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 the Experimental Department to Ferodo Ltd. discussing test results of brake drum samples S.6611 and VM.20.
| Identifier | ExFiles\Box 141\1\ scan0222 | |
| Date | 22th December 1936 | |
| 1180 (Experimental Dept.) Rm{William Robotham - Chief Engineer}/AFM{Anthony F. Martindale}3/R.{Sir Henry Royce} 22nd December, 1936. J.N. Longley, Esq., Chief Chemist, Ferodo Ltd., CHAPEL-en-le-FRITH. Dear Mr. Longley, I have tested the samples of S.6611 and VM.20 that you sent us recently, and the results on the rig have been as follows:- S.6611 has not squeaked or scored the drums. It is suitable for use with our Experimental aluminium drums, but is not especially suitable for operation up to 300°C. Under no conditions are its friction properties very consistent. We are running it 15,000 miles on a car in France. VM.20 has not squeaked. It has a low coefficient which is remarkably constant when run up to 200°C repeatedly, but if run up to 300°C it becomes vicious as do S.6611 and MR. I should like to know how it compares with S.6611 or S.5805 for scoring drums in your tests, also its wear resistance figure on the same scale which gives the following values, which you dictated over the telephone:- FBA - 200 S.5805-360 MR - 450-500 BZ - 600 S.6611-600 F.J. Hardy points out to me that on the servo rig, VM.20 had a high fade value and a normal figure, and I was able to tie up his figure with mine. On the brake rig when dead cold on first application of the brakes would rise rapidly to a high figure and equally rapidly fall again. This happens so quickly that the readings are difficult to | ||