This engine was originally introduced by Matthew Murray in 1802. It was one of a number of engine designs produced after the Boulton and Waft patents expired. It could be classified as a portable engine, in that it was not house built, being self contained it could be erected anywhere. It was of about 5hp and was condensing, working at a low pressure. A unique feature of the engine was the hypocycloidal motion, whereby reciprocating motion was transformed into rotary motion. The geometric principle is that a point on a circle rolled around the inside of another circle of twice the diameter will scribe a straight line. In practice the small circle is a spur gear which rolls around inside a ring gear with internal teeth. As the piston rod rises and falls, the end is pivoted on a pin fixed on the periphery of the small gear. The small gear rolls around and through a crank drags the crankshaft round.

This model was built from an article in CQ by Howard Somerville.

Build date 11-09-2011