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"The steam arm is keyed to the valve spindle which passes loosely through a bracket on which the bell—crank lever turns, and the spindle is packed to make a steam—tight joint where it enters the cylinder. Motion of the steam rod toward the right will turn the bell—crank lever and raise the hook stud." —Derr, 1911

Close up of Reynolds Corliss Gear from Steam Engine

"The steam arm is keyed to the valve spindle which passes loosely through a bracket on which the bell—crank…