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).
Practical reasons for brake squeaks and the factors contributing to them.
| Identifier | ExFiles\Box 102\6\ scan0205 | |
| Date | 15th December 1936 | |
| Hs.{Lord Ernest Hives - Chair} from Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux}6/R.15.12.36. BRAKE SQUEAKS. With reference to the memo Rm{William Robotham - Chief Engineer}/AFM{Anthony F. Martindale}2/R.2.12.36., I have noted the remarks. In my opinion, from a practical point of view, the report is very misleading. The main reasons of squeaks I should place in the following order:- (1) Varying values of coefficient of liners. (2) Brake drum stiffness. (3) Bad bedding of linings. (4) Over-heated linings. (5) mating up of linings and metal drums. --------- It should be clearly understood that brake squeaks complained of in service are caused by a medium load on the brakes. Squeaks do not occur with maximum braking or very light braking. It is a condition when the load applied is such, that a vibration of the drum is set up, with no damping effect. Drums that are very flexible are less prone to squeak due to the rapping effect on the shoes through distortion, as the brake drums are stiffened up, so are they inclined to vibrate. A stage can be reached when the period of vibration is such that it does not become audible under the same conditions. The tipping shoe was not designed for rusty drums. (1) The vibrations of the drums increases with the increase of the coefficiency of the liners. (2) As stated the stiffness of the brake drum as a whole, i.e., the back plate, is as important as the actual friction surface. Weight and material form a chief item. The actual vibrations in many cases which are heard as a squeak, are due to weak back plates. Bugatti cars which have the brake drums built right into the wheel are not, as far as I am aware, prone to squeak. | ||