From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Potential improvements to the 20/25 chassis steering and back axle.
| Identifier | ExFiles\Box 107\1\ scan0279 | |
| Date | 11th April 1935 | |
| - sheet 2 - E.6/HP.11.4.35. (2) 20/25 Steering. We have always been mystified that the 25-HP. steering should be so heavy relative to the Phantom, having regard to the scale effect of the two chassis, and we, therefore, think that the reduction in the cross steering poundage mentioned in Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KW.6.4.35 is absolutely justified. Also we think the time is certainly overdue for lowering the overall steering ratio on this chassis, having regard to its increase in weight and the modern development towards lower overall ratio steerings. I am, therefore, in favour of the shorter pendulum lever which reduces the ratio from 12¾ to 14 and has very little adverse effect on the steering geometry as an immediate measure of improvement. We have issued a scheme for fitting the SpectreCodename for Phantom III Marles steering box to the 20/25 chassis. This would give us the maximum amount of improvement available in providing a light steering free from joggles. (3) Back Axle. Here again the 20/25 chassis has fallen behind in respect to improvements which have been applied to the Phantom and Bentley. The two latter chassis are fitted with hypoid gears with a very rigid mounting for the crown bevel now universally employed, and the axle box is of a composite steel and aluminium construction. The bevel gears have also fewer larger teeth. I would recommend adopting the stronger crown bevel wheel and mounting as soon as standardisation would permit, together with some alternative sets of gears having coarser teeth. The adoption of the Wraith axle with the lower ratio would have modernised this unit and the difficulty with silencing the present axle was one of the reasons for urging it. It should not be forgotten that our noise isolation scheme will probably be beneficial in helping us with this question of axle noise. We have found that the difficulty has been intensified by the modern types of bodies fitted with boots and tails at the rear, but if these features, | ||