Trip valve gear

Trip valve mechanisms are a class of steam engine valve gear developed to improve efficiency. The trip mechanism allows the inlet valve to be closed rapidly, giving a short, sharp cut-off. The valve itself can be a drop valve or a Corliss valve.

Trip valve gear was applied to larger stationary engines. It was not used in transport applications,[ft 1] as it was not suitable for high speed.[1]

The trip point of the valve mechanism, and therefore the cut-off, would be adjusted either manually or automatically by the governor. The valve is opened by the mechanical valve gear mechanism, and when the trip gear trigger releases the mechanism the valve is snapped closed, usually by a spring acting against a dashpot.


  1. An exception was the very early London Steam Carriage (1803) which had a form of trip gear.


  1. Lowe, David Allan (1933). Heat Engines. London: Longmans, Green & Co.
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