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Why would anyone want a single gab valve gear for stopping the engine? Why not just close the steam valve? Starting and stopping are not normal functions for a valve gear. Biscuittin (talk) 16:50, 27 February 2012 (UTC)[reply]
Winding engines were the usual need, where the engine has to be stopped very precisely. This is described in the article, with a photograph of someone driving a winding engine and an illustration of a single gab gear (several more at Commons).
Another use for valve gear (although not relevant here) is for speed control. For high-speed steam engines driving generators, the old Watt or Porter-Allen governors (controlling a throttle valve) don't give accurate enough control, so these engines used inertia governors that controlled the valve gear cutoff, usually with a simple eccentric gear. Andy Dingley (talk) 17:08, 27 February 2012 (UTC)[reply]
