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).
Testing a tappet 'holding off' scheme for the Phantom III engine.
| Identifier | ExFiles\Box 96\2\ scan0099 | |
| Date | 17th January 1936 | |
| To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} X352 Hs{Lord Ernest Hives - Chair}/Swd1.1/JH.17.1.36. Phantom III We have tested the tappet " holding off" scheme to LEC.4537 whereby the bottom tappet is held off from the base circle of the cam by a washer adjustment to the extent of .001-.002". This was devised in order to prevent wear in the form of badly grooved tappets when the latter, which are of S/ZN, e normally hardened. After running 2 hrs. at speeds from 4000.RPM-4500.RPM, the hold off adjustment was checked to compare with the original setting and the tappets dismantled for inspection. According to the measurements, some had increased by .001 and others decreased by .001. There were no cross grooves worn in the tappets, but the faces were badly scratched, also the cam contours were in a similar condition. In previous tests with normally hardened S/ZN tappets we have had the same results. Other than this, the setting of the hold off amount is most impractical, each washer having to be specially ground to suit each tappet. In its present form it takes approximatley 3 days to fit up a complete set. Having this clearance and running with the existing short toe camshaft the valves are very noisy on seating. The above results rather condemn this scheme as at present with Fescolised tappets we are obtaining very good results with only slight wear and excellent surface, both on the tappets and the camshaft. Hs{Lord Ernest Hives - Chair}/Swindall. | ||