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).
Investigation into the causes and remedies for brake squeaks, particularly concerning bedding of the brake liners.
| Identifier | ExFiles\Box 47\3\ Scan015 | |
| Date | 24th January 1931 | |
| -2- Hd{Mr Hayward/Mr Huddy}/WT2/MW24.1.31. Generally speaking we have found that the standard of fitting work on brakes is good, although we have found instances where, for instance looseness in the mounting of the shoes has aggravated the trouble. In this connection we have tried the effect of spring loading the shoe guides or pivots without however being sure that it has effected a great deal of improvement. In one instance of rear brake squeaks we found that the bosses of the brake shoes at the pivots were too big and were actually binding one against the other. This incidentally is the only complaint of squeaks from the rear brakes which we have had to deal with on Ph. II The complaint was of squeaks when the brakes were applied lightly at slow speeds, and although we corrected the binding above referred to, and also fitted new brake drums, this did not effect a cure. Afterwards we carefully bedded the liners and up-to-date it has completely cured the squeak. To sum up this section of our investigations, we think it is correct to say that every conceivable point in connection with the fitting work of our standard parts have been carefully checked, and the results show that it will not be possible to eliminate squeaks by tightening up our production limits, although in certain cases of squeaks we have found that this factor does have a definite contributory effect. Bedding of the Brake Liners (b) Our efforts in this direction are generally much more successful. It is fortunately a fact that a brake which is bedded to the best advantage from the point of view of brake squeak elimination is at the same time the most efficient brake. We have proved that brake squeaks can be made much more pronounced, or on the other hand greatly reduced and in some cases lost entirely, by suitable alterations to the bedding of the liners. The most effective non-squeak, and at the same time efficient, brake is obtained by bedding the forward (wrapping) shoe rather heavily at the toe and gradually relieving it towards the heel. The non-wrapping shoe should have a similar graduation of bedding but is generally not so heavily bedded. In connection with this, we have carried out a series of experiments with eccentrically pivotted brake shoes, by means of which we could move the pivot inwards or outwards over a limited range. The effect of course is to shift the bed from the heel of the liner to the toe as the pivot is moved inwards, and the results confirm that the bedding of the liners is one of the most important factors in the prevention of squeaks. CONT'D.{John DeLooze - Company Secretary} | ||