASOLINE AUTOMOBILES come together, the spring S will allow the gear wheel to revolve until the teeth do mesh. When the gear wheel is meshed with the flywheel as in Fig. 151 the spring S will be tightly compressed and the power of the electric motor becomes effective for turning the engine. The spring S acts like a cushion when turning the engine over against compression, or if the engine backfires. As soon as the speed of the engine is higher than that of the starting motor the flywheel will drive the gear wheel A at a higher speed than that of the armature shaft of the starting motor, so that the gear wheel will be turned in the opposite direction on its screw thread and be automatically released from the teeth on the flywheel. The starting switch must be released as soon as the engine starts on its own power. If this is not done the starting motor shaft will increase in speed also and the gear A will not disengage. This device thus prevents the engine from driving the starting motor. "When the starting motor drives the engine by means of a silent chain or similar method (see Fig. 148) as used on Ford, Dodge, and Franklin automobiles, for example, the engine is prevented from driving the motor by the use of an over-running clutch, which slips when the engine tends to drive the motor. A typical construction of an over-running clutch, shown in Fig. 152, consists of a star-shaped inner member, which is FIG. 152. Overrunning Clutch. keyed to the shaft, free to rotate inside the intermediate gear. Four rollers R are inserted between these two members in such a way that they will bind in the angles of the star when the shaft is turned in one direction, but will rest free from tho outer member if the shaft is turned in the opposite direction. ELECTRIC STARTERS 173 There is also another type of starting . motor drive which depends for its action on the magnetic pull of the strong electromagnets attached to the motor to draw the entire armature and the gear wheel at the end of its shaft into a position where the gear wheel meshes with teeth on the fly- wheel. In this device the armature is mounted on a hollow shaft which has a slot in the middle into which is fitted a projection on the inside of the hub of a small gear wheel. A shifting rod inside the hollow shaft and fastened to the projection on the hub of the gear wheel, is attached at one end to a large piece of soft iron which fits inside a coil of wire. When the current from the storage battery goes through the coil the piece of soft iron is pulled into the coil and draws with it the shifting rod and the attached gear wheel, so that it is brought into mesh with the teeth on the flywheel. All starting motors require a large current at the moment they start to revolve; and since this large current flows also through the coil of the shifting magnet, it gives sufficient magnetic pull to overcome the tension of a spiral spring on the shaft intended to oppose this motion. As soon as the teeth 011 the gear wheel mesh with the teeth on the flywheel the current required to turn the engine is large enough in the electromagnet to hold the gear wheel in mesh against the tension of the spring. But as soon as the engine runs on its own power, the current needed for the starting motor is very small and the coil of the electromagnet is weakened, so that the spring is stronger than the magnetic pull and the gear wheel is drawn out of contact with the fly- wheel. Starting Motor Switch. The Delco starting motor switch is shown by Fig. 153. It is installed on the floor boards of the automobile and is operated by the driver's foot. By pressing the foot button a connection is made between the battery lead and the starting motor lead. The leads are heavy copper cables, usually No. or No. 00 size, made of stranded wire, heavily insulated. The leads are also very often protected against chafing by an outside winding of metal, called armor. 174 GASOLINE AUTOMOBILES The terminals of the switch are large and imbedded in insulation. The size is important because of the large amount of current used by the starting motor and the insulation is very necessary because the battery would be short-circuited if the battery lead became grounded. The switch terminals are also self-cleaning, which is desirable because heavy sparks SetfCkam'ng Double Cup Contact Battery Lead FIG. 153. Delco Starting Motor Switch. occur when a circuit, in which a large current is flowing, is suddenly broken. Reverse Current Cut-out. In some starting and lighting systems an automatic switch operated by electromagnets is connected in the battery charging circuit between the electric generator and the storage battery for the double purpose: (1) to make electrical connection between the generator and the battery when the generator voltage is high enough to charge the battery; (2) to cut off this charging current from the battery as soon as the voltage of the generator falls below the battery voltage (usually because of low speed). This device is necessary when the engine is not running, as without some arrangement of this kind the battery would discharge itself by sending its current through the wires of the gen- erator. One type of an apparatus for this purpose is shown diagrammatically in the center of Fig. 154. It consists of a vertical iron magnet; a winding of fine wire, called the voltage coil; a winding of coarse wire, called the current coil; and a set of contact pieces which are normally held apart by the small spiral spring as shown. One of these contact pieces ELECTRIC STARTERS 175 is over the top of the iron magnet. This magnet, by its pull, draws the contact pieces together when the voltage of the generator becomes six and a half or seven volts (if the storage battery has three cells) or between thirteen and fourteen volts (if six cells in the battery). These voltages usually correspond to an automobile speed on direct drive (without gearing) of about ten miles per hour. Fuse Series Fie id Winding Ma in Brushes - ..Shunt Field Wmding Jhirc/ Brush JoHorn To Lighting and Ignition Switch FIG. 154. Diagram Showing Reverse Current Cut-out. When the direction of the current is such as to charge the storage battery, the voltage coil and the current coil exert their magnetic pull in the same direction ; that is, to keep the points of the contact pieces together, so that the current from the generator goes through the battery to charge it. When, however, the voltage of the generator falls below that of the battery and the battery begins to discharge through the wiring of the generator, the directions of the magnetic pull 176 GASOLINE AUTOMOBILES of the voltage coil* and the current coil are opposite, so that the contact pieces are released and the flow of current from the battery is stopped. The operation of the cut-out can be tested by observing the light produced by the headlights when the speed of the engine is varied. The test can best be made when the automobile is not running. If the engine speed is gradually increased to that corresponding to about ten miles per hour of the auto- mobile, the lights will become suddenly brighter. At the moment of this change in brilliancy the current comes from the generator instead of from the battery; and the generator voltage for charging is about one and a half volts higher than the battery voltage (when the battery has three cells). Starting systems, like the Delco (Fig. 147), which do not have a current cut-out device of this kind, avoid most of the difficulty by designing the generator to give . the required voltage for charging the storage battery when the speed of the automobile is only about seven miles per hour. At very low engine speeds when the voltage of the generator is not high enough to charge the battery there will be a small amount of current discharged from the battery through the generator wires. In systems of this kind the ignition switch cuts off the battery current from the generator. This switch, there- fore, should never be left closed when the engine is not run- ning, because in several hours this loss of current would practically discharge the battery. Third Brush Regulation. In all well designed electric starting systems there is a means by which damage to the storage battery by overcharging may be prevented. A suit- able device for this purpose should give increasing current for charging as the speed is increased up to about twenty miles per hour, but at higher speed the electric current should be constant or should be reduced. *The current of the voltage coil is shunted to a grounded connection, and is not affected by the change of direction of the charging or battery current. ELECTRIC STARTERS 177 When the speed is about forty to fifty miles per hour, the generator current, as a rule, will be only about a third of the maximum value. There is a distinct advantage in this method of regulation in that the -maximum current or charging rate for the battery is obtained at the normal driving speeds. The method most used is called third brush regulation and is difficult to explain without a full discussion of the theory of electric generators.* Briefly stated, however, this method is usually applied to electric generators with only two electromagnets, which normally would have only two brushes for collecting the current on opposite sides of the commutator, but in this method a third brush is put on the commutator between the other two. It is a well-known fact that as the speed and amount of current of such a generator increase the magnetic field due to the electromagnets (field magnets) becomes distorted and unequally distributed. By taking the current, used for the magnetization of the field magnets, from two brushes . that are not diametrically opposite a variable current is obtained, which tends to get weaker as the speed of the generator is increased. The position also of the third brush may be changed so as to alter the maximum charging current. Adjustment of Third Brush Device. The amount of cur- rent permissible for charging depends on the construction and size of the battery plates. In the Delco and Westinghouse systems, for example, the maximum charging rate is about fifteen amperes, and on the North East system it is only about six amperes. If the ammeter on the instrument board indi- cates a higher current than the maximum charging rate, adjustment can be made, if the third brush method is used, by shifting the third brush slightly in the opposite direction to the rotation of the armature. Shifting the third brush in the direction of rotation of the armature increases the charg- ing current. Whenever the third brush is moved in either *For detailed explanation see Consoliver and Mitchell's Automotive Ignition Systems, published by McGraw-Hill Book Co., New York. 178 GASOLINE AUTOMOBILES direction, care should be taken that it makes good contact with the commutator. If the contact is not good, the brush will seat imperfectly and the charging current will increase only when the brush seats properly after wearing into place. Eecent practice in automobile engineering tends to the simplification of starting and lighting systems and for this reason the third brush method of regulating charging current is superseding most other, more complicated methods. In case the battery is disconnected, as for example, when taken out for recharging, and the automobile is operated with another source of current, precaution must be taken that the generator does not "build up" voltage which would damage the winding of the armature. One way to accomplish this is to "ground" the main generator terminal by attaching it firmly to a clean surface on the automobile frame. Another way is to remove the shunt field fuse (Fig. 154). Since one terminal of a storage-battery is always grounded, a dangerously large current would be taken from the battery if by accident or deterioration of materials the insulation should be removed from wires which are near enough to the engine or to the automobile frame to touch either of them. For protection from this danger in the Delco system there is a vibrating circuit breaker in the main wiring system next to the ammeter. This circuit breaker prevents excessive current in the same way as when fuses are used ; but with the advan- tage that after the cause of the excessive current has been removed, the apparatus goes automatically into normal operation again. It is not needed for the wiring of the ignition system as the safety resistance coil or similar device on the induction coil prevents excessive ignition current, but the wires for the lights and horn have no protective device except this main circuit breaker. Whenever an excessive cur- rent flows through . the circuit breaker, it opens the circuit intermittently, causing a clicking sound. This circuit breaker can be operated by hand by pressing on a small flat disk on the back of the switchboard between the ammeter and the ignition switch. ELECTRIC STARTERS 179 North East System. In the North East system shown in Fig. 155 the starting motor and electric generator are a single unit, with only one armature, one commutator, and one set of windings on the field magnets. In this system the third brush is set on the commutator in such a position that it can be adjusted by turning the screw in the end cap or cover over the brushes. The starter-generator is mounted at the left- hand side of the engine, and is connected to the engine crank Igm Starting 'Snitch ancf Reverse Current Cuf- out J Lighting and Ignition Horn Button Switch FIG. 155. North East Starting and Lighting System. shaft by a chain drive. The generator is driven by a ratchet or over-running clutch. When the engine speed is 350 revolutions per minute or over, the starter-generator changes automatically into a gen- erator and supplies current for charging the battery as well as for the lighting and ignition. A typical two-unit system which has a starting motor and a generator, each as separate units, is shown diagrammatically in Fig. 156. This system as applied to a Ford automobile is shown in more detail in Fig. 156A. The Westinghouse system shown in Fig. 157 has two units, and many of the Delco starting and lighting systems have this arrangement. 180 GASOLINE AUTOMOBILES Westinghouse Starting and Lighting System. Some recent Westinghouse designs use the usual third brush method of regulating the amount of current going through the battery FIG. 156. Diagram of Two-unit Electric Starting System. for charging. A method of current regulation by automatic voltage control is applied in the Westinghouse design shown in Fig. 157. The device used is near the center of the figure and Generator ...... . -- Blue- Commut/rfar W/ra -to No. I Terminal Ground -to Housfnq-' / .- ted " " "M>.2 " l/f ;' .-Hue "NbJ - : ' sGrttn ttn " " "Mo.4 -Magneto Contact . . Ammetar or Otarginglndicator Coil Terminal ...Stltcfive Snitch ..