Stationary Engine Kits

Anthony Mount Models

Scotchcrank Engine 1846

The Scotchcrank engine is unusual in that no connecting rod is required. The reciprocating motion is converted to rotary motion by the piston rod having a horizontal slot in which fits the crankpin. As the piston rod rises and falls the crankpin moves along the slot giving rotary motion to the crankshaft.

I have never seen an explanation as to why the motion is called “Scotchcrank”.

The design is attractive not only for the unusual motion but for the delightful architectural features of the period in which it was built.

Due to the form of construction most of the parts are fabricated. Gunmetal castings are only used for the flywheel and cylinder. The slide valve is of conventional form but is housed in a steamchest as used for long D valves. Also of interest is that the steam inlet and exhaust come up through the columns and enter and leave the cylinder along the same centreline.

The entablature core and beading are fabricated. The base is a 5mm thick mild steel plate.

The flywheel is 9” (228mm) diameter and has eight spokes. The cylinder is 3 1/8” (80mm) long and F’ (25mm) bore. A Watt type governor is fitted.

The model can be built on a 3 ½” (89mm) lathe, a milling machine is a help but a vertical slide should cope with most of the milling operations. A full set of 26 drawings of A4 size are available, and have imperial and metric dimensions.

The model was described in Model Engineer from 20th November 1998 to 4th June 1999, alternate issues.