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).
Report discussing modifications to servo multiplication and brake linings to reduce squeaking.
| Identifier | ExFiles\Box 41\1\ Scan105 | |
| Date | 20th October 1929 guessed | |
| - 2 - We have tried this in several modifications now for some two years and in every test find (1) About 30% increase in servo multiplication. (2) Consistent servo multiplication and freedom from jerky action throughout several thousand miles of use. We find that the increase in servo multiplication can conveniently be kept within reason from the driver's point of view by increasing the tension of the pedal return spring. (2) BRAKE LININGS. The increase in servo multiplication has held us back from suggesting this change before, because we found that the increased braking power caused front brake squeak, and wound up the front axle. The latter objection is met by axle control. The former objection can we think be overcome by using the new Johns-Manville "squeakless" brake lining, which is die pressed asbestos with a rubber composition binder. This is now being very widely adopted and appears to give entire freedom from squeaking. This material however is very soft and is we think designed for a lighter brake pressure than we use. We are asking for a somewhat harder lining of a "bus" or "truck" type. The softer material does not appear to imply rapid wear. The present standard "hard" linings appear to wear principally by cutting the drums. We think however that with the softer linings it will be essential to grind the drums instead of turning them in order to avoid the screw thread cutting effect of minute turning marks. Summary: (1) "Ball-Thrust" cam levers are suggested. (2) The new Johns-Manville brake lining is recommended for freedom from squeaking. Yours faithfully, ROLLS ROYCE OF AMERICA, INC. Maurice Olley | ||