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).
Technical note on experiments with valve and tappet clearances, noise, and wear on Phantom and Bentley units.
| Identifier | ExFiles\Box 96\2\ scan0132 | |
| Date | 1st September 1936 | |
| (3) Hs{Lord Ernest Hives - Chair}/smdl.14/JM.{Mr Morley}1.9.36. Reduced guide clearance controls the valve on keeping square on its seat, the tilting of which is responsible for a lot of tappet noise. Less liability of oil getting down the valve guides as results of overoiling show that there is as much oil gets down the exhaust guides as the inlet guides. Tappet noise somewhat quieter by running with less tappet clearance. On one Experimental Phantom chassis the hydraulic tappets were put out of action and the tappets set in a normal manner in conjunction with the camshaft Hm.{Capt. W. Hallam - Head Repairs}44 which had toes to suit normal tappet clearances When first fitted the tappets were reasonably quiet but not a 100% job. During the latter stages of running the tappets became very noisy and upon examination were found badly grooved, also the camshaft scored, with flats on the cam tips as though at some time or other the tappets had been choc-a-bloc. During the early development of Phantom III when the face of the bottom tappets were normally hardened and not Pescolised the face of the tappets were good when run with the auto-adjustment out of action and only became badly grooved when the auto-adjustment was in action. This leads us to believe that there was something other than just normal running which caused the tappets to wear so badly on the recent experiment. We have had no previous experience with chromium plated tappets without hydraulic adjustment. Due to the large diameter base circle and consequent high rubbing velocity there will always be the tendency to more rapid tappet wear relative to that of the Bentley and 25/30 Units. For the Continental Phantom unit which we hope to run without silent tappets, we are starting off with the camshaft Ex.3245 which we think will give reasonable slow running and improved power at high speeds. | ||