Read Part 1 of David’s Memoirs here
Part 2 – The Second Round
With my studies now complete I left Allard’s to do two years National Service in the Royal Air Force and some two years later I had to consider my future. After a brief chat with Sydney Allard I gave up thoughts of going for an interview with de Havillands and rejoined the now much smaller Allard Motor Company.
The Gran Tourismo Jaguar powered car was based on the Palm Beach/JR tubular chassis and was to be built at the South Side Clapham workshop. My first task was to design the mountings for the Salisbury 4HU differential unit for the prototype G.T. which originally had a live axle and was to be converted to a De Dion axle. The axle used the fully floating rear hubs, as used on the JR and had trailing link rear suspension with lateral location by Panhard rod.
The front suspension was based on the MacPherson system using laminated torsion bars connected to the vertical sliding pillar by ball-jointed link. It’s design originated from Dudley Hume and the consequence of this linking system produced very heavy steering. As the ‘new boy’ it was not for me to try and convince Sydney that there was no simple solution to reduce the heavy steering loads. Reductions in castor angle had virtually no effect. At the same time the existing drum brakes were to be replaced with front disc brakes, new hubs and adapter plates had to be designed to mount the Girling callipers. As a single master cylinder was used a proprietary brake booster was fitted which allowed additional pressure to be applied to the front disc brakes so that it was possible to achieve an acceptable brake balance.
Most similar applications had used a servo to achieve acceptable brake pedal pressures, however the booster worked satisfactorily, albeit with a slightly long pedal. The Salisbury differential unit had to be fitted with backplates and brake drums, which was relatively easily achieved. However the handbrake operating linkage was only achieved with considerable difficulty.