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).
Report page analyzing valve bounce and spring oscillation at high camshaft speeds.
| Identifier | ExFiles\Box 43\3\ Scan114 | |
| Date | 13th January 1927 guessed | |
| contd :- -2- It will be seen that they both start to bounce, or the valves leave the cam, at approximately the same speed of 1350 r.p.m. of the camshaft. At this stage it is only just before the valve is seated that the lag occurs. It must be remembered that this test is on the rig where gas velocity and suction do not enter into the case, whereas on the engine it is possible that suction and friction effects would further multiply the deviation from the true path observed here, or produce the same effect at a lower speed. Another diagram is given shewing the valve track at a camshaft speed of 1550 r.p.m. - a speed never obtained on the engine. In the case of each spring the valve leaves the cam before maximum lift and continues with a series of bounces. The greatest lift of the valve is approximately one-eighth of an inch higher than normal. Once the valve has left the cam we should expect it to obey simple harmonic motion under the action of the spring and return in a smooth curve, hence the wavy motion observed on the last diagram suggests spring oscillation. It may be thought that the above observation is of little value due to the speed being outside our range but we think that perhaps suction effects on the engine would result in similar tendency, though probably in a less exaggerated form, at low speeds. These pictures, although shewing what takes place when the valve leaves the cam, fail to display the two springs or supply the reason for the breakages in the one case and not the other. contd :- | ||