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).
New clutch spring test rig for 10' & 11' Borg & Beck clutches and the findings from its use.
| Identifier | ExFiles\Box 129\4\ scan0142 | |
| Date | 16th February 1938 | |
| To RHC.{R. H. Coverley - Production Engineer} from Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler} c. Hs.{Lord Ernest Hives - Chair} c. By.{R.W. Bailey - Chief Engineer} c. Da.{Bernard Day - Chassis Design} c. Mx.{John H Maddocks - Chief Proving Officer} (110 CLUTCH SPRING TEST RIG. FOR 10" & 11" BORG & BECK CLUTCHES. We have now got the above rig working very satis-factorily, and since making the knife-edge levers, which have eliminated the friction of the finger levers, readings correct to 2% to 3% are quickly and easily obtained, and this limit is fully adequate for all practical requirements. We have tried a number of both 10" and 11" clutches fitted with springs of tested poundage, and several interesting results have already been revealed. The springs of the 10" clutch are found to be compressed to .100 to .120 shorter than their nominal working length, which means that on many 10" clutches, the actual thrust on pressure plate is 150 to 200 lbs. more than would be accoun-ted for by the tested poundage of the springs, but in the case of the 11" clutches tested, the actual working length is fairly close to the nominal length. Another point the rig has revealed, is the considerable strength of the finger anti-rattle springs, also the variation on different clutches. The force these springs exert, measured at the inner ends of the fingers, varies from 6 to 10 lbs., which, being multiplied by 5.5 and by the number of fingers, may reduce the thrust on the pressure plate by anything between 100 lbs on a 10" clutch to 220 lbs on an 11" clutch, the average being 120 and 160 lbs. respectively. The nett result of these possible variations in total thrust pressure may account for some of the apparently "mysterious" variations in clutch performance we have observed from time to time. All this shows the desirability of having a rig which shows at a glance the actual thrust on the pressure plate without having to dismantle a clutch and re-setting the fingers. | ||