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).
Cause of 'brake thumps' and proposing the experimental use of an oil dashpot.
| Identifier | ExFiles\Box 30\6\ Scan203 | |
| Date | 20th August 1932 | |
| HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} } FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} } X 1559 R5M20.8.32. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} DA.{Bernard Day - Chassis Design} BRAKE THUMPS. One very much likes to get at the exact reasons for any of these objectionable phenomena. There are good reasons to concluded that it must be entirely a question of the speed at which the brake is applied. It was thought at one time that the back brake came on first, and having taken up the slack the action and energy of the servo and foot caused the front brakes to be applied at twice their normal speed, until they too had taken up their slack. It is understood that the dashpot shewn in the sketch accompanying HS{Lord Ernest Hives - Chair}/LID{A. J. Lidsey}'s memo. is an air dashpot, and as it would naturally add some resistance to the application of the front brakes. It would not prevent the rear brakes being applied first, and therefore, except as a slower down, it is difficult to understand what it is doing. Personally I should like to try experimentally an oil dashpot in the position we shew as I should expect this to have much more definite slowing down effect compared with air, which is so elastic. The use of oil would only need a small piston and could be used as a temporary expedient in the first instance, as the air dashpot, if it will do the work as stated, will probably be preferred, and finally adopted. R.{Sir Henry Royce} | ||