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).
Engine development regarding combustion chamber design, valve materials, and methods to reduce lead attack.
| Identifier | ExFiles\Box 173\1\ img333 | |
| Date | 9th February 1934 guessed | |
| -3- ENGINET 5. Reason that air cooled are more immune from lead attack is because of shape and combustion chamber, hemispherical head considered to be definitely best shape, and development on alternative shapes of combustion chamber was recommended, which apart from improved combustion gives increase in stiffness, and prevents distortion which Heron states is sole cause of valve troubles. 6. Stellite reduces lead attack but it was discovered that stellite we have been using is wrong grade being much too hard (particulars of re-casting obtained which will be dealt with in subsequent report). 7. Spinning valves reduces lead attack. This can be done by cooling inner and outer springs same direction with slightly offset Tappet. It is claimed that Cyclone Exhaust Valve, in spite of their size, turns with this arrangement. 8. Lead attack is more critical on our cooled engines at higher power output, in the case of conqueror was thought to be worse at lower power results were however contradictory. 9. Stellite Valve seats were not considered to be desirable. 10. Heron suggested that ultra flexible valve seat made to sketch, should be tried. [Sketch text: JUST CLEAR SEAT .050 WIDE x .100 DEEP] 11. Also that tests should be repeated on very narrow valve seats [Sketch text left: SEAT WIDTH .031 TO START] [Sketch text right: VALVE SEAT .08 EQUAL OVERLAP EACH SIDE] 12. No further improvement in Valve Steel XAC developed, K E 965 considered best tests are proceeded with H R Crown Max I have also obtained from Ex-Cell-O valuable information on diamond boring, use of CARBOLOY and development of surface broaching which will be dealt with in subsequent reports. [Handwritten Note] Perhaps you would arrange for rig tests to proceed to try out Bearing modifications outlined to ascertain whether whether improved lubrication with high Oil pressure will permit of reduced Bearing clearance. RobCoverley | ||