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).
Investigation into the cause of 'brake thumps' and the effectiveness of a vertical oil dashpot.
| Identifier | ExFiles\Box 84\2\ scan0040 | |
| Date | 4th July 1933 | |
| X 2056 To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to Wor.{Arthur Wormald - General Works Manager} c. to Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}9/KT.4.7.33. BRAKE THUMPS. We have carried out tests on 2.B.IV. chassis on the vertical oil dashpot to N.Sch.3709. For the tests the swinging arm poundage was the minimum possible under which condition the front brakes thumped if the pedal were depressed at all quickly. On this car the front brakes came on before the back, the swinging arm moving backwards as the front brakes came on. The dashpot even when set at a very high load had no effect on the thumps. We subsequently found by watching the brake mechanism that while the front brakes came on, the dashpot hardly moved and only damped movement of the top end of the T lever to the rear brakes. We think we can say that the same would apply to a late thump in which the rear brakes come on first and then the front as again the rotation of the balance lever is about the swinging arm pivot and not about its own centre. Only movement about its own centre affects the dashpot. We understand Da.{Bernard Day - Chassis Design} is sending us a design for a dashpot to prevent rapid movement of the bottom end of the balance lever. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} | ||