-Horn 'Ho. 6 Grey > > Headlight Fie. 156-A. Liberty Starting and Lighting System for Ford Automobile. is marked "regulator and cut-out." This kind of constant voltage mechanism is much more expensive to construct than the third brush device, and is therefore not so much used. ELECTRIC STARTERS 181 When the electric generator is driven at a speed which is too low to give the required voltage for charging the battery the regulator contacts shown in the figure are closed; but they are opened when the speed is sufficient to produce cur- rent at the charging voltage of the battery. When, however, 182 GASOLINE AUTOMOBILES the voltage and current tend to exceed the established rate the magnetic pull of the electromagnets under the contact arm is increased and pulls open the contact points. The effect of this opening of the contacts is to put additional resistance into the circuit supplying current to the electromagnets (field magnets) 011 the generator, with a resulting drop in voltage and current so that the magnetic pull of the electromagnets under the contact arm is immediately decreased so that the contacts close again. This opening and closing of the contacts is so rapid that the voltage and current are held constant. The maximum charging current can be increased by turning the regulating adjusting screw on top of the contact arm so as to increase the tension of the spring on the contact points. The charging current in the apparatus should not exceed twelve amperes. The Westinghouse system shown in Fig. 157 has a Bendix drive on the starting motor ; but this system is sometimes made with an electromagnetic gear shift on the starting motor (see page 173). Large electric head lights require a great deal of current. Unless the storage battery is fully charged the requirements of lighted head lights for electric current will reduce the battery capacity so that there will be little reserve power for running an electric starter, especially in cold weather when the starter requires a large amount of current. It is a good idea, therefore, to turn off the head lights if there is likelihood of difficulty in starting the engine. On many automobiles there is a device for "dimming" the electric head lights which reduces the amount of light by passing the electric current through a high-resistance coil. As this device is used there are two electric switches controlling the lights. One of these is for the circuit including the "dimming" resistance; the other for the "undimmed" lights. The dim lights are intended for use when the automobile is standing or when passing other automobiles if the bright lights are objectionable because of glare. The best way to use switches of this kind is to close the "dimming'* switch ELECTRIC STARTERS 183 whenever the switch on the circuit for bright lights is closed. It is then a very simple matter in passing other automobiles to open quickly the switch for bright lights and the electric current will continue to go through the lights of the " dim- ming" circuit. The other way of using these switches is very ojectionable : that is, by opening the switch for bright lights and then closing the switch for "dimming." This method leaves a short interval when the head lights give no light at all. There is a further advantage of having the "dimming" switch closed whenever the head lights are used, as it is not very likely that one will then leave an automobile standing without lighted head lights. There is a small elec- trical loss in the use of a high-resistance "dimming" device of this kind; but practically all this loss is eliminated when the two switches are used together as explained, because then very little electric current goes through the "dimming" resistance. It is a good idea for owners of automobiles to study the wiring diagrams of their automobiles and to trace from time to time the current from the battery through each light, through the ignition system, through the horn, and through every other electrical device used on the automobile, including the generator and starting motor. It is also a good practice for the owner to carry the wiring diagram of his automobile when touring so as to give information and assistance to inexperienced garage men. CHAPTER VIII CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS Any kind of gasoline engine suitable for automobiles has the disadvantage of not being able to start when loaded or to draw any considerable load at very low speed. Inter- mediary devices called clutches for starting and speed-change gears or transmission gears for speed changes are therefore necessary to make the engine adaptable for general road service. In this respect a gasoline engine is unlike a steam engine which is adaptable for such service without these inter- mediary devices. When a steam engine is started, full boiler pressure can be immediately effective behind the engine piston with maximum available force. The same condition exists for the use of this kind of engine at very slow speed. In fact a steam engine of good design will usually have slightly more tractive pull at slow speed than at high. The steam engine is also self-starting without auxiliary devices. In spite of these disadvantages in starting and slow-speed power, the gasoline engine has so many other advantages especially as regards simplicity of operation and fool-proof construction, that it has almost "universal" application in automobile service. Clutches. A gasoline automobile engine must be set in motion before it can take up its load, so that a device must be provided to detach it from the rest of the automobile mechanism in order to get it started, and such a starting device must be arranged so that after the engine is started, it will permit gradually applying the driving load of the automobile mechanism. A device for this purpose is called a clutch. There are two general types: (1) the cone clutch, and (2) the disk clutch. Both types depend for their action 184 CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 185 on the friction of relatively large surfaces. Ideal friction materials for this service must permit some slipping so as to permit gradually increasing speed. The friction materials most used are asbestos fabric or leather for one surface and cast iron for the other. Dry leather is a good material but when wet or greasy, its frictional FIG. 158. Cone Clutch Engaged. Fie. 159. Cone Clutch Disengaged. value is cut in half. Cork on cast iron is also sometimes used. It is not much affected by water or oil as to friction value. Cone Clutches. A typical cone clutch is shown in Figs. 158 and 159 in its closed and open positions. It consists in essential parts of a fabric covered metal cone C which can be held tightly by springs against the inside of the iron fly- wheel F on the engine shaft. The cone C is mounted on a 186 GASOLINE AUTOMOBILES sleeve or hub M which is arranged to slide back and forth on the shaft S so as to engage or disengage the cone from the flywheel. At the rear end of the sleeve M is a ring R connecting the clutch with the clutch foot pedal P which is located in the automobile in front of the steering column. The operation of releasing the clutch from the flywheel is as follows : Pressure on the clutch foot pedal P is transmitted by a connecting lever L to the yoke T fitted around the top of the ring R. By this movement the cone C is pulled away from the flywheel F against the tension of the springs T, T. Clutch Disc Drum FIG. 160. Diagram of Disk Clutch. When pressure on the clutch foot pedal is removed, the lever and yoke fall back into their original position and the springs T, T, by their tension hold the cone C and the flywheel in close engagement so that they turn together and transmit the engine power; usually, however, through intermediary gears a^id shafts, to the rear axle of the 'automobile. Multiple Disk Clutches. A section through a disk clutch or what is commonly called a multiple disk clutch, is shown in Pig. 160. In essential parts it consists of a series of alternate driving and driven disks. The driving disks A, A, receive the power from the flywheel F on the engine shaft by the bolts 0, 0. In this type of clutch the driving disks CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 187 are thin steel plates, fastened together by bolts. The driven disks, B, B, consist of plates sometimes with holes in them into which pieces of cork are pressed. In the position for transmitting power the tension of the clutch spring T holds the driving disks A, A, and driven disks B, B, in close contact. Pressure on the clutch foot pedal compresses the clutch spring T so that the two sets of disks separate, and the driving disks gradually come to rest and stop the automobile. The driving plates of disk clutches, also, are often thin disks faced with molded asbestos fabric, which has been /^ / ^x^^ -\ > : RRK FIG. 161. Multiple Disk Cluteh. treated with linseed oil and baked, and the driven disks are plain steel plates. A modification of this diagrammatic arrangement is shown in Fig. 161 in which the driving disks are connected to the drum D on the flywheel by sliding projections P, P, P, fitting loosely into grooves or slots G, G, G. The holding power of a disk type of clutch is the sum of the holding powers of the several disks. Therefore, by increasing the number of disks, the holding power of the clutch is increased. The advantage of this type over the cone clutch is that a very large total frictional surface can be obtained with the use of comparatively small diameters of the parts. 188 GASOLINE AUTOMOBILES The type of disk clutch described is intended for dry f ric- tional surfaces. Some clutches of this type are made to operate in a bath of oil, so that in their disengaged position the surfaces of the disks are partly covered with oil. When the clutch foot-pedal is released and the springs pull the disks together, the coating of oil on the frictional surfaces is gradu- ally squeezed out. The oil bath makes possible a very gradual engagement of one set of disks on the other so as to avoid jerky clutch operation. Speed-change Gear Sets. Transmissions. When an auto- mobile engine has just been started and the clutch has been released, the engine must be run relatively fast and the auto- FIG. 162. Leverage of Gearing. mobile slowly to avoid 4 'stalling." Gradually the speed of the automobile should be increased to get efficient, quiet operation. Such speed changes suggest the use of gears. Some may have difficulty in understanding the underlying principle of gearing, so that a practical illustration in simplest terms will be explained. Fig. 162 shows two gear wheels A and B meshed so that the teeth of one are between the teeth of the other. Obviously in this position they must turn together. Every time a tooth on the driving gear B advances by rotation on its shaft the width of one tooth, the driven gear A in contact with it will also advance one tooth. If both gears have the same number of teeth they will turn at the same speed. On the other hand, if the driving (smaller) CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 180 gear has ten teeth and the driven gear has sixty teeth, the driving gear will make six (60-^-10) times as many revolu- tions as the driven (larger) gear. The above explanation applies only to the principle of speed changes, but force or "power" changes with gears in automobile operation are equally important. A portion of each of the gears in Fig. 162 is drawn with shading to explain the force changes occurring with speed changes. When driving an automobile, one changes to the slowly moving gears ("low gear") to get larger forces at the wheel for heavy pulling. In this "gear change" the engine continues to give the same horsepower as before, but the forces are different. These forces and speed changes may be explained by comparison with a lever as in Fig. 163. The ratio of the lengths of the FIG. 163. Example of Leverage. lever arms on each side of the point of support F is six; (6-^1) so that with a load of ten pounds at the right-hand end, the smallest amount of load in excess of sixty pounds will overbalance the right-hand end and in the resulting move- ment this end will move six times as far as the left-hand end. The ratio of movement (or speed) is therefore, the exact opposite (inverse) of the ratio of weights. Similarly, a gear rotating one-sixth as fast as its driver has six times as much turning force at its shaft. In other words, if the gear in Fig. 162 with radius R^^ is six times as large as the one with radius R 2 , it turns only one-sixth as fast, but has six times as much turning, pulling or pushing force at its shaft.* * This idea of increased tractive pulling power at low speed over that at high must not be confused with the previous statement that gasoline automobile engines have very little power at very low speed? as shown by the "stalling." Very low speed in this Connection mean* 190 GASOLINE AUTOMOBILES There are three general types of speed-change gear sets: (1) Selective sliding gears, which are arranged so that any of the speeds can be selected at will. (2) Progressive sliding gears, which do not permit selection of speeds at random, but the speed changes must be in a definite order or in succession, that is, one cannot for a three-speed gear move the gear shifting lever out of the position for high speed, put it into "neutral" position, and then immediately into the low-speed position. When using this kind of speed-change gears, it is necessary to actually put in contact the gears of the inter- mediate speed before low-speed gears can be put together. (3) Planetary gears, which are a combination of a clutch and a simplified sliding gear set. The first and third arrange- ments are most used. Selective Sliding Gear Type. Fig. 164 shows, somewhat simplified as to details, a speed-change gear set of the selective FIG. 164. Direct Drive on Selective Sliding Gears. FiQ. 165. Low-speed Gearing. kind arranged for sliding operation. Two shafts 8 and T are shown in this figure. The left-hand end of the shaft 8 is rigidly connected to the clutch and therefore rotates normally at engine speed. This shaft as shown here is not continuous but is really two separate shafts which meet end to end and are coupled together. The two shafts can be separated as shown by dotted lines in Fig. 165. When the shaft 8 Z is coupled to Sj, as in Fig. 164, both shafts will rotate at engine that the power strokes, although powerful, are so far apart that there is not sufficient carrying power from one power stroke to the next, and as a result the engine stops. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 191 speed. This is called direct drive or high speed. In either position of S 2 , however, the gear wheel A on ^ x is meshed with the gear wheel B, which moves the shaft T. When the automobile is to be operated at lowest speed, the gear wheels A, B, C, and D are used. Since the gear wheel B is always in mesh with the gear wheel A on the shaft $! the shaft T is always rotating when the engine is running. On the shaft S 2 is a gear wheel D which is free to slide on its shaft. When the shafts Si and 8 2 are discon- nected, if by some method or device the gear wheel D is made to slide into contact or mesh with the gear wheel C opposite on the shaft T, the shaft S 2 will be driven through the four gear wheels A, B, C, D. The engine shaft S^ will then rotate much faster than the shaft S 2 . Difference in the sizes of the gear wheels makes this speed change. Suppose A has half as many teeth as B, and that C has half as many as D. Then the shaft T will rotate half as fast as 8 t ; and the shaft S 2 will rotate half as fast as T, or one-fourth as fast as S lt which is a satisfactory speed reduction for low-speed gears as actually used in automobiles.* An intermediate speed between direct drive (engine speed) and low speed can be obtained very simply by providing, in addition, a sliding gear wheel E on the shaft T and a stationary gear wheel F on the shaft S 2 . When E and F are meshed and C and D are out of mesh, the shaft T will rotate at half the speed of the shaft S l ; and if E and F have the same number of teeth, the shaft 8 2 will rotate also at half the speed of 8^ For reverse speed, the gearing arrangement is shown diagrammatically in Fig 166. An auxiliary gear wheel R on a short shaft U is made to mesh with another sliding gear wheel K on the shaft T. This is not a practical case, but in a simple way shows the principle. The directions of rota- tion of the shafts 8 lf T, U and S 2 are shown clearly by arrows in the figure. As the gears were arranged in Figs. 164 and * Sliding speed -change gears are really only a modification of the back-gearing used commonly on lathes of various kinds. 192 GASOLINE AUTOMOBILES 165 the shaft S 2 was driven anticlockwise in the same direc- tion as $!, while its rotation in Fig. 166 for reverse speed is clockwise, which gives a backward or reverse movement of the automobile. Fig. 167 shows a commercial design of sliding speed-change gears somewhat differently arranged, and provision is made for mechanically shifting the gears by the use of a hand operating lever L, shown attached to a joint / at the top of the gear case. The letters in this figure correspond to those used in Figs. 164, 165, and 166. In the operation of shifting gears, the lever L moves back and forth so that the short lever or "finger" F engages with the shifting forks or yokes H and J. One of these controls the low speed, and the other K. FIG. 166. Reverse Gearing. the intermediate speed and the high-speed gears. In order to move the one or the other of the shifting forks or yokes H or J the lever L can be moved back and forth through the top of the gear box by swinging on the joint /. The operator of the automobile . can pass directly from any set of gears to any other ; that is, he can select any gear desired. For this reason this arrangement is called the selective type to distinguish it from the progressive type which was once commonly used on automobiles, but is now only used on motor- cycles. The important advantages of selective speed-change gears ire that the gears can be shifted rapidly and the gear teeth are less likely to be broken off or "stripped" than in the progressive type. Selective gears are also more compact, CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 193 making possible shorter and therefore, stiffer shafts in the gear box. These descriptions of sliding gear sets have referred to _..... Main Shaft- -5 Z Jo Axle Drive Shaft- '-Drive End ^!:;* Lai/Shaft- ^ForLowSpeed 'Forlni-ermedicrhe Speed FIG. 167. Typical Speed-Change Gears or Transmission. three speeds ahead and one reverse. Some sets, however, particularly those intended for very high speed automobiles Neutral Gear Position Fig. 168. Gear Wheels A and B connected. are supplied with gears giving four speeds ahead. The fourth speed is sometimes arranged to drive the axle drive shaft corresponding to 8 2 in the preceding figures faster than the 194 GASOLINE A UTOMOBILES engine shaft 8 lf and the third speed is direct drive at engine speed. There are some automobiles especially when designed for continuously high-speed operation which have the third speed on gears and get the fourth on direct drive. It seems to be the best practice, however, to get the fourth speed by Low Gear Position FIG. 169. Gear Wheels A, B, C, and D Connected. the suitable use of gears and have the direct drive on the third speed. All gear drives are more noisy than direct drive so that most operators prefer direct drive on the speed they intend to use most. Intermediate Gear Position FIG. 170. Gear Wheels 'A, B, E, and F Connected. The teeth of sliding gears are not made with "square" or right-angle corners as in ordinary gears, but the ends of the teeth are rounded so that they will readily fit into each other when they are to be meshed. Figs. 168-171 show the gear positions for three speeds ahead CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 195 and neutral in a typical selective sliding gear set. In the neutral position shown in the first of the figures, the gears A and B are the only ones meshed and the axle drive shaft $ 2 or the "main drive shaft" is idle. High Gear Position Fie. 171. Shafts 8t and 8, Connected. Shifting 1 Lever for Speed-change Gears. Fig. 172 shows the positions of the shifting lever on the speed-change gears or the transmission as operated on automobiles with the Reve termediate FIG. 172. Usual Type of Gear Shifting Lever. usual type of selective sliding gears as shown in Figs. 167 and 168. The usual position of the shifting lever and speed- change gears with respect to the engine is shown in Fig. 173. Dodge Automobile Speed-change Gears. In the speed- change gears described the method of continuously driving 196 GASOLINE AUTOMOBILES the counter shaft S 2 has been used, and this is the general practice. A notable exception is in the Dodge automobile Detachable CylimkrHead Exhaust Hani fold Univtrsal Joint .