Photo print of horizontal Tandem Compound Engine

Photo print of horizontal Tandem Compound Engine, 1200 indicated horse-power fitted with Inglis patent Corliss valve gear, 1863, and Knowles supplementary governor 1883

The engine represented is fitted with a modification, patented by Mr. W. Inglis in 1863, of the Corliss valve gear originally brought out in 1848. The valves are operated by "wrist plates" rocked by eccentrics on a countershaft connected with the crankshaft, but the closing of the steam valves is effected, when released or tripped, by helical springs in small air dash-pots. The period of release is determined by a high-speed governor, assisted by a supplementary one patented by Mr. W. Knowles in 1883, its function being to vary the length of the rod from the main governor to the trip gear, and so remove the slight change of speed that had caused the main governor to alter its height. The engine is of the tandem two-stage expansion type, with cylinders 32 and 54 in. diam. by 6 ft. stroke; under steam at 85 lb. pressure, it makes 51 rev. per min. and indicates 1,200 h.p.