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).
Serious situation and potential causes for the failure of hydraulic tappets.
| Identifier | ExFiles\Box 158\4\ scan0189 | |
| Date | 29th October 1937 | |
| 1360 By.{R.W. Bailey - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} c. Sg.{Arthur F. Sidgreaves - MD} c. RHC.{R. H. Coverley - Production Engineer} c. Mr. c. LA.{L. A. Archer} HYDRAULIC TAPPETS. Rm{William Robotham - Chief Engineer}5/R.29.10.37. In view of the serious situation with regard to hydraulic tappets revealed at the last Depot Conference, we have been over again the ascertainable facts in connection with our experimental work on the subject. We have by now built up a considerable experience of the P.III tappets in the Experimental Dept. We are, of course, repeatedly taking tappets from production and running them in our experimental engines. We have no evidence to show that the quality of chromium plating has suddenly deteriorated, or that the characteristic behaviour of the tappet in the engine has altered appreciably. If we go back to the work done prior to standardisation, there is no doubt that experimental cars built up to the production specification and have run large mileages since, prove that the bottom tappets were far from being hopelessly unreliable. We accept that occasional cases of bad plating will occur, but we have never in our experimental work had a suggestion of trouble similar to that recently experienced after the parts were fitted up correctly. As far as we know there are only two ways of destroying tappets wholesale:- (1) For the tappet mechanism to become choc-o-bloc due to the grummets not having settled down when valve springs were changed. (2) For the valve to be held permanently off its seat due to the leakage on the hydraulic mechanism being too low. It occurs to us that with the large number of valve guide changes which have been made, it is very possible that new grummets have caused the valve spring to become choc-o-bloc. As the car runs the grummets settle down, so the evidence is destroyed. (3) The fact that many of our experimental cars have covered large mileages under all sorts of conditions without the bottom tappets wearing badly | ||