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).
The causes of brake squeaks and the necessary alterations to fix the issue.
| Identifier | ExFiles\Box 12\5\ 05-page195 | |
| Date | 27th June 1930 guessed | |
| Copy for File. x7930 BRAKE SQUEAKS. The principle is to cause the brake shoe to move sideways not more than .010" by the varying pressure on the shoe, and thus causing a disturbance in the bedding. Owing to the flexibility of the brake drum the drum will become tapered when full pressure is applied. This will give the brake shoe the tendency to get near the pivot pin. Now if we spring load the shoe to be as near to the road wheel as possible when the brake is off, providing the spring load is correct the shoe will travel to and fro across the drum as the shoe pressures vary. If the movement was large the strap would not wear evenly so we used the present sideway movement as given on production .010". Alterations found necessary. (1) Guide for brake strap. G.74224. A guide giving similar clearance is built up from 2 steel bushes and a spring of a small load is put between. The strength of the spring has not yet been arrived at, but is something very small. (2) Steel distance bush for brake strap. G.74229 i.e. bottom spigot for shoe G.74229. On production they are making a point to get at least .010" side play here. This is all wrong and should be reduced to nothing as long as the shoe moves easily. If some method to keep this clearance at nothing were used, such as spring loading, I feel it would be more lasting. However this would considerably complicate matters and cause more working parts. (3) The reamering jig for the carrier plate G.75925/6 used on production needs attention. The carrier plate is not held ridged. This causes the centres of the shoe pivots to be out and prevents the shoe from falling freely in the guide for brake strap (G.74224) owing to an inclination for the shoe | ||