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).
Technical report on inlet valve tappet clearance, rod types, and camshaft performance.
Identifier | ExFiles\Box 134\2\ scan0198 | |
Date | 1st February 1939 | |
-11- RM{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}2/MH.{M. Huckerby}1.2.39. Regarding the differential expansion rate as affecting the inlet valve tappet clearance we find that steel rods are nearer to a constant figure than the Dural rods. The figures are as follows. Conditions: Steel Rods. Dural Rods. Cold .010 .010 Water at 80°C. Oil at 50°C .014 .005 Water at 80°C Oil at 90°C .013 .003 Upt to .010 clearance the valve gear is quiet and well up to R.R. standard and even reasonably quiet up to .014 clearance. In respect of the type of rod, we consider that the Wraith type of solid steel up-ended rod is the best proposition both for expansion and cost. Regarding the increased weight as compared with tubular rods we have found on Wraith that this only makes 100 r.p.m. difference to the bounce speed. Since thickening up the base of the bottom tappet and deleting the oil hole in the side we have had no failures. The tappet rotation is not as consistent as we should like and as soon as possible wish to try the narrow cam as against the present chamfered tip to increase the moment of rotation. The lubrication of the valve gear is now excellent and obtained by an annular groove in the rocker bush .125 wide and .020 deep in line with the oil hole. This can only be carried out on B.60 and 80 as the feed to the valve tip and push rod are not in line. As designed, the rubbers under the rocker cover nuts are too flimsy and squeeze through the holes in the cover, the steel cover washers also necessitate being stiffer, likewise the sheet steel side tappet doors. CAMSHAFT & PETROL PUMP. It has been found that the original camshaft EB.4026 is a better all round job than the shaft EB.4332, both in respect of idling, which is reasonably good, and output. The latter has more overlap and longer duration inlet but for an increase of 4 BHP at the high speeds there is a loss of 3-4 lbs/sq.in. MEP at low speeds. | ||