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 Velocette - 500 Roarer (compresseur)
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Velocette Roarer (compresseur) motocyclette motorrad motorcycle vintage classic classique scooter roller moto scooter
Photo ou archives : J-P. Praderes

Capacity : 500
Model : Roarer (compresseur)
Production : 1939 -
Category : (R) Racing


500 Roarer Supercharged Twin -1939

Unfulfilled promise

The Veloctte Roarer was a casualty of WWII. Conceived in late 1938 by designer Harold Willis, it was constructed during the spring of 1939. It only ran in practice for the 1939 TT, and the postwar ban on superchargers brought an end to its career. This unique British attempt to strike back at BMW might have given Velocette the same dominance at the highest level that it already enjoyed with its KTT clubman racer.

Geared Crankshafts

Designed in parallel with a twin-cylinder tourer, the Roarer had nothing in common with the road-going machine save the original layout of its engine, which had two transverse crankshafts geared together for perfect balance. Each cylinder had its own independent single overhead-camshaft driven from a common kingshaft. Cylinders and cylinder heads were of aluminum and the crankcase was entirely made of magnesium.

Enormously Flexible

The supercharger, built into the rear part of the engine unit, fed the cylinders at the front by two backward-sloping intake pipes whose length ensured tremendous engine flexibility. The transmission shaft - chosen to prevent oil from getting onto the rear tire – ran inside the swing arm of the rear suspension in the most modern manner. The planned telescopic forks had been replaced, at the request of Stanley Woods, by a classic girder fork. Tried over the TT course during the 1939 practice session, the Roarer showed its immense potential. It steered like a dream and was turbine smooth.


Engine: 496cc (68x68mm) air-cooled twincylinder four-stroke; dry-sump lubrication

Power Rating: 54 hp @ 7000 rpm

Valves: overhead-camshaft driven by shaftand- bevel gearing

Fuel System: supercharger and carburetor

Transmission: 4-speed, multi-disc clutch; shaft final drive

Suspension: Webb girders (front); swing arm

with twin Dowty oil dampers (rea r)

Brakes: 10 inch drum (front & rear)

Wheels: wire (front & rear)

Weight: 370 lb

Maximum Speed: 145 mph


The legendary Roarer is once again in running order, thanks to an extensive restoration by marque specialist Ivan Rhodes.


Le fichier Moto Passion réalisé par François-Marie Dumas réunit près de deux mille photos accompagnées d'un historique très complet des machines présentées.
Il sera progressivement mis à jour ici et toute information complémentaire est la bienvenue sur info@moto-collection.org.

Cette documentation unique, qui constitue sans doute l'encyclopédie la plus exhaustive jamais écrite sur l'histoire de la moto, a été réalisée avec l'assistance de nombreux spécialistes dont principalement Didier Ganneau, Christophe Gaime, Mick Woollett, Jean Goyard, Bernard Salvat, Christian Rey, Yves Campion, Helmut Krackowizer, Michael Dregni, Michel Montange, etc. que je remercie ici.

Disponible sur demande :
- Les fiches originales sur papier
- Les photos et archives signées de mon nom en haute définition ou les documents originaux.
Me contacter sur info@moto-collection.org pour les conditions et droits d'utilisation.