Subject to Revision. [TRANSACTIONS OF TEE AMERICAN INSTITUTE OF MINING ENGINEERS.] LATEST DEVELOPMENTS IN COMPRESSED AIR-MOTORS FOR TRAMWAYS. BY D. S. JACOBUS, HOBOKEN, N. J. II (New York Meeting, September, 1890.) Compressed air-motors are specially desirable, if economically practicable, for underground haulage, because they require no fuel, involve no danger of fire, and not only avoid Keating and fouling the atmosphere with smoke and combustion-gases, but by the emis¬ sion of expanding fresh air, cool and improve it and aid venti¬ lation. The highest developments in the use of compressed air-motors for locomotion are to be found, in the opinion of the writer, in the principles of the Mekarski car-motor as applied to street tramways, and it is thought that notes taken regarding this system, during a recent trip to Europe, where two plants are in successful operation, at Nantes and Vincennes respectively, will be interesting to mining engineers. The plant at Nantes operates a street-line 5.2 miles long, re¬ quiring about twenty motors; the one at Vincennes about 7 miles of road. Each car at Nantes carries its own motor. At Vincennes, however, the motor-car is arranged to tow a second car containing no motor. The road at Nantes is the older, having been in successful opera¬ tion for ten years, during which time neither the American consul, Mr. Shackelford, who has resided at Nantes for about five years, nor the vice-consul, Mr. Bennett, who has been at Nantes ever since the road started, has ever seen anything go wrong with the motors. Description of the Railroad at Nantes. Motor-Car.—Two small engines are connected so as to rotate the front axle of the car, a reversing lever being used to alter the cut¬ off and run the motor in either direction. The compressed air is stored in ten tanks, fastened under the car, eight of these tanks being 1 FZ 3? 15" 2 COMPRESSED AIR-MOTORS FOR TRAMWAYS. connected together and constituting what is called the battery, and the other two forming the reserve. Air may be admitted from either the battery or the reserve to the tank, A, Fig. 1, where it Fig. I. passes through a mass of hot water before it reaches the regulating- valve, the construction of which can best be seen in Fig. 2. The valve is opened and closed by a difference of the air-pressure acting on the two sides of the diaphragm, a, a. The pressure in the space, E, will therefore be governed by the air-pressure that is brought to bear on top of the diaphragm, which pressure can be varied at will by means of the piston, D. From the regulating- valve the air passes to the three-way cock, B, Fig. 1, which causes it to pass either to the engines or to the air-brakes. The dimensions are as follows: Diameter of cylinders of engines, 13J centimeters or 5T5g- inches. Stroke of engines, 26 centimeters or 10J inches. Compressed air-cylinders, about 18 inches diameter and 5 feet long. COMPRESSED AIR-MOTORS FOR TRAMWAYS. 3 The cylinders containing the compressed air are not all of the same size. The total capacity of a set of connected cylinders, as given in Mekarski's circular, is such that each kilogramme of pres¬ sure per square centimeter corresponds to 2.5 kilogrammes weight of air in the battery and 0.8 kilogramme of air in the reserve. The pressure of air employed at Nantes when the motors are fully charged is 30 kilogrammes per square centimeter in both the battery and the reserve.* The motors run very steadily, there being no appreciable teetering or rocking when the car is at full speed. In starting, there is no Fig. 2. jerking motion experienced, and as air-brakes are used for stopping, the quickness with which this is done may be varied at will. The air exhausted from the motors makes a slight noise, but not enough to cause annoyance to persons residing near the car-lines. Air-Compressors and Storage-Tanks.