Allen Engine

Designed by John F. Allen, built 1862 in conjunction with Chas. T. Porter. The Allen valve-gear embraced the following features: 1st, giving separate and different movements to valves for admitting and exhausting the steam, so that a variable cut-off was po ible with fixed release and compre ion; 2d, effecting this by a fixed link driven by one eccentric standing at the same angle as the crank, the cut-off varied by the position of the block in the link; 3d, the use of a double-opening valve, occupying le room than a gridiron valve; 4th, an adjustable pre ure plate, resting on inclined supports, and held by the steam-pre ure as close to the valve as adjusting screws will permit. The engines built by Mr. Allen and embodying these principles were not intended to run at the high speeds which were adopted by C. T. Porter. An Allen engine of 1868, still extant, was designed to run at 75 revolutions per minute.