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).
Front wheel brake judder, referred to as 'jaggers', and proposing two experimental damper designs to address the problem.
| Identifier | WestWitteringFiles\L\Jan1924-March1924\ Scan16 | |
| Date | 1st January 1924 | |
| H.R. 235A (100 T) (S.H. 159 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2500 ORIGINAL SECRET AND CONFIDENTIAL. TO HS.{Lord Ernest Hives - Chair} RG.{Mr Rowledge}) FROM R.{Sir Henry Royce} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} R1/M21. 1. 24. C. to CJ. BJ. BY.{R.W. Bailey - Chief Engineer} WOR.{Arthur Wormald - General Works Manager} EP.{G. Eric Platford - Chief Quality Engineer} PN.{Mr Northey} re. FRONT WHEEL BRAKES. 19940 HS.{Lord Ernest Hives - Chair} report of the 11th. I was very pleased indeed to receive re. JAGGERS. This is a very important item in this report. The test-I understand shews that this feature is present if the front brakes are really effective and applied suddenly. I suspect the phenomenon was more manifest in the early experiments than in the last car I saw at WW? The cause appears from the latest test to be due to the difference between friction at rest, and friction in motion. This difference should be tested - i.e. when a brake is holding on to a stationary drum what force does it need to make it slip compared with the force required to keep it turning up to the speeds we meet in practice. From other experiments we may find that the undamped elasticity of the mounting - i.e. parts other than the road springs such as the frame ends, axle, etc. have some importance in the case of starting the jaggers. We may also find if more damping of the road springs would make it impossible to start. I have schemed many arrangements of damping the axles torsionally movement but I fear none are practical. Here are two that might be tried experimentally to tell us something:- (1) Double shock damper - i.e. 7" arm looking forwards & backwards. Axle section. (2) Vertical damper. Axle. Torsional damper. No.1 seems the more practical but has many parts. But I think we shall not fit anything more than the most simple arrangements and that we shall not hear anything of jaggers when we get the parts right. Certainly with EAC.2. we ought not to be able to vigorously apply any of the brakes suddenly enough to start jaggers, owing to the sudden foot pressure being insufficient & the additional pressure supplied by the slow running servo not being sudden even at high speeds. (1) | ||