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).
Troubleshooting issues with oil supply to the rocker shaft, plunger housing fitment, and tappet mechanism performance.
| Identifier | ExFiles\Box 106\5\ scan0105 | |
| Date | 12th September 1932 | |
| -3- strong enough to do its job, two of them having distorted badly. This matter has been reported to R.{Sir Henry Royce} Our main trouble now is an inadequate supply of oil to the rocker shaft at low speeds when the oil is hot. We have rigged up an oil gauge in the rocker feed line and whilst we get a pressure of 15 lbs./sq.in. at max. R.P.M. with an oil temperature of 77oC, as the R.P.M. decreases so does the oil pressure, until at 720 R.P.M. we have no oil pressure at all. A small bye-pass hole drilled through the main pressure relief valve gives 3 lbs./sq.in. rockers and 6 lbs/sq.in. main, when ticking over with hot oil. This is a passable condition. Other points arising from our experiences with these tappets are the plunger housings fouled the cylinder head holding down nuts, and we have had to replace the full nuts with lock nuts. The push rods have fouled every set of plunger housings fitted, and we have ground the housings to clear same. There appears to be a difference in the outside diameter of the plungers, because after trying 24 plungers in one housing, some fitted quite nicely, others fitted too tightly, and some would not fit at all, and we have had to ease them off with emery cloth to get them to work freely. We think this is probably due to a slight distortion when the end caps are fitted, and would suggest that the final grinding of the outside of the plunger should take place after the complete plunger assembly. With regard to hs{Lord Ernest Hives - Chair}/Mtha.3/MA.12.9.32. on bronze bushes between the eccentric and the rocker, we have done all our experiments with the bushes relying on the eight .062" dia. holes only, and no annular oil space or grooves, and although both the eccentrics and the rockers show a bronze discolouration, the bushes have not picked up in any way. We can now say that we have reached the stage when the tappet mechanism is working without a succession of seizes and breakages, and that the tappets on 1.J.III car at all events are much quieter than when the standard tappet mechanism is fitted, but there is still work to be done on the oil feed, plunger spring strength, and cam forms before we can really say the system is quiet. hs{Lord Ernest Hives - Chair}/G.H. Whyman. | ||