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).
Three modification schemes for the Wraith III cylinder head to prevent valve seat warping.
| Identifier | ExFiles\Box 8\6\ 06-page26 | |
| Date | 30th May 1938 | |
| BY/HS{Lord Ernest Hives - Chair} c. Rm.{William Robotham - Chief Engineer} 619 D4.S/G.30.5.38. WRAITH 111 - MODIFIED CYLINDER HEAD. Please received herewith E.CD.704 Stiffened Valve Seats - Wraith 111. Cylinder Head. The object of this design is to overcome the trouble of valve seats warping local to the area where the inlet and exhaust valve seats approach each other as reported in Rm.{William Robotham - Chief Engineer}1/R.27.5.38. There are three schemes shown on the design as follows :- Scheme 1, shows a partial stiffening of the metal between valve seats by machining the valve throats conically, this scheme is applicable to existing castings (unmachined). Scheme 2, shows valve throat machining as in (1) with additional metal added above the valve throats between inlet and exhaust ports obtained by adding flats in ports internally, otherwise there is no further alteration to patterns or cores for the cylinder head. This alteration could be obtained by rubbing away the sand to suit on the present port cores. Scheme 3, shows a final proposal embodying the points in scheme (2) extended, to bring the cooling water nearer the valve seats, this calls for alterations to the coring, both inside and outside the ports of the cylinder head. It is only intended to go to Scheme 3 should scheme 2 not prove a complete cure. We understand there are about 100 cylinder heads cast, and it is proposed that all those that are not already machined in the valve throats should be machined as scheme (1). Any further castings made should be as scheme 2. Further instructions will be issued if it is decided to proceed with scheme 3. The Experimental Department have already ascertained that the conical throat in the inlet valves does not give any power loss, and they are at present trying an engine with exhaust valve throats reduced in diameter to 1.300 parallel; if this is found to have no detrimental effect on engine power the exhaust valves will probably be reduced in diameter to suit at a later date, as this will further increase the amount of metal between valve seats. | ||