Drawing of Boulton and Watt's Bell Crank Engine

Drawing of Boulton and Watt's Bell Crank Engine 1802

This arrangement of engine was introduced by Messrs. Boulton, Watt & Co. in 1799 to 1806; it was designed with the object of obtaining an engine that was self-contained, and more compact than the established beam engine. The cylinder is vertical and double-acting, and by two vertical return connecting rods oscillates the horizontal arm of a bell-crank. From the vertical arm of the bell-crank a horizontal connecting rod proceeds to a crank on the fly-wheel shaft. A vertical air-pump is provided and is driven from the bell-crank. The engine foundation and the condenser tank are formed by one casting which carries the crank-shaft bearing. The steam is distributed by a long D slide valve worked by an elliptical cam bolted to the fly-wheel arms. These engines were made of from 4 to 8 h.p.; one was supplied in 1805 for Robert Fulton's paddle steamer Clermont"; another was in use at the Soho works till 1896.