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).
Letter from Ferodo Ltd. detailing the test results of a 20 HP plate clutch lining.
| Identifier | WestWitteringFiles\J\February1923\ Scan53 | |
| Date | 30th January 1923 | |
| COPY. Ferodo Ltd. Sovereign Mills, Chapel-en-le-Frith, Eng. FJF/MVH. Jan. 30th. 1923. Messrs. Rolls-Royce Ltd., Nightingale Rd., DERBY. Dear Sirs, Attention of Mr. Bailey. Re. 20 HP. PLATE CLUTCH. Following the writer's interview with your Mr. Bailey on the 9th. inst. as then promised we have tested an average lining of the same material and dimensions as fitted to your 20 HP. clutch and enclose copy of results. The figures represent the best and worst obtained. Under 1000 lbs. pressure at 1000 r.p.m. the work was very severe and the lining and metal parts were raised to a high temperature but with no perceptible effect on the lining except as expected its co-efficient of friction fell considerably, but after a number of trials the lowest value was 0.266. We could hardly imagine any car owner submitting a component of his machine to tests of such severity i.e. absorbing the full power of the engine through the friction linings against the clutch plate, except perhaps for a second or two; our test was sustained for several minutes. Judging by what we have established we feel confident in stating that a pressure of 960 lbs. i.e. your eight 120 lb. springs, is very largely in excess of the requirements and we think it is open to question if any circumstances could possibly be imposed to justify such a heavy pressure. We have no doubt that 500 lbs. pressure would be sufficient to provide a satisfactory drive, but it would be perhaps advisable to add a further 20% when any question of slip could be disregarded. This leaves a balance of 360 lbs. to be accounted for. It occurs to us that either the surfaces of the clutch you tested may be lubricated to some extent, or the clutch parts themselves are not free to slide into engagement under the normal pressure required. If you care to see the test run here we shall be glad to give you the opportunity at any time on receipt of an hour or two's notice. Yours faithfully, FERODO LIMITED. F.J.Field. Chief Engineer. Enc. copy of Test result. | ||