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).
Analysis of clutch separation, torque transmission, and slipping issues across various models.
| Identifier | ExFiles\Box 13\7\ 07-page133 | |
| Date | 9th July 1932 | |
| -2- WE/Gez.11/dm.{D. Munro}9.7.32.Cont'd.{John DeLooze - Company Secretary} We have measured the actual clutch separation on a L.H. Chassis and find it to be .061 against a drawing figure of .087. The losses were measured to be as follows :- Due to bending of the clutch fingers .007. " movement " cover plate .006. " losses before the trunnion .014. _____ .027. A further .012 of the separation is lost due to the spring loaded movement of the inner Ferodo. On the 25h.p. the actual clutch separation is .107 against a drawing figure of .125 of which .025 is lost due to the set up of the driven plate. The maximum engine torque that the clutch has to transmit is for :- 25HP. 161 lbs ft STD.P.II. 311 lbs ft 19-EX. 358 lbs ft Assuming that the standard 25HP and P.II clutches are just about to slip at full torque, they are working at a coefficient of friction of .179 and .175 respectively. This same coefficient of friction has been arrived at on both cars independently. It would indicate that it is not safe to rely on a figure higher than .175 for average conditions. The unit pressure is greater on the 25HP being 35.8 lbs/sq.in. against 29 lbs/sq.in. With the 15 % stronger springs in 19-EX (253 lbs instead of 220 lbs-) the unit pressure rises to 33.4. We have evidence on both 19-EX and 18.G.IV. that synchromesh gearboxes cause a very considerable amount of slipping of the clutch when changing gear. The driven plates of both these cars are very distorted from heat. It is to lessen this slipping that we are increasing the clutch spring strength. Experiments on the maximum coefficient of friction at which our clutches will work give very inconsistent results. As we have pointed out above it is the length of time of | ||