Connaught's PDK

Sir,
In his article on the Porsche PDK gearbox (Motor Sport, November 1987), MLC mentions various other gearboxes, including the Wilson gearbox used by ERA, HWM and Connaught. This, and the description of the PDK gearbox, reminded me of the gearbox/final-drive unit inspired by Rodney Clarke and designed by Robert Clerk while I was working for Connaught, which was intended to be fitted to the rear-engined monocoque J5-type 21/2-litre GP car which we dropped when the Godiva engine was shelved. Parts for six of these ‘boxes were made, and one was assembled, but never used. All were sold at the Connaught Engineering auction in 1957 and seem to have disappeared.

The gearboxes were, as I say, in unit with the final drive (transaxle) and incorporated the usual Connaught provision for rapid final-drive ratio change. The gearboxes were of five-speed epicyclic Wilson-type pre-selector design, with self-contained hydraulic gearchange actuation, to reduce the clutch pedal load. Selection upward was automatic as on Roesch Talbots, engagement of first selecting second, of second selecting third, and so on. The gear selector lever was intended to protrude through the instrument panel, convenient to the driver’s hand, and had three positions: central (into which it was spring-loaded), down and up, the latter being over-ride. The lever was only for downward selection, and was pushed down as many times as it was required to go down gears, Gearchange was effected by a light dab on the pedal, hydraulics in the gearbox doing all the work.

The complete diff/gearbox unit, designed for about 300 bhp, was required to weigh no more than the magnesium alloy cased four-speed gearbox and differential unit as used on A and B series cars, and! think this was achieved. This gearbox/dliff unit was designed and made in 1953 and I think is another indication of Rodney Clarke’s brilliance, together with his mid-engined coupes in 1950, advocation of the wedge-shaped car in 1951, anti-lock braking, hydraulic roll sensing and correction (active suspension) in 1952, ground effect investigation from 1953 onwards (Connaught built its own wind-tunnel and had its own aerodynamicist). Of course there was also the J5 rear-engined monocoque GP car of 1953, among other ideas. But Colin Chapman thought of all these things — later).

CE Johnson, Woking, Surrey