1966 Alpha Centuri

Alpha Bearings started shortly after the Second World War, making big-end bearings for motorcycles. The company started out with Frank and Norman Cutler making parts in a shed; the company grew, first to a factory in Oldbury and then in Dudley. In the early 1960s, Alpha became part of the E and H P Smith Group, which included Royal Enfield and the Albion Gear Company. Alpha provided main bearings, big-ends, connecting rods and cranks to the motorcycle industry. While these parts provided a decent revenue, Frank Cutler, managing director at the time, wanted to make his own engine. Initial attempts to make a single cylinder rotary valve engine made some progress, producing two prototypes, which were underpowered. So Frank decided to produce a 250cc rotary valve twin. Traditionally, rotary valves are mounted on the side of the engine crankcase as seen in the Bridgestone twin earlier in this article. This would have required Alpha to make the gearbox as well as the engine and make the unit prohibitively expensive. The solution Frank adopted was to mount two disc inlet valves in the centre of the crankshaft, fed from a single carburettor. Albion provided the gearbox and primary drive. Initial testing used Bantam cylinder heads and cylinders from the Velocette Viceroy Scooter. The engine was named ‘Centuri’ and the unit was mounted in a DMW chassis. Frank’s son Mike rode the DMW every day, clocking up 1000 miles. After the initial tests, a second engine was built, which used Alpha’s own cylinders and heads. The porting and expansion chamber exhausts were designed by Fred Hadley. This was fitted into a DMW Hornet racer, then Royal Enfield loaned the project a GP5 and the second engine