- Transmission Countershaft Ctu ** FIG. 173. Automobile Engine and Speed-change Gears. Direct Drive -. Flywheel" Spring Plates i Emergency Brake Levtr ' ' - tr+ - Speed Change Layer Ma in Shaft- UniYtrsatJoi'rrf DriveSftaft Countershaft StirftGear Drive 6ear FIG. 174. Dodge Speed-change Gears or Transmission. in which the counter shaft as shown in Fig. 174, is put out of engagement with its gear connections when the connection is CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 197 made for direct drive. Fig. 175 shows the shifting lever for the speed-change gears on this type of automobile. VVIntermediate R FIG. 175. Gear-shifting Lever on Dodge Automobiles. Planetary Gear Transmission. In distinction from the sliding-gear types described there is another important kind of speed-change gears which is not shifted in or out of mesh for the different speeds ; but is always in mesh. This kind Jup/f'or Venus Mars- Earth FIG. 176. Planetary Gear Wheels. is called a planetary gear or planetary transmission, because of a fancied resemblance of the movements of its small and large gear wheels to the revolution of the planets around the sun (Fig. 176). This device is complicated when all its parts are assembled so that a description will first be given of a relatively simple 198 GASOLINE AUTOMOBILES example of planetary gears as sometimes used on machinery for reversing the direction of rotation of a shaft. Fig. 177 shows a diagram of such gears. The central gear wheel G is attached to the engine crank shaft S, over which is loosely fitted a hollow shaft K. A larger gear wheel / with teeth inside the rim is firmly attached to the shaft K. Either shaft may be moved independently of the other the shaft 8 may turn in one direction and the shaft K in the reverse direction ; or they may rotate at different speeds. The central gear wheel G meshes with the four small gear wheels marked y which BandBrake a FIG. 177. Simple Planetary Transmission. are supported on the four small pins marked P, which are fastened to the flat surface of the disk-plate D. A circular band a (like a brake band) which is shown heavily shaded in the figure can be tightened by pulling on the rod R, usually by means of a foot pedal. When this band is tightened, it grips the disk plate D and prevents it from turning, and the four pins marked P are held stationary. As a result the four small gears marked g, rotate on the ''internal" teeth of the large gear wheel / and turn it in the opposite direction to the rotation of the gear wheel G, attached to the shaft 8. The gear wheel 7 when thus rotated turns the hollow shaft K in the opposite or reverse direction to the rotation of the CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 199 shaft 8. If the diameter of the gear wheel G is one-half the diameter of the gear wheel / the shaft K will rotate at half the speed of 8. Thus it will be seen this set of planetary gears not only gives reversed direction but also speed reduction. Ford Planetary Speed-change Gears. An assembled view of the speed-change gears of the planetary transmission used in Ford automobiles is shown in Fig. 178, and the respective Flywheel-... Triple. Gear'" Triple 6eaf Pin-D Driven Gear Slow Speed Gear Reverse Gear-- Reverse Drum f Clutch Discs I (Clutch Disc Drum ,..- Clutch Disc Push ffing fIufc/7 Springs -Clutch Shift ._Dr/ver Gear Transmission \ Shaft ' Brake Drum FIG. 178. Ford Planetary Transmission. parts are shown disconnected in Fig. 179. The engine fly- wheel F is rigidly attached to the engine crank shaft C. Three steel pins D are fastened to the flywheel. A gear wheel with three sets of teeth E, F, G is fitted loosely so that it can turn on each of these pins. Another gear wheel K fits over the crank shaft C and meshes with the "E" teeth of each of the gears on the pins D. The number of teeth on K is the same as on E. There is, therefore, no speed change through these gears, as, all move with the same number of revolutions. The gear K is attached to the hollow shaft N 200 GASOLINE AUTOMOBILES which fits over the crank shaft C. Another hollow shaft which fits over the shaft N is made with a gear wheel L which meshes with the "F" teeth of the gears on the pins D. A gear wheel M fits loosely on the hollow shaft and meshes with the "G" teeth of the gears on the pins D. There are fewer teeth on L than on F, so that the gear wheel L has more revolutions or turns faster than the gear wheels on the pins D. On the other hand there are more teeth on M than Triple Gear. Driven 'Gear^ Reverse Drum and dear.. F/ytvheef- FiG. 179. Ford Planetary Transmission Disconnected. *rakeDrurrr ShwSpsed Drum and6ear on G, so that the gear wheel M turns slower than the gears on D. The gear wheel K is attached to the hollow shaft N which turns with it, as well as also the disk T. Likewise the gear wheel L is on the shaft attached to the drum 8, and the gear wheel M is attached to the disk R. The hollow shaft N with its attached gear wheel K and disk T moves freely on the crank shaft C. Similarly the hollow shaft with its attached gear wheel L and disk 8 moves freely on the shaft N. The gear wheel M with its attached disk R moves freely on the shaft 0, when all parts are assembled as shown in Fig. 178. The irregular disk V, however, is rigidly fastened to the crank shaft C to which are attached the alternate plates of a mul- tiple disk clutch. The other set of plates of this clutch is fastened to the disk T which in turn is bolted to the rear axle drive shaft. Brake bands are arranged to fit over the outside surface CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 201 (circumference) of the disks T, S, and R. When these brake bands are loose, the gear wheels on the pins D drive the disks T, S, and R at different speeds, proportional to the number of teeth on the engaged gears. High-speed drive is simplest to explain, as all the brake bands are loose. The multiple-disk clutch is engaged by pushing the clutch hand lever forward. The clutch plates on the irregular disk V attached to the crank shaft engage with the clutch plates on the disk T, which is permanently fastened to the axle drive shaft. Engaging the clutch plates makes, therefore, a direct drive between the engine crank shaft C and the axle drive shaft. The entire planetary mechanism is locked together and turns at the same speed and in the same direction as the engine crank shaft. Low-speed drive is obtained by tightening the brake band on the disk S by pushing the clutch foot pedal forward. Then the disk 8 and the attached gear wheel L (on the hollow shaft 0) are held stationary. But since gear wheel L is meshed with the "F" teeth of the gears on the pins D, the rotation of the flywheel will make these gears rotate on the pins. Because of the smaller number of teeth on L than on F the gears on the pins D will not make as many revolutions as the flywheel, actually they turn at almost exactly two- thirds the engine speed, and in the same direction as the flywheel. In practical effect, this means that with respect to the rotation of the flywheel, the gears on the pins D have turned backward one-third of a revolution during each revolu- tion of the flywheel. The "E" teeth on these gears are meshed with the gear wheel K and both have the same number of teeth. Turning back the "F" and "E" teeth one-third of a revolution, as explained, turns the gear wheel K the same part of a revolution ahead, with respect to the rotation of the flywheel. It is a general principle that the teeth on any two meshing gear wheels move in opposite directions. In every revolution of the flywheel, therefore, the gear K will move about one-third as fast as the flywheel and in the same direction. The axle drive shaft will also be driven at about 202 GASOLINE AUTOMOBILES one-third engine speed and in the same direction, because the gear wheel K is fastened to the hollow shaft N on the clutch disk T which moves the axle drive shaft, the same as in direct drive. Reverse drive is obtained by tightening the brake band on the disk R, by pushing the reverse foot pedal forward. At the same time the hand lever must be in middle position or the clutch pedal pressed down to release the clutch. The disk R and the attached gear wheel M are then held stationary. The gear wheel M is meshed with the "G" teeth of the gears on the pins D, but the number of teeth meshed on the pins D is now less than on the connected gear wheel. With this gear arrangement the teeth "G" are turned through about one and a quarter revolutions for each revolution of the flywheel, which means that the teeth "G" and also the teeth "E" are moved ahead of the flywheel one-quarter of a revolu- tion for each revolution of the flywheel. Since the number of teeth on E and K is the same, the net result of these gear movements is that the gear wheel K with its attached shaft N, the clutch disk T, and the axle drive shaft are driven at about one-fourth the engine speed in the opposite or reverse direction to the engine rotation. This device gives only two forward speeds (low-speed and high-speed) and reverse, and is considered suitable only for use on light automobiles like those of the Ford make. The brake on this kind of transmission is a band on the brake drum (Fig. 178) on the outside of the end driving plate. The foot pedal is in the position nearest the driver's seat. Summary. The Ford planetary transmission is operated by the back and forth movement of a foot pedal. For slow- speed operation the foot pedal is in the position farthest from the driver's seat, when the gripping strap is on the middle drum and holds it stationary. This makes the triple gears rotate on their shafts as the flywheel rotates. This rotation of the gears drives the gear K (Fig. 179) and with it the drive shaft slowly forward, because of the difference in the size of the gears. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 203 For reverse operation the reverse foot pedal is pushed to its extreme position toward the engine and the end drum R is gripped. This makes the triple gears rotate on their shafts as the flywheel rotates, but since the reverse gear is larger than the driven gear, the motion of the triple gears drives the gear K slowly backward. For high speed the foot pedal is in its back position and the whole mechanism is gripped together and rotates at the speed of the engine. Steering Gears and Front Axles. Practically all auto- mobiles are steered or given direction by some means of turn- FlQ. 180. Steering Column. ing the front wheels without turning the whole front axle. Steering is done by a steering wheel, attached to a steering column (Fig. 180), which transmits the movement of the wheel through a screw or worm gear to a system of levers and rods as shown (Fig. 182) to the steering knuckles K, one sup- porting each front wheel. Each front wheel is attached to the knuckle spindle (Fig. 181) supported on roller or ball bear- ings. At the lower end of the steering column is the arm L 204 GASOLINE AUTOMOBILES (Fig. 182)'. From this arm, motion is transmitted to the short arm K on the steering knuckle by means of the drag link D which moves directly the front wheel of the automobile on w FIG. 181. Steering Knuckle. the driver's side. The other wheel is moved by the tie rod R (sometimes called transverse drag link). The steering knuckles are fastened to the front axle by hinged connections FlG. 182. Steering Gear and Front Axle. on king bolts, so that the front wheels are free to swing through nearly a quarter circle about the king bolt as a center. This gives the wheels the necessary turning movement in steering. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 205 Fig. 180 shows the essential parts of a typical well-made steering gear. Inside the steering column is the steering tube; the upper end is connected to the steering wheel H and the lower end to a worm gear W. When the steering wheel is turned it moves the steering tube and the worm gear at its end in the same direction. The gear segment G meshing with the worm gear turns the attached arm L (Fig. 182) or steering lever so that it pulls or pushes on the drag link D, and indirectly on the tie-rod R. The drag link and the tie-rod move the steering knuckles on the front wheels. A worm gear is an ideal device for steering gears as it is non-reversible. While the slightest movement of the steering wheel is readily transmitted by this device to the front wheels, the up and down movement and jarring of the front wheels on rough roads cannot appreciably jar or turn the steering wheel. Inside the steering tube are (1) the tnrottle rod B, going to the carbureter and (2) the spark control rod A con- nected to the ''timer" which is the device for regulating the time of ignition in the engine cylinders. These two rods within the rim of the steering wheel are turned by the levers T and 8. The spark lever S is attached to the rod A at the center of the column and operates the small short rod A at the lower end. The throttle lever T is attached to the tube B and operates the short tube B. A foot lever, called an accel- erator, is connected in most automobiles to the rods between the short tube B on the steering column and the short lever on the throttle valve of the carbureter. The front axle of an automobile, unlike in an ordinary wagon, is fastened by means of the springs to the frame of the automobile and does not turn. The front wheels are not parallel, but foregather slightly so that if the lines of the wheels are projected forward far enough, they would meet and make a pointed effect, like the bow of a boat. The effect of this foregathering is to bring a slight but constant pressure upon both wheels and makes them less likely to swerve through contact with road unevenness. Also the wheels undergather, called camber, so that the load is thus brought over the center 206 GASOLINE AUTOMOBILES of support of each knuckle so as to minimize the bending stresses, as shown in Fig. 181. This deviation of the wheels produces a slight wear on the tires, but is more than com- pensated by the advantages. If the tie rod or the front axle should be accidentally bent so that the foregather is increased, there would be excessive wear of tires. Bear Axles. The front and rear axles together support the weight of the automobile. The front axle with its steer- ing gear and links serves for steering, and the rear axle with its gears transmit the power of the engine to the wheels. When the axle is stationary and is held firmly in place like in a horse-drawn wagon, an automobile trailer, or some kinds of trucks with chain drives, there is no special mechanism necessary on the rear axles as the wheels are free to turn on the ends of the axles. Such axles are called "dead" axles. With this kind of wheel equipment there is no difficulty in going around turns as each wheel is adjustable to its own speed. In modern automobiles, however, the two rear wheels are rigidly fastened to the rear axle which is set in bearings so that it can rotate with the wheels. Such a wheel and axle arrangement is called a "live" axle. If this axle were made continuous, in one piece, the wheels could only move together and with the axle, so that in going around a sharp curve, if the wheel on the outside of the curve moved normally, the one on the inside would have to move at the same speed on account of their connection together and must therefore slip on the ground. At every turn in the road there would be some slipping, and at every sharp turn there would be very much slipping with excessive wear on tires. Besides the automobile would not steer easily when making turns. It would be something like running an automobile with a brake set on only one wheel. On account of these difficulties it is obvious that some device must be used to make possible separate and independent movement of the two rear wheels and still permit the rigid fastening of the wheels to the axle so that it can be used to transmit the driving power of the engine to the wheels. