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).
Collected data on clutches, comparing pedal effort and separation across various chassis and proposing methods for improvement.
| Identifier | ExFiles\Box 103\1\ scan0154 | |
| Date | 4th February 1935 | |
| 45300 To R.{Sir Henry Royce} c.c. to Wor.{Arthur Wormald - General Works Manager} c.c. to Da.{Bernard Day - Chassis Design} c.c. to By.{R.W. Bailey - Chief Engineer} c.c. to Hdy.{William Hardy} Hs{Lord Ernest Hives - Chair}/Cry.D/KW.4.2.35. Clutches. We attach herewith data we have collected concerning the clutches on our various chassis. Sheet No. 2 shows a marked decrease in pedal effort over the clutches of two years ago. This has not been obtained without an adverse effect on other features. The only way to reduce the pedal effort without affecting the separation or pedal travel is to increase the size of the clutch, which we know cannot be done. Comparing the SpectreCodename for Phantom III with the Phantom we notice a decided drop in pedal effort, but also a large decrease in separation of the pressure plate. The Phantom with a theoretical separation of .086 - .012 is on the verge of not having enough. Clutches in the Test Dept. only just free. When the clutch stop was left off they reduced the cushioning to .005 or the clutches would not free. The new 20/25 clutch to R.Sch.3948 only just frees. We do not expect therefore the SpectreCodename for Phantom III Clutch with a theoretical separation of .061 minus, at least .015 due to stagger of the driven member, to free sufficiently. The argument that with synchromesh 2nd gear this does not matter is not true, as gear changes are adversely affected by a dragging clutch. Also reverse gear is not synchromeshed. There are three methods of increasing the separation - (1) Lower the pedal ratio, which will increase the pedal effort. (2) Lower the spring poundage. Although the clutch will still transmit full torque it will not "bite" so quickly after bad gear changes. (3) Increase the pedal travel. | ||