Velocette Supercharged 500
Racing Bikes Velocette Supercharged 500 | |
Class | Racing |
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Manuals | Service Manual |
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Overview[edit | edit source]
Velocette Supercharged 500 1939
1939 VELOCETTE SUPERCHARGED 500. The war can be I-1 blamed for
a lot of things, and it certainly caused the premature
dropping of development on one of the most interesting racers ever to see the
T.T. course. This was the 500 c.c. supercharged Velocette, which appeared for
only one practice period in the 1939 T.T. The war started in September, so the
machine was stored away for the duration. After the war there was a ban on
"blowers" in international racing, so the "Roarer", as the model was
affectionately known at the works, was never raced again.
The machine was completely different from any racer ever to
appear before it. It was a parallel-twin which was virtually two 250 c.c.
singles mounted side by side, with their crankshafts parallel to each other and
geared together; this meant that, as the two halves of the engine obviously
revolved in opposite directions, they achieved almost perfect balance. Both
crankshafts were extended rearwards (they were in line with the frame), and the
one on the near-side drove the gearbox built in unit with the motor. The other
crankshaft extension drove the supercharger, which was mounted alongside the
gearbox. Final drive was by a shaft and bevel gear in the rear hub.
The engine was originally designed for liquid cooling, and so
the exhaust ports could safely be faced rearwards. To get the machine complete
in time for the T.T., air-cooled heads and barrels, with deep "square" finning
reminiscent of the KTT, were made and fitted but, surprisingly, the
rearward-facing exhaust ports were retained.
A special frame was employed, with swinging-fork rear
suspension of the type used so successfully on the 350 c.c. Mk. VIII KTT, and
front forks were also KTT-style Webb girdersbut both wheels had very special
full-width alloy hubs. *
The machine did not shine in its one practice session and was taken back to the
factory for further development. If the war hadn't . . .
If looks could win races this machine should have beaten them
all; the deep Velocet tank, massive engine unit and small forks gave the model a
cobby appearance. Note ti shaft drive and, in close-up, the supercharger driven
from the "right" crankshaft. Tl magneto and rev-counter drive are just behind
the barrels.
SPECIFICATION
Engine: parallel twin 500 c.c. o.h.c; two-geared crankshafts; drive to camshafts
by shaft and bevels. Ignition: magneto.
Transmission: shaft drive via four-speed gearbox bu
in unit with the engine. Frame: duplex cradle with pivoting-fork rear suspension
Forks: Webb T.T. girders with single compre:
spring and friction dampers.