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).
Various engine design considerations, including cylinder layout, valve types, combustion chambers, and supercharging.
| Identifier | ExFiles\Box 178\3\ img181 | |
| Date | 14th May 1924 | |
| (2) I had imagined that the complete engine, if it had 12 cyls., would be vertical and inverted, not a Vee engine. The reason for this is that the inertia of the pistons would be so helpful in reducing maximum pressure on the big end, and that we should make so much better con. rods if we avoid load on the joint of the B. E.{Mr Elliott - Chief Engineer} block, which in this case look as though they would return to a very substantial type of fork and blade rod. Since you have done all the negotiations with the Air Ministry in this matter, we assume that you are really carrying on the design by Mr. Underwood and Mr. Gass, but when I arrived home E.{Mr Elliott - Chief Engineer} showed me the designs as far as they had got them, and it did not seem as if your influence had been upon the work. Although the calculations for this poppet valve type engine seemed very favourable the design was not sufficiently perfected and practical for such calculations to be of any value, that is, it is no use calculating something which it is not possible to have. As regards any of the types of these engines I think that we should make a strong preference for an open type combustion chamber. One cannot imagine the bulb type to be correct or economical for a high speed engine, and I do not believe that such a type will be found possible to meet our requirements. I think UD. agrees very largely with this view, and I believe also that Mr. Ricardo does. It would seem also to put us to so great a disadvantage in construction, so that I believe the limits of a complicated combustion chamber must not exceed those of Mr. Ricardo's pot. I think UD. mentions that the open type of combustion chamber was not very suitable for supercharging. I cannot see how we can get much supercharging on a 2 stroke engine even if we thought it desirable, which I doubt. The reasons for my doubting supercharging are economy of fuel, noisy exhaust, and the extra stress to which the engine may be subject. This will make a basis for discussion when we meet on Thursday next. R.{Sir Henry Royce} | ||