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).
Development and testing of Thermoid and Ferodo clutch plate facings.
| Identifier | ExFiles\Box 93\3\ scan0371 | |
| Date | 31th August 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler} c. Sg.{Arthur F. Sidgreaves - MD} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. Mx{John H Maddocks - Chief Proving Officer} 312 Ph. III. Clutch. Clutch plates with Long type cushion springs and Thermoid facings are now fitted to 34 customers and trials cars. One on 32EX has now done 15,900 miles, and one in America over 11,000 miles. No complaint, and all reports entirely favourable. This plate has been standardized, and will be fitted on production almost immediately. With regard to replacements on Customers cars, we are very anxious to find a satisfactory facing which can be rivetted to the existing R.R. clutch plates and cut in segments, so as to save the cost of several hundred new plates. With this object, Thermoid segments were fitted to a standard R.R. plate and run in 33EX for 1,290 miles, but the Thermoid broke away, as when segmented, it entirely lacks radial strength, for which it depends only on the strength of the adhesive between the layers, which are spirally wound, there being no fibres running in a radial direction. The unsuitability of Thermoid when cut into segments is further clearly demonstrated by the high speed bursting tests carried out at the Ferodo works, and reported in our letter of Aug. 28th. to Ferodo, attached. Meanwhile Ferodo are developing an improved form of their S6777 woven facing, which has fibres running in a radial direction, and an improved method of impregnation. Facings tested on Aug. 27th. withstood bursting tests up to 6800 R.P.M. the limit of the test rig, without failure, both as continuous rings and when cut into segments. We expect to receive 6 pairs of these facings within a fortnight, for road tests to ascertain whether or not they have the durability, pick-up and frictional qualities of the American Thermoid. 2/Le Copy | ||