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).
The Phantom III clutch and pedal, comparing different clutch plates and discussing potential modifications.
| Identifier | ExFiles\Box 93\3\ scan0330 | |
| Date | 5th July 1937 | |
| To E/Hdy.{William Hardy} c. to By.{R.W. Bailey - Chief Engineer} c. to Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} 312 Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler}2/JH.5.7.37. Phantom III Clutch & Pedal. Attached is curve Rm.{William Robotham - Chief Engineer}407, showing the cushioning obtained from the Ex.27309 and American Long driven plates, and the R.R. standard Phantom III plate is also shown for comparison. The Ex.27309 is the plate with English cushion springs and Thermoid facings, which is now in use on 9 Experimental and customers cars, so far with very satisfactory results. The Long plates have only just been received from America but are similar to one which has already done a considerable mileage on a Phantom in America. The small discrepancy between the two curves for the Ex.27309 plate observed by Borg & Beck and ourselves, may be due to different facings being used for the two tests, but in any case the deflections shown by the two observations agree fairly closely. We do not yet know whether the low rating of the Long springs is better or worse for judder, but the Ex.27309 springs will work in better with the clutch servo springs. The servo spring scheme was first fitted to 33-EX and is now on 32-EX in conjunction with the increased pedal travel now standardised. In both cases it works very satisfactorily, providing a remarkably light pedal pressure and is very smooth in operation. With regard to clutch leverage, we think that in view of the very light pedal pressure provided by the servo spring, the radius of the operating pin on the pedal should be increased from 1.300 to 1.400, which would increase the theoretical separation from .092 to approx .099, so that ample allowance can be made for preventing drag in the disengaged position without encroaching on the wear allowance, and still retaining a light pedal pressure, & this we are trying experimentally. [Handwritten in left margin]: Rm{William Robotham - Chief Engineer}|NRC.{N. R. Chandler}17/SH.6.7.37 | ||