Issue of servo-brake thumps on the 20/25HP car and a proposed solution using a modified dash pot.
| Identifier | ExFiles\Box 105\4\ scan0087 | |
| Date | 26th May 1932 | |
| X 5370. x5360 R. {Sir Henry Royce} From Hs {Lord Ernest Hives - Chair} /Ltd. c. to Sg. {Arthur F. Sidgreaves - MD} Wor. {Arthur Wormald - General Works Manager} c. to E. {Mr Elliott - Chief Engineer} Da. {Bernard Day - Chassis Design} c. to AV. HS {Lord Ernest Hives - Chair} /Ltd.2/HA.26.5.32. 20/25HP CAR SERVO-BRAKE THUMPS. On the 20/25HP car it has always been more difficult to cure front brake thumps than on the P.II model. Since the adoption of the hinged tip ante squeak brake shoe this trouble has again increased due to the greater front brake clearances required. Under the best conditions the swinging arm friction is only just sufficient to damp out brake thumps. As the result of trouble we have experienced in this direction on experimental cars we have carried out some experiments in which an attempt was made to use the dash pot, (provided to cure servo clanks) modified to work both ways and connected to the bottom of the servo balance arm, to act both as a damper for thumps in the one direction and for servo clanks in the other direction. The dash pot was made to work both ways by stopping up the transfer passage and by providing a non return valve at each end, this made it work as a damper to quick movements in both directions. The damper was then mounted in such a position that it could be connected to the bottom of the balance arm; in this position it is effective for curing front brake thumps and equally as effective as when in the present position for curing servo clanks when the brakes are released. The results obtained were very good, the damper was so effective that the thumps were transferred from the front brakes to the rear brakes; a relatively small amount of friction on the swinging arm was then sufficient to stop the rear brakes from thumping. The damper was also effective in curing servo clanks when the brakes were released. | ||
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).