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 207 Differential Gears. Gears for driving a divided rear axle are shown enlarged in Fig. 183. At the end of the axle drive shaft 8 is a pair of bevel gears* B and C, one of these gears (<7), meshes with the side of the larger gear (B). Two other gears D and E are firmly attached respectively to the axles A t and A 2 and these in turn are attached to the wheels. An inter- FiG. 183. Simple Example of Differential Gears. mediate bevel gear on the shafts connecting D and E, is sup- ported on the frame F. If, now, each of the axles A l and A 2 offers the same resistance to turning, both will rotate at the same speed. If, again, the automobile is making a sharp turn to the right, so that the left-hand wheel has the longer distance to go, the right-hand wheel resists going as fast, and the intermediate bevel gears D and E will roll slightly on the bevel gear F which is on the short shaft s. The right-hand wheel will conse- quently turn at a slower speed. There is another interesting case to study. If the right- hand wheel is lifted from the ground as one does when changing tires, and the engine is started and put "into gear" * Bevel gears serve the same purpose as ordinary (spur) gear wheels. The teeth must be made on an angle instead of on the periphery so that they can mesh at an angle. 208 GASOLINE AUTOMOBILES so as to drive the rear axle and wheels, the right-hand wheel will spin around in lively fashion but the left-hand wheel on the ground will not move. This is exactly what happens when one rear wheel is in soft mud without chains on the tire (without resistance), and the other wheel is on firm ground. The slipping wheel will spin in the mud but the one on firm ground will not move. As rear axle differential gears are actually made there are usually three or four of the intermediate bevel gears like gear F, called the differential gears, and they are made much smaller relatively than those marked in Fig. 184. All Differential Gears Driving .Gears \ ^^ Axle Shaft No >J jSearffal Driven Gear ^ s^S^p^m^i... QearNo.2 \le Shaft Ho. FIG. 184. Differential Gears. of these gears are supported in a small, compact case which is built up as a part of the main casing or housing which is really included in one continuous axle and differential casing somewhat as shown in Fig. 185. The bevel gear on the end of the axle shaft is shown inside the main casing or housing which includes also the axle tubes. Inside the axle tubes are the bearings (roller or ball types) both for supporting the differential gearing and the axles. Extending from the differential housing toward the engine is a casing similar to that for the axles for the protection of the axle shaft, and in this casing are roller or ball bearings for supporting this shaft with minimum friction. Automobile axles that are to go into the bevel gears are usually made with square or else with ribbed ends CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 209 to slip into similarly shaped openings in the hubs of these gears. The method of attaching the wheel ends of the axles determines the type of axle construction. FlG. 185. Casing or Housing of Differential Gears, Kear Axle, and Roller Bearings. Fig. 186 shows very clearly the differential gears, differ- ential axle, axle shaft casings, roller bearings and wheel con- Fio. 186. Parts of Standard Type of Rear Axle Differential Gears. struction of a Ford rear axle. The small differential gears !, s 2 , s 3 , are very clearly shown. Types of Differential Drives. There are several approved methods of transferring the power from the axle drive shaft 210 GASOLINE AUTOMOBILES to the differential gears in the rear axle. Ordinary bevel, spiral-bevel, and worm gears are most used. Fig. 187 shows the standard type of ordinary bevel gear drive. Roller bearings are used for all bearing surfaces. Bevel gears always produce an end thrust, caused by the inclination of the teeth and this thrust tends to separate the gears; for this reason the conical roller bearings shown have an ad- vantage. If straight roller or ball bearings were used special thrust bearings would have to be provided. FIG. 187. Differential Gear Showing Boiler Bearings. In a spiral-bevel gear the teeth of both gear wheels are cut so as to be of the same spiral shape. A gear of this type with spiral cut teeth will give more even and more continuous driving power and overcome to some extent the larger thrust or ordinary bevel gears, as well as being stronger. Worm drives are used mostly for large and heavy trucks where there is a very large reduction of speed. Unless very carefully made the friction of such gears is excessive; and in any case, lubrication must be given careful attention. For this reason they are not much used on pleasure cars. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 211 Types of Rear Axles. There are two kinds of rear axles for vehicles in general. The so-called "dead" axle as used on wagons, trailers and for some chain drive trucks where the axle does not rotate has already been mentioned. The other kind of this general classification refers of course to those having a rotating "live" axle for transmitting power through gearing at the middle of the axle. Live axles are sub-divided into a further classification according to the method of construction, particularly as to the attachment and driving of the wheels, as follows: Simple live rear axle is well illustrated by the Ford rear axle shown in Fig. 188. It has two distinctive services : Q- T1 " FIG. 188. Simple Live Bear Axle (Ford Type). (1) to carry the weight of the rear of the car (on the axles), and (2) to transmit the power from the axle drive shaft to the wheels. The wheels are securely fastened to the axles. Because all the weight of the automobile, supported on the rear springs, is carried by the roller bearings shown directly on the "live" axles at the wheel a broken shaft is likely to let a wheel pull itself out of the wheel casing and let down one side of the automobile. This is a disadvantage, which is not, however, so serious for a light as for a heavy automobile. Semi-floating rear axles (Fig. 189) have the bearings at the wheels carried on an extension of the differential casing or housing. This type is an improvement over the simple live axle to the extent that the load is not put 212 GASOLINE AUTOMOBILES directly on the axle ; but there is in this type also the danger of a wheel running- off with a part of a broken axle and FIG. 189. Semi-floating Axle. letting down the automobile. The removal of stress on the axle in this type merely makes the axle a little less liable to break. FIG. 190. Three-quarter Floating Axle. Three-quarter floating rear axles differ from the semi- floating type essentially in the method of supporting the CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 213 weight at the wheel end of the axle. Fig. 190 shows details clearly as to supporting bearings. This type has the ad- vantage over the two types already explained in that all bending stress is removed from the axle and all the load at the wheel end of the axle is carried by the bearing located in the body of the wheel directly over the spokes. It has the disadvantage, however, of the other types mentioned in that if the axle breaks, the wheel may come off. This danger is fully prevented only in a so-called full-floating con- struction. Full-floating rear axles are made with double roller or double ball bearings on the wheel end of the axle (Figs. FIG. 191. Full-floating Axle. 191 and 192) which are made in such a way that the wheel will remain on the axle casing even if the axle should be broken. The shaft receives only the twisting stresses due to transmitting power to the wheels. Further, the shaft can be taken out of the shaft casing and replaced by merely taking off the wheel cap at the hub. At the wheel end the shaft is keyed into the hub cap. Another construction is to have the axle made with a squared or ribbed end to fit an opening of corresponding shape in the hub cap. Some- times the outer end of the shaft is made with a toothed or "jaw" clutch which fits into corresponding recesses in the hub cap. This latter construction permits a little "lost 214 GASOLINE AUTOMOBILES motion" at the point of axle attachment and relieves the shaft from possible distortion which might be caused by a bent axle casing. FIG. 192. Full-floating Axle. Universal Joints. The axle drive shaft cannot run straight from the change gear set (transmission) to the gears in the rear axle where the engine power is applied because the gears in the rear axle (differential) are at a much lower level. The engine shaft runs parallel to the frame of the car to the change gear set ; but from that point the driving shaft slopes downward toward the rear. Further, the change gear set is bolted firmly to the frame of the auto- mobile and the rear axle is free to move with the giving of the springs, making a rigidly constructed shaft between the change gear casing and the differential gears imprac- tical. The necessary (1) freedom of movement and (2) change of direction of the axle driving shaft are secured by the use of universal joints. A universal joint of typical shape is shown in Fig. 193. It consists of two forked members or yokes F^ and F 2 which are keyed or otherwise rigidly fastened to the shaft 8 t and S 2 to be joined flexibly. Between the forked members is bolted a block in shape somewhat resembling a Greek cross. In the ends of the arms of this cross are threaded CLUTCHES, TRANSMISSIONS, AND DIFFERENTIAL* 215 holes into which the pins P, P, P, P, are screwed to fasten the forked members to the arms of the cross. By this arrange- ment either fork with its attached rod can be made to swing like on a hinge around the pins fastening it to the cross. This kind of movement of the two forks make a joint which can be turned in any direction "universal" in direction. By the use of this device it is possible to bend a driving shaft in any direction, either momentarily or permanently, and use it for the efficient transmission of power. FIG. 193. Example of Universal Joint. It is also necessary to provide for the horizontal move- ment forward or backward of the rear axle. This is cared for by providing a slip joint on one of the shafts connected to a universal joint to move freely back and forth in a splined or squared hole in the yoke of the joint. It is the best practice to fit the axle drive shaft of an automobile with two universal joints, one at each end of this shaft. One reason for this is that if two shafts are connected to a universal joint, and the driving shaft rotates at a constant speed, the driven shaft will rotate at a rate which will be constant only if the two shafts lie in one straight line but will vary if they lie at an angle. This variation will fluctuate four times to a revolution, twice reaching a maximum and twice a minimum. The extent of this variation will be proportional to the angle between the shafts. If, however, the axis of the driving shaft and of the driven shaft are parallel, and the driving shaft and 216 GASOLINE AUTOMOBILES J ;he driven shaft are connected by an intermediate shaft fitted with a universal joint at each end, and if these joints be arranged with their adjacent yokes in the same plane, then the variations in speed of the first joint will be exactly neutralized by the similar variation of the second joint, and the axle drive shaft will rotate at a uniform speed. It is obvious that the tendency of a single universal joint is to give a jerky motion to the automobile, this jerky motion increasing with the angle through which the universal joint acts. Therefore, if properly installed, an axle driven shaft with two universal joints is always better than one with only one universal joint. Another reason for the use of two universal joints is that much greater range of action is permitted between the rear axle and the frame which carries the power plant and body. This allows the necessary freedom of movement of the rear axle when passing over uneven road surfaces, with- out producing excessive stresses which are unavoidable when only a single universal joint is used. This explains why the single- joint construction is not much used except in light- weight automobiles. Some automobiles of recent design have the engine set so that the shaft tilts downward towards the back. The axle drive shaft runs straight from the transmission to the normal position of the differential. This is said to be a straight-line drive. Fabric universal joints which have been adopted by several manufacturers are made by joining the ends of two shafts by means of circular fabric (cotton and rubber) disks. A forged steel spider having three arms is welded or otherwise fastened to the end of each shaft. The circular disks, usually three in number, are placed between the spiders. Each spider is independently bolted to the disks so that the arms of one come between the arms of the other, necessitating six holes in the disks. The arms are said to be "staggered." The "give and take" of the disks is said to be sufficient to supply the neces- CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 217 sary end motion. Advantages claimed for this type of joint are that it does not require lubrication and will not rattle. Torque members. Torque means twisting effort. A simple illustration of twisting effort and reaction is as follows: A person stands in a boat on water and twists a pole held on shore. The boat tips in the direction opposite to the twisting force. To produce the same twist on the shore end of the pole and keep the boat from tipping it can be supported to the shore or lake bottom. The condition is similar to the turning force of the drive shaft on the rear axle. The engine and body are supported on the frame which rests at the rear end on springs attached to the rear axle. The engine twists the drive shaft. The axle and wheels rest on the ground and the frame tips on the springs just as the boat tipped. For best results the frame and axle should be fastened together so that the frame cannot twist but can work up and down as the springs bend. It may be said that the springs will accomplish this and so they do to a certain extent. The sole use of springs to take up this twist is very common and will be spoken of later. The springs have their own particular work to do and may be made smaller if they are relieved of this additional strain by use of torque members, rods, or tubes, which prevent this twisting reaction. Radius Rods. In addition to the twisting stress there is another stress developed between the rear axle and frame due to the power transmitted to the rear wheels. This is the reaction of the axle to the driving force. This stress may be resisted by the springs or to relieve them, radius rods may be used. If the rear wheels of an automobile rested on rollers, free to turn, there would be no forward movement. If the wheels rest on something solid something that can "push back" the car is pushed ahead and the push comes through the axle to the frame of the car. One cannot row a boat unless the oar locks are fastened down. The oars push the row locks and the row locks push the boat. Just so the wheels push the axle and the axle pushes the car ahead or back. Rods transmitting the driving force and fastened to 218 GASOLINE AUTOMOBILES the frame, which pivot and allow the axle to move up and down on a radius are called radius rods. If the car has no torque members or radius rods it is said to employ the Hotclikiss metTiod of driving. This method has come into wide use. The springs and bolts connecting the automobile frame to the rear axle are necessarily stronger than when torque and radius rods are used. The entire stress of driving the car comes through the front ends of the rear springs. Brakes. Both the foot brake (service brake] and hand brake (emergency brake] usually act on brake drums attached to the rear wheels. Many cars are, however, now equipped with the hand brake acting on a drum on the drive shaft directly back of the transmission. This is called a trans- mission brake. The emergency brake is mainly used to hold the automobile at a standstill after it has been stopped. It should always be set when the car is not moving. Brake Drums. A rear axle is usually equipped with service and emergency brakes. Brake drums are made out of pressed steel and shaped like large round box covers from ten to fifteen inches in diameter and two or three inches deep. They are fastened rigidly to each rear wheel. Inside and outside of the edges of these drums are circular bands of steel faced or lined with asbestos fabric which has been treated with a compound and baked. These bands are arranged so they may be expanded or contracted to bind on the brake drum. They are operated by levers, and rods or wire cables which are moved by the foot pedal or hand lever. Equalizers. When either the brake pedal is depressed or the hand lever is pulled back, the corresponding band on the brake drum of each rear wheel is tightened. If, as is often the ease, a device is used to make each brake band grip the same as the other, that device is called the brake equalizer, sometimes brake differential. It may be only a simple lever like the whipple-tree of a wagon or it may consist of bevel gears. