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).
The examination and identified issues with a silent tappet mechanism after 2000 miles of use.
| Identifier | ExFiles\Box 106\5\ scan0108 | |
| Date | 23th September 1933 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Wym.{G. Harold Whyman - Experimental Manager} Hs{Lord Ernest Hives - Chair}/Wym.{G. Harold Whyman - Experimental Manager}3/KT. 23.9.33. SILENT TAPPET MECHANISM ON 1.J.III. In continuation of our report of 14.9.33., we examined the condition of the eccentrics and rocker shafts after approx. 2000 miles, and although no seizure had occurred, there were distinct signs of picking up. We do not consider this scheme good enough, and a set of eccentrics with the bearing surfaces white metalled, and a new system of oil feed holes in the rocker shafts to LeC.3641 have been instructed. With regard to the oil feed, we consider the bi-pass hole in the main valve very satisfactory for the purpose of oil delivery under all conditions, but we found that with the existing plunger housings, when the engine was stopped with the oil very hot, the oil had a tendency to leak past the plunger and down the delivery hole, back to the relief valve, thus emptying the oil reservoir. To overcome this we intend to try a set of housings with a downward oil feed instead of the existing upward feed, thereby preventing any possibility of the oil draining away. There was an audible valve flutter at high speeds with plunger springs E.59630 fitted, giving a working load of 3.75 lbs., and a set of stronger springs E.12121 were fitted, giving a working load of 4.75 lbs. These springs appear to have cured the flutter. It seemed that when the oil got very hot, the leakage was much greater, and the E.59630 spring was not strong enough to lift the plunger fast enough to allow sufficient oil through the ball valve to replace that lost through leakage. We have experienced trouble with two plungers sticking in the housings, due to foreign matter getting through with the oil. As the clearance here is a very fine one, it definitely calls for the fitting of an efficient filter through which all the oil should pass prior to it reaching the silent tappet mechanism. Attached is a table of oil flow to the rocker shaft. The rocker shafts show signs of having "fidgeted" in the pedestals. E.{Mr Elliott - Chief Engineer} is investigating this matter re. strength of stud. A further examination of the bottom tappet springs | ||