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).
Revisions to an engine specification for the Air Ministry, covering performance, consumption, and design comparisons.
| Identifier | ExFiles\Box 179b\3\ img293 | |
| Date | 1st March 1933 | |
| -2- Ha.4/WL.1.3.33. Cont'd.{John DeLooze - Company Secretary} should have to very quickly revise our specification and make it more attractive. We went over our original letter to the A.M. and found there were a number of reasons why we could revise our specification without altering the design of the engine. (1) On our original specification the speed of the two stroke engine was limited by the rate of acceleration on the exhaust valve and this was based on the Kestrel running at 2250 R.P.M. We have since type tested a Kestrel at 2500 R.P.M. We are also standardising 2600 R.P.M. normal on the Goshawk, and we have considerable experience to believe that it will not be long before this speed is increased. This means, therefore, if we still stick to the Kestrel condi-tions we can increase the normal speed of the C.I. from 1400 R.P.M. to 1625 R.P.M. This, of course, is still modest because it is certain that the normal speeds of the Kestrel engine will have gone up by the time we have ever completed a C.I. engine. (2) The consumptions we gave for our engines were based on the information which was available at that time. Since then however tests on other engines have shewn that much lower consumptions could be obtained with the form of engine as suggested by us. If we really thought we could not obtain these lower consumptions then it means that we are proposing to build the wrong type of engine. We therefore think we could safely reduce our consumptions from .43 lbs. per BHP. to .40 lbs.per BHP. (3) The A.M. have queried the Stroke/Bore ratio we have adopted. Mr. Ricardo also criticised this point. We explained to Mr. Tweedie that the Stroke/Bore ratio of the engine was arranged to suit the unit run with the open type combustion chamber and side injection. It was agreed that if we were definitely going to use an anti-chamber there are several advantages in a shorter stroke but if we made the engine with a shorter stroke it would then prevent us from ever testing it with side injection. We have to accept that the Junker engine is a proved engine. The fact that the Junker engine has proved what can be done with the two-stroke compression ignition this should give us a lot more confidence in our proposal. We are trying to obtain some more particulars of the Junker engines, the port areas, etc., but they must be very much worse off than our proposals. We have gone over the specification we went in with Ha/Ud. and he has gone down to the A.M. today to discuss various | ||