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THE WALSCHAERT VALVE GEAR
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