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).
Failure of Stellited exhaust valves and proposals for further testing and material experiments.
| Identifier | ExFiles\Box 88\4\ scan0188 | |
| Date | 16th November 1936 | |
| 237 To HPS.{Horace Percy Smith - Experimental Factory Mgr} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} EXHAUST VALVES. The failure of exhaust valves in S/SLV (Stellited) is disconcerting in the fact that it is a low expansion steel as compared with KE.965. For this reason and also that it is considerably cheaper we should like if possible to endeavour to make it a success. We are endeavouring to delete the use of silent tappets on Ph.III. and have just proved that with KE.965 exhaust valves as run on No.10 unit, the wear on the face of the exhaust bottom tappets, after approximately 1 hour running at high speeds, was much worse than 5 hours running on No.8. unit which had S/SLV. exhaust valves, both engines being run under the same conditions with regard to clearances etc. The whole crux of the matter is that with a permissible setting of the tappet clearance to ensure quietness of operation, the higher expansion of the KE.965 valve takes up this clearance at high speeds and brings the full load of the valve spring on to the bottom tappet which causes the wear. We should be pleased if you could carry out some experiments with regard to stelliting of S/SLV. which due to its heat on application causes the burning and consequent failure of the valve. Some valves appear to be burnt worse than others from inspections of the sections in which case some conditions of stelliting are worse than others. We have instructed that No.9. unit be fitted with S/SLV. valves non-stellited for the 15,000 miles test but would feel much happier about their prospects if we could successfully stellite. Mr.Talbot of the steel Laboratory informs us that he has a sample of material which might be tried for exhaust valves and some experiments could be made with regard to its suitability for stelliting. Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} | ||