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).
Analysis of Phantom III valve gear clearance figures, temperature effects, and material substitutions.
| Identifier | ExFiles\Box 96\2\ scan0100 | |
| Date | 23th January 1936 | |
| FILE. +354 Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell}9/JH.23.1.36. Ph.III Valve Gear. In conjunction with the fitting of standard type of tappets and deleting the automic adjustment scheme, the following clearance figures have been taken. (1) From a cold setting to reaching a water temperature of 80°C as quickly as possible, the clearance increases by .005. (2) By continued running until the oil temperature also reaches 80°C, the clearance is reduced from an increase of .005 to .003 from the setting. (3) Tests on KE.965 exhaust valves shows that when running at high speeds full throttle, the expansion is .008. Tests are now in hand to prove whether it is possible to substitute KE.965 material by stellited Silchrome for use as exhaust valves. If this is found satisfactory, and basing upon the comparative expansion of Silchrome to KE.965, there should only be approximately .005-.006 expansion of the exhaust valves. This means that under the condition (2) the necessary clearance would have to be .005-.006 and under the condition (1) the warming up period, the maximum clearance, .007-.008. The cold setting would be .002-.003. By water heating the push rods the expansion of the block would synchronise with that of the push rods, thus keeping the clearance constant, which with Silchrome valves is necessary at .005-.006. With this clearance the camshaft toe must be altered and be in line with Ph.II practice in order to have quiet seating valves. The timing of such a camshaft in conjunction with the overlap, in order to get good slow running should be as follows. Overlap area on this modified camshaft running with .005-.006 clearance should be equivalent to that of the existing Ph.III camshaft running with approximately .001 clearance. | ||