_a._ The valve motion levers must be steel, wrought iron, or steel
castings. Cast iron is not acceptable. Steel castings, if used, must
be deeply stamped with the name of the makers, with letters one-eighth
inch high, near the upper end of each lever, where it can easily be
seen,—thus “....._Steel Castings_.”
Cast-iron arms, if bulky enough to be safe against external blows,
are awkward in shape. The sectional area necessary for any arm
depends upon the means provided for preventing a sidewise strain on
the lever, due to rotation of piston or friction of its connection
to piston rod. The spool or crosshead on the piston rod should be so
designed that no sidewise strain can be thus produced on the lever.
_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.