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).
Investigating clutch issues on a Bentley, focusing on uneven finger springiness and clutch housing distortion during testing.
| Identifier | ExFiles\Box 130\2\ scan0173 | |
| Date | 6th October 1936 | |
| X 113 To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Cricklewood, Oct. 6th, 1936. I have been at Kingsbury this morning, Mr. Ferguson's Bentley is not ready. It was decided to have a look at the clutch and at the same time attend to the brakes. Upon measuring up the clutch fingers on the race clutch plate, they were found uneven to the extent of .011". Another feature which we noticed during this test, was the uneven springiness of the fingers, which looks as if the strength of these fingers varies, with the result that although you are now getting Borg & Beck to tighten up these limits, the declutching is uneven due to varying strength of the fingers. This was so pronounced on this clutch that I decided it would be a valuable asset for investigation therefore I have instructed the clutch housing to be sent up to you. To obtain the above result the clutch housing should be bolted down on a face plate with the Borg & Beck solid plate. Then try depressing the fingers and you will find one practically solid while the other two have a considerable springiness. Another feature which was noticeable during this bench test was that no consistent reading could be obtained in getting at the correct setting of the fingers. If you bolt the clutch housing down on to the face plate, take the reading of the fingers, unbolt it and rebolt it up again a different set of readings is obtained. Again if the clutch fingers are held open by the keys provided while bolting down a different reading of the fingers will be obtained as against no keys being used. The explanation of this is, the clutch case is distorted all-ways during the bolting down process, and in each case, alters the setting of the fingers. To obtain more consistent results, and to lesson distortion, the complete load of the clutch springs should be taken by the three keys (which require to be approximately 3/8 thick ) while the clutch is being bolted up to the flywheel. I trust this is clear to you, as it is obvious that some of the troubles we are up against are due to the flexibility of the pressing of the clutch housing. | ||