Locomotive Engine Running and Management

by Angus Sinclair

ARRANGEMENT OF THE MOTION

Fig. 27.

In the Stevens motion two valves are employed, one at each end of the cylinder, as can be seen in [Fig. 27]. The valves have supplementary passages for steam and exhaust, being an improvement on the Allen valve. Valves without the supplementary exhaust-port have been designed by Mr. Stevens for his engines, and they are shown in two positions in the supplementary figures 2 and 3 [[p. 288]]. These valves closely resemble the Allen valve; but, in operating, steam is admitted to, and exhausted from, the cylinder through the same passage. This arrangement provides double area of admission and double area for exhaust steam,—an important consideration, especially with high piston speed.