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).
Issues and failures during the development of drum liners, including material tests and design flaws.
| Identifier | ExFiles\Box 159\5\ scan0089 | |
| Date | 5th November 1940 | |
| - 2 - Cont'd. {John DeLooze - Company Secretary} Therefore, for a working temperature of 100 deg. C. maximum possible interference with Birmal is only .005" and this is not sufficient and the liner always slips. 5. We tried iron with .040" interference cold but this always automatically reduced itself to .026" when once it had been heated to 200 deg. C. We adopted .026" - .030" as the best interference. 6. We tried steel liners. These have virtually the same exp: coefficient as iron, but they always burst the aluminium. The only possible reason is the difference in Youngs modulus. This is why I have always been opposed to thick liners. I was terrified of a serious drum failure. An iron liner .200 thick should be just as detrimental as a steel one .100 thick. 7. We ran into a little trouble with liners turning out only .090" thick instead of the designed .100". We forgot that with an interference of .026" the alum. expands and the iron is compressed, about .010" it appears. We altered the dimensions accordingly. A liner .090" thick gives little latitude for drum wear. 8. We ran into serious trouble with "ageing" of aluminium, i.e. permanent expansion of .012" per 12" after casting. The first lot of drums aged naturally owing to colossal time of manufacture. The next lot were made in a hurry and were a frightful failure - lack of interference fit, liners came loose. We instituted an "ageing" heat treatment of the cases before turning. 9. Ev. {Ivan Evernden - coachwork} for his convenience, designed a drum with the outside rib too far in, like this :- [Drawing of an incorrect drum design, labelled with handwritten text: WRONG] [Drawing of a correct drum design, labelled with handwritten text: RIGHT] [Handwritten note next to drawings: This edge must be continuous - no nicks.] They all burst. We never did it again. | ||