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 from The British Piston Ring Co. Ltd. discussing the suitability of Tungum Alloy for aero engine rings.
| Identifier | ExFiles\Box 148\3\ scan0176 | |
| Date | 17th November 1936 | |
| C O P Y. THE BRITISH PISTON RING CO. LTD. HOLBROOK LANE, COVENTRY. Your Ref: Roy{Sir Henry Royce}/Dn15/ME. Our Ref: Sales JHP. 17th November 1936. Messrs. Rolls-Royce Ltd., Derby. Dear Sirs, We acknowledge with thanks your letter of the 16th inst. advising that you are considering trying out a small quantity of rings, Part No. A.1572 in Tungum Alloy. We should be pleased to make up some rings for you, but would like to point out that we have very thoroughly gone into this material from a piston ring point of view, and while it has quite good mechanical properties at the ordinary temperatures, the hardness falls very considerably when heated, and the rings tend to lose their outward spring at quite moderately low temperatures. For example after 8 hours at 300°C the original pressure is reduced to only a small proportion of that given by internally hammered rings in cast iron to 4K6 or 5004 specification. After heating successively for 8 hours at 200°C, 250°C, 300°C and 350°C, the rings in Tungum alloy close in almost completely. As regards hardness, a short treatment at 450°C reduced this from 190 Brinell to 127. In our opinion (which we have given to The Tungum Co.) the material is not likely to be successful for Aero Engine rings unless of composite design, in which the outward spring depends on an inner member of more highly elastic material. Even here it is possible that a hard drawn bronze might be more suitable as we understand that Tungum is more in the nature of brass, and so far no composite ring using a non-ferrous outer member has been successful. In view of our remarks we shall be glad to know if you still wish us to proceed with this matter - in which case we will have a quotation got ready for you. Perhaps you will drop us a line by return, and oblige. Yours faithfully, THE BRITISH PISTON RING CO. LTD. (sgd.) J.H. Pitt. SALES DEPARTMENT. | ||