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).
Tests on camshafts and valve springs to resolve high-speed engine trouble.
| Identifier | ExFiles\Box 17\6\ Scan241 | |
| Date | 15th June 1934 | |
| -3- Hs{Lord Ernest Hives - Chair}/Swd1.1/KW.15.6.34. During tests with E.{Mr Elliott - Chief Engineer} 82448 camshaft and double valve springs of 166 lbs/inch rating, the speeds at which trouble started were plotted against various seat loadings, obtained by adjusting washers and it was found that by producing the curve, it would be necessary to use a seat loading of 135 lbs. in order to run up to 3500 R.P.M. without trouble. Similar figures were taken with springs of 250 lbs/inch rating and in this case it was found that only 105 lbs. seat loading would be required to run up to 3500 R.P.M. The above seat loadings were far too high to obtain quiet seating of the exhaust valves in a consistent manner. An LeC. scheme is coming through, having lighter exhaust and inlet valves, and it is hoped that this will enable us to reduce the valve spring loading which overcomes this high speed trouble. Our best results as described at the beginning of this report are with E.{Mr Elliott - Chief Engineer} 80070 camshaft and springs of 156 lbs/inch rating and 85 lbs. seat loading, which are not unduly high when it is considered that the load at the valve spring exerted by the plunger return spring is approximately 20 lbs. This brings down the effective seat loading to 65 lbs. as compared with 70 lbs. the figure of the standard production valve spring, although there is an appreciable difference in the rating of these springs. In this latest combination it is only No. 4 cylinder inlet valve which is giving any trouble, for if we prevent this valve from being held open, full power is developed both at 3400 and 3500 R.P.M. We can only account for this as being some irregularity of the cam contour and as yet we have not compared this with another cam. Attached is the curve which compares the power obtained with E.{Mr Elliott - Chief Engineer} 80070 camshaft and the latest large semi-expanding carburetter against the standard camshaft E.{Mr Elliott - Chief Engineer} 82448, with the standard semi-expanding carburetter. Although these curves were not carried out on the same unit, there is practically no difference at the high speeds and in order to confirm this, these tests will be carried out on the same unit as soon as possible. | ||