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 Phantom II car and the proposal for a new 12-cylinder engine.
| Identifier | ExFiles\Box 4\1\ 01-page001 | |
| Date | 30th September 1932 | |
| Sg.{Arthur F. Sidgreaves - MD} From Me. Mr. C. Cx.{Major Len W. Cox - Advertising Manager} A.{Mr Adams} Hy.{Tom Haldenby - Plant Engineer} Bn.{W.O. Bentley / Mr Barrington} XH694 No.3/RT.30.9.32. X.2624 PHANTOM II. CAR. A discussion has taken place at Conduit Street (Sg{Arthur F. Sidgreaves - MD}; C; Cx{Major Len W. Cox - Advertising Manager}; Bn{W.O. Bentley / Mr Barrington}; Me) as regards what size the proposed new phantomCodename for PHANTOM I engine should be. On the original Silver Ghost cars we had a capacity of 7428 (tax £49). On Phantom I and Phantom II the capacity of the engine is 7668 (tax £44). This means on the 40/50 so far we have had a big engine which was running very much throttled on both inlet and exhaust. This has enabled us to produce a soft silent engine, and still meet the requirements for performance which existed at that time. Since then the demand for increased performance has gone up, and in order to meet it we have had to obtain more power from the same engine size, by allowing the engine to breathe more freely. At the same time we have had to struggle to see that when giving the increased power we were not spoiling the car for silence and smoothness. We have now used up all our reserve and any further increase can only be obtained with a sacrifice of R.R. characteristics. The 12 cyl. engine will give us an engine with a wider speed range. The limit of the present Phantom is approximately 3600 revs. With the 12 cyl. engine the limit would be approximately 4000 revs. The proposed size for the 12 cyl. engine 3 x 4¼, 6352 cc's capacity means that we shall have an engine 18% less in capacity than the present Phantom. Therefore, in order to obtain the same power as on the present car we should have to run faster and use up most of the gain from the engine being able to run faster. The demand for increased performance is always with us, and therefore in starting off a new design we should anticipate what the requirements will be in the future. If we assume two years before we are ready to sell the car, and four years production, it means that we have got to look ahead six years. We attach herewith power curves based on engine revs. and road speed base. It will be seen that the 3 x 4¼, when geared with the same axle ratio as the present 25 HP, will give us very little increase over the latest Phantom II car. The HP. we give for the 12 cyl. leaves us no reserve and may be difficult to attain. | ||