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 analysis of clutch performance, wear on different linings, and potential improvements under various driving conditions.
| Identifier | ExFiles\Box 19\4\ Scan033 | |
| Date | 13th June 1930 guessed | |
| -2- Phantom, regardless of mileage." (This is expl. clutch with fabric on driven disc). "All the improvements which have been made from time to time in manufacture, whilst they have undoubtedly rendered the clutch nicer to handle when new, are definitely shown by these figures not to have the least effect in improving the life ---- " "Conditions of traffic driving in places like New York are undoubtedly the underlying cause of the harsh treatment that clutches receive and with increased congestion of traffic and increase in the use of traffic-lights throughout the country, we can only expect this condition to get worse rather than better." It may be that the three speed box of which the two upper speeds only are used in starting from rest, may increase clutch-slipping relative to the 4 speed box on which three speeds are normally used. Under congested traffic conditions, however, one can always count on the driver using the least number of speeds which will avoid stalling the engine, and this is specially so on P.I because of the slow action of the clutch brake, which prevents quick changing when oil is warm. I have given the above figures simply to point out that the improvement in the clutch is considered one of the most vital of the proposed alterations. It might be well to add that what we have found happens to the clutch linings: (a) When heated by slipping the coefficient of friction rather rapidly falls below the critical value (.193) which will transmit the full engine torque. (b) When a lining which has been slipping badly is removed, it has a normal polished appearance, but the non-metallic material is found to be charred or carbonized to a depth of about 1/32". This is sometimes so loose that it can be blown out with an air blast. (c) An alternative lining (Johns-Manville) of similar construction to the Ferodo, was tried experimentally and gave a much smoother-operating clutch with little attention to adjustment. It even gave smoother operation without using a spring-pressure plate. In the standard clutch it lasted longer than Ferodo under slipping tests. cont'd.{John DeLooze - Company Secretary} | ||