The bellcrank engine was introduced by Boulton & Watt in 1802. The design was formalized by William Murdoch and his Soho iron foundry manager,  Mr Southern. The aim was to supply a small self-contained engine for the smaller manufacturer who could not afford a house-built beam engine.

The design was called bellcrank due to the shape of the rocking levers which resembled the levers that transferred the pull of the ropes  in a bell tower. It was in production until 1806 when the company introduced a small self-contained beam engine.

A fascinating project for anyone seeking a  rarely seen model for which Anthony Mount’s design and castings were introduced by Bruce Engineering and are now understood to be available from Polly Model Engineering. Drawings and building instructions can also be found in Anthony’s book Historic Engines Worth Modelling Vol 1.