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).
Confidential internal memorandum discussing the phenomenon of 'jaggers' in front wheel brakes and proposing solutions.
| Identifier | ExFiles\Box 73\2\ scan0204 | |
| Date | 21th January 1924 | |
| 49740 To HS.{Lord Ernest Hives - Chair} RG.{Mr Rowledge} } E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} } FROM R.{Sir Henry Royce} SECRET AND CONFIDENTIAL. RL/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. X.9940 X.9420 X.9430 I was very pleased indeed to receive HS.{Lord Ernest Hives - Chair} report on the 11th. RE. JAGGERS. This is a very important item in this report. The tests I understand shew that this feature is present if the front brakes are really effective and applied suddenly, but surely 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 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 ease 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 torsional movement but I fear none are practical. Here are two that might be tried experimentally to tell us something. SEE ORIGINAL FOR SKETCHES. 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 fear 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 to start jaggers, owing to the sudden foot pressure being insufficient and the additional pressure supplied by the slow running servo not being sudden even at high speeds. This confirms that for the brakes as well as engine efficiency nothing should stand in the way of EAC.2. getting into production as quickly as ever possible. FLOATING FULCRUM BRAKES. There appears to be an important mystery about these because they avoid jaggers. If we can make them efficient and they will still avoid jaggers then I believe contd:- | ||