b. The levers must have a double or bifurcated end at crosshead.
The double end is less likely than a single end to put an undue strain on the lever as the rod turns, and is also likely to give trouble from lack of lubrication or from a loosening of any small parts, and has proved to be the most satisfactory arrangement.
18. Valve Motion Stand.
a. The valve motion stand must be securely dowel-pinned to the yoke castings, to prevent any movement after being once adjusted.
19. Cushion Valves.
a. Cushion-release valves regulating the amount of cushion steam retained at ends of stroke must be provided.
b. The cushion release must be through an independent port as shown in [Figs. 2] and [3], so located as to positively retain a certain amount of cushion steam.
The old form of cushion release through bridge between ports is not acceptable. This form while leading into the exhaust passage as formerly, differs by starting from a small independent port (about 1⁄2-inch wide × 21⁄2 inches long) through the cylinder wall, located about 3⁄8 or 1⁄2 inch back from the cylinder head. (The exact position for affording the best action has to be determined by experiment with each different make of pump, as it depends somewhat on the extent of clearance space and on the point of closure of exhaust by piston and somewhat on the weight of reciprocating parts.)
Fig. 2.