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).
Brake 'jaggers' and backward efficiency, suggesting modifications to brake shoes.
| Identifier | WestWitteringFiles\L\Jan1924-March1924\ Scan84 | |
| Date | 13th February 1924 | |
| P.R. 255a (100 T) (S.H. 158, 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 ORIGINAL SECRET TO HS.{Lord Ernest Hives - Chair} RG.{Mr Rowledge}) FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design}) R3/M13. 2. 24. Copy to CJ. BJ. WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} HP E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. X9940 re. BRAKES. JAGGERS AND BACKWARD EFFICIENCY. Now that we have decided upon slow speed servo which can add to the foot pressure by say 3 or 4 times, and be divided between the back and front wheels in any desired proportion, say 5 back and 3 forward, by making the leverage suitable, we can reconsider other possibilities, and the following re-suggests itself:- Since a long shoe is thought to increase the risk of jaggers, (as I originally believed was the chief cause) if not the difference of co-efficient change by speed, it might be thought advisable to fit short shoes forward, and long shoes backward. The long shoe could be tested stiff, semi-flexible, and jointed. (There would only be one stop for the last named.) My chief object in suggesting this is to increase the backward holding efficiency, (which is lost the greater the added proportion by servo) so that it is made up by the self servo long lapping shoe when used backwards, (and incidentally it will be found to make a more consistent, better equalised, and less liable to jagger forward brake. The want of equalising and varying efficiency is largely due to the variation of bedding on the long forward lapping shoe, and the proportionate pressure between the 2 shoes. With a shorter shoe this variation should be less and with the floating fulcrum again also less. You will remember that inamongst all our other troubles we are seeking for a consistent brake, which we fear our present standard ones, and all other makes, are not, from the above cause or difference in the condition of surface or oiliness. You will remember that I asked some time ago for you to test also the difference of the co-efficient at rest and in motion at various surface speeds up to our probable maximum. I do not remember having seen these figures which would bear so directly upon the cause of jaggers. Naturally the long self lapper backwards would have plenty of pressure upon it, as the lapping shoe forwards is the one which must always wear most. R.{Sir Henry Royce} | ||