Al BLOWN 30-9S VAUXHALL A NEAT INSTALLATION EMPLOYING A CHAIN-DRIVEN MARSHALL CENTRIFUGAL SUPERCHARGER.
MOST of us at one time or another have toyed with the idea of fitting a super-charger on a standard sports car, mostly with the idea of improving the distribution and power-output at low speeds ; for any substantial rise in maximum power output is apt to be resented by big-end bearings and other highly stressed parts. Unfortunately, the standard types of supercharger, whether of the single or the twin rotor type, are costly in the larger sizes, and are not easily accommodated under the bonnet of the average car, while the supercharging effect is more than is really required in the case which we are considering.
An interesting solution of the problem has been arrived at by Dr. R. A. Beaver, whose 30-98 Vauxhall has put many younger vehicles to shame on the Brooklands Mountain Circuit during last season. The engine had already been brought to the maximum efficiency obtainable on Ethyl, and develops some 115 h.p. and reaches something near the hundred mark in the short run from the Members Bridge to the Vickers Sheds. The next stage was either to raise the compression, which would have made the car unsuitable for road use, or to use a supercharger.
Dr. Beaver decided in favour of the latter plan and obtained one of the new Typhoon centrifugal blowers made by Marshall Superchargers Ltd., which cost £9 10s. Od and blow at 11 lbs. at 5,00C r.p.m. The Vauxhall runs up to about 4,200 r.p.in. and the blower runs at 2* times engine speed. At maximum revs a supercharge pressure of about 3 lbs. is expected, while the horse-power should be in the neighbourhood of 150. The blower is only four inches deep, and so it was found possible to find room for it between the radiator and the front of the engine. It is supported on a cage-like structure of steel rods, bolted on to the
fan mounting, and the water pump is now accommodated inside the cage and driven from the spindle of the supercharger. The latter is driven by roller chain from a sprocket mounted on the fan-belt drive-shaft, and runs at just over twice engine speed. before the first Brooklands Meeting, so it will probably not be possible to get the job completely ” an point” before its first public appearance. A remarkable thing about this ten-year old car, with its 4flitre engine, is that its total weight is only 26 cwts., comparing favourably with
The original induction pipe is used, but in an inverted position. One of the greatest problems was to find a suitable carburettor, since the aeroplane-type vertical Zenith could not be adapted to the horizontal intake of the blower, but in the end a horizontal R.A.G. has been pressed into service. Unfortunately, the job was not completed until a short time
many of its contemporaries of half the capacity.
the installation of the supercharger was carried out by Messrs. West and Chitte:ndon of 306A, Walworth Road, S.E. 17, who, it will be remembered, also constructed the interesting LambdaDilambda combination mentioned in these pages last year.