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"An eccentric on the main shaft gives an oscillating motion to a circular disc called the wrist plate, pivoted at the center of the cylinder. It transmits motion to each of the four valves through adjustable links known as steam rods or exhaust rods, according to whether they move the admission or exhaust valves." —Derr, 1911

Steam Engine with Reynolds Corliss Gear

"An eccentric on the main shaft gives an oscillating motion to a circular disc called the wrist plate,…