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).
Continuation sheet from Ferodo Ltd. discussing brake lining temperatures, wear, and energy dissipation.
| Identifier | ExFiles\Box 121\1\ scan0319 | |
| Date | 28th September 1940 guessed | |
| FERODO LTD TECHNICAL DEPT. Continuation Sheet No. 2 Messrs. Rolls-Royce Limited, D E R B Y. time in their life, have to withstand a temperature at least as high as this. 3. So far we have found it impossible to carry out even crude measurement of the actual surface temperatures reached where the lining is in contact with the drum. There is no doubt that this temperature is extremely high, as indicated by experiments which were described by Dr. Bowden in a general discussion on "Lubrication and Lubricants" before the Institute of Mechanical Engineers in 1937 - measurement of brake drum surface temperatures immediately following contact with the lining show no appreciable difference between leading and trailing shoes, but no doubt this factor can be attributed to the generally excellent conductivity of most brake drum metals. With regard to your suggestion that leading shoe lining surfaces reach higher temperatures than trailing linings, this is undoubtedly true for the actual surface where the brake shoes are operated by a floating expander, such as a double piston hydraulic cylinder, or a wedge mechanism, as in these cases the shoe tip efforts will be equal and opposite, and full play will be allowed to the self-wrapping characteristics of the leading shoe. The latter will inevitably carry the major portion of the energy dissipation, and it is logical to state that the surface temperature at the rubbing faces must, therefore, be higher than on the trailing shoe. However, these conditions will not hold good for a symmetrical located cam operated brake, as the geometrical restraint of the system enforces equal lining wear, and an equal division of energy dissipation between a pair of shoes. In this case, the lining temperatures must also be equal. We note your suggestion that the leading portion of an individual lining on a shoe may become noticeably hotter than the trailing end, but we fear we can hardly agree with this, unless the radial displacement of the shoe causes the leading edge of the lining to wear at a greater rate than any other portion of the same shoe facing. The disposition of the lining on the average brake shoe, with respect to the shoe fulcrum, usually results in the greatest rate of wear at the centre of the lining, in fact if such a lined shoe is used to the limit, metal to metal contact will first occur at the centre of the arc subtended by the lining, indicating that as this is the region of the greatest wear it is also the zone of greatest energy dissipation. It is P.T.O. | ||