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).
From 'R' discussing technical solutions for brake issues referred to as 'jaggers and chunking'.
| Identifier | ExFiles\Box 73\2\ scan0218 | |
| Date | 28th January 1924 | |
| X. 9940 To RG.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} & DA.{Bernard Day - Chassis Design} FROM R.{Sir Henry Royce} S E C R E T. R1/M28.1.24. c.c. to CJ. BJ. Wor.{Arthur Wormald - General Works Manager} HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} EP.{G. Eric Platford - Chief Quality Engineer} FRONT WHEEL BRAKES. X. 9940 Perhaps I am repeating much of what has already been said by others or myself, but I am most anxious that we are not delaying the work for any decisions from me. JAGGERS AND CHUNKING. Most of the troubles we are at the moment experiencing seem to be due to too sudden application of the brakes and cannot be cured by any other practical way than by preventing such extremely sudden application. (In future work we propose to do this simply by the slow speed servo, and the speed of the servo will be made so that when at the highest speed we are likely to be running, the take up application will not be sudden enough to cause jaggers, or the snatching at the rear brake ropes). In the meantime we ought to get perfectly satisfactory in this respect by allowing the pedal to descend at the desired speed independently of any change of pressure or other conditions. This is not any easy problem, an ordinary fluid dashpot being too variable, varying with, and subject to change of fluid used, temperature, and pressure, whereas we want some scheme which is as constant under all conditions as possible, even to being proof against the wrong fluid being used. I have thought of many things - (1) the first being a box with external lever connected to pedal, the box containing geared centrifugal brake, (Royce Ltd. lowering gear for cranes, Gramaphone motor, telescope motor, etc.) (2) No. 2 was a ratchet driven by the speed indicator gear, (this would vary with the speed of the car) but otherwise constant and reliable, and perhaps simple and suitable. Perhaps the pedal might descend as quickly as one wishes for about the first third of the stroke which would be taking up the clearance. (3) The third idea was to use any kind of a dashpot with a release such as a gear pattern oil pump driven by the speedometer drive, or a release valve control by centrifugal force depending on the speed of the descent of the pedal. I think this matter should have the attention of the committee to see what form of retarding device should be worked upon. I fear a simple dashpot with an adjustable leakage hardly proof against variable people, fluid, temperature, and I have found the brake depending on centrifugal force quite good, simple and reliable, - i.e. below a certain speed no retard, after a certain speed retard increasing rapidly with speed. R.{Sir Henry Royce} | ||