The Locomotive Of Today

The Engine: Cut-off. 117 amount of wiredrawing, owing to the slowness with which the valve closes the port as the point of cut-oft' is approached. It is not, as a rule, advantageous to cut off steam at less than 20 to 25 per cent, of the stroke of the piston, owing to the faet that the steam is wire-drawn by being fbreed into the cyl- inder through so small a port opening, also the cushioning be- comes very great at this travel of the valve, and if the latter is arrangeel so that the cushioning is lessened, the comparative coolness of the exhaust steam would lower the temperature of the ports, etc., so that the entering steam for the next stroke would be further reduced in pressure by coming in contact with them. These various effeets depend upon the correctness with which the valve motion has been designed and con- structed, and the exact amount of influence which each has upon the engine, can only be determined from the engine itself by the use of the steam indicator.