—The air-compressors are of the compound type, in which air is first compressed into an inter¬ mediate receiver, and from this enters the high-pressure cylinder, where it is compressed to the final pressure. The air-cylinder pistons are both fastened to the same rod. The cylinders are single-acting, the pressure in the receiver being made to act con¬ stantly on one side of the high-pressure piston. The steam-cvlinder is set parallel to the air-cylinders, and the pistons of all the cylin¬ ders are connected to the same flv-wheel shaft. The dimensions are about as follows: * A pressure of 1 kilogramme per square centimeter is equivalent to 14.22 pounds per square inch. 4 COMPRESSED AIR-MOTORS FOR TRAMWAYS. \ Four Compressors at Two Compressors at Sup Main Station. Inches. plementary Station. Inches. Length of stroke of air-cylinders, . 23.6 Length of stroke of steam-cylinder, . 39.4 Diameter of high-pressure air-cylinder, 9.4 Diameter of low-pressure air-cylinder, . 19.7 Diameter of steam-cylinder,. . .19.7 17 28 7 15 14 The compressors are made to force air into a receiving-tank until the arrival of a motor that is to be charged. The motor is first con¬ nected to the receiving-tank so that its cylinders become charged to the pressure of the tank ; they are then connected directly to the compressor until the required pressure is reached, at which point an automatic valve acts to prevent any excess if the person charg¬ ing the motor does his work in a careless manner. The receiver is always at a lower pressure than that required for the cylinders of the car, so that all the work of storing the air is not done against the maximum pressure. At the same time that the air-tanks are being charged, the water in the tank, A, Fig. 1, is heated by passing steam into it. The loss of water by vaporizing during the trip is just about the same as the amount of steam that is required to be condensed in the water in order to heat it, so that there is no escape of steam or hot water at the charging-station. No opportunity was offered to measure the temperature of this water, but, according to Mr. Mekarski, it is 160° Cent, when the motor starts from the sta¬ tion, and about 100° Cent, when it returns. Method of Running the Motors.—The reversing-lever is first thrown forward to the last notch from the center; the hand-wheel, H, is then slowly turned so that it forces the piston, D, Fig. 2, downward, and opens the valve admitting air to the chamber, E, from which it passes through the cock, B, Fig. 1, to the engine. The lever is held in the forward position until the motor begins to start, and then it is brought to the notch nearest to the center. When the lever is for¬ ward in the last notch, the cut-off occurs at j-stroke; in the notch nearest the center the cut off is About 6 to 10 kg. per square centimeter are used on the engines at starting, and this pressure is preserved until the motor attains a speed a trifle faster than the average. The pressure is then shut off from the engines, provided the track is quite level, and the reversing lever is thrown forward ; the car then runs a short time by its inertia. When the speed diminishes, the lever is brought back to the first notch, and 6 to 10 kg. again brought on the engines. By COMPRESSED AIR-MOTORS FOR TRAMWAYS. 5 working the air in this way, it can be used more efficiently than if a constant low-throttled pressure were used. In going up grades the pressure is constantly on the engines and, if possible, the lever is in the first notch. There was no grade at Nantes so steep that this could not be done. To stop the car, the handle of the three-way cock, B, Fig. 1, is turned, and the required amount of air-pressure brought to bear on the brakes by screwing down the hand-wheel, A. When the pressure in the battery, which is the first set of cylinders drawn from, becomes too low to start quickly, or to drive the motor up a grade, the three-way cock shown at G, Fig. 1, is turned so as to allow the pressure of air from the reserve to be communicated to the interior of the tank, A. The cock is then turned back to its former position, so that there will still be a high pressure of air in the re¬ serve to be used again in case of need. Stationary Plant.