Technical analysis of clutch separation, torque, coefficient of friction, and performance issues.
| Identifier | ExFiles\Box 5\6\ 06-page175 | |
| Date | 2nd July 1932 | |
| -2- HS {Lord Ernest Hives - Chair} /SRH.11/Ms.2.7.32.Cont'd 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 .008. * " " losses before the trunnion .011. ---- .027 A further .012 of the separation is lost due to the spring loaded movement of the inner Ferodo. On the 25HP the actual clutch separation is .107 against a drawing figure of .125 of which .024 is lost due to the set up of the driven plate. The maximum engine torque that the clutch has to transmit is for :- 25HP. 181 lbs ft STD.F.II. 211 lbs ft 19-XX. 356 lbs ft Assuming that the standard 25HP and F.II clutches are just about to slip at full torque, they are working at 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 30.8 lbs/sq.in. against 28 lbs/sq.in. With the 15 # stronger springs in 19-XX (253 lbs instead of 238 lbs) the unit pressure rises to 33.4. We have evidence on cars 19-XX 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 time of | ||
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).