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).
Test report conclusion recommending the use of Graphite Bronze clutch facings on Bentley models.
| Identifier | ExFiles\Box 129\4\ scan0103 | |
| Date | 13th December 1937 | |
| -4- Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler}4/JH.13.12.37. At the conclusion of the test the bronze had "picked-up" and was adhering to the steel plate in patches, although the wear of the driven plate was less than .001. The facings of this 10.5" clutch are only 1.05 radial depth, as compared to 2" for the average clutch of this size, this means that the pressure per square inch is nearly double, and we think it probable that deeper facings with lower unit pressure would be likely to show still better results, but the 20/25 type of clutch does not lend itself to modification in this respect and this together with the excessive heat transmission to the springs indicate clearly that this type of clutch cannot take full advantage of the possibility of metallic facings as might a clutch designed for the job. Summing up these tests indicate the possibility of softening the thrust springs by severe slipping, but this has not so far been experienced on the road. An increased life of between four to one and eight to one is indicated, so that the increased cost of the material should be covered many times over by saving in dismantling costs. We therefore recommend that we continue to use Graphite Bronze facings for replacements on the 20/25 and 3 1/2 litre Bentley. Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler} | ||