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 219 Adjustment of Brakes. A type of shaft or transmission brake operated by the hand lever has replaced one of the two sets of rear wheel brakes on many cars. Springs are combined with the brake band, as they are also in the case of rear wheel brakes, so that when the lever or pedal is released the band will separate itself from the brake drum an appreciable distance. Additional springs are supplied to hold the brake pedal and the hand lever in a non-engaged position. A ratchet is provided to hold the hand lever in an engaged position unless it is desired to release it. On all brakes there are provided means for tightening or adjusting the rods and bands. It is needless to emphasize that brakes should be kept in adjustment. In a released position it should be possible to insert a small saw blade or case knife blade between the brake band and drum all around. Too much opening interferes with the quick action of the brake. If the brake band rubs it will overheat and burn the asbestos facing. Brake adjusting screws should be kept oiled as well as all parts of the brake levers. Road water and water used in washing the car rusts the brake parts quickly and adjusting screws give considerable bother if they become rusty. Several foreign cars have adopted front wheel brakes which supplement the action of the rear wheel brakes, permitting a quicker stop. Operation of Brakes. Brakes should never be applied quickly when the car is moving at more than fifteen or twenty miles on a slippery road, level or down grade. If they are the car will skid or slide and cannot be steered. Accidents are continually happening due to this cause. Anti-skid tire chains offset the liability to danger from skidding, but are not an absolute preventive. The engine is a very effective brake when thrown into low or intermediate speed. If other brakes fail, or to help them out, shift the gears into low speed and let the clutch 220 GASOLINE AUTOMOBILES back, so that the engine is in gear. If more braking action is needed cut off the ignition. On a long hill do not use the foot brake continually. Long grades should be descended at a comparatively slow speed and the hand or emergency brake used alternately with the foot brake so that neither brake will become overheated. If one brake is used continually in going down a mountain road or a very long steep hill, or if the hill is descended at a high speed the brake will get so hot that the brake lining will be injured. Perhaps one of the greatest causes of brake failure is oil. The oil which gets on the brakes usually works through the rear axle housing from the differential gears. The owner may put too much oil in the differential and it travels along the inside of the axle tube. The oil works over the wheel bearing and into the brake drum. It will often be noticed that the oil collects mostly on the right-hand brake. This is because the crown on the road, and the ditch alongside which are used in passing other automobiles, tilt the automobile so that the right-hand wheel is lower than the left-hand wheel. Shock Absorbers. Shock absorbers slow up the movement of the springs. They operate on either one of two general principles ; ( 1 ) the springs are made stiffer by the addition of supplementary springs or (2) the movement of the springs is dampened by some friction or compressed air device. An automobile often rides smoothly on roads with good surfaces, yet when driven over rough roads at moderately high or high speeds it jounces the occupants around badly. If the shock absorbers only stiffen the springs the car will ride smoother on the rough roads but will ride harder on good roads. The simplest form of shock absorber is a small rubber bumper which is placed so as to come between the frame and the axle when the spring has been considerably compressed. A common type is a supplementary coil spring which only stiffens the car springs. This makes it possible to carry heavier loads and ride more comfortably over rough roads, yet the car will not have the same slow spring action on boule- vards. CLUTCHES, TRANSMISSIONS, AND DIFFERENTIALS 221 More efficient types are made to connect the axle and frame of the car with some friction or compressed-air device. With the compressed-air shock absorber an air-cylinder shock absorber and piston are connected, one with the frame and the other to the axle of the car. By regulating the escape of the compressed air the movement of the spring is slowed up as is necessary. A variation of this principle is the employment of oil instead of air. Another type employs the principle of two levers, one connected to the axle and the other to the frame of the car, turning on a friction pad. The friction between these levers may be varied. Still another type permits the axle to deflect towards the frame but in so doing winds up a strap which has to unwind before the spring comes back to normal. This last type is called a "snubber" shock absorber. Automatic Gear Shifts. Attempts have been made to eliminate the gear-shifting lever in order to simplify the driving of a car. One method, used on the Owen Magnetic automobile, only partially accomplishes this but is very dis- tinctive. On this car there are only two change-speed gears, one forward and one reverse. When the gear lever is placed in ' ' forward ' ' the different speed changes are made by simply moving a selector lever on the steering wheel. The changes in engine and car speed are not obtained by gears. All the power of the engine is converted into electric power and the car is driven by an electric motor mounted directly behind the engine and dynamo. This dynamo is what converts the engine power into electricity. Shifting the speed lever on the steer- ing wheel controls the speed of the driving motor by changing the brushes which supply current to it. The Sauer, a German automobile which has been imported into this country, has done away with the gear-shift lever. On this car there is a set of gears and the desired speed or combination of gears is chosen by a selecting mechanism in conjunction with the clutch pedal. The driver may set the selector lever at any time. Then when the clutch pedal is depressed the gears shift automatically into the combination 222 GASOLINE AUTOMOBILES selected. There is also a magnetic gear shift which American automobile engineers have used experimentally and have adopted on some automobiles. The gear set or transmission is retained, as with the Sauer, and the desired combination of gears is obtained by a selector lever on the steering wheel. CHAPTER IX LUBRICATION AND COOLING SYSTEMS Friction. There is always friction between any two sur- faces which rub or "bear" on each other. Of two sets of rubbing surfaces each of the same materials, the smoother set will obviously have the less friction. But even what we may call a smooth surface will appear, when looked at through a microscope, to be not at all smooth as it appears to the naked eye. Fig. 194 shows the relative roughness as seen through the microscope of two carefully polished plates of brass and of steel. There are a greater number PIG. 194. Surfaces of Brass and FIG. 195. Surfaces of Brass and Steel. Steel with Lubrication. of rough places in the steel than in the brass, yet some of the rough places will fit into each other, and the surfaces, especially if pressed together as they would be when weighted, will offer resistance to any sliding movement, tending to increase the roughness. Practically all the resistance to sliding can be removed, however, if such moving parts are separated by a film of engine oil as illustrated in Fig. 195. The oil acts as a sort of cushion and to a large extent prevents the fitting together of the rough places in the two surfaces. This figure gives an exaggerated idea of the fundamental principle of all methods of lubrication; and lubrication is successful only 223 224 GASOLINE AUTOMOBILES so long as a film of lubricating liquid is maintained between the polished surfaces bearing on each other. The oil film may be destroyed either (1) because no more oil can be supplied to the bearing surfaces; or (2) because the bearing surfaces are loaded too heavily and are pushed together with so much force that the oil film is broken and the conditions shown in Fig. 194 results. In either Case the removal of the oil film will make the surfaces wear away rapidly. Surfaces Requiring Friction. It is essential that the fric- tion of the various bearings in the engine, speed-change gears, axles, etc., be made small so as to waste as little as possible of the driving power. On the other hand there are parts of an automobile such as the brakes which should have no lubrication, or the friction clutch which in most types should also have none. The brakes, friction clutch, and the tires depend for their efficient action on large frictional resistance over relatively small areas. Oil in the Cylinders. Primarily, the tightly fitting cast-iron rings on the engine pistons are to prevent the explosive mixture admitted to the cylinders above the pistons from escaping downward past the pistons into the crank case. Inside the engine crank case of modern type engine oil is splashed and sprayed continuously so that on the up-stroke of each of the pistons the inside of the cylinder is wetted completely by the oil. On the down-stroke of the piston, practically all this oil should be swept down by the piston rings, leaving only a thin film on the cylinder walls for lubrication. If the engine oil used is too thin or the piston rings do not fit tightly enough, too much oil will accumulate on the cylinder walls and some of it will get into the explosion space at the top of the cylinder. This excessive oil will be only partly burned as it is not so combustible as gasoline and will make a black deposit of carbon on the inside of the cylinder, on the spark plugs, and on the valves. If this leakage of oil is in sufficient amount it will make a whitish exhaust smoke. Whatever LUBRICATION AND COOLING SYSTEMS 225 system is used for lubrication, one must be cautious to avoid getting too much oil past the piston rings to the top of the engine cylinder. If there is continual trouble with carbon deposits in engine cylinders, a little kerosene poured in through the priming cocks or through the holes for the spark plugs will loosen the carbon so that it will be discharged with the exhaust gases. Kerosene will not, however, prevent the formation of carbon and the treatment must be repeated once or twice a week. When the engine is running with the throttle valve of the carbureter nearly closed, there will be only a small amount of explosive mixture entering the cylinders and in consequence there is a decided vacuum on each intake stroke of the piston. This vacuum has a tendency to draw oil past the piston into the combustion chamber, where it burns and forms smoke. This is why, when an automobile is left standing with the engine running for any length of time, it will often be found to start away with clouds of smoke issuing from the exhaust. Kinds of Lubricants. Commonly used lubricants are either liquids, called oils; or semi-solids, called greases and semi-fluid oils. Oils are ordinarily used for the lubrication of all parts of the engine and its auxiliary parts included in the engine casing. Greases and semi-fluid oils are used for the speed-change gears, differential gears, axles, wheels, steering gear and springs. Some of the latter are lubricated in many of the latest designs with oil, especially for such parts like springs where only small amounts of oil or grease are needed. One reason for the more extended use of oil instead of grease is that grease is difficult to handle and the filling of grease cups or containers is "messy" work. Some dealers now sell grease in tablets to fit the standard sizes of grease cups. This method eliminates much of the objection to the use of grease for small bearings. Only mineral oils should be used for the oil supply of gasoline engine cylinders. A vegetable oil, castor oil, is 226 GASOLINE AUTOMOBILES generally used for the engines of racing automobiles and for aeroplane engines because of the very high temperature which it will withstand; but is unsuitable for ordinary automobile engines which operate at much lower cylinder temperatures, because it tends to produce an excessive amount of carbon in the cylinders and is besides expensive. Steam engine cylinder oil is not suitable, first, because it is as a rule too thick (too heavy "body") and if of ordinary power plant grade will not withstand the heat in the cylinders of gasoline automobile engines. It has its proper place for engine lubrication in steam automobiles. The ideal oil for gasoline engine cylinders would have either of the two following qualities: (1) burning up com- pletely if it got up past the piston rings, so that there would be no carbon deposit, or (2) not burning at all and would remain as oil no matter how high the temperature in engine cylinders. No oil can be made to meet such a requirement. To determine quality, oils are tested (1) for flash point; that is, the temperature at which a film of it will break down by vaporization, and (2) for viscosity, showing at what tem- perature it becomes so thin as to be worthless as a lubricant. A good oil should have enough "body" to maintain an oil film between the piston and the cylinder at the usual tem- peratures in automobile engines and still it should not be so thick as to interfere with the easy movement of the piston rings in the cylinder. A good quality of engine oil should be free from acids, which have a tendency to make the working surfaces of both the cylinder and pistons rough. Flash-point Test. If oil is heated slowly in a cup in which the bulb of a thermometer is immersed and the flame of a taper or lighted match is held over the surface, it is not difficult to observe the temperature at which there is sufficient vapor escaping from the oil to be ignited. This temperature at which the oil vapor ignites is called the flash point of the oil. A good automobile engine oil should have a flash point not much less than 400 degrees Fahrenheit. LUBRICATION AND COOLING SYSTEMS 227 Fire Test. If the procedure as outlined above for the flash test is continued so that instead of having momentary ignition flashes near the surface of the oil, the whole surface of the oil takes fire and continues to burn, the observed tem- perature is called the fire test. Acid Test. A simple method to test for acid in oil is to dissolve a small amount of the oil in warm alcohol and dip a piece of blue litmus paper in the solution. If there is acid in the oil it will turn the paper red. Litmus paper can be purchased at drug stores. Oils and Greases for Automobiles. Most dealers in auto- mobile engine oils have three grades according to thinness: (1) light, (2) medium, and (3) heavy. Only the light and medium grades should be used in engines having reasonably tight or close-fitting piston rings. Heavy-grade oil may be used for engines with piston rings which are not as tight as they should be, and is invariably used for all kinds of air-cooled automobile, and motor cycle engines. Sometimes because of faulty ignition or other causes an engine becomes so much heated that light and medium oil give little lubrica- tion and are used up too rapidly. The only remedy then is to use a temporarily heavier grade. The very thick oil (semi-fluid) of the kind used for the lubrication of speed-change gears or transmissions as well as also for the differential gears in the rear axle should be of a kind that will adhere to the gear teeth for cushion- ing effect, thus reducing both wear and noise. The speed- change gears should be well provided with oil, so that the lower teeth of the smallest gears will be in oil for their full length. The differential gears should be filled with heavy semi-fluid oil up to the level of the filling hole, making the gear casing in the rear axle about one-third full. The rear axle is not fluid-tight so that if relatively thin oil is used in the differential casing it may leak from the ends of the axles and splash over the brake bands, wheels, and rear axle. This leakage oil may interfere with the proper action of the brakes by reducing their friction and its 228 GASOLINE AUTOMOBILES removal is difficult without spoiling the paint. In case oil in the differential works out at the ends of the axles, either a heavier grade of transmission oil should be used or closer fitting washers should be put at the ends of the axles. Wheel bearings are packed in thin cup grease which need not be replaced often if the wheels are not removed. Heavy grease will not cling to roller or ball bearings such as are used in the wheels of automobiles. The lubrication of the steering gear is important as its failure may cause a serious accident. Its parts should be inspected when oiling an automobile to make sure there is no undue wear. Grease and oil cups on the steering gear, including the rods and levers connecting it to the front wheels should always be kept well filled and should be tested to see that the lubrication gets to the joints for which it is intended. It is a good practice, especially where grease is used to screw down the thread on the grease cups till just a little grease can be seen oozing out from the bearing. Insufficient lubrication in the engine is often the cause of very large repair bills, and in the steering gear, of dis- astrous accidents. It pays to look carefully after the lubri- cation of an automobile. Lubrication is cheaper than bearings. When an expert looks into the condition of an automobile, one of the first places he inspects for wear is at the steering knuckles. A constant supply of good grease or oil is needed to prevent excessive wear at the knuckles. It is worth while to screw down on the grease cups on the steering knuckles every time oil is put in the engine. When a grease cup is screwed down so that it cannot be turned further, it should be filled immediately. There should be enough grease in the cups to keep forcing it out, so that grit cannot get into the bearings. The spring shackle bolts are sometimes equipped with grease cups, and often the passages for the grease become clogged so that one may screw down on the cup and only force the grease out of the thread of the cup, instead of into the bearing, as the grease-cup cap fits loosely upon the LUBRICATION AND COOLING SYSTEMS 229 thread. In that case the grease cup should be taken off and the passages cleaned. There are fewer grease cups used on automobiles now than formerly. Oil cups are being used instead, largely because they are more conveniently filled. At least once a year a small amount of grease should be put between the leaves of automobile springs to keep them in good operating condition without squeaking. This can be done by raising the frame with an automobile jack which has been blocked up high enough for the purpose. When the weight on the frame is supported by the jack it is not difficult to insert between the leaves of the spring a wedge-shaped clamping device made for the purpose, or even the ends of a screw-driver will do. After the leaves have been separated, the very small amount of grease needed can be easily put in. Oil in a sense wears out in any lubricating system and should be replaced with new oil occasionally. Some of it will work up past the piston and be burned, but most of it will remain in the sump longer than it should be used. All of the gasoline that is taken into the cylinder is not burned. Some of k is forced past the piston on the compression stroke into the crank case, where it condenses and mixes with the oil. This thins the oil sometimes to a point where it has little or no lubricating value. Most automobile instruction books advise draining all the oil from the engine, from the speed-change gears, and from the differential case at the end of every 1,000 or 2,000 miles, depending somewhat on whether the driving has been heavy or light. After removing the old oil or semi-fluid grease from these parts, they should be flushed with kerosene in order to remove all sediment and metallic dust that may have accumulated. Heavy continuous service requires more attention to lubrication than light service. Both before and after a long touring trip over rough roads an automobile should be given careful inspection for loose parts, excessive wear in important parts, and lubrication. 