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).
Valve seat failures in Wraith and Bentley cylinder heads and outlining production recommendations.
| Identifier | ExFiles\Box 8\6\ 06-page38 | |
| Date | 14th September 1938 | |
| -2- RM{William Robotham - Chief Engineer}1/W.14.9.38. (3) mal-treatment such as starting up and running full throttle from cold seems to aggravate valve seat failure. (4) We have no evidence to show as yet how much worse, if any, the small exhaust valve Wraith heads are than the large exhaust valve heads, but it is clear that we cannot take the risk of going into production with either in view of the failures we have managed to produce on the test bed. (5) We understand the position is that 32 Wraith cylinder heads are completed, 6 part-machined and 75 cast. Our recommendations are that work should be suspended on these cylinder heads, except in so far as it is necessary to maintain continuity of output. In the meantime, Wraith cylinder heads can be brought into line with best 25/30 and Bentley practice, and any further cylinder heads produced should be to these modified drawings. It would appear that the valves and fittings already produced will be satisfactory for the altered cylinder head. (6) It is clear that the cars already produced are unlikely to give any trouble for at least 5,000 miles' running. (7) Cracks on the present production Bentley cylinder heads in the position in which they have recently appeared on Wraith, are practically unheard of in the service department. We have, however, discovered cracks on C.B.IV cylinder head after 24,000 miles proto type testing. Investigation of these seat failures are receiving priority over all other experiments, and we hope to be able to obtain some further information in the immediate future. For the time being in order to maintain continuity of output there seems to be no alternative but to revert to what we know is giving satisfaction in customers hands, even though in the case of C.B.IV we have proof that this is not absolutely immune from the trouble. RM.{William Robotham - Chief Engineer} | ||