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 phenomenon of front brakes thumping on a four-wheel brake system.
| Identifier | ExFiles\Box 73\3\ scan0198 | |
| Date | 1st September 1924 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} X9940 9940 EXPERIMENTAL REPORT. Expl. No. 9941 REF. Hs{Lord Ernest Hives - Chair}5/LG10.9.24. To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. BJ. c. to RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to DA.{Bernard Day - Chassis Design} BY.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} S E C R E T. FOUR WHEEL BRAKES. Front Brakes Thumping. With reference to the phenomena of the front brakes thumping which is manifest on 46-PK car at W.W. The following experiments have been made :- On all cars which have been tried which have this complaint, it cannot be produced if the brake is applied when the car is going backwards. The only condition one can see which alters when the car is going backwards, is that the wrapping shoe becomes the non-wrapping. Our tests show that the torque rod used in conjunction with front springs will reduce the effect of the thumping. With the torque rod on, the noise is considerably reduced and there is no feeling of any twist on the front axle. We have made tests by applying friction to the links which support the balance lever. If we add friction at the top support of the links, we have been able to prevent thumping on all the cars we have tested. It, however, brings up another fault and that is the balance lever does not return to the zero position. The reason for this is that owing to there being less leverage to the front brakes, there is more movement on the end of the balance lever operating the front brakes, than there is on the end operating the rear brakes. This means that the links supporting the balance lever have to move if the contd :- | ||