—Fig. 3 will give a general idea of the plan of the tracks at Nantes, although there are many more curves in the lines than are here represented. Fig. 3. Plan of Route at Nantes. The motors start from the main station, B, charged to about 30 kg. per square centimeter in both the battery and reserve, go to A, then to C, and back to A, and, finally, to D. At the supplementary station, D, the tanks are re-charged to about 20 kg. per square cen¬ timeter, and the motor returns to A and then to B. There are several stations along each route at which inspectors enter the cars to see if all the passengers have tickets, these tickets having been purchased from a conductor who rides on the car. The track is quite level, the heaviest grade being where the road crosses bridges the road-beds of which are higher in the middle than at 6 COMPRESSED AIR-MOTORS FOR TRAMWAYS. the two ends. The maximum grade is 1 to .045, and all the grades are short. There are four compressors at the main st ition at Doulon and two at Chatengay, the dimensions of which have been already given. Two of the compressors at Doulon are run on Sundays and fete days, at which time there are twenty motors in use, whereas on week-days, one, and only for part of the time two, compressors are run and sixteen motors are in use. At Chatengay both of the compressors run on Sundays and only one during the week. The motor-cars have seats for sixteen persons without crowding, and eighteen with slight crowding. The back platforms are quite large, however, so that sometimes thirty or more passengers will be carried at one time. There are in all twenty-two motors belonging to the company. Record at Nantes for the Year Ending July, 1889, as given by Mr. Mekarski. Fuel, 1300 tons at $5 per ton, delivered to station, . . $6,500.00 Oil and waste for rolling-stock at $80 per ton, . . . 862.00 Oil and waste for stationary plant at $80 per ton, . . 300.00 Total number of men employed at Doulon Station, . . 7 " u " " Chatengay Station, . 5 Number of trips made by each motor per day, . . 6 Length of each trip (one full charge of air and one two-thirds charge for each trip), ..... 10.4 Miles. Number of miles made by each motor per day, . . . 62.4 u " motors in use on week days, . . . .16 i( " " a " Sundays and Fete days, . . 20 Time of starting the first motor from the station, . . 7 A.M. Time of starting the last motor from the station, . . 7.08 P.M. Total number of miles run during the year, . . . 346,700 The cost of repairs for this particular year could not be obtained, but in a statement of expenses for the year 1888, Mr. Mekarski places the maintenance of rolling-stock at 26,011 f., or about $5,200, and of the stationary plant at 15,803 f., or $3,200. Tests of Speed.—Table I. shows the trip-records taken at Nantes, while Table II. gives the totals and averages of .all the results. They clearly exhibit the following points : 1st. The motors started with about the same rapidity as an ordi¬ nary street car, i. e.y they attained full speed in 12 to 16 seconds, and could be started quicker than this, but at a greater expendi¬ ture of compressed air. 2d. The total distance run over in order to measure the speed was 22.55 miles, and the number of stops made was 61. The rate of COMPRESSED AIR-MOTORS FOR TRAMWAYS. 7 speed, including stops was 7.58 miles per hour, and excluding stops 8.52 miles per hour. 3d. The greatest distance run with a single charge of air was 6.6 miles; this required 30 kg. per sq. cm. In returning from the supplementary to the main station the motors ran a distance of 3.8 miles, being charged at the start to about 18 kg. per sq. cm. The recorded number of passengers in the tables gives the num¬ ber on the car at the time of starting after a stop; this number does not include the driver and conductor. The average number of passengers is obtained by taking the average of the number on the car at each minute of the time required to make the trip. Horse-Power and Coal Consumption of Compressors.—The mean effective pressure for 60 rev. per minute, as shown by indicator cards taken by Mr. Mekarski, is 32 lbs. per square inch. We also have: Diameter of cyl. = .5 m. = 19.7" Stroke = 1 meter = 3.28 ft. xx n D 305 x 32 x 3.28 x60x2 , ,K Hence H. P. = = about 115. 