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).
Engine development for the Spectre model, detailing a new camshaft design and comparing piston types.
| Identifier | ExFiles\Box 4\1\ 01-page077 | |
| Date | 25th June 1934 | |
| - 2 - E.A/HP.25.6.34. Cam W.S.A.S. We have considered the m.e.p. curves attached to Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}4/KW.13.4.34 and PSN. has also some other results giving the relative effect of running a 20/25 camshaft against a standard Bentley camshaft, both on a Bentley engine, and as a result of this we propose to produce a new camshaft for the SpectreCodename for Phantom III on the lines of the Cadillac but not going quite so far, so as to avoid the drop in m.e.p. at the high speed. This timing is as follows:- [DIAGRAM] Ec 10. 5 10 205 IN 205 N 35 IC EO 30 .020 CLEARANCE [/DIAGRAM] and calls for a cam with the duration of 205, the displacement curve for which we have put in hand. The shorter duration required for this timing will call for higher valve spring loads, but this point will be investigated in connection with the acceleration values to be employed. In connection with the high c.r. used on the Cadillac, E/PSN. points out that the cold air intake used on the Cadillac chassis probably has some effect in reducing detonation on the road by keeping the inlet temperature down. The SpectreCodename for Phantom III, however, will have the advantage of a reduced under bonnet temperature compared with our present product owing to the use of bypass temperature control and no radiator shutters. We may also find it beneficial to arrange some free air flow which does not pass through the radiator matrix. Another point that arises on the SpectreCodename for Phantom III is the pistons. The first engine is instructed with pistons of the semi-split RR. pattern and these come about mid-way between the standard Bentley piston and the Aerolite in avoiding piston losses. We should like the second spectreCodename for Phantom III engine fitted with a set of Aerolite pistons to see if they will pass our standards for noise, and to confirm the advantage gained in using them, which ought to be quite appreciable on a 12 cylinder engine. E.{Mr Elliott - Chief Engineer} CE | ||