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).
The testing and analysis of a shock absorber, including calculations and observed issues.
| Identifier | ExFiles\Box 152\1\ scan0071 | |
| Date | 12th January 1933 guessed | |
| - 2 - tested before despatch to Messrs. Rolls-Royce, and that the valves were then in perfect condition. The cause of the trouble which subsequently developed in the air valves is therefore unknown. The shock absorber was dismantled and it was found that the air valves had been damaged beyond repair. It was therefore decided to replace the shock absorber with one of the latest design - Type "RMP". This type has a C.I. body which forms the working chamber, and is cast integral with the flange. The back is closed by a flat screwed steel plug. The construction is therefore very much stiffer than that of the "MP". The air valves are replaced by vent channels. In their letter Messrs. Rolls-Royce say that they require a load of 100 lbs at the end of a 8½" lever when the shock absorber is working either with a 4" stroke at 70 double strokes/min., or with a 1" stroke at 450 double strokes/min. The dimensions of the shock absorber taken from the drawing are as follows:- Bore of casing 2.875" Dia of rotor hub 1.249" Effective blade length (2.875" - 1.249") / 2 = .813" Radius to centre of pressure (2.875" + 1.249") / 4 = 1.031" Axial length of rotor blade 1.5". If the pressure difference in the working chamber required to produce a load of 100 lbs at the end of an 8½" lever is P, then P x .813" x 1.5" x 1.031" = 100 x 8½. whence P = 676 lbs/sq.in. In taking indicator cards from the working chamber of shock absorbers, an unexpected difficulty arose which should be explained at this point. The first shock absorber tested was a single acting type. The first cards taken from the L.P. side were such as was to be expected, but those from the H.P. side showed that on the return stroke the pressure did not drop to atmospheric. It remained at a pressure which was steady during any one stroke but which varied in amount up to as much as about 500 lbs/sq.in. (See Card No.1).Page 3. Some indicator error was at first suspected, but could not | ||