33000 Sixty revolutions per minute is, according to the judgment of the writer, about the average speed that would be obtained by adding together the revolutions made by the two compressors during the day and dividing the sum by the number of minutes, for the compressors run ordinarily at about 45 turns, and one runs all day, and the other only occasionally. The compressor in the supplementary station compresses only to about two-thirds of the pressure obtained at the main station, so that to fill a given volume its horse-power would be about two-thirds of 115, or say 75, provided the indicator-cards of the air-cylinder have the same mean effective pressure. As, however, the indicator- cards will be smaller, we may say that about 60 horse-power is re¬ quired at this station, making the total requisite horse-power at both stations 175. The engines have a condenser; if we therefor assume 3 lbs. of coal per horse-power per hour we obtain : Coal per hour = 175 x 3 = 525 lbs. " " day of 12 hours = 6300 lbs. Figure given by Mr. Mekarski = 1300 tons per year. " " " " = 7100 lbs. per day. 8 compressed air-motors for tramways. Description of the Railroad from Vincennes to Nogent. Plant.—Figure 4, from which many curves have been omitted, will give an idea of the route, the distances being taken from Mr. Mekarski's pamphlet describing his system. The motors on this line are larger than at Nantes, and are charged to a higher air-pressure. The motors on the main line D, A, E, B, draw a supplementary car; they are charged at D and run to E, where they are replaced by another motor that has been charged at E ; from E the second motor and car either proceed to B, and return to E, without a further charge at B, or they return to D without going to B. The motors that run on the branch road do not draw a supple¬ mentary car; they are charged at E and run to A, and to C, and then return to E, making the round trip with a single charge of com¬ pressed air. There are seats on the top of the motors and the cars, as well as inside of both". The number of passengers given in the record is only approximate, as it was not possible for one person to keep an exact tally for both motor and car. At some portions of the trip the motor and car had all the passengers that could be accommodated. The principal results obtained are: I compressed air-motors for tramways. 9 Tests of Speed.—The details of a number of trip-records, taken on this line, are given in Table III., and the total and averages are shown in Table IV. 1st. The motor with a car in tow started in from 20 to 40 seconds, which is about twice the time required by an ordinary street-car. 2d. The total distance over which a record was kept, in order to determine the speed of a motor when drawing a car was 11.9 miles. The average speed including stops was 8.58 miles per hour, and ex¬ cluding stops 9.26 miles per hour. 3d. The motor alone ran on the branch line at 8.81 miles per hour, including stops, and at 10.65 miles per hour excluding stops. 4th. The average distance run by a motor with a single charge of air and drawing a supplementary car, was 3.97 miles, and this re¬ quired the air in the tanks to be compressed to about 40 kg. per square centimeter. Time Required to Change Motors.—The only case in which this has to be done quickly is at Vincennes Station. The motor is dis¬ connected from the car, run to the charging station, about 75 yards distant, charged there and then run back to be connected to the same car. In timing these operations the motor was disconnected from the car, turned at right angles to the track on a turn-table, and run to the charging station in three minutes. The air and steam were turned on three-quarters of a minute after the motor came to rest on the platform, and exactly three minutes afterward the motor was disconnected and started back toward the turn-table. At Nantes the motors are left on the charging platforms about 15 minutes, during which time the driver oils up the engines. Estimated Cost in the United States. As a basis for estimating the cost of equipping and operating a line in this country, we will take a double-track road 3J miles long, i.e., 7 miles of track, two terminal charging-stations, and cars run¬ ning at four-minute intervals for twelve hours a day. One gang of men is to be employed at each station. Two charging-stations are required, one at each end of the line, unless the track is quite level and is kept perfectly clean. In the case of a city where wagons are continually crossing the tracks, thereby causing the motors to be slowed down and started up very often, and where the streets