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).
Analysis of the pressure dynamics within an oil-filled damper system during high and low-pressure strokes.
| Identifier | WestWitteringFiles\S\June1928-August1928\ Scan070 | |
| Date | 9th July 1928 guessed | |
| contd :- -2- Now on the high pressure stroke, the pressure at low velocities as in the present series of tests almost entirely due to valve spring pressure and so built up almost entirely in the cylinder, and when the oil passes into the communicating passage the only pressure tending to eject a quantity through the air is that due to expansion. Apparently, when the oil is starting from cold it warms up very rapidly, but while it is still thick it cannot pass through the air vent under its own pressure; as rapidly as it expands. Thus, during the high pressure stroke the whole of the rest of the damper becomes filled with oil considerably above atmospheric pressure. Hence on the low pressure stroke, when the low pressure valve opens, the high pressure side is still at a considerable positive pressu-re and the incoming oil prevents this pressure dropping immediately. As the low pressure stroke proceeds the excess oil is forced out of the air vent as this vent is now under a pressure dictated by the low pressure load, and the closed circuit of the damper ceases to be 'too full' of oil. It is clear that if the theory is correct, the higher the low pressure load the more oil will be forced out of the vent during the low pressure stroke and the less the peculiar bump on the high pressure diagram which we are invest-igating. This is borne out in practice for, as soon as we increase the low pressure load by restrictions or other means, the bump vanishes. Again, with the standard damper, the higher the oil temperature the more oil will be able to pass out through the vent and so the bump should get progressively smaller as the oil temperature rises; that this actually does happen | ||