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).
Potential causes and evidence for brake squeaks.
| Identifier | ExFiles\Box 85\1\ scan0268 | |
| Date | 2nd December 1936 | |
| 206 E.{Mr Elliott - Chief Engineer} from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} c. to Hs.{Lord Ernest Hives - Chair} c. to Da.{Bernard Day - Chassis Design} c. to Hdy.{William Hardy} c. to Ev.{Ivan Evernden - coachwork} c. to By.{R.W. Bailey - Chief Engineer} BRAKE SQUEAKS. Da.{Bernard Day - Chassis Design} has asked us to put on paper anything we know about the cause or cure of brake squeaks, as we have so many complaints about them. The causes of brake squeaks are both numerous and elusive. Four of the chief of them seem to be:- (1) Rust on braking surface. (2) Too high values of coefficient of friction. (3) An overheated lining. (4) Bad bedding of linings. The evidence is as follows:- (1) Our standard instruction to the Experimental fitting shop is that all cars fitted with aluminium brake drums must have the tipping shoes set solid. Occasionally we have noticed on these cars, including the car with Girling brakes, that on the first application of the brakes after the car has been standing some time a very light squeak occurs. We have never known this light squeak to occur on more than two successive brake applications, and seldom more than one. It is a very inoffensive noise, and we think should not give rise to any complaints. The testers in France noticed this phenomenon and were able to get rid of it by releasing the tipping shoes, after which they had no squeaks until they wore the Ferodo down to the rivets. We have noticed that an obviously rusty drum squeaked rather badly, and there is a good deal of outside evidence that damp conditions give rise to squeaks. We must admit that we have no direct evidence that rust is the cause of this type of squeak, it might possibly be due to the high coefficients of friction which obtain in a dead cold drum, but we incline to the rust theory. (2) We have some direct evidence that high values of M cause squeaks. On our brake rig we have frequently run a drum at a constant speed against Ferodo at a constant pressure. On several occasions a loud squeal suddenly started, and simultaneously the driving engine slowed down and stalled. The increase of brake torque appeared to be 50%, but our rig, which is only an adapted chassis, does | ||