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while air during compression opposes a ment of the stroke of one side is here force increasing towards the end of the transmitted by the crankshaft to the stroke; thus the power rapidly falls off other side of the machine, to help out as the resistance increases, causing a per- the deficient pressure of the expanded ceptible reduction in 'speed at the end of steam when the stroke is nearly finished. each stroke. If such a machine could be Such a machine has no “dead centers,” run at high speed, the weight (or more and can be run at very slow speed when correctly, the mass) of the pistons and necessary. connections would, by inertia, help out As it is generally desirable to maintain the decreasing steam pressure when slow- a constant air pressure, and to vary the ing to pass the centers, and thus produce speed of the machine according to the a more even effort on the crank; but quantity of air required, speed governors sufficiently high speeds are not possible for the steam cylinders are not needed for the automatic-lift valves generally except to prevent racing in case of a used on small compressors. The varying bursting pipe or other excessive dispower and resistance can be very satis- charge of air. Some form of adjustable factorily balanced by connecting steam cut-off valves is very desirable in order and compressing pistons to separate to allow of suiting the work of the steam
s set at right angles. Having pro- cylinder to the load. The pressure is vided two frames and cranks, a slight controlled by automatic devices actuated additional outlay will supply an extra by the rise and fall of the air pressure, pair of cylinders tandem to the first pair, either shutting off the air intake, opening making a full duplex compressor. The a by-pass around the compressor piston, excess steam pressure at the commence or (in case of duplex machines which
can start from rest without attention) shutting off steam and stopping the machine.
A description of the standard types of commercial compressors would be incomplete without reference to the most remarkably wasteful "steam eater" known to the compressor trade-a machine using ten times as much steam as would be necessary for pumping the same amount of air by means of a fairly eco
nomical compressor, and yet a device resistance that its strokes are smoothly most ingenious and entirely satisfactory made at any speed from slowest to fastfor its work. This is the air-brake pump, est, and all with maximum simplicity and which, for actual conditions of train minimum weight. These machines are service—where it stands idle until the also built with compound steam and twoclosing of the throttle and the application stage air cylinders, and in these cases of brakes leave a large and heavily fired have pressures in the cylinders so nearly steam boiler to blow off at the safety uniform that the steam distribution may valve until the fire can be checked-is be considerably more economical than it seen to be well adapted. Indicator cards is possible to obtain in the single-stage show that the entering steam is throttled compressor. through about half the stroke, while the The selection of general types anul exhaust is similarly choked at first and special details for compressors must be only let out freely about the time of full based, as in all other cases of machine opening of the valve. The result is a design, on the practical condition of get"straight-line” compressor having no ting the best return from the money incrank or fly wheel, with nothing moving vested, with due regard to the importance but its two pistons and one rod, and yet of reliability and durability in each ITso perfectly balanced between effort and ticular case.
motive which can draw six or eight cars tives, whether single-expansion or comover a well-built track at the rate of pound, and in four-cylinder types such seventy or eighty miles an hour; but the as the tandem and the original Vauclain problem of reducing the amount of fuel compound, the reciprocating parts are consumed, and of lessening the strain on counterbalanced by rotating weights in the rails caused by the vertical shock of the driving wheels. This arrangement the rotating weights in the driving of balance becomes unsatisfactory, parwheels, without sacrificing either speed ticularly for heavy locomotives and in or power, has proved much more diffi- cases where extremely high speeds are cult.
attained. By balancing their reciprocatOf the many attempts made to solve ing parts against one another, the rotatthis difficulty, undoubtedly one of the ing balance in the wheels used to commost successful so far has been that of plement these parts can be eliminated, S. M. Vauclain, who two years ago de- avoiding to a great extent the vertical signed a locomotive to which the name shocks, and reducing the strain upon the of the Vauclain Balanced-Compound was track to that directly due to the weight given. Since then, several of these en- of the locomotive. Consequently, with gines have been built by the Baldwin a self-balanced arrangement of reciproLocomotive Works, and have been used cating parts, the weight on the driving
wheels may be increased without damage with the corresponding crank pins ing the track, and higher speed is attain in the wheels. The pistons, therefore, able without undue strain upon the work- travel in the opposite direction; and the ing parts of the locomotive. The bal- reciprocating parts act against and balanced-compound engine is intended to ance one another to the extent of their accomplish these results, and to simplify, corresponding weight. as far as possible, the arrangement of the The distribution of steam is shown in working parts.