230 GASOLINE AUTOMOBILES If the oil supply should be exhausted while the auto- mobile is in use, the engine will get stiff, lose its power, and the friction of the unlubrieated parts will generate sufficient heat to melt out the lining of the bearings. If the engine runs for any length of time in this condition, it may be wrecked beyond repair. An automobile owner should not rely entirely on his chauffeur for the care of parts of the automobile requiring lubrication, unless he has found out that the man knows the importance of lubrication. Nor should it be taken for granted that the garage man is attending to the lubrication of an automobile when he charges for that service. "Make sure yourself" is the best rule. Methods of Engine Lubrication. Lubricating systems for automobile gasoline engines are usually of one of the three following: (1) simple splasli system, which is entirely auto- matic, no pump being used; (2) splash system with an oil pump, as an auxiliary; (3) fully forced feed (pump] system. Simple Splash System. In many medium and low-price models of automobile engines, engine oil is poured into the crank case to a level where the engine crank shaft dips into it at each revolution. The rapid rotation of the cranks through the oil in the bottom of the crank case splashes it in all directions and produces a sort of oil foam that covers the entire inside surface of the crank case and of the cylinders below the pistons Each bearing has a hole drilled at a place where the "splashed" oil can reach and then run down into the bearing. The difficulty with this system is that if the oil level is a little too high there will be over-lubrication, that is too much oil will be splashed, especially into the cylinders, and if the crank shaft does not dip deeply enough there will be too little splashed oil to lubricate the bearings properly. Frequent filling is therefore necessary to maintain the proper oil level. This system is shown dia grammatically in Fig. 196. LUBRICATION AND COOLING SYSTEMS 231 A modification of this method is used in the Ford auto- mobile engine. Besides the crank shaft the flywheel (which is enclosed in the engine casing) runs with the lower part of its rim below the normal oil level, and by its rotation picks up and then throws oil in all directions. Some of this splashed oil is caught in a nearby horizontal tube having a funnel shaped opening along side of the flywheel for collecting the oil which it discharges from the other end of the pipe upon the timing gears. As the friction clutch and planetary gears (transmission) of a Ford engine are intended FlG. 196. Splash Spstem of Lubrication. to run in oil, they are lubricated also by the splash from the flywheel. Some device such as a float indicator, gage, or try-cock must be provided so that the level of oil in the crank case can be readily determined. Allowance must always be made for the possible sticking of floats and for the automobile being lower on one side than the other. Observations of oil level taken when the engine is running mean nothing as at slow speed nearly all the oil may be in the crank case while at high speed comparatively little may be there. Ob- servations should be made a few minutes after the engine has been stopped. Splash System with an Oil Pump. As an improvement over the simple splash system a method has been devised to control the oil level by mechanical means. A typical device of this kind is shown in Fig. 197, which is in use in a great many makes of automobiles. As shown, there is a little pan or cup under each crank. These are so arranged as to height that when filled with oil, a short 232 GASOLINE AUTOMOBILES "spoon" at the lower end of the connecting rod touches the surface of the oil at its low point in each revolution and splashes oil in all directions over the inside of the crank case, and over practically all the working parts of the engine. This splashing and agitation of the oil makes a fog of oil in the crank case so that a film of oil is deposited even on those parts which the splash does not reach. At the right-hand side of the figure an engine-driven pump is shown also diagrammatically which, when the engine is running, pumps oil from the reservoir or "sump" in the bottom of FlG. 197. Splash and Pump System of Lubrication. the crank case to a horizontal distributing pipe, P. There are holes in the side of this pipe from which oil discharges into the pans to keep them constantly over-flowing and, therefore, also at a constant level. The oil is constantly drained back into the reservoir to be pumped back again into the pans. This system maintains constant conditions of lubrication irrespective of the amount of oil in the reser- voir, consequently this reservoir can be made large to hold a large amount of oil and makes frequent refilling unneces- sary. This method is also sometimes called the constant-level splash, but although left out of this name, the pump is an essential part. LUBRICATION AND COOLING SYSTEMS 233 In this system the principal cause of trouble is too much oil in the sump, so that the level reaches above the splash pans. Sometimes the projections on the connecting rods are so large that too much oil is splashed when the level is normal. There are so many varieties of oil pumps that no descrip- tion will be given here. There is usually sufficient informa- tion regarding the oil pump in the automobile instruction books furnished by manufacturers. A small oil gage or pres- sure gage is shown in the figure in a branch of the pipe leading from the pump to the oil pipe P. There is no flow of oil through the gage. It shows merely the pressure in the oiling system. This gage is intended for attachment to the dash or instrument board so that the driver can see from his seat whether oil is being properly distributed. One will soon observe what the reading should be for ordinary operating speeds. When the needle at the usual speeds does not nearly reach this gage reading, it is an indication that there is not enough oil in the reservoir to run the pump full, or the pipe is clogged. This is a warning to get more oil or to investigate for trouble in the oil piping. When the gage .needle hangs at zero on its scale, the danger point is being reached as regards oil supply. If the oil gage reading increases as the speed of the engine increases, there is a good indication that the oil is circulating. Fully Forced (Pressure) System with a Pump. In a fully forced system there are no splash devices of any kind and the oil for lubrication is distributed to all parts of the engine and its auxiliaries through a system of branch pipes carrying oil under pressure from the oil pump, which draws the oil from a reservoir in the crank case. This system is shown diagrammatically in Fig. 198. Pipes carry oil from the pump to the main crank shaft bearings B, B, B, and there are holes drilled through the inside of the crank shaft (H, H, H, H,) so that the oil forced into the main bearings is also forced through the shaft and out into the connecting rod bearings on the' crank shaft. Since the oil is always 234 GASOLINE AUTOMOBILES under pressure in all the main bearings it insures positive lubrication in distinction from "hit and miss." Bearings oiled by this method are likely to last a very long time. The Fie. 198. Fully Forced (Pressure) System of Lubrication. oil escapes from the forced system at the edges of the con- necting rod bearings and is discharged with so much pres- sure that it is distributed as a fine spray penetrating to Pressure Oacje -., Adjustable Pressure Ya/ve- Connecting Rod Bearings^ Camshaft Bearings __ Reservoir Oil Pump FIG. 199. Lubrication System for Eight-cylinder ("Twin Four") Engine. every part including the pistons, cylinders, and cam shaft bearings. This system is used in nearly all eight- and twelve-cylinder engines, as well as also in many six-cylinder engines. A typical example is shown in Fig. 199. LUBRICATION AND COOLING SYSTEMS 235 Lubrication of Knight Slide Valves. One method of lubricating the sliding sleeve valves of Knight engines is a modification of the fully forced system described, except that instead of all the oil going through the crank shaft being sprayed from the ends of the connecting rods, some of it passes up through a tube inside the connecting rod to hollow piston pins and from the two open ends of their pins it flows by gravity over the sleeves and is distributed through holes and oil grooves over their cylindrical surfaces. ENGINE COOLING SYSTEMS Very high temperatures result at the tops of both the cylinders and the pistons of gasoline engines every time there is an explosion stroke. At these times the temperature rises to about 2800 degrees Fahrenheit, a sufficiently high temperature to make the iron of the cylinder red hot, and all the oil provided for lubrication would be burned up, if no special means of cooling are provided. The first prin- ciple of engine cooling is to get the most economical opera- tion, and this means that the engine should be kept just cool enough to prevent the cylinder lubricating oil from burning off the curved surface of the piston. The most commonly used method of reducing the temperature of gaso- line engine cylinders is by the circulation of water in an enclosed space, called the water jacket, which is made a part of the outside of the cylinder casting, and surrounds also the valve chambers. By keeping a supply of water passing through this jacket the engine cylinder can be kept cool enough to prevent distortion of the metal surfaces as might result from overheating and to prevent also the burning up of oil provided for lubrication. In some engines the water is self-circulating through the water jackets of the engine cylinders, but in others the water is pumped so that there is a positive circulation at all times when the engine is runnirig. Air-cooled engines have arrangements to provide un- usually efficient air circulation and in large volume over 236 GASOLINE AUTOMOBILES the hottest parts of the engine cylinders, which are provided with ribs or flanges of metal on the outside surface of the cylinder which are in most cases made as a part of the cylinder casting. These ribs perform a service similar to that of the water jacket on other engines. The method of air cooling circulates air in large volume for cooling the engine cylinders and the other method circulates water. The ribs are surrounded by a circular aluminum sheet. The air spaces between the ribs and this sheet are the only openings between the top and bottom compartments separated by a plate. There are fan blades on the flywheel so that it is used for a suction fan. The cool air enters at the front of the engine hood into the top compartment, goes down be- tween the ribs on the engine cylinders and passes out under the frame of the automobile. The amount of air for each cylinder is thus mechanically controlled and each gets about the same amount and with most efficient contact with the cylinder walls. A good air-cooled automobile uses no more oil than one that is water-cooled. Air-cooled engines are usually made of light construction so that they are not intended for large engine power. A few makes of automobiles use this method of air cool- ing, and it is used almost exclusively on all kinds of motor cycles. The method of air cooling is so simple in principle that no further explanation is needed. Pump System of Jacket Water Circulation. Water for cylinder cooling is circulated through the water jackets of an automobile engine and its radiator as shown in Fig. 200 by means of a small pump C. The direction of flow of the water is shown by arrows. The pipes, made usually of flexible rubber hose, are connected to a cooling vessel, R, called a radiator. The top hose is connected to a pipe connection at the top of the radiator, and the lower hose to the bottom of the radiator. Most water pumps used for this kind of service are like this one of the centrifugal type, and are operated by gear wheels driven by the engine crank shaft. They are similar in construction to an ordinary fan blower for air. They consist simply of a set of blades or vanes LUBRICATION AND COOLING SYSTEMS 237 extending out from a central shaft like the spokes of a wheel. A pump of this kind depends, as its name indi- cates on centrifugal force and must therefore be operated at a high speed to be effective. Water enters the pump around the shaft and is driven outward by the centrifugal force of the rapid rotation of the blades and discharges from FIG. 200. Pump System. a pipe connected to the outside circumference of the pump casing. The faster the engine runs, the faster the water circulates. Another type of circulating water pump is also used. It consists simply of two small gear wheels which are placed side Thermostatlc Valve FIG. 201. Pump System with Thermostatic Valve. by side with meshing teeth. These gear wheels are supported on horizontal bearings in a casing closely fitting the teeth all around, except at the places at the top and bottom of the casing where the teeth are in mesh. The water is taken into the pump at the bottom of the casing and the rotation of the gear teeth forces it from a discharge opening at the top of the casing. Fig. 201 shows a pump system of cooling water circulation 238 GASOLINE AUTOMOBILES which is controlled by a thermostatic valve. When the engine is cold, this valve is open and by-passes the cooling water in the engine jackets through the small pipe D and there is no circulation through the radiator R. When the water in the jackets becomes heated the valve closes and the circulation is through the radiator. A device of this kind as applied to a Cadillac engine is shown in Fig. 202. A trap for collecting overflow of water or anti-freezing solutions which are sometimes used for engine FIG. 202. Cadillac Thermostatic Control. cooling in winter, is also shown. A detail of the pump and thermostatic valve is shown in Fig. 203. A similar thermo- static system of cooling water control is used in Packard and other makes of automobiles. Thermo-syphon Jacket Water Circulation. The method of jacket water circulation depends on the principle that cold water is heavier than hot water. An engine cooled by thermo-syphon circulation is provided with two water con- nections or pipes, one at the top of the jackets A and the other at the bottom B, Fig. 204. When the engine cylinders become heated, the hot water in the cylinder jackets tends to rise and flow upward and out of the top of the water jackets into the top of the radiator. At the same time that hot water LUBRICATION AND COOLING SYSTEMS 239 is being taken out of the water jackets at the top, cool water flows in through the bottom hose from the radiator, and this circulation is automatically maintained as long as the engine FIG. 203. Cadillac Water Pump and Thermostatic Valve. cylinders are hot and there is enough water in the radiator so that the hot water hose from the water jackets to the radiator contains water. This means that the radiator must FIG. 204. Thermo-Syphon System. be kept practically full all the time. If the hot water hose becomes empty, there will be no circulation, the water in the water jackets will boil away, and increasing temperatures in the engine cylinders will interfere with operation. The cir- culation of water in the engine cylinder jackets, piping, and 240 GASOLINE AUTOMOBILES radiator by this system is shown in Fig. 205. Fig. 206 shows the cooling water circulation in the Ford engine. Radiator Air Cool Wafer FIG. 205. Thermo-syphon Cooling System Showing Water Circulation. ______ RadiaforCap --;.". ..... Filter Neck _____ Top Tank --".