This internal combustion engine incorporated a ported sleeve-valve to control the flow of the incoming petrol/air mixture and the exhausting of the products of combustion. This single-sleeve-valve replaced the more conventional mushroom shaped inlet and exhaust poppet-valve used on most internal combustion engines. Barr & Stroud are better known for their optical instruments, but after World War I, when demand for their products (notably range finders) dropped, the company diversified into motor cycle engines, partly in order to keep its skilled workers employed. The single-sleeve-valve design that they chose was the result of separate work by Peter Burt, a Scot, and L J McCollum, a Canadian.
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