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 valve performance, testing modifications to valve seat angle, head shape, and material.
| Identifier | ExFiles\Box 38\4\ Scan049 | |
| Date | 15th August 1923 | |
| R.R. 493A (40 H) (KL 42 12-7-23). J.H.D. -3- EXPERIMENTAL REPORT. Expl. No. 2764 REF: He1/2615.8.23. to the inclined seating it tends to lift the valve and neutralize the downward alongation of the stem. In other words the 45° angle valve is more nearly adjusts itself. We have proved that if we take a present standard valve and only alter the angle of the valve seat from 30 to 45° it reduces the clearance necessary for the valve to seat from .009" to .005". (2) Shape and thickness of head. If we take a present standard valve and fill in the tulip recess at the top and make it into a flat headed valve and use the 45° degree angle seat, we then get the same degree of expansion and can run with the same tappet clearance as with the pre-war valve. If we take a pre-war valve and retain the same shape of head, alter the angle of seat from 45° to 30°, it is then necessary to increase the tappet clearance from .002" to .006". We have tried a pre-war shaped valve made in Quickstep steel and find that it does not affect the results. To confirm this we have also tried a present type valve with 3½% nickel. This confirmed that there was no difference in the material. We could not prove that the width of the valve seat made any appreciable difference. We were not able to notice any appreciable differ- ence in H.P. with the 45° angle valve compared with the 30° angle valve. With the 45° valve we were still able to obtain above the average power. contd:- | ||