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).
Extract from a report on American practices for fitting aero engine valve seats.
| Identifier | ExFiles\Box 140\3\ scan0226 | |
| Date | 27th April 1937 | |
| EXTRACT FROM REPORT - 27.4.37. AERO ENGINE VALVE SEATS - U.S.A. VISIT. With regard to putting in valve seats the Americans have tried and abandoned all sorts of mechanical features, threads, etc. for holding the seats. The trick they do say is effective, and which has been adopted as standard practice, is to sink the seat just below the mouth of the socket bore using a plain shrink fit (see fig.I) or, alternatively, reduce the external diameter of the seat for a short distance (as in Fig.2) to provide the same effect. The free band of metal .040 wide beyond the interference fit is said to provide an effective lock which it is claimed has been proved over and over again by leaving out this feature. Figure I is used for spherical heads, figure II is applicable to any type. It has been found important to use a large radius in the corner of the socket hole with a chamfer on the seat, as showen in fig.I and II, or, alternatively, a fillet, as in fig.III. Wrights use the former, and Pratt & Whitney the latter, and there seems little to choose between the two on results. ------------ [Diagram annotations]: FIG I FIG II FIG III .040 .040 ALUM. CYL HEADS | ||