the accompanying diagram. The live steam port in this design is centrally located between the induction parts of the high-pressure cylinder. Steam enters the high-pressure cylinder through the steam port and the central external cavity in the valve. The exhaust from the high-pressure cylinder takes place through the opposite steam port to the interior of the valve, which acts as a receiver. The outer edges of the valves control the admission of steam to the low-pressure cylinder. The steam passes from the front of the high-pressure cylinder, through the valve, to the front of the low-pressure cylinder, or from the back of the high-pressure to the back of the low-pressure cylinder. The exhaust 'from the low-pressure cylinder takes place through the external cavities under the front and back portions of the valve, which communicates with the final exhaust port. The starting valve connects the two live steam ports of the high-pressure cylinder, to allow the steam to pass
over the piston. CYLINDER
The dimensions of the high-pressure
cylinder are 15 by 26 inches; and of the The cylinders are a development of the low-pressure, 25 by 26 inches. The workoriginal Vauclain four-cylinder com- ing pressure is 200 lbs. The fire-box has pound type, with one piston slide-valve a heating surface of 168.5 square feet; common to each pair. Instead of being and the grate, one of 34.69 square feet. superimposed and located outside of the The rigid wheel-base is 13 feet 6 inches, locomotive frames, the cylinders are and the total length of the engine 27 feet placed horizontally in line with one an- 5 inches. The total weight of the locoother, the low-pressure outside and the motive is 160,000 lbs. Its water capacity high-pressure inside the frames. The is 5,500 gallons, and the tender holds slide-valves are of the piston type, placed 10.5 tons of coal. above and between the two cylinders As an illustration of the superiority which they are arranged to control. A of the new Vauclain engine over other separate set of guides and connections types in common use, two recent trial is required for each cylinder. The two runs may be cited. These took place on high-pressure cylinders being placed in the line of the Chicago, Burlington & side the frames, the pistons are neces- Quincy from McCook to Akron, Col., a sarily coupled to a crank axle. The low- distance of 143 miles, including an elevapressure pistons are coupled to crank tion of 2,150 feet. A Vauclain balancedpins on the outside of the driving wheels. compound locomotive drew the mail train The cranks on the axle are set at 90 de- of ten cars weighing 664 tons these 143 grees with each other, and at 180 degrees miles in 2 hours 56 minutes, at an average speed of 48.6 miles an hour, reach- tion. On the trial trip between New ing at times a velocity of 68 miles an Haven and Boston, November 12, 1904, hour. The usual time made by the mail a new Vauclain locomotive broke the rectrain drawn by single-expansion loco- ord by 19 minutes, making the run of motives from 17,000 to 35,000 lbs. 160 miles, including three stops, in 2 heavier than the Vauclain, was 3 hours hours 55 minutes. It is not unreason36 minutes. On a second run over the able to prophesy that when the railway same division with a train of twelve cars, company shall have completed its new the Vauclain made an average speed of bridges at Coscob, Bridgeport, and West42.46 miles an hour, which was thirteen port, it will be possible to make the run minutes faster than the heavier locomo- from New York to Boston in a little over tive carrying only eight cars could make. four hours, representing a saving of On these trials the Vauclain engine from 40 to 50 minutes over the fastest burned, each trip, 32 per cent less coal time now made by the special limited and used 20 per cent less water than the expresses. One of the new Vauclain enothers.
gines could, if necessary, haul the train The managements of several of the the entire distance without having to large Western roads have been quick to re-coal on the way. perceive the great advantage of the new It may be gathered, then, from the locomotive; and nearly 100 of them are facts thus briefly set forth, that the Vaunow in use on the tracks of the Burling- clain balanced - compound locomotive ton, Santa Fé, and other systems. In the seems destined to work a revolution East, the New York, New Haven & along the lines of freight and passenger Hartford Railroad is the only road thus traffic by increasing greatly the speed far to adopt the new engine. They have and power of locomotion, as well as very ordered twenty, two of which have been appreciably lessening the expense for received and are already in daily opera- fuel and maintenance of track,