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).
Co-efficient of friction for Ferobestos clutch material with and without graphite for the Goshawk 11 flywheel clutch.
| Identifier | ExFiles\Box 74\2\ scan0328 | |
| Date | 24th August 1921 | |
| R.R. 199 (250T) (SD676 19-7-17) MP18086S X4244 FC RECEIVED AUG 24 BY1-P24.8.21. Hs.{Lord Ernest Hives - Chair} from HY.{Tom Haldenby - Plant Engineer} X4244 X3409 GOSHAWK 11. FLYWHEEL CLUTCH. Referring to the question of the co-efficient of friction suitable for use when using Ferobestos impregnated with graphite, we have received a reply from Messrs. Ferodo, to the effect that they consider .1 to be the figure we should work to, as this represents, in their opinion, the co-efficient for moving friction, possibly for static friction, that is, the co-efficient before the clutch begins to slip is possibly higher. We have written Messrs. Ferodo more fully, and possibly may get some further information, as apparently they intend to test out the material, but at the moment it is certain they have no definite data that we can rely upon. It seems to me of the utmost importance that we should try Ferobestos without graphite as well as with it, as we should satisfy ourselves in the first place that Ferobestos without graphite is, or is not satisfactory, before we go on to the further question of including graphite in the structure, as the material without graphite is of such a much higher co-efficient of friction and therefore demands far less spring pressure. Working upon the figure now submitted by Messrs. Ferodo Ltd, the total spring pressure will have to be 1450 lbs, that is, each spring will have to exert 181 lbs instead of as at present 80 lbs. This figure does not allow any factor of safety, and apparently if Messrs. Ferodo's figures are correct, the clutch would even then slip if the clutch was dropped in suddenly. This, however, is of course good, providing the slipping does not continue. HY.{Tom Haldenby - Plant Engineer} | ||