The first Douglas OHV models gained fame at Brooklands where they set records for 200, 300 and 500 miles in the 350cc class in 1921.
Very soon afterwards their first production models were revealed at the Motor Cycle Show later that year for the 1922 season. The RA model, which took its initials from the British Research Association which designed the "disc" brakes fitted to the new machines, which boasted a new frame with the engine mounted to lower the centre of gravity. The engine, in addition to being OHV, was a wet sump unit with the gearbox mounted above the rear cylinder. Throttle control was by twist-grip.
At the 1923 TT they absolutely blitzed the mountain circuit with their 9 machines and many of the finest riders of the day including Cyril Pullen who had earlier taken a Douglas to over 100mph, the first rider to do so on a 500cc machine.
They also took the sidecar class with a "leaner" machine ridden by Freddie Dixon (who designed the banking sidecar) and his partner Walter Denny.
By 1924 the RA was marketed as the IOM model.
In 1926 it was renamed the TT Replica.
From the 1925 Catalogue:
ТHE "25 I.O.M." 3½ h.p. Douglas will make a particularly strong appeal to the speedman and the competition rider. Its design and construction are based upon experience gained in successfully contesting speed events throughout the world; it combines perfect road holding and marvellous cornering abilities with phenomenal acceleration.
The "I.O.M." Model has carried off practically every classic race in which it has been entered. It won the 1923 T.T., and was the first motorcycle to do the T.T. course at and over 60 m.p.h. officially timed. It finished 1st, 2nd, 3rd, 4th, and 5th in the San Sebastian Grand Prix, 1924; won the French Grand Prix, and also the Spanish 12 hours' race, and in the hands of private owners has gained innumerable awards at Club hill climbs and track events.
Unlike many speed machines, the "I.O.M." model is extremely tractable and flexible, and may be ridden to the venue with perfect safety and even used for fast touring work.
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