-.~ Splash Plate * "Over flow Tube ----- -Radiator Jnlef Connection -~""~"^\~~"_~~"~~^ Cylinder Outlet Hose -7^-a ..... ,-?! " ........... Hose Clip ^^5 a- '"'" -"- ....... r -Qflinekr Head \ '\-Lowerffose Cfip \- Radiator Outlet ....... Cylinder Casting . Blinder In le-f' Connection \ \Connecfion \DrainCock * Lower Tank FIG. 206. Cooling Water Circulation in Ford Engine. Radiators. As used on most pleasure automobiles, a radiator is composed of an irregular front and back surface, somewhat resembling a honey comb in many designs. Two of this type made of a large number of square tubes about LUBRICATION AND COOLING SYSTEMS 241 four inches long which are "flared" or spread out at the ends E, E, are shown in Figs. 207 and 208. When a number of these flared tubes are held together closely with their ends \ / '-- Wafer Air Passages FIG. 207. Honeycomb Kadiator. touching and are dipped into a bath B of tinsmiths' solder as shown in Fig. 209, a bundle of tubes will be made with square openings, 0, 0, 0. Between the openings there will FIG. 208. Honeycomb Kadiator with Crimped Tubes. be very narrow spaces, all communicating with each other. A large number of these flaring tubes when soldered together in this way make a typical automobile radiator. As radiators are set up the flared openings are toward the front of the automobile for the purpose of having air pass through their openings to cool the hot water entering the top of the radiator from the water jackets. The cooling action by means of this 242 GASOLINE AUTOMOBILES air circulation is increased by a chain or belt driven fan placed behind the radiator as shown in Fig. 205 which by its suction through the openings of the radiator increases the FlQ. 209. Simple Method of Making Eadiator Tubes. & 'Air Space FIG. 210. Zig-Zag Radiator Construction. amount of cooling air going through. The narrow communi- cating spaces, 8 (Fig. 209) comprise the principal storage space for water in the radiator, and it is therefore obvious that LUBRICATION AND COOLING SYSTEMS 243 in proportion to the amount of water, an enormous cooling surface is obtained by this kind of construction. This air circulation induced by the fan is not necessary when the automobile is going at high speed but is very much Cooling Flanges Tubes for Wafer FIG. 211. Vertical Water Tubes and Horizontal Air Tubes. needed when the engine is running ("idling") and the auto- mobile is standing still, or when the automobile is running slowly through traffic-congested city streets. This kind of radiator is called a "honeycomb" or cellular type. Other FIG. 212. Vertical Eadiator Tubes. methods of radiator construction are shown in Figs. 210 and 211. Some radiators are, however, made of vertical tubes with small rings over the outside surface as shown in Fig. 212. Liquid Solutions for Jacket Cooling in Winter. In northern climates where water in an automobile radiator is likely to freeze in cold winter weather, a substitute for water must be used. Such substitutes are called anti-freez- 244 GASOLINE AUTOMOBILES ing solutions. The solutions most commonly used are the following: Denatured alcohol, kerosene, glycerine, and cal- cium chloride. Denatured Alcohol is in most respects very satisfactory for mixing with water to make a mixture or solution of low-freezing properties. The following table gives for various percentages by volume of alcohol mixed with water, the corresponding freezing points and specific gravities: FREEZING POINTS OF COOLING LIQUIDS FOB WINTER USE Denatured Grain Alcohol Mixed with Water Per cent by volume Specific gravity Freezing of alcohol of solution point 10 0.99 24 F. 25 0.97 7 F. 50 0.93 -32 F. 70 0.90 -57 F. Denatured Grain Alcohol and Glycerine (equal parts) Mixed with Water Alcohol and Freezing glycerine Water point 15 per cent of mixture 85 per cent 20 F. 25 per cent of mixture 75 per cent 8 F. 50 per cent of mixture 50 per cent -33 F. An alcohol and water solution has no destructive effect on rubber tubing or on any kind of metal. The only dis- advantage is that it evaporates more rapidly than water, so that in refilling a radiator, it is necessary to add more alcohol than water in order to keep the solution of a standard strength. For this replacement mixture the values of specific gravity given in the above table are convenient. Kerosene mixed with water makes a very cheap anti- freezing solution and it does not vaporize readily. In such a solution the wastage may be safely assured to be all water unless the kerosene is allowed to leave the radiator through the overflow pipe or through a leak. Kerosene has the great disadvantage that it very rapidly deteriorates rubber hose LUBRICATION AND COOLING SYSTEMS 245 connections and if it is used, the only safe way is to use radiator connections of some other material than rubber. A flexible brass tubing is made which has no rubber inser- tion packing in the flexible folds which can be used. Kero- sene has the further disadvantage that it does not mix well with water. Glycerine has the same disadvantage as kerosene as regards deteriorating effect on rubber hose connections. It is, however, very expensive, and sometimes contains acids which are likely to attack the brass in the radiator. Test is explained for oils on page 227. A mixture of twenty per cent by volume of glycerine, twenty per cent of denatured alcohol, and sixty per cent of water, gives more satisfactory results than glycerine alone, as the alcohol has apparently a tendency to reduce the deteriorating effects of the glycerine on rubber and on the other hand the presence of the glycerine reduces the vaporiza- tion loss of alcohol. In the proportions given, this solution will be safe from freezing at twenty degrees Fahrenheit below zero. There are numerous commercially prepared anti-freezing solutions sold at high prices. Most of them are made up of the liquids mentioned here, although calcium chloride is favorite material for such solutions. If used at all in radiator solutions it should be chemically pure. The greatest dis- advantage from its use is that as the result of evaporation, a whitish crust will be formed in the water jackets, pipes, and top of the radiator which has a tendency to clog up and interfere with good water circulation. This crust is, however, soluble and can be dissolved when fresh clean water is put into the radiator and jackets and then heated by "idling" the engine with retarded "spark." Calcium chloride solutions should be te'sted for acidity as suggested for glycerine. Commercial calcium chloride (not chemically pure) is almost certain to set up electrolytic action when two kinds of metals are joined together, as for example, in the parts of a centrifugal pump or at a brass drain 246 GASOLINE AUTOMOBILES cock. The following table gives the freezing temperatures for several mixtures (by volume) of saturated solutions of calcium chloride and water. FREEZING POINTS OF CALCIUM CHLORIDE SOLUTIONS MIXED WITH WATER Per cent by volume of Specific gravity Freezing calcium chloride of solution point 10 1.085 22 F. 20 1.119 F. 25 1.219 -18 F. 28 1.268 -42 F. CHAPTER X AUTOMOBILE TROUBLES AND NOISES Modern automobiles have been perfected to such a degree by high engineering skill in both mechanical and electrical work that the troubles and noises now occurring are indeed few in number compared with the automobiles made several years ago. In this connection it is worth while noting that dealers in second-hand cars, who decide their buying points for an automobile by the amount of noise it makes when running make their prices on more than a little basis of fact. The noise an automobile makes is a fairly good index to its condition as to wear, repair, care in operation, lubrica- tion, etc. Many automobiles that are four or five years old but have been carefully used and kept in good repair are as free from noises as some cars that have been operated only a few months, and their serviceableness for future use is correspondingly large. Carbon Deposit in the Cylinders is probably the most common cause of trouble in automobile operation. It is always the result of the imperfect combustion (1) of engine oil which gets to the top of the cylinders, past the piston rings or (2) of gasoline which has not mixed in the right proportions with the air supply or (3) the mixture of gaso- line vapor and air has not been completely ignited on every power stroke because of imperfect spark plugs or other defects in the ignition apparatus. The remedy is to clean out the carbon. The easiest way to get an idea as to the condition of an engine cylinder as to carbon deposits is to take out a spark plug. If there is enough carbon deposit in one or more of the cylinders, there will be a peculiar "pounding" of the pistons due to particles of red hot carbon igniting the explosive mixture before the spark is made. 247 248 GASOLINE AUTOMOBILES The "pounding" therefore is the same kind of noise heard when the spark is advanced too far or with a heavy load going up a grade, the spark is not retarded. If the plug has been in that particular cylinder for some time and has a considerable coating of carbon on the porcelain or mica center piece, it is to be assumed that the walls and exhaust valve are also coated and need cleansing. The best way to remove carbon deposits is to have it burned out at a repair shop with oxygen-acetylene flame apparatus. Another method is by scraping off the carbon deposits by the use of tools of slightly different shapes which are bent so that they will reach into and scrape over the end of the piston and the walls of the cylinder. The usual method is to scrape all the loose carbon to the exhaust valve and when the work of scraping is finished, turn the engine by hand till the exhaust valve is opened wide when the carbon refuse can be pushed into the exhaust pipe, and when the engine is started it will be discharged with the engine exhaust. It is recommended that after finishing with the scraping tools, that a small brush be used to remove all loose particles and that finally a little kerosene be poured into the cylinders to serve as a "wash." When through, examine the exhaust valve and its seat carefully to be certain no particles of carbon remain attached which would interfere with proper closing. It is a good idea to make a paste of flake graphite, finely powdered, and "cup" grease for use on the threads of the cylinder plugs over the valves. When replacing the plugs, be sure the copper gaskets or "washers" are put in under the plugs, as putting these, together with using the graphite paste on the threads is good insurance for tight joints. The same precautions as to tightness of joints should be observed whenever replacing spark plugs. Whenever greasy spots are observed around valve plugs, it is an indica- tion of loose joints, which are always wasteful of power and prevent getting the natural pressure on the compression stroke necessary for best efficiency. The use of copper gas- kets and graphite paste is the best remedy. AUTOMOBILE TROUBLES AND NOISES 249 When examining spark plugs to test for the presence of carbon deposits, it may be observed that in some cases the deposit is very black sticky substance which adheres firmly to knives and tools. This kind of deposit is an indication always of an excessive amount of engine oil getting past the piston rings and finding its way into the cylinder. It may be that most of the carbon in such case is deposited because of improper mixtures from the carbureter of gaso- line and air, but in any event the excess of oil is the cause of part of the deposit. On the other hand, if the carbon deposit is dry and brittle it is likely to be due almost entirely to improper mixtures of gasoline and air, to the same cause as that producing thick black smoke in the discharge from the engine exhaust pipe. Kerosene put into the engine cylinders in small quan- tities, about two or three tablespoonfuls at a time, will, in most cases, remove small carbon deposits, and if used regularly, say once a week, may prevent further trouble from this cause. It can be put into the cylinders most easily by fitting the little cups on the priming cocks or by squirting into the main air valve of the carbureter from small (com- pression bottom) oil can, just before the engine is stopped. When kerosene is put into the cylinders by either method, the engine should not be run again for several hours, and when it is started there should be thick black clouds of smoke coming from the exhaust, indicating that carbon has been removed. Another method sometimes used is to run the engine for about fifteen minutes once a week, with the spark well retarded as for starting, and inject kerosene at the air inlet of the carbureter, with the float valve of the carbureter held down and closed. Grinding the Valves. It is a good plan to grind the exhaust* valves of the engine at the same time that the valve * The intake valves make less trouble than the exhaust valves because through them passes cool, fresh, unburned mixtures, while through the exhaust valves pass hot soot, burned or partly burned gases. 250 GASOLINE AUTOMOBILES plugs are removed for the removing of carbon either by burning or by scraping. When the pressure on the com- pression stroke is less than it should be, it is most often the result of leaky exhaust valves, which do not close tightly on the compression stroke, because of the lodgment of particles of carbon and therefore permit leakage through them. Valve grinding begins with the removal of the valve plugs on the cylinders requiring valve grinding. Next the spring (see Fig. 173) on the valves must be removed so that the valves can be turned. Then lift the valves for grinding and put a thin coating of grinding paste on the bevel (conical) part of the valve. A satisfactory paste can be made of powdered emery mixed with enough kerosene to make a thick paste and then add a few drops of oil in the proportion of about one drop to each tablespoonful of kerosene used. Exact proportions are, of course, not essen- tial. It is best to make two kinds of this paste, one with rather coarse emery for rough cutting and another with very fine emery to give a smooth, clean surface for finishing. Valve grinding pastes, mixed for use, can be purchased at most automobile supply stores. After these preliminary operations, a special valve grind- ing tool, a carpenter's brace with attached screw-driver or a plain hand screw-driver may be used for the grinding. The tool or screw-driver fits into a notch like the head of a screw in the top of the valve. The grinding is done by rotating (oscillating) the valve back and forth until the entire bearing surfaces of both the valve and its seat are made clean and smooth. The valve should not be turned all the way round, as one would bore a hole with a brace, but should be rotated only about a quarter turn with light pressure. Now and then the valve should be lifted, turned half way round while the grinding is continued. This turn- ing is for the purpose of getting good seating of the valve in all positions, as without the turning it might fit well in only one position. Powdered glass is sometimes used. AUTOMOBILE TROUBLES AND NOISES 251 After the valve grinding is finished, the valve, its seat, and its guide-rod should be well washed in gasoline, so that none of the emery paste remains to scratch the surface of the valve as it operates. To test the work to see that it is well done, put a narrow lead pencil line all the way round the bevel edge of the valve and turn the valve all the way around several times. If the line is rubbed out over the whole circumference the valve is likely to be satisfactorily tight. "Knocking" or "pounding" in the engine cylinders may, in addition to the causes already mentioned, such as red-hot particles of carbon deposit, or an excessively hot engine igniting the explosive mixture before the spark is made, spark being too far advanced for the speed and kind of load, also be caused by loose connecting-rod bearings, loose piston wrist-pins, and loose crank shaft bearings, all of which are in most cases due to overheated bearing surfaces caused by insufficient lubrication. Infrequently, however, it is also caused by the engine getting too hot on a warm day, when heavily loaded, or because of a loose piston or broken piston ring. Trouble with bearings such as are listed here are best remedied by a skilled mechanic. Amateurs who are not well experienced are likely to make bearings much too tight after having them apart for repairs and there is unend- ing trouble until the bearings get either "worn in" or "burned out." A rhythmic "knocking" is also