are not kept clean, it would require much more power to operate the motors than at Nantes, where there was little interference with the continuous running of the motors, 10 COMPRESSED AIR-MOTORS FOR TRAMWAYS. except for taking on or letting off passengers, and where the rails were kept as clean as possible by a couple of track-walkers em¬ ployed for the purpose. Besides this, in many cities snow has to be contended with. There would also be many more stops for passen¬ gers in one of our larger cities than at Nantes. For these reasons the length of the assumed line, which has no intermediate charging- stations, has been limited by the practice developed at Vincennes, near Paris, where the motor and tow-car travel with one unre¬ newed charge of air an average distance of 3.97 miles. The cost of coal per mile per motor at Nantes, at $5 per ton, is 1.875 cents ; or at $3.50 per ton, 1.31 cents. Assuming that motors running in this country would require one and one-half times the power that they do at Nantes, the coal per mile per motor will be 1.96 cents. The total number of miles made by the motors per day on the proposed plant is 6^° x 12 x (3J x 2) — 1260, and the cost of coal per day about 1260 x 1.96 cents == $24.50. The waste and oil for rolling-stock at $80 per ton at Nantes, or about 30 cents per gal., is 0.25 cents per mile per motor, or $3.15 per day. If oil is 50 cents per gallon, this comes to about $5.2.5 per day.* The oil for the stationary plant at this same price is about $1.75 per day. The cost of maintenance of the rolling-stock as given in the printed statement by Mr. Mekarski is .052 f. per kilometer, or 1.67 cents per mile per motor. Assuming that the greater price paid for labor in the United States will add 50 per cent, to this figure, we have for 3 the repairs per mile per motor 1.67 x 7* — 2.5 cents or $31.50 for the entire number of motors per day.f The cost of maintenance of the stationary plant obtained in a similar way is $19.50 per day. * This assumes that the price of waste in the United States is sixty-six per cent, higher than at Nantes. f Although it is fully appreciated that this figure is one of the most important in an estimate of this kind, it has been impossible to check it by directly observ¬ ing the number of men in the repair-shop, because all repairs are made in Mr. Mekarski's shop at Doulon, and this shop is usually employed on other commercial work. There are 22 motors in all belonging to the company, and it is said that 20 of these have been run every Sunday and fete day since the road was started, so that it appears to be exceptional to have more than two motors undergoing repairs at the same time. \ COMPRESSED AIR-MOTORS FOR TRAMWAYS. 11 The number of men, exclusive of those making repairs, that would be required at each station are: 1 engineer, 1 oiler, 2 firemen, 2 workmen, and 2 charging-men, or 8 men in all, and an extra engineer who would take the place of either of the others in case of sickness. These figures correspond with what Mr. Mekarski gave me for the main station at Nantes. The items for supplies and repairs for both stations are therefore : Cost of coal per day at $3.50 per ton, $24.50 Oil and waste for rolling-stock, 5.25 Oil for stationary plant, 1.75 Maintenance of rolling-stock, 31.50 Maintenance of stationary plant, 19.50 Cost per day—total supplies and maintenance, . . $82.50 The labor items are : 3 engineers at $3.00 per day, $ 9.00 2 oilers at $2.00 per day, 4.00 4 firemen at $2.50 per day, . . . . . . . 10.00 4 workmen at $1.75 per day, 7.00 4 charging-men at $2.00 per day, . . . . * . 8.00 Total expended for labor in two stations per day, . $38.00 If we assume the cost of the two buildings required for this plant to be the same as that of a single larger one which would be re¬ quired if horses were used, then, so far as plant is concerned, we have only the charge for depreciation of the machinery and motors in Mr. Mekarski's system to balance against the replacement and acclimating of horses in a system in which horses are the motive- power. The approximate cost of the machinery will be: 4 compressors, $15,000 4 boilers, 5,000 22 motors, 25,000 Total cost of machinery, $45,000 Taking interest and depreciation at 10 per cent., we have for this item $4,500 per year, or about $12.50 per dav. The total cost per day of the plant, neglecting the wages of con¬ ductors and drivers and also repairs and interest on buildings and such portions of the motor-cars as have their equivalent in an ordi¬ nary street-car, will be: 12 COMPRESSED AIR-MOTORS FOR TRAMWAYS. Fuel, oil and repairs, $82.50 Labor, 38.00 Interest and depreciation of machinery, .... 