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).
Resolving brake thumping and knocking issues by modifying springs and adding friction.
| Identifier | ExFiles\Box 73\3\ scan0199 | |
| Date | 10th September 1924 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} -2- EXPERIMENTAL REPORT. Expl. No. REF: Hs{Lord Ernest Hives - Chair}5/LG10.9.24. brakes are applied from the off position to the full on position. If the friction is sufficient to prevent the links from moving, then the front brakes come off only the same amount as the rear brakes, - as the front brakes require more movement to return to their off position, it means that there is slack between the driving pegs on the servo drum and the levers so that every time the servo is applied, there is a knock. Our tests however shew that if we increase the tension of the pull off springs on the front brakes and add sufficient friction to the links so that the pull off springs are strong enough to return them to the proper zero position, we can prevent thumping without introducing any other ill affects. On the last car we sent to France fitted with the 12 1/2% springs, we made a special test on the brakes fitted to that car to see whether the thumping would come on with running. On that car we eased off the bedding of the wrapping shoe for a distance of 4" from the toe end. The daily reports on that car for the whole of the 10,000 miles show that thumping was non-existant. This rather goes to show that it requires very little modification in order to permanently overcome this compalint. We recommend making the pull off springs on the front brakes to exert at a pressure of 10 to 12 lbs. each when in the off position. We find with the torsion springs, considerable variation can come in. We also recommend adding friction to the top support of the links holding the balance lever. Tests are in hand to prove how much this should be. Hs.{Lord Ernest Hives - Chair} | ||