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 causes of brake thumping on the 25HP car and a proposed update for the instruction manual.
| Identifier | WestWitteringFiles\U\August1930-November1930\ Scan042 | |
| Date | 5th September 1930 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to E.{Mr Elliott - Chief Engineer} ORIGINAL 25HP. CAR (JAPAN). BRAKES. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} S/WJ.5.9.30. x5770 x5360 x5420 y5370 With reference to R1/M20.8.30. It is quite correct that when the front brakes require adjustment, brake thumps are liable to occur. For this reason it is certainly a most useful point to include in the Instruction Book, and we are inserting the following paragraph :- "Should the front brakes develope a tendency to go on with a thump when the pedal is depressed it is probable that they are in need of adjustment. Loss of front braking will of course indicate that the brakes require adjustment even though they show no sign of thumping. In either case the clearance should be checked by measuring the movement of lever 'B' on the front axle etc.--------" Though front brakes in need of adjustment do cause thumping, in our experience they are not the fundamental source of the trouble. We have always found that if the servo becomes inefficient for any reason so that the whole of the rear brake clearance is taken up before the servo starts to pull the front brakes on, then thumping will occur. The friction on the swinging arm is a palliative and in the case of the 40/50 very effectively so, in the case of the 20 HP we experience difficulty in getting a constant value for this swinging arm friction and for | ||