Photo ou archives : M. Woollett
7503
RALEIGH
500 Grand Prix - 1931
A wizard bikeÂ…
Famed for its bicycles, Raleigh of Nottingham also built motorbikes between 1899 and 1933 – even racing a very quick 500cc machine in a number of Continental Grands Prix between 1928 and 1931. The engines were built by Sturmey-Archer, which was better known for its gearboxes; the design was by the famous Daniel "Wizard" O'Donovan, who had made his name with his exploits on Nortons, both as rider and tuner.
Six of the Best
The 500 Raleigh of 1930 could reach 100 mph, and despite fierce opposition, Arthur Tyler won the 500cc class in the Austrian GP. The marque also took third place in the Belgian GP. Spurred on by these results, O'Donovan devised a new machine for 1931. Six examples were built – three 500s and three 350s. They were virtually identical – the smaller capacity being achieved by retaining the stroke of 101mm but reducing the bore to 66.3mm.
Costly Construction
Noble metals were widely used; the crankcase and gearbox castings were made from magnesium. The engine internals were polished, and instead of a total-loss oiling system, the new engines had dry-sump lubrication with a system that incorporated at least three oil pumps. The valves gear was totally exposed, the intake manifold was inclined at 15 degrees and a Bowden carburetor was fitted. Tyler finished seventh in the Senior TT, but the Raleigh could not match the new ohc Norton, and the Nottingham company withdrew from competition at the end of the season.
SPECIFICATIONS
Engine: 495cc (79x101mm) air-cooled single-cylinder four-stroke
Power Rating: 36 hp @ 5700 rpm
Valves: overhead
Fuel System: Bowden carburetor
Transmission: Sturmey-Archer 4-speed, chain final drive
Suspension: girder forks (front); rigid (rear)
Brakes: drum (front & rear)
Wheels: 21 inch (front); 20 inch (rear)
Weight: 298 lb
Maximum Speed: 105 mph
The works Raleighs of 1931, like this 500, made extensive use of magnesium castings. The cost of building the six GP racers was around $100,000 – a fortune for the period!