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).
Technical memorandum detailing tests performed on aluminium brake drums with varying liner thicknesses.
| Identifier | ExFiles\Box 120\2\ scan0107 | |
| Date | 9th November 1936 | |
| 1029 To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} o.{Mr Oldham} to Hs.{Lord Ernest Hives - Chair} o.{Mr Oldham} to E.{Mr Elliott - Chief Engineer} o.{Mr Oldham} to Ds. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale}1/AP.9.11.36. ALUMINIUM BRAKE DRUMS. In reply to your By.3/G.5.11.36. in which you question the suitability of a liner .100" thick. The following tests have been made:- 1. Two drums ran 15,000 miles with liners only .090" thick. The braking was excellent. 2. A drum was run on the road with no interference, and no lock plates. Except on two occasions lasting about a second each, the liner never slipped, and the brake force was always good, even when the liner was slipping. (The liner was made of a high expansion iron.) 3. We tried to get a liner out of a drum. The interference was standard, i.e. .026" - .030". This liner would come loose about 200°C. The lock plates were removed and the drum placed on a rig, and heated up by using the brake. At 300°C. we attempted to pull the drum off with a hub extractor, holding the liner by keeping the brakes applied. We could not shift the drum, but we did shear both brake shoes. On releasing the brakes we removed the drum, held it mouth downwards and the liner dropped out. These tests, 2 & 3, shew that a large proportion of the grip between liner and aluminium housing is due to the brake pressure expanding the liner against the aluminium and this effect must be greater with a thin liner than with a thick one. 4. We have certainly had trouble with scoring of liners, but since this has taken place with abnormally thin liners and has not affected the braking, obviously our standard thickness is sufficient and gives us a margin for cleaning up. 5. We are now trying to replace the liner of a worn drum and clean up it's mate which is not so badly worn. The job seems quite easy so far. There are definite reasons for prefering a thin liner, they are:- continued. | ||