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).
Policy document outlining future design considerations for new aero engines, including various cylinder configurations and power outputs.
| Identifier | WestWitteringFiles\I\June1922\ Scan79 | |
| Date | 7th June 1932 guessed | |
| (2) Engine design - future Policy. Apart from the swash plate engine which is purely an adventure and will probably never be anything else, it is understood that we are considering designs for another aero engine on more conventional lines which shall be a sufficient advance on the best 12.cyc. Vee or the Napier Lion type to justify making an experimental one. MR. Rowledge thinks that the HP. should be about 500 to be of any use for military requirements. I think we should make the engine large enough to enable it to compete with existing engines. I feel sure this engine must be capable of high speed, and therefore it is a sine qua non that it must be perfectly balanced. The turning moment must also at least be as even as a 12.cyc. was to admit gearing being fitted, which seems absolutely necessary for our 400.HP. There are 2 schemes proposed which are worthy of investigation at present, e.g. a 12.cyc. with 3 blocks of 4 cycs. arranged at 120 deg. intervals around a four throw zig-zag crank. and a 20.cyc. with 5 blocks of 4 cycs. arranged at 72 deg. intervals around a four throw zig-zag crank. The zig-zag crank is part of a previous engine I suggested (has this scheme been patented or could it be) and has for it's object, to relieve the crankcase of bending moment, the bearings of load, and the crankshaft of stress. It necessitates the use of balance weights, but only 2 and not very large ones. I think we should also try the conventional 4 throw crank for comparative purposes since it can be done in the same engine merely by substituting a new camshaft. It might be a good policy to make both the 12 (480.HP) and the 20.cyc. (800.HP) engines, using the same cyc. blocks and other interchangeable parts, and thus have 2 sizes of engine to offer. The connecting rods constitute one of the greatest problems of the job, and Mr. Rowledge points out that the obliquity of articulated rods situated remote from the main rod is so great as to throw a very heavy stress on the main rod. In the case of the 12.cyc. engine where we have 3 rods only on one pin, it occurs to me that we might fork one rod the full width of the big end bush and put 2 superimposed rods side by side inside of the fork. The 12.cyc. engine would have one cyc. block on top vertical to allow the pilot a good view forward, and 2 cyc. blocks underneath. Three equal carburetters could be arranged underneath at the rear end, with pipes to the 3 blocks of cylinders. Mr. Rowledge suggests that instead of using a central power unit in an aeroplane and driving multiple propellers with clutches and gearing (which I have never favoured), or a twin engine installation, it would be far more reliable if made to have 3 separate and distinct power units, one on the nose and 2 wingers. Then in the event of any one engine stopping it is still possible to perform quite usefully with the remaining two. The power of engines for such a scheme on a commercial 'plane for modern use would be 200.HP. each. I think this is quite a sound idea and that we might still do better, and suit our stock of parts, (commercial policy) by using an Eagle on the nose with reduction gear, and large propeller, and half an Eagle | ||