12.50 Total, . $133.00 In the case here considered the men work on very long shifts —say 13 hours per day. Ordinarily, if there is sufficient traffic to require the cars to be run at four-minute intervals during the busy part of the day, they will have to be kept running in the evening, and the number of working-hours per day will be increased to eighteen. If the trips are so arranged that the same number of miles is made by the motors in a day of 18 hours as in one of 12—the motors running more frequently during the busy part of the day than in the evening and very early morning—the cost per day with two gangs of men at each station will be $38.00 x 2 = $76.00 for labor; add¬ ing to this $95.00 for fuel, etc., gives $171.00 as the total expense, apart from other items which would be common to roads operated either by compressed air or by horses. Comparison with Horse-Traction.—The writer has received an estimate for operating by horse-power a road of the above descrip¬ tion, namely, a 3J-mile, double-track line, running cars on a four- minute headway for 12 hours a day. It Cost of feeding 350 horses per day, 20 stablemen at $1.75 per day, 1 stable-foreman, ..... 1 stable-doctor, ..... 4 hitchers at $1.50 per day, . Medicines, Replacement of horses and acclimating, Shoeing, '. as follows Total, $105.00 35.00 2.50 3.00 6.00 2.00 37.50 14.00 $205.00 In order to compare these figures with the results obtained for the Mekarski motors, we must add to the total sum the interest on the capital invested in horses. Assuming each horse to be worth $100, we have for the value of the horses 350 x $100 = $35,000; five per cent, on this is $1,750, or about $5.00 per day, making the total per day 205 -f- 5 = $210. The following, therefore, is the comparison obtained : Mekarski compressed air-motor cars for a day of 12 hours, . $133.00 " " " " " 18 " . 171.00 Horse-traction for a day of 12 hours, ..... 210.00 (Neglecting in all cases wages of conductors and drivers, and interest and repairs on buildings and cars.) 4 / COMPRESSED AIR-MOTORS FOR TRAMWAYS. 13 It must, however, be borne in mind that the figures for repairs of the Mekarski motors, given in the estimate, are for a plant that has been in operation a long time, and in all probability brought to its best condition in regard to attendance. If a new plant were started in the United States, inexperienced men would have to be put in charge of the motors, and in all probability the repairs for the first year would far exceed the figures above given. The extra wages that men could earn for running the motors over those of an ordi¬ nary driver are also left out of consideration. Again, men not used to running the motors would use the air with less economy than they now do at Nantes ; and probably the addition of 50 per cent, to the fuel-cost per mile, on account of dirty tracks, etc., will not be a sufficient margin. It is also probable that the pressure of air stored in the tanks will have to be made very much higher than is actually necessary for the trip, so that an extra amount of air can be drawn on in case of an emergency, and as this was not done at Nantes, at which place the reserve had to be thrown in toward the end of nearly every trip, an extra allowance should be made on this account. Taking all this into consideration, it may be that the coal consumed per motor per mile in the United States will be twice, or even three times, that at Nantes. The greatest drawback to the Mekarski motor is to be anticipated when snow can not be kept from the rails; for as each motor has only a definite charge of air which may become exhausted in con¬ tending with the snow, the car may come to a standstill on the track. This condition would not, of course, occur on underground-lines, so that the objection does not require to be considered for cases of mine- haulage. 