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).
Investigation into valve seat erosion caused by valve rotation during engine over-run.
| Identifier | ExFiles\Box 106\5\ scan0004 | |
| Date | 8th August 1926 | |
| To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} c. to RG.{Mr Rowledge} Hs.{Lord Ernest Hives - Chair} X5060 E1/M18. 8. 26. RE. VALVE SEAT EROSION. X.4005 X.5060 We performed a simple experiment on the two car engines at WW. to observe if, and how, the valves rotated, by marking the upper valve spring washers and running the engines at various speeds. We assumed that the washers and valves stay together, as we have always found these have to be forcibly disengaged when dismounting the valve. It was found that with the engine running steadily at any speed there was no perceptible movement or creep, but when the engine was run up to high speed and then the throttle closed, the valves rotated on the over-run. On the Phantom various exhaust and inlet valves rotated as shewn below after running the engine up 4 or 5 times :- (Diagram shows three pairs of valves labelled ⑥, ③, ① from left to right) 1/4 turn 1/8 turn. 1/8 turn 1/8 turn. 1/4 turn 1/4 turn. The direction of rotation was clockwise, which corresponds to the direction of movement of the valve spring when being compressed. During the period of over-run of the engine some of the valves oscillated rotationally at a low period instead of creeping in one direction. A similar experiment on the 20 HP. engine caused 3 or 4 of the inlet valves to move half a turn, and others to oscillate. The oscillation appeared to be a species of creeping first in one direction then in the other, during the time that the valve was on, or nearly on, its seat, which was the only time at which the spring washer was visible to the eye. We think it would be worth while observing on the test rig if the erosion can be caused by rotational creep of the valve. E.{Mr Elliott - Chief Engineer} | ||