Designed in the 1930s for generating and pumping. The twin cylinder engine with its square 1 in bore and stroke has a fully-enclosed cast-iron crankcase containing a steel 180 degree throw crankshaft. There are cast iron pistons and a stainless steel piston valve. Stuart says 0.4 bhp at 2800 rpm on 80 psi superheated steam. This engine was used during the war in the Alco Firefly generating set where it was run at 30 psi for radio battery charging duties. After the war it enjoyed much success in flash steam hydroplane racing.