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"When set full gear forward, the valve admits steam to the crank end of the cylinder, and the crank revolves as shown by the arrow. As the crank turns, both eccentrics impart motion to the link, but the "go ahead" link pin H approximately coincides with the link block." —Derr, 1911

Eccentric Motion of the Steam Engine Crank in Full Gear

"When set full gear forward, the valve admits steam to the crank end of the cylinder, and the crank…