HRD/Cross Rotary Valve

Roland Cross founder of Cross Manufacturing Company purchased from HRD in 1934 a Model P `rolling chassis` (frame, wheels, tank, seat etc.) into which he installed his revolutionary 500cc Cross Rotary valve engine on top of a Rudge Ulster crankcase with the drive through a 4 speed Burman gearbox. The Cross Rotary Valve engine (an alterative to a poppet valve version) has an aluminium liner-less cylinder barrel together with a special piston and high carbon steel piston rings, all designed and manufactured by this ingenious, innovative engineer. Running at 10.5 : 1 compression ratio and at 7,500 rpm the bike was capable of achieving almost 100 mph. A characteristic of a Cross Rotary Valve engine is considerable torque. An exhibit from the company private museum in Bath, it is on display by kind permission of Richard & Edward Cross (Directors).