1925 Douglas 596cc RA Model OB

Registration no. BF 5631 Frame no. 5759/3 Engine no. OE 124

• Rare overhead-valve sports model
• Originally used for off-road racing
• Completely restored in 2010

Douglas had built racing and experimental overhead-valve motorcycles prior to WWI but the first production OHV models did not emerge until after the war's end. In September 1921 at Brooklands an overhead-valve Douglas set new 350cc records at 200, 300 and 400 miles. The first production models appeared at that year's Motor Cycle Show and soon demonstrated an enviable combination of speed and reliability. Sales were boosted considerably when in March 1922 Cyril Pullin became the first man to exceed 100mph on a '500' riding one of the new OHV Douglas models. Having made a successful start, Douglas improved upon the concept with the successor RA model, which took its name from the British Research Association, designers of the novel disc brakes fitted front and rear. There was a new frame and the gearbox was relocated above the rear cylinder, enabling the engine to be mounted lower down. Instead of a separate oil tank, engine lubricant was contained within a large aluminium sump. Another novel feature was the use of a twist grip for throttle control instead of the customary lever. Extensive use of aluminium kept the weight down to an admirable 275lb.

Riding an RA, Manxman Tommy Sheard won the 1923 Isle of Man Senior TT while Jim Whalley won that year's French Grand Prix and Spanish 12 Hours race. Capitalising on the RA's success, Douglas marketed it as the 'IOM Model', claiming that it was identical with the TT winning machine. The first standard production versions of the RA were launched at the Olympia Show in October 1923 designated OB/24 (596cc) and OE/24 (346cc).

The Model OB offered here has larger brakes than the standard production version, which may indicate that it was specially built as a 'works' machine. We are advised by the private vendor that it was originally used for off-road racing before being modified for road use with mudguards and road tyres. The vendor advises us that the entire machine was restored in 2010, the engine being re-bored and fitted with new pistons; the paintwork refurbished; and the nickel brightwork re-plated. Accompanying documentation consists of a Douglas Club dating letter and a V5C Registration Certificate.