The Velocette prototypes Roarer and model O


The Prototypes : Roarer and Model O
The ROARER : (1939) A supercharged twin cylinder racing bike aimed at winning against the supercharged contemporary BMW. One single prototype was manufactured. 2 vertical cylinders, 4 stroke, OHV, 2 carburators 2 parallel contra-rotating crankshafts, geared together (a technical layout which will inspire the Model O) Cylinder : 497,7 cc (Bore : 68 mm ; Stroke : 68.25 mm) Compression rate : 8.78/1 then 7.5/1 Boost pressure : 4 psi Measured engine power : 54 bhp 3 plate clutch 4 ratio gearbox shaft driven This bike was raced at the 1939 Senior Tourist Trophy, where it experienced overheating and plug issues, leading to the decrease of the compression rate down to 7.5/1. Supercharged bikes being banned after WWII, it's never been raced again. It's been rebuilt rather than restored by its new owner Ivan Rhodes and his son Graham, starting in 1983. They needed to manufacture all internal engine elements from an exploded artist's drawing since no original drawings were available. Its official debut was the Historic Parade on the Isle of Man in 1989. Click here to see the details of the engine

The Model "O" : (1939) This is the prototype of a commercial bike which never went into production probably because of WWII. 2 vertical cylinders, 4 stroke, OHV, 2 carburators 2 parallel contra-rotating crankshafts geared together (a technical layout inspired from the Roarer) Cylinder : 688 cc Bore : 74 mm ; Stroke : 68.25 mm 3 plate clutch 3 ratio gearbox Shaft driven It's been fully restored during the 70's by Michael Postlethwaite and now belongs to Titch Allen. It is usually on display at the Stanford Hall Museum.