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).
Letter to Templewood Engineering Co., Ltd. regarding interference fits when casting an aluminium drum around an iron liner.
| Identifier | ExFiles\Box 170\1\ img039 | |
| Date | 1st November 1938 | |
| -2- Templewood Engineering Co.,Ltd. Our interference is .026" - .030" on a 12" dia. drum with six times as much aluminium cross sectional area as iron. We understand that you intend to cast the aluminium round the liner. Provided you tin the iron with your solder, this may be satisfactory, and we should anticipate that the resulting interference would be about right, or about .014" - .018". This is assuming that the liner gets as hot as the melting point of aluminium during casting. The natural interference due to aluminium solidifying round a piece of iron as hot as itself is very considerable, but we have never succeeded in retaining more than .030" interference on a 12" dia. drum even with our thin liners as the loading expands the aluminium plastically. We imagine this does not improve the drum strength. We should, therefore, expect to find an interference of .030" after casting. We presume that aluminium cast round a liner will be just as much subject to 'growth' as aluminium cast any other way; this growth amounts to .012" and we eliminate it by 'ageing' treatment. This would give a final interference of about .018" as stated before. The object in telling you our experiences is merely to accelerate production of the final drum. You will have an advantage in that your drums will be die cast: all ours have been sand cast, also, our latest drums have more sensible proportions. We are having drawings prepared of the drum we would require and will forward these in due course. Yours faithfully, For ROLLS-ROYCE LTD. | ||