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 Dept. to Leyland Motors Ltd. regarding brake drum performance, friction, and wear.
| Identifier | ExFiles\Box 140\3\ scan0169 | |
| Date | 11th June 1938 | |
| 1175 (Experimental Dept.) Rm{William Robotham - Chief Engineer}/AFM{Anthony F. Martindale}1/R.{Sir Henry Royce} 11th June, 1938. Messrs. Leyland Motors Ltd., Farington Foundries, Leyland, Lancs: Your Ref: Farington WW/DH.{D. Henderson - Showroom} For the attention of Walter West, Esq. Dear Sirs, Brake Drums. In reply to your query regarding brake drums, we regret that we have not any very exact knowledge concerning the relationship of graphite content with performance, but our experience has been as follows:- Coefficient of Friction. Although we are assured by Friction lining manufacturers that metal specifications have a profound effect both on the cold value of coefficient of friction, and the 'fade' due to temperature rise expressed as a percentage, we have never been able to endorse this statement. We have tried Austenitic irons, malleable iron, and ordinary cast iron with varying carbon content and steel, and any variations we have noticed have been within the range of variation of friction which we get when using a particular test drum against a lining of given specification, the tests being made on different occasions and with the same or different samples of the test lining. Road experience confirms this. Although we are keeping an open mind, we at present consider that the only variable of importance is the Friction lining. Wear & 'Crazy Pattern Cracking'. We recently effected a considerable reduction in scoring of drums by changing from an iron of 2.5% total carbon to one of 3.25%, with graphite contents as in the photomicrographs enclosed. Almost at the same time we ran | ||