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 description of a poppet valve's operation and comparison with ball valves.
| Identifier | ExFiles\Box 17\6\ Scan305 | |
| Date | 4th September 1934 | |
| -4- Poppet Valve. As has been shown, for the same amount of valve ride during the lifting operation, less oil is taken past the valve than with ball valves, the downward movement of the poppet contributing to compensate for the movement of the plunger. Thus, at high speeds, although the plunger is moving up and down by the same amount with either type of valve, the amount of oil being taken in and leaked away is less with the poppet than with the ball valves. This applies to plunger movements during valve riding at high speeds, but not to clearance adjustment in the base circle at low speeds. In the former case the plunger momentarily moves up, a little oil is drawn in and the valve moves down. Almost immediately the plunger is loaded again and moves down until the valve is back on its seat. The rest of its movement - that taken up by the oil flow - will be retraced more slowly as the oil leaks away. When slow running the mechanism is allowed the whole of the base circle period in which to compensate for the upward displacement of the plunger, a period some 60 times as long as in the other case. In this instance, as before, the movement of the plunger will at first be accompanied by a downward movement of the plunger valve, but the valve has sufficient time to close under the influence of its spring whilst the latter is still lifted by the plunger spring. As the valve closes, an amount of oil, equal in bulk to the volume of the poppet withdrawn from underneath the plunger, passes through it. Hs{Lord Ernest Hives - Chair}/F.Ll.Smith. | ||