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).
Valve spring load inconsistencies causing valve bounce speed issues in a Ph.II engine.
| Identifier | ExFiles\Box 17\6\ Scan291 | |
| Date | 24th July 1934 | |
| To By.{R.W. Bailey - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} c. to Sft.{Mr Swift} c. to MX.{John H Maddocks - Chief Proving Officer} X7060 Valve Springs. Differences in valve bounce speed between different valves on the same engine have led us to suspect inconsistencies in spring loads as a contributory cause. The loads required to open the valves of a production Ph.II engine have been measured and found to vary between 85 1/2 lbs. and 96 lbs. This is sufficient to cause some 200 r.p.m. difference in the bouncing speeds of the best and worst valves. The variations in spring load were traced to two sources. (1) Variation in the length of the valve spring with the valve closed. On the particular head examined this amounted at the most to .050" - sufficient to cause a difference of 5 lbs. in the spring load. (2) Variation in the free length of the spring. A set of production springs were tested and it was found that the greatest difference in free length was .100. This is sufficient to cause a discrepancy of 10 lbs. in the seat loadings. There was no serious variation in the ratings of the springs, indicating that the diameter of the wire was fairly regular. In this connection it may also be noted that the spring ends were not parallel, as called for on the drawing (E.81550). In view of this it appears that we must work to a smaller tolerance on the free length of the springs, and if possible, reduce the tolerances which determine variations in the distance between the valve spring washers. We should be glad if By.{R.W. Bailey - Chief Engineer} and Sft.{Mr Swift} would build up a head in which these points have been attended to as far as is practicably possible, so that we may see just how consistent production valve spring loadings may be. Hs{Lord Ernest Hives - Chair}/Smth. | ||