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).
Letter detailing engine compression pressures, testing apparatus, and various valve timing specifications.
| Identifier | ExFiles\Box 134\1\ scan0248 | |
| Date | 6th April 1940 | |
| Continuation Sheet No. 1. From F.{Mr Friese} M.{Mr Moon / Mr Moore} Aspin & Co. Ltd., Bury. W.A. Robotham, Esq., Rolls-Royce Ltd., DERBY. 6th. April, 1940. is between 800 and 900 R.P.M. Therefore, the maximum compression pressure would be at the same speed, but unfortunately at the moment we have not the set-up to motor at this speed. We are however, building a new Test House with two new dynamometers which will be fitted up with Friction Reading apparatus and an arrangement whereby we can motor the engine from 150 R.P.M. to 4,000. We are also considering a Cathode Ray Indicator, and Air Consumption Testing Apparatus. The M.E.P. obtained at 375 R.P.M. was 135 and the bore and stroke 4⅛" x 6". We have found that our valve area over piston area is not of very great importance, however, I have asked the drawing office to look up one or two engines and give you some typical examples. These should be along in the course of a post or so. With regard to valve timing. We have got this fairly well taped with regard to what timing is necessary in relation to the cylinder dimension and the position in the power curve where maximum torque is required. The timing of the engine you saw is as follows:- The valve opens 5 degrees before T.D.C and closes 30 degrees after B.D.C. The exhaust opens 35 degrees before B.D.C. and closes 6 degrees after T.D.C. The timing on the 10 h.p. job which has a bore of 63 m.m and a stroke of 95 is asfollows:- Inlet opens 15 degrees before T.D.C. and closes 40 degrees before B.D.C. Exhaust opens 45 degrees before B.D.C. and closes 15 degrees after T.D.C. On a high speed engine as per drawing No. S.110 the timing was:- Inlet opens 20 degrees before T.D.C. and closes 50 degrees after B.D.C. Exhaust opens 55 degrees before B.D.C. and closes 25 degrees after T.D.C. This engine developed 160 M.E.P. at 6,400 R.P.M. using 70 octane fuel, it was calculated to develope at its maximum torque of 6,000 R.P.M. and straight off the drawing board produced the readings given. With reference to the poor mechanical efficiency | ||