caused by "missing" cylinders, meaning that the engine cylinder or cylinders making the noise are not firing the explosive mixture they are receiving. This is a different sound from the knocking, due to loose bearings or to too early ignition, and further, if only one cylinder is missing the sound will be heard only once in a revolution. It is less observable in engines of eight or twelve cylinders than in those or four or six cylinders. It is usually due to a sooted, defective, or broken spark plug, although may be caused by a broken electric wire from the distributer to the spark plug. 252 GASOLINE AUTOMOBILES "Tapping" valve rods are another source of trouble. The "tapping" of valve rods does not indicate that there is any- thing seriously wrong with the engine. It will continue to give approximately its full power at about the usual gasoline consumption. It is merely an annoying noise com- parable with squeaking of springs or the rattle of doors. The "tapping" noise is caused by gradual wearing away of the bevel faces of valves or of their seats. When the valve stems are properly adjusted with respect to the push rod on the side shafts carrying the cams for opening the valves, there is a little space, clearance, between the bottom of the valve stem in the closed position and the top of the adjusting screw on the push rod. When properly adjusted, the space between the bottom of the valve stem and the top of the adjusting screw is not much more than the thickness of a sheet of good letter paper. It should be noted that there is much more likelihood of getting poor engine results if the clearance is made too large when adjust- ing than there is likely to be from any wear in the direction producing valve tapping. Adjust carefully therefore to see that the clearance is not made too large, because if it is too large, the push rod does not lift the valve the full amount, cutting down both the height the valve is lifted and also the time it is open. Of course one could imagine the condition where the valve stem and the top of the push rod would wedge each other so closely (no clearance) that the valve could not in any position get down on its seat. This would be especially bad in the compression stroke, when the explosive mixture in the cylinder must be put under pressure by the upward stroke of the piston. If either the exhaust valve or the inlet valve does not close properly, the necessary pressure for efficient combustion cannot be obtained. Some authorities claim that a weak spring on the exhaust valve can be a cause of poor engine economy. The effect produced is that the exhaust valve because of the light spring will open automatically on the suction stroke intended AUTOMOBILE TROUBLES AND NOISES 253 for sucking in the explosive mixture from the carbureter, and that some of the burned gases from the previous power stroke will be sucked into the cylinder from the exhaust pipe. Recent experiments, however, show that the efficiency of combustion is actually improved by the mixing of a small amount of the burned gases with the fresh charge. Valve Timing and Setting are properly the work for only good experienced mechanics. Instruction books prepared for and going with the different kinds of automobiles, ex- plain the method for each kind of engine in detail, with the help of marks of various kinds on the flywheel, on pointers, and on timing gears. The principles have been explained in the various preceding chapters. Wrong Explosive Mixtures are the result of incorrect proportions of gasoline vapor and air in mixture sucked into the engine cylinders from the carbureter. Flooded Cylinder. The most troublesome condition is when the mixture in the cylinder is much too rich in gaso- line, so that it will not explode. Most often this is caused when the engine is turned over a number of times, either by hand or with a starter, and because of temporarily defec- tive ignition there are no explosions. As a result, there is an accumulation of drops of gasoline, on the inside of the cold cylinders, which have separated from the mixture, most of which, of course, goes out through the exhaust pipe. This accumulation of drops of gasoline is rapid, because for start- ing, especially in cold weather, mixtures very rich in gaso- line are used. In this way it is easy to get a mixture so largely gasoline that it cannot explode even when the tem- porary difficulty with the ignition is corrected. The simplest remedy is to open the priming cocks on all the cylinders and continue to turn the engine over a number of times, so that on the compression strokes the mixture, excessively saturated with gasoline will be driven out through the open- ings in the cocks. If this condition in the cylinder is very bad, the gasoline vapor may be seen at the discharge open- ings of the cock. If, after this cleaning, the priming cocks 254 GASOLINE AUTOMOBILES are again closed, the engine will usually start after a few turns of cranking. Flooded Carbureter. Somewhat similar results to those explained above result from getting the carbureter thor- oughly wetted inside with liquid gasoline. Some people are in the habit of always manipulating the float valve on the carbureter by hand to make starting easier. This is called "priming the carbureter" with the object of getting an excessively rich mixture. Not infrequently this car- bureter manipulating is done a few times too often when there is some temporary trouble with ignition, so that by the time ignition trouble has been corrected the mixture going into the cylinders from the carbureter has too much gasoline to be exploded. There are two simple remedies: (1) by cranking with priming cocks open as for flooded cylinder; or (2) by not doing any more cranking for about ten or fifteen minutes, after which time the excess of gaso- line in the carbureter passages will probably be evaporated, so that cranking will then start the engine without difficulty. Test for condition of carbureter flooding by putting a finger into the air inlet tube. Sometimes it happens that a bit of rubber or of wood gets under the float valve of the carbureter. At one time this was a common carbureter trouble but does not occur so frequently now since so much gasoline is purchased from reliable dealers who know enough to avoid the use of hose connections on gasoline filling machines which contain rub- ber or rubber compounds. A particle of rubber or other foreign material when stuck in the float valve may cause continued cylinder and carbureter flooding. The obvious remedy is to remove the cause. Sometimes it can be removed by shaking the float valve, but usually it is necessary to take the carbureter apart. Now, a word of caution ! Unless circumstances are unusually urgent, do not spoil the adjust- ments of a good carbureter by taking it apart unless besides knowing all about the theory of the carbureter, you have had practical experience in the adjustments of the kind of AUTOMOBILE TROUBLES AND NOISES 255 carbureter used. The level at which the float must be set is always determined by experiment and inexperienced per- sons will usually do a great deal of experimenting before they get even reasonably satisfactory adjustments. Carbureter flooding results also sometimes from the float losing its buoyancy by filling with gasoline. If a cork float is used in the carbureter, partial loss of buoyancy is not unusual. The effect is to make the float heavier than it was when originally adjusted with respect to the float valve and will permit the gasoline to stand higher in the gasoline or float chamber than was intended. High gasoline level may make gasoline stand in the orifice tube so high that it might be overflowing continually, whether or not the engine is running. The remedy is to take out the cork float and after drying, paint it with shellac. Baking in a shellac baking oven is desirable if equipment of this kind is available. If the float is of the hollow metal kind, the loss of buoyancy is due to holes in its surfaces. The remedy is to empty and dry the float and then close the hole or holes with solder. Floats should always be carefully tested for buoyancy for several hours before they are put into place in the carbureter. Color of Flame from Priming Cocks. In this connection, it is interesting to observe that the color of the flame from open priming cocks is a good indication of the correctness of the proportions of the explosive mixture in the engine cylinders. If the mixture is of satisfactory proportions to give most effective explosions, the flame has a bluish color. When the flame is tinged strongly with red, the mixture is too rich in gasoline ; and when it has a whitish color it is much too weak in gasoline. Back-firing into the Carbureter. Most modern automobile engines are designed so carefully that there is little trouble with back-firing into the carbureter (see page 101) except when the mixture going into the cylinders is too weak. Weak mixtures may be due (1) to incorrect adjustments of the carbureter or (2) gasoline supply being nearly exhausted 256 GASOLINE AUTOMOBILES so that there is not enough to maintain the proper level in the carbureter for a sufficiently strong mixture. A weak mixture from the carbureter at low engine speeds is usually due to too little gasoline in the mixture (float valve set too low) ; and when the mixture is too weak only at high speeds it is due to too much air through the auxiliary air valve (auxiliary air spring too weak). INDEX Advance of spark, 125, 129, 165 Air cooling, 235 Alcohol for fuel, 50, 51 in radiator, 244 Alternating current, 112, 168 rectifier, 112, 113 Ampere, 105 Aniline, 53 Armature, 149 Atwater-Kent ignition, 144 Automatic gear shifts, 221 Automatic spark advance, 125, 142 , Delco, 125 , North East, 142 Automobiles, electric, 3 , gasoline, 4 , steam, 2 , types of, 2, 4 Axle drive shaft, 9, 208, 211 Axles, front, 13, 14, 203 ,live, 211 , rear, 9, 11, 206, 211 Back-firing, 255 Batteries, dry, 105 , storage, 106 Battery charging, 107, 177 connections, 115 ignition, 12x troubles, 110 Baume hydrometer, 54 Bendix drive, 170 Benzine, 49 Benzol, 51 Bevel gear drive, 207, 210 Block cylinders, 44 Bodies, types of, 4, 5, 8 Bore, cylinder, 45 Bosch magneto, 156 battery ignition system, 147 Brakes, 10, 218 , adjustment of, 219 , equalizers, 218 , failures, 220 Braking with engine, 219 Burton process, 49 Cabriolet, 5 Cadillac cooling system, 238 Calcium chloride, 246 Camber of front wheels, 205 Cam shafts, 26 Carbon deposits, 103, 247 Carbureter adjustments, 101, 103 , auxiliary air valve, 67 troubles, 100-103 priming, 69 Carbureters, 63-103 , Cadillac, 93-94 , Holley, 80-81 , Johnson, 89-90 , Kingston, 73-75 , Marvel, 75-76 , Packard, 94, 98-100 , Puddle type, 74 , Kayfield, 85-86 257 258 INDEX Carbureters, regulated nozzle, 70 , Schebler, 82-83, 91-92 , Stewart, 79-80 , Stromberg, 77-78 , Tillotson, 89 , Zenith, 87-88 Cars, (See Automobiles) Cells, (See Batteries) Chain drives, 170 Change gears, 9, 12, 188 Charging batteries, 107, 177 Chassis, 8 Clearance, 48 Clutches, 9, 11, 28, 184 Coils, vibrating, 127, 131 , non-vibrating, 136, 138 Color of exhaust, 102, 255 Compression, 25, 50 Condensers, 130, 136, 142 Cone clutches, 185 Connecticut ignition system, 124, 143 Connecting rod, 23 Cooling systems, 235 solutions, 243 Coupe, 4-6 Cracking gasoline, 49 Crank case, 23 Crank shafts, 9, 34, 46, 47 Cycles, 23 , four, 23-28 ,two, 23 Cylinder arrangements, 28, 36 cooling, 235 oils, 226, 227 Cylinders, engine, 9, 28, 44 Dash control, 83 Delco ignition, 126, 140 starter, 170, 173 Detachable cylinder head, 45 Differential gear, 10, 207 Dimming resistance, 138, 182 Direct current, 112 Direction of current, 114, 115 Disk clutch, 186 Displacement, piston, 48 Distributor, 122, 163 Distributing arm, 122 Doped gasoline, 51 Double ignition, 158 Drag link, 204 Drive, Hotchkiss, 218 shaft, 9, 208 Dry cells, 105 Dual ignition, 158 Electric automobiles, 3 starters, 167-183 Engine, 9, 19, 21-48 as brake, 219 , Cadillac, 41 -- cycles, 23 cylinders, 44, 45 , Dodge, 44 , Ford, 159 , four-stroke, 23-28 horse power of, 47 , Knight, 30 , Packard, 42 speeds, 36 , two-stroke, 23 Exhaust gases, 22 Explosive mixture, 21, 22 force, 22, 25 Feed systems, gasoline, 56 Fire (gasoline), 70 Fire test for oils, 227 Firing order, 45 Flash point of oils, 226 Flow of power, 7, 38, 39 Flywheels, 8, 28 Forced feed oiling, 233 Ford axle, 211 cooling system, 240 engine, 159 ignition system, 133 magneto, 157 INDEX 259 Ford planetary gears, 199 rear axle, 209 timer, 134 transmission, 199-203 Four-stroke engine, 24 Frames, 9, 14, 15 Franklin, air cooling, 235 Friction, 223 clutch, 9, 11, 28, 184 Front axle, 13, 14, 203, 205 Fuelizer, Packard, 98-100 Full floating rear axle, 213 Gasoline, 49-51 and benzol, 51 carbureters, 63-103 , doped, 51 , heating value of, 55 mixtures, 50 substitutes, 49-51 tanks, 56 Gears, differential, 10, 207 , planetary, 190, 197 t progressive sliding, 190 , selective sliding, 190 , speed-change, 9, 12, 188 Glycerine for cooling, 245 Gravity feed system, 61 Greases, 227 Grinding valves, 249 Head, detachable cylinder, 45 Head lights, 182 Heating value of gasoline, 55 High-tension magneto, 151 Holley carbureters, 80 Honeycomb radiator, 241 Horse power formulas, 47, 48 Hot air connection, 83, 96 Hot spot on manifold, 95, 96 Hot water connection, 86, 97 Hotchkiss drive, 218 Hydrometer, battery, 111 , Baume, 54 , specific gravity, 54 Idling, 86, 88 Ignition, 104-147 systems, 121, 138-147 troubles, 161-166 Insulators, electrical, 105 Intake manifold, 42, 94 valve, 25 Kerosene, 244, 249 King bolts, 204 Kingston carbureter, 73 Knight engine, 30-31 , oiling, 235 slide valves, 30-31 Knocking in cylinder, 52, 251 Leaves of springs, 15 L-head cylinder, 28 Limousine, 5 Low-tension magneto, 151 Lubricants, 225 Magnetism and electricity, 116 Magneto adjustments, 160 armatures, 149 , Bosch, 156 , care of, 160 , Dixie, 150 ,Ford, 157 timing, 160 troubles, 161-164 Magnetos, 148-161 , high- and low-tension, 151 Magnets, demagnetized, 161 Manifolds, intake, 42, 94 Marvel carbureter, 75-76 Master vibrator, 135 Mixtures, explosive, 21, 22 ,rich, 101, 102 , weak or lean, 101 Motors, (See Engines) , starting, (See Starters) Mufflers, 10 Multiple disk clutches, 186 260 INDEX Non-vibrating induction coil', 136, 138 North East ignition, 141 starter, 177, 179 Oiling, (See Lubrication) Oil pumps, 231 Oils, cylinder, 226, 227 Over-running clutch, 172 Packard fuelizer, 98 Parallel battery connections, 116 Peened piston rings, 33 Pistons, 22, 32, 41, 42 Piston displacement, 48 rings, 32 Planetary gears, 190, 197 Plugs, spark, 24, 25, 119, 161, 165 Power diagrams, 39 Power, horse, 47, 48 plant suspension, 43 Pressure feed systems, 61 Primary coil, 119 Priming carbureters, 69 Progressive sliding gears, 190, 192 Eadiators, 9, 240 Eadius rods, 217 Kayfield carbureter, 85 Bear axles, 9, 11, 206, 211 Rectifier alternating current, 112, 113 Kemy ignition, 145, 147 Resistance, electrical, 104 Eeverse current cut-out, 174 speed-change gears, 191 Eittman process, 49 Eoadster, 5 S. A. E. horse power formula, 47, 48 Safety resistance, 123 spark gap, 155 Schebler carbureters, 82, 91 Secondary coil, 119 Sedan, 5, 6 Selective sliding gears, 190, 192 Semi-floating rear axle, 211 Series battery connections, 115 Shafts, cam, 26 , crank, 9, 34 , drive, 9, 208 Shifting gears, 13 lever, 195, 197 Shock absorbers, 220 Short circuit, 105 Slide valves, 29-31 Smoke from exhaust, 102 Spark advance, 125, 129, 165 coil, 132, 133 plugs, 24, 25, 119, 161, 163, 165 Specific gravity, 55 Speed-change gears, 9, 12, 188 Speeds, engine, 36 Spiral bevel gears, 210 Splash oiling system, 230 Springs, 14-19 Starter-generator, 167 Starters, 167-183 ,Delco, 170, 173, 177, 179 , electric, 167-183 , Liberty (for Ford), 180 , North East, 177, 179 , Westinghouse, 177, 179, 180, 181 Starting in cold weather, 182 motor drives, 169 motor troubles, 182 Steam automobiles, 2 Steering gear, 13, 203 knuckle, 203, 228 Stewart carbureter, 79 vacuum feed system, 56-60 Stopping, 12 Storage battery, 106, 107 , charging, 107, 112, 114 hydrometer, 111 in winter, 110 INDEX 261 Storage battery, refilling with aeid, 108 , sulphating, 109 Stromberg carbureter, 77-78 Testing electric wires, 114, 115 T-head cylinder, 28. Thermostatie cooling system, 237 Thermo-syphon cooling, 238 Three point motor support, 43 Third brush regulation, 176 Tillotson carbureter, 89 Timers, 129 Timing, magneto, 160 Tires, 10, 206, 208 Torque members, 217 Transmission gears, 13, 188 (See also Speed-change gears) , planetary, 190, 197 Two-cycle engines, 23 Two-stroke engines, 23 Two unit starting system, 179 Universal joints, 13, 214 Vacuum gasoline feed, 56-60 Valve stems, 26 -in-the-head, 29 Valves, adjustment of, 253 , arrangement of, 28 , grinding, 249 , Knight sliding, 30 , needle, 71 , timing, 253 Vibrating induction coil, 127, 131 Vibrator, 127, 135 Volt, definition of, 104 Voltage, constant, 180 Voltage of dry cell, 105 of spark, 119 storage cell, 175 Water-cooling systems, 236 Westinghouse ignition system, 143 starters, 177, 179, 180, 182 Wheel alignment, 205 Winter cooling solutions, 243 Worm differential gear, 210 Worm steering gear, 203, 205 Zenith carbureter, 87. 18 University of California SOUTHERN REGIONAL LIBRARY FACILITY 305 De Neve Drive - Parking Lot 17 Box 951388 LOS ANGELES, CALIFORNIA 90095-1388 Return this material to the library from which it was borrowed. 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