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).
The testing methodology for Graphite Bronze clutch facings on a 20/25 & 3 1/2 litre Bentley.
| Identifier | ExFiles\Box 129\4\ scan0100 | |
| Date | 13th December 1937 | |
| To Hs.{Lord Ernest Hives - Chair} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Mx.{John H Maddocks - Chief Proving Officer} 1160 Rm{William Robotham - Chief Engineer}/WAC.4/JH.13.12.37. Tests of Graphite Bronze Clutch Facings. 20/25 & 3 1/2 litre Bentley. Some twenty of the above cars have been fitted with metallic clutch facings made by the Cleveland Graphite Bronze Co., the Bronze facings being made to the same drawing as the Ferodo R.A.D.11. All these clutches are so far behaving well on the road, and no measurable wear has been recorded. Object, Methods of test. In order to measure the relative rates of wear of R.A.D.11 & Bronze facings, it was decided to use a 3 1/2 litre Bentley unit on a dynamometer, in preference to road tests because of (a) the impossibility of reproducing hundreds of slips of equal severity and (b) the excessive time that would be occupied to produce instructive results. The tests for both facings were carried out as follows - The dynamometer was set to hold the engine at 800 r.p.m. at full throttle and every 30 seconds the clutch was disengaged by a hand lever, till the engine reached 3000 r.p.m. and then re-engaged. With a clutch in normal condition the average time required to pull the engine from 3000 to 800 r.p.m. and the dynamometer from 0 to 800 r.p.m. was about 2 seconds. It will be appreciated that the heat generated in a given time by this method is far greater than that generated by rough handling on the road, and this statement is confirmed by the colour of the driven plate, and the softening of the thrust springs., but the object of the test was to produce wear. | ||