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 development of a differential valve for the Farnboro' indicator on an 'R' single cylinder unit.
| Identifier | ExFiles\Box 178\4\ img104 | |
| Date | 26th May 1932 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Yng. c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Rg.{Mr Rowledge} E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Yng.2/KT.26.5.32. X4687 REPORT ON THE DEVELOPMENT OF A DIFFERENTIAL VALVE FOR THE FARNBORO' INDICATOR - 'R' SINGLE CYLINDER UNIT. - In order to obtain indicator diagrams from an R.{Sir Henry Royce} engine it was necessary to make and develop a special valve for the Farnboro' instrument, as the high maximum pressures put up by these engines would have necessitated the use of dangerously high pressure, air bottles, if the conventional type of valve had been employed. A valve of the differential plunger type was accordingly made up to overcome the difficulty, the ratio being 1 to 4, so that the air bottle pressures were a quarter of the cylinder pressures. Photographs of the complete valve and also the various component parts are attached hereto. The points of difficulty experienced in order to make the valve function satisfactorily were - (a) The weight of the pistons (b) Making a good fit of the pistons in the valve body coupled with perfect freedom. In order to eliminate the effects of the former the pistons were drilled out to make them as light as possible and the float of the smaller piston, between the contact faces, was cut down to the absolute minimum - .004" being found to give the best results. The latter point was overcome by making the pistons of a case hardened nickel-chrome steel and lapping both the pistons and the bores separately thereby obtaining perfect freedom with a fit which was close enough to be perfectly gas tight. In the case of the smaller piston the contact disc which was of stainless steel was rivetted on. Seizing of the cut off cock made it necessary to water cool the valve and this resulted in better functioning since the pistons then operated at a much lower temperature than before, due to the absorption of the heat which the valve body previously transmitted to the pistons by conduction. Attached hereto is a photograph of an actual contact print from a diagram taken under boosted conditions on the | ||