Q. Describe the automatic by-pass valve of the American articulated compound engine. A. Fig. 353 shows these valves when assembled in their chamber, and their relation to the cylinder steam ports. (Each cylinder has a pair of these valves, in chambers cast outside them.) With open throttle the steam-chest pressure acting through the small ports, S, keeps the valves closed as shown in view B, Fig. 353. Fig. 353. By-Pass Valve, Articulated Compound Engine. With open throttle, they are automatically opened by the atmospheric pressure admitted through the air vent (shown below in the cut) and they then connect the admission ports at either end of the cylinder, as shown in view A. Q. What is their object? A. To permit the engine to drift freely when running with a long cut-off. Q. What is the advantage of the "articulated" engine? A. No dead weight; for a given weight per axle, greater hauling power; or conversely, for a given tractive power, less weight per axle. The articulation halves |