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).
Production practices for brake linings, comparing the company's methods with those of other firms.
| Identifier | ExFiles\Box 102\6\ scan0197 | |
| Date | 31th March 1937 | |
| c. to UWH. RH{R. Hollingworth}/AFW2/R.31.3.37. BRAKE SQUEAKS - ALL CARS. PRODUCTION PRACTICE OF OTHER FIRMS. Of all the people to whom Ferodo's supply brake friction linings, we are apparently unique in detailing the holes in the Ferodo to register exactly with the holes in the brake shoe, and then expecting the Ferodo to be in contact with the shoe between rivets. It is almost universal practice to drill the Ferodo at closer spacings than the shoes, and to stretch the Ferodo while rivetting it on. The accepted degree of stretch per inch of brake shoe outside circumference is as follows:- Millboard base linings (VM30, VM20, Bendix Standard) .0025" Woven linings, 1st quality (R.R. Standard) .0050" Woven linings, 2nd quality .0100" This is irrespective of lining thickness, and is used by cheap car manufacturers, using thin linings and lorry makers using thicker linings than ours. Bendix allow no gap at all between shoe and liner, and recently were amazed to find that on a batch of their shoes there was a gap of .003". The liners were scrapped. At the moment of writing many of our shoes in the assembly bay have a .015" gap between shoe and liner, but we believe the inspectors turn them down if it reaches .025". We have had a piece of Ferodo stretched as recommended in this note while being rivetted to a shoe, and it is unquestionably a much better job than production can achieve. We made a rough jig to do the stretching. | ||