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).
Technical letter discussing the clutch defects of the Silver Ghost and comparing them to the Phantom model.
| Identifier | ExFiles\Box 74\2\ scan0226 | |
| Date | 13th March 1929 | |
| -2- 13th March 1929. The defect of the Silver Ghost clutch was that its mass prevented easy gear changing, and R.{Sir Henry Royce} considered this to be so serious a defect that he was prepared to face the fact that the Phantom clutch could not be used as a 'slipping' member without causing trouble, rather than be handicapped with the real difficulty in gear changing which must exist with the Silver Ghost combination. The fact that the Phantom clutch would not stand nearly as much punishment as the Silver Ghost was fully appreciated at the time the design was got out and during its experimental testing, but it was considered that the flexibility of the engine and its capacity for slow speed running was such as to negative the need for clutch 'slipping', and our experience in England (taking say London conditions) has justified the change. There is no doubt at all in my mind that the grabbing and slipping you refer to is the result of excessive clutch slipping resorted to in order to run slowly in traffic instead of throttling the engine back or in the extreme changing down to meet such conditions. With reference to the proposal to ventilate the clutch, I cannot see the possibility of doing any good in this direction, as the plate itself during the 'slipping' is insulated from the air by non-conducting asbestos fabrics, this being so it is pretty certain that no amount of air passing through the clutch is likely to cure the trouble, even if it took the form of a positive air blast. The Silver Ghost was doubly protected by having in the first place a large mass of steel to heat up, and secondly it exposed large surfaces in direct contact with the air, which surfaces were larger in diameter than the clutch surface, but with enormous areas between the two, so that the temperature gradient was low, and therefore the temperature on the clutch surfaces was very little above the temperatures of the exposed outside diameter and angular faces of the flywheel. The only remedy that I can see for the trouble you are in is to instruct owners that the clutch is not intended for 'slipping' for long periods. The use of the gears should apparently obviate entirely the need for 'slipping' except for the purpose of starting the car or gear changing. We are sending a copy of your note to R.{Sir Henry Royce}, so that he will know your difficulty, and may possibly suggest something further than I have been able to do in the foregoing explanation. Yours faithfully, M Harvey Bailey TECHNICAL PRODUCTION ENGINEER. FOR ROLLS-ROYCE LIMITED. | ||