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).
Page 2 of a letter to British Belting Co. regarding the composition and performance of brake linings, including lead content and squeaking issues.
| Identifier | ExFiles\Box 140\4\ scan0015 | |
| Date | 26th March 1937 | |
| British Belting Co. -2- 26.3.37. in the transverse threads of the lining. We are having some linings made with 25% by weight of lead. Linings exist with 35% of lead, and, of course, in the U.S.A. many linings contain lead, usually introduced to prevent scoring of the cheap drums they use. The lining containing the non-drying castor oil has also given good results, and has a high coefficient of friction and a not very marked fade. We are now having made a lining containing both lead and castor oil, 13% of lead only. The reason for this move is that we have been able to obtain very slight squeaks from either type on overheating the lining, also in service, linings are usually worse than on our rig. Owing to the particular manner in which you make your linings, lead wire would not be suitable, but in the U.S.A. lead powder is commonly used, chiefly in the moulded linings so popular there. We have been sent samples of powdered lead by Mr. E.J. Bisiker of London, and tests in our Laboratory show that it does not oxidise very easily. If you have any information concerning lubricants in brake linings, we should be very glad to hear from you. You will understand that we are not interested in making linings, only in buying satisfactory ones. Your linings, though excellent in many ways, we regard as particularly prone to squeak, whether used in a brake, or, in our brake servo motor, these being such entirely different mechanisms that they have no features in common which might cause squeak. We regard squeaks as being characteristic of the friction forces between linings and the ferrous mating surface. We should be very grateful for your comments on these remarks. Yours faithfully, For ROLLS-ROYCE LTD. | ||