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ing to each other-so that both forces can never be on the dead-centres at the same time.
This plan of arranging the four cylinders and their delivery of power is being used on some of the most recently built American locomotives, but our engines are compounded, only two of the cylinders receiving boiler pressure direct: the Vauclain Balanced Compound, and the Cole Balanced Compound, both previously noted, are of this type, with the large, lowpressure or second-expansion cylinders outside the frame, and the smaller, high-pressure or first-expansion cylinders located inside, or between the frames; in starting a train-particularly a heavy one—the power of the cylinders termed high-pressure is temporarily suspended, thus removing an immensely twisting effect from the cranks in the axle at a critical time, and full boiler pressure at long cut-off is admitted to the large cylinders outside of the frame. After the train is under way, and the action is changed to com pound, the inside cylinders receive direct boiler pressure and exhaust it into the large, outside cylinders in which the final expansive power of the steam is obtained, and from which the exhaust to the atmosphere takes place.
If the Stephenson valve gear is used on engines of this type it necessitates placing the eccentrics on some other than the crank axle, for there will not be room
left after considering the main cranks; and taking the power to actuate the valve from any other pair of wheels is highly undesirable, both on account of the extra amount of lost motion introduced and the entire disability of the engine in case one side rod should break, if it should be the section between the wheels to which the main rod is attached and the pair carrying the eccentrics-on either side of the engine. The application of the Walschaert gear eliminates the possibility of such troubles, as this gear has no dependence on the axle for anything, and the eccentric can always be placed on the main pair of wheels.
The assertion that the Walschaert valve gear can be applied to engines of odd design without addition of complicated parts, where the Stephenson motion would have to include so much more weight of metal as to be almost prohibited, is proven in the case of this Belgian engine in Fig. 21.
In this engine live steam is used in all of the four cylinders and the operation of each is controlled by a separate piston valve of inside admission-a design of valve quite unusual in European practice-and both valves on each pair of cylinders are actuated by but one set of Walschaert's gear.
To glance at the set-up of the gear in Fig. 21,—the eccentric placed ahead of the main pin and the valvestem connected at the extreme top end of the com