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 pressure build-up in a single-acting system using an indicator diagram.
| Identifier | ExFiles\Box 152\1\ scan0072 | |
| Date | 12th January 1933 guessed | |
| - 3 - TYPE "MP" - single acting. 8" lever arm - 4" stroke - 70 revs. Adjusting Screw 4 turns open - H.P. side. Spring 350 lbs/sq.in. per inch. Piston 1/4 sq.in. be traced. The only interpretation of the card therefore was that the pressure in the working chamber was of the amount shown by the card on both sides of the rotor, since it occurred during the return stroke when the non-return valve would be open. If this was the case it should be shown on the card taken from the L.P. side. These cards however showed maximum pressures of the order of 40 lbs/sq.in. with a fall to atmospheric pressure on the return stroke. It therefore appeared that the building up of pressure was an effect which occurred only when the indicator was coupled to the H.P. chamber, and not when it was coupled to the L.P. chamber. It appears to be due to the action of the indicator piston itself. When the pressure rises in the H.P. side on the working stroke, the indicator piston is forced outwards and the volume of the H.P. side of the working chamber is increased. Less oil is therefore returned to the L.P. side than corresponds to the motion of the rotor and oil is sucked in through the recuperating valve on the L.P. side. In this way the pressure in the working chamber would tend to build up to the maximum occurring on the H.P. side, except for various leakage effects which occur. The indicator is provided with two interchangeable pistons and cylinders, one of which has an area of 1/4 of a sq.in. and the other 1/8 of a sq.in. The tests up to now had been made with the 1/4 of a sq.in. piston, and it was found that a change to the 1/8 of a sq.in. piston greatly reduced the building up effect, and in some cases it eliminated it altogether. Where it was found that building up effect was still occurring the practice adopted in taking the cards was to run the shock absorber | ||