A well engineered model of a Boulton and Watt ¾ll crank' steam engine, built by Mr D. Russell of Fraserburgh from drawings by Anthony Mount based on the 1802 original engine, the single cylinder approximately 1 1/2 inch bore by 2 1/4 inch stroke, with open crank and side rod linkages, steam valve operated from a rim on the flywheel, steam control valve, spoked flywheel 22cm diameter and small spoked belt drive wheel, finished in black paintwork, mounted on hardwood plinth measuring 29cm x 16cm, overall 31cm high. Note: The ¾ll crank' engine was introduced by Boulton and Watt in 1802. The design was formulated by William Murdock and the Soho foundry manager a Mr Southern. The aim was to supply a small self contained engine, to the smaller manufacturer who could not afford a house built beam engine. The design was called a ¾ll crank' on account of the shape of the rocking levers. These resembled the levers that transferred the pull of the ropes in a bell tower to the bells. The design was in production from 1797 until 1806, when Boulton and Watt introduced their small self contained beam engine mounted on a cast iron cistern. The earliest engines were filled with a form of drop valve. Then came the long 'D' valve, followed by the slide valve. This model is based on one from 1802 and has a long 'D' valve.