One of the excellent engines by John Cogden, built without castings, photographed at the Harrogate exhibition. John is a regular exhibitor with the City of Sunderland Society.

This one is based on a rotary design from 1880 by W.A.Coomber, engineer, of Scotland Street, Ironworks, Birmingham, and described in The Engineer on January 21st 1876. The unusual design features a double ended piston with rollers at each end that follow the inside profile of the cam. The cylinder is a one piece unit that rotates with the shaft. Valving at one Bearing admits steam just as one roller starts pushing downhill on the Cam, causing the Cylinder and Shaft to turn.

A Constructional Series by Tubal Cain in Engineering in Miniature commenced October 1990, Vol 12 No. 5.