14 compressed air-motors for tramways. Table I. Record of MeJcarski Air-Motors at Nantes. •rH tn OS ®"0 O o O) a a a> A *» ttH o a o •f-H o t- 0) £ *-6 ■SS « a3 »- w <-> co o a o T3 a o o CO co pn a ^ £a c 8 •PH # cj1 '3 M « ^ » t- o> -M -M cS PP A V +3 <0 oS a> to a b O OS c' •*- cc l-l a> ft o S3 a) 1=1 a> ft ■*3» S3 a t- <4H 16% 20 20 Level. Level. Level. 11% 20 12% 9% 8 21% Arrived at the main charging- station at B, where the motor is re-eharged. Started on another motor fully charged at main charging- station B. Delayed on switch. Arrived at Station A. Started from Station A. Arrived at Station C. Started from Station C. Arrived at Station A. Started from Station A. Slowed down for a short time to wait for cart to be removed from the track. Reserve used at starting. Reserve used on level track. a a a a Started on another motor ch'gd to two-thirds of its capacity at supplementary station D. Only 4 kilos per sq. cent, on en¬ gines at time of starting. Only 6 kilos persq. cent, on en¬ gines at starting, Arrived at A. Nearly all of the passengers left the car, there¬ fore record w as not continued. Took another car at A, 21% 9 kilos per sq. cent, on engines at starting. 21% 5 kilos per sq. cent, on engines at starting. * This delay is not included in the time expended in intermediate stops. Table II.—Totals and Averages of the Records Given in Table 1. Per Single Trip. Per Single Charge of Air. Station at -which the motor was charged with compressed air. ft © > o i=l a S-i © G ■ rH r—H © -t-3 o a O •rH © © co CO t-t © be s= © to co S3 G G O t-i © rO a 3 G te o3 © > m ft o cfl • rH -a 0) a f-t © =1 •1rH <+H o t-i © 3! a a r—< 03 -u o ft o3 H-S 0> o rH rH <3 •rH ft Time required to make trip. Miles per hour. t-i CD G oo CD he a © co co o3 G o.£ a a a O ft to © r-H •rH a a •rH a? © rH "3 > S-t H-> Q O £ HH> 0Q •rH ft Miles per hour. © H-J c3 •rH 'd 0> a S-. S CO G ft .a o . he OQ a •rH a! G r—1 © a i—i ID H-> c3 •rH *d a © . -tJ to a g —> O te & a •rH a r—1 a W ft a u CD j: co G ft .£ o he co a •rH a> a r—H o a i—i •rH *d 0) a fH . g Qi •rH Q kf to g • rH CO a r—H o >4 ft © c3 • rH as © a © • 4-> co a g — O be to a •rH aJ a © a h-1 © .a a5 © a © . 4-S CO a G t ° be+^ a <° •rH as 3 © ft D B B B B d D B B B B D d A to B B to A A to C C to A A to D D to A A to B B to A A toC C to A A to D D to A A to B 20 8 9.8 8 6.1 9.8 10.4 7.8 28 6.5 9.2 16.7 18.1 10 3 3 2 6 6 3 6 3 2 4 7 6 1.75 1.75 1.40 1.40 2.05 2.05 1.75 1.75 1.40 1.40 2.05 2.05 1.75 15 minutes. 12 m. 15 sec. 11 m. 30 sec. 11 m. 45 sec. 15 m. 30 sec. 16 m. 45 sec. 12 m. 13 m. 12 m. 30 sec. 11 m. 17 m. 45 sec. 17 m. 13 m. 11 m. 50 sec. 11 m. 10 sec. 9 m. 30 sec. 9 m. 55 sec. 14 m. 25 sec. 15 m. 45 sec. 11 m. 15 sec. 11 m. 50 sec. 12 m. 10 m. 25 sec. 16 m. 14 m. 25 sec. 11 m. 20 sec. 7.0 8.6 7.3 7.1 7.9 7.3 8.7 8.1 6.7 7.6 6.9 7.2 8.1 8.9 9.4 8.8 8.5 8.5 7.8 9.3 8.9 7.0 8.1 7.7 8.5 9.3 8.0 14 6.6 7.76 8.80 10.1 9 3.8 7.93 8.44 12.9 15 6.6 7.30 7.88 17.4 13 3.8 7.60 8.85 Totals f Averag or all runs e 158.4 12.2 *61 22.55 179 minutes. 159 m. 50 sec. 9&.5 7.58 110.7 8.52 * Number of stops, including those at main stations, 74. compressed air-motors for tramways. 17 Table III. Record of the Mekarshi Air-Motors at Vincennes and Nogcnt, near Paris. The Motors draw a car on the main line, and run alone on the branch line. m c3 O a> . o i a ^ mrA -P rP O p O c3 c/: cc Time 1 u o3 l/l p o <£ cs s ' " S i/2 S~ <+H r* o o o £ ca p rz 03 be s tsi 5 32 03 s- p -4-> y Pi ci Vj g P.O _G s C > Vi x O o o tn g O O a' CO & o c G <0 V> a S-, g « c s : g 8' ■r- Cj x . g.G| Condition of Co the track. *■* o> /C o> ^ i— cr r t ' f d> s H o> ■*—I1 CS X o £—i Ph p« c5 t/T J— O be P o y. o CJ cr 'Jl cr. ■ if.} ► O > £-i pi Remarks. CO o pp >> S- 0> PP D DtoA D AtoE E P. M. 12.03% Eto B 12.29% 12.31% 12.41% 1.12% 1.23 P. M. : 1 80 44 36% J 2.09 12.12 30 30 10 40 Up slight grade 80 80 43 21 i 1 1 ! 1 1 12.13 *240 Heavy grade... 100 12.22 20 25 Slight d'ngr'de 100 12.25 12.26 10 20 20 25 Li Li >> Down grade 100 100 12.28 Heavyd'ngr'de 100 100 45 44 99 1 29 j 12.35| 25 30 Slight up grade 19 27 44 12.38 12.41 15 10 30 45 Slight up grade 4. it 44 40 40 40 25% 7% 75 39 20% 1.17 55 20 Level 75 1.18 1.21 5 i 20 Down grade Up grade and on a curve 70 70 i 70 39 14 i i Motor drawing a car, start¬ ing from Station D. 8 kilos per sq. ct. on engines at starting. Reversing lever last notch from center for 20 sec., and on first notch afterwards. 