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 future development of the Wraith and Bentley engines.
| Identifier | ExFiles\Box 161a\4\ scan0045 | |
| Date | 30th March 1936 guessed | |
| (sheet 2) Future Wraith Engine. As it is probable that the future Wraith engine will be a small twelve cylinder the simplest possible layout of power unit will be necessary. In this connection it is considered desirable to obtain side valve engine data. It is agreed that the Packard engine power output should be investigated and for this purpose the test bed originally intended for the Straight '8' Wraith could be used if agreement to complete this bed were obtained. In the meantime other side valve engine data will be collected and investigation designs will be made of a 12 cylinder engine suitable for Wraith II, so that information can be obtained for making up a single cylinder unit, which may be of side valve pattern, to carry out development. Bentley Engine Development. A Bentley engine is being tested with six separate fixed choke carburetters to establish comparable conditions with the single cylinder unit test. It is found that the output is down at high speeds although extra power is being obtained at medium speeds. Larger carburetters are being obtained. It is proposed that we should develop a Bentley head for a 6 cylinder engine to give increased output on the standard 4 1/4 litre engine, having larger inlet valves and ports. The problems of what alterations may be required to cylinder stud positions etc. will be investigated, following which it is proposed to prepare a single cylinder head for test. It is agreed that the cross sectional area of gas passages should be made if possible always larger than actual valve port area in all new developments contemplated on any power units whatever. Curves of production and experimental engine output on the 4 1/4 litre Bentley have been compared, the former being taken with and the latter without silencers fitted, to show the exhaust silencer losses. E.{Mr Elliott - Chief Engineer} has asked Mx.{John H Maddocks - Chief Proving Officer} to take a power curve with an open exhaust for comparison. Experimental will prepare an exhaust silencer loss analysis for the 4 1/4 litre chassis for comparison with the one already available for the 3 1/2 litre, so that the design of | ||