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 issues of glazing and squeaking in Ferodo brake and clutch linings, and tests of alternative materials.
| Identifier | ExFiles\Box 120\2\ scan0180 | |
| Date | 12th July 1937 | |
| -2- Rm{William Robotham - Chief Engineer}/AFM{Anthony F. Martindale}12/R.12.7.37. After Ferodo linings have been in service some time they develop a high glaze, and then they start to squeak. This usually takes 8,000 or 10,000 miles. GWH.{George W. Hancock - Head Chateauroux} is very insistent about this. With servos, the glaze develops and the efficiency falls, when RAD.13 is used, and in clutches, VM.20 is satisfactory when new, but it too develops a glaze and the clutch starts to judder. We use very thick brake linings, and in 10,000 miles they have absorbed enough B.H.P. hours to wear out completely the thin linings used by our competitors, the latter will not be so troubled by this glazing as we are. The glaze is due to the resinous bonding working into a smooth face on the surface, where it acts in the same way as the resin on the bow used to play a stringed instrument. Obviously we have to try to find a lining which does not develop this glaze to the extent our present ones do, and the speed with which we can do this depends largely on the speed with which lining makers are prepared to work. A metal bonded lining obtains some of its strength from the wire bonding, and so need contain less resin. Also different bondings behave differently. In the U.S.A. more seems to be known about bondings than we know here, and we are contacting with them. The frictional peculiarity of resin is that it grips hardest when it is not slipping: this is the reason for the squeak. Certain substances have the opposite characteristic, e.g., lead, and oils. We have accordingly tried Ferodo ML, which contains lead wire: it seems an improvement on our standard MR., and is running in France on 32-EX. We have also tried MR3, which contains non-drying boiled castor oil. We are having a lining made up containing both lead and castor oil, and another containing double the quantity of lead. We have tested the following linings for squeaks:- Ferodo ML. Better than standard. Fitted to 32-EX, 35-EX, 37-EX, 1-B-IV, B-56-BN{W.O. Bentley / Mr Barrington}, 21-G-IV. Ferodo MR.3 Better than standard. Ferodo BZ. Better than standard. Fitted to 3-B-IV, B-23-AE and one customer's car. | ||