12.15. Heavy grade. Reserve used. Went up the hill slowly with 1(5 kilos per sq. cent, on engines. Reversing lever in 2d notch from center. Only 3 kilos per sq. cent, on engines at starting. Longest hill. 5 kilos per sq cent, constantly on brakes. Arrived at Station A. Contin'd run on same motor. 6 kilos per sq. cent, on en¬ gines at starting. Arrived at E. Motor dis¬ connected from car and run into station to be charged. Started on another motor, drawing a car. 11 kilos persq.ct. on engines at starting. Revers'g lever in last notch fr'm cent'r for 10 sec. and in first 10 sec. 10 kilos per sq. cent, on en¬ gines. Reversing lever in 1st notch from center. Arrived at B. (Continued.) * This delay is not included in the time expended in intermediate stops. <• 18 compressed air-motors for tramways. Table IIL—(Continued.) Record of Meharski Air-Motors at Vincennes. t- o o s 3J : O) cc Tj m e V C '/i -c.2 i> 03 S3 o CJ CO cc . e': ?.S TJ e o o a> '/) P. o 32 <1-1 o a o 3 Q x ci 3 £-3 w 3 O 3 3 '3 ^ ci x iTJ 73 P. 2 * 3 3 cr 3 0) rj 3 3 Condition of the track. 3 +■> ci P O u> P.' & ci i tT ; su ! 0) bp; Z I 5 c3 ! 6 3 3 CO 3 « s_ 3 m Remarks. E i B to E \ M.! ■28% P. M. E iEtoA 1.30 1.33 1.33 1.33% 1.36 1.37 r( 1/ % 1.41%! 10 10 10 f) 25 : 1.55 : i E A to 0 2.37^ E C to A E j A to D 2.46% 3.15% 3.25 3.37% 1.47 1 .50 1.51 25 20 35 2.40 2.42 2.43 2.45 3.17 35 3.18 15 3.20 10 3.21 20 10 40 15 45 20 Slight upgr'de. Slight upgr'de. 10 12 15 20 20 25 25 o.s 39 33 29% •I' 40 43 ..42 .142 39 . '50 .... . 50 39 Down hill 45 Down hill 44 Slight d'n gr'de 42 Level 11 40 40 15 j Level. 14 41% 32 27 41 Returned from B. Reserve thrown in. Arrived at E. Motor discon¬ nected from car and ran into the station to he charged. Took another motor, drawing a car. Started by using air from reserve, and afterwards changed over to battery. 1.48 P.M. Going up hill. 10k. on engine, lever in 2d. notch from center. This motor went on to Vin¬ cennes. Started on a motor that came from E without draw'g a car. Did not draw car on branch line.* Up longest hill. 40% 26%; ' 26% 3.39% Up longest hill. 41 !40% 26 36 37 38 38 70 36 41 70: 3.40 | Up longest bill. 70! Slight up grade 70 3.41 I 20 | 25 10 3.59 3.42 3.45% j 3.46 i : 3.48 150* 3.53 I 40 I 30 37 Down grade 75 Short up grade:75 Down grade 75 70 38 Level 55 65 33% 15 25 6% Arrived at C. Returned on same motor to A. Arrived at A. Motor ret'd to E. Motor drawing car. When gr'de was reached, air-pressure of 16 k. per sq. ct. was used, and the lever was at 2d notch. 14 k. on engine, rev. lever in 2d notch ; motor going about as fast as a horse in a slow walk. Nearly at the top of the grade when this stop was made. It required 8 k. per sq. cent, on the brakes to bold the train from starting backw'd down the hill. Arrived at D. * This delav is not included in the time expended in intermediate stops. compressed air-motors for tramways. 19 Table IY. Totals and Averages of the Records given in liable III. Motor drawing a car on the main line D A E B. Motor alone on the branch line A B. Total distance run in the round trip 11.9 miles. 2.68* miles. Total number of stops made 22 8 Number of times that the motor is charged to make a round trip 3 1 Average number of passengers, approximate 59 38 Time to make run, including all stops except at the main stations and two delays mentioned in tables I. and III 83 m. 15 s. 18 m. 15 s Time, excluding all stops 77 m. 5 s. 15 m. 5 s. Miles travelled per hour, including stops 8.58 8.81 " " " " excluding stops 9.26 10.65 * This single motor runs, in addition to this length of 2.68 miles, the double dis¬ tance of A from E, which distance I do not know, but should judge it to be about 1 \ miles—so that the total distance run by the motor without re-charging is about 2.68 + 2 X H = 5.68 miles. Note by the Secretary.—Comments or criticisms upon the foregoing paper, whether private corrections of typographical or other errors, or communications for publication as "Discussion," or independent papers on the same or a related subject, are earnestly invited.