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).
Testing procedures and results for a shock absorber, including calculations.
| Identifier | ExFiles\Box 152\1\ scan0073 | |
| Date | 12th January 1933 guessed | |
| - 4 - for a short time with the indicator cock open to eliminate all air. After this the indicator cock was closed, or the test rig stopped long enough to allow any accumulated pressure to leak away. A card was then taken of the first cycle after opening the indicator cock, or after starting up again. If a series of cycles were taken it was found that whilst the building up process was going on, the upper part of the card was unaffected, and it is therefore reasonable to assume that the card obtained from the first cycle is approximately a true record of what would happen under normal running conditions without the indicator attached. The indicator cards for this report were obtained in the above manner. In many of them the result of the "building up effect" can be clearly seen in the form of one or more return lines at pressures considerably above atmospheric. The shock absorber was first run with a 4" stroke at 70 double strokes/min. Cards were taken at temperature intervals of 5° from 20° to 65°C. The temperature was measured by dipping the bulb of a mercury thermometer into the oil in the recuperating chamber. The temperature of the shock absorber increased steadily as it ran, and the maximum temperature was attained in this way without any external source of heat. There is no doubt that under these conditions the oil in the working chamber was very considerably hotter than the recorded temperature, but no steps were taken to find out the exact difference. The cards taken are numbered 371-410 and photostat reproductions are attached. The conditions under which each card was taken are shown on the attached record sheets No's 43 to 46. It will be seen that the slow speed cards are almost rectangular in form, especially at the lower temperatures. The rise of pressure in the working chamber of the shock absorber is retarded by the presence of the indicator. The amount of this effect can be calculated approximately as follows:- The area of the indicator piston is 1/8 of a sq.in. The indicator pencil movement is .143" for each 100 lbs/sq.in. pressure. The pencil leverage is 2:1. The volume swept by the indicator piston for each 100 lbs/sq.in. rise of pressure is therefore .125 x .143 / 2 = .009 cu.in. Taking cards No's 371 & 390, the pressure rises to 600 lbs/sq.in in an average length of .21" on the card. The average total length | ||