HRD/Cross Rotary Valve

Roland Cross founder and Managing Director of Cross Manufacturing Company purchased in 1934 from HRD a Model P `rolling chassis`. Frame, forks, wheels, petrol tank , etc. Historical records show the components (frame, wheels etc.) being built by Ted Hampshire the racing frame specialist at HRD Motorcycles and being inspected and `signed off` for delivery by the legendary Phil Irving. Upon receiving the `rolling chassis` Roland Cross installed a 500cc Cross Rotary Valve engine with drive through a 4 speed, foot change Burman gearbox. The ingenious engineer that was Roland Cross designed and manufactured his rotary valve engines using aluminium liner-less cylinder barrels, aluminium pistons of special design, Piston rings were produced from high carbon steel wire by a unique Roland Cross manufacturing process. These rings were far, far superior in performance and durability to the cast iron versions of the day. With no cams, push rods, valve gear etc. the Cross Rotary Valve engines ran quietly compared to the OHV or side valve models. Running at 10.5 : 1 compression ratio and 7,500 rpm performance was outstanding for the mid – 1930`s with this HRD/Cross Rotary Valve powered motorcycle capable of achieving a top speed of almost 100 mph. A characteristic of a Cross Rotary Valve engine is the amazing torque with this motorcycle flexible to low speeds (a fast walking pace) in top gear and then accelerating to its maximum. From the Cross Manufacturing Company private museum and exhibited by kind permission of Richard and Edward Cross.