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).
Necessity of hydraulic tappets on the Phantom III.
| Identifier | ExFiles\Box 96\2\ scan0129 | |
| Date | 2nd September 1936 | |
| X 354 To E.{Mr Elliott - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Mx.{John H Maddocks - Chief Proving Officer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}3/KW.2.9.36. Hydraulic Tappets on the Phantom III. On the Ph.II, where an aluminium head was used with a cast-iron block, the differential expansion between the valve gear and the engine was such that there was a definite valve clatter when warming up. The only way to avoid this valve clatter was to use hydraulic tappet adjustment. We rather assumed that the same thing would happen on the Ph.III, and for this reason hydraulic tappet adjustment was essential. In order to prove the point, however, we carried out some experiments and were surprised to find that without this hydraulic lash adjustment we are little, if any, worse off than the standard 20/25. Since we have got the noise insulation on the dashboard it cannot really be said that the 20/25 valve gear worries the customer appreciably. The other reason for providing automatic tappet adjustment is to keep the valve clearance constant when wear takes place between the valve and its seat. On the Ph.III having an aluminium head we have of necessity to fit inserts, and we can therefore ensure that these inserts are of such a material that the prospect of wear is almost negligible, in fact far better than the present 20/25. In view of these two facts we think that the Continental Ph.III should certainly be started off without hydraulic tappet adjustment. The trouble which we had with wear of the tappets on the road is somewhat mysterious, as of course in the early stages of the Ph.III we found that as long as we locked up the silent tappets we had no trouble whatever with camshaft and tappet surface failures. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||