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 speed, compression ratios, and performance negotiations with the Ministry.
| Identifier | ExFiles\Box 36\2\ scan 235 | |
| Date | 20th February 1929 guessed | |
| contd. :- ratio to 5.5, if we increase our speed to approximately 2350 r.p.m. we can then give them the performance they are now obtaining with the 6/1 comp. ratio pistons. Major Ross and Capt. Forsyth came to Derby with the idea of persuading us to put up the normal speed of the engine to 2350, or in other words, to give them the same power as the engines we have already delivered but at the same time get rid of the detonation by lowering the compression ratio. It was argued that although we had no reason to fear the extra 100 revs, it was unreasonable for the Ministry to keep increasing their demands from the engine. We pointed out that we would prefer to still run at 2250 r.p.m. We also pointed out that the performance we were giving with the 5.5 pistons at 2250 r.p.m. was better than we originally promised. The Ministry's side was - now that the performance figures have been established on machines with engines giving high power, it is very difficult to reduce them. Finally the position arrived at was: (1) Type tests on the M.S/C. and F.S/C. engines should be run at 2250 normal r.p.m. (2) In the case of the F.S/C. we should still retain the 6/1 comp. ratio pistons and make tests to see whether, if we reduce the normal boost pressure on the ground, we can come within the A.I.D. detonation point. If we are still outside the range of detonation allowed, we shall run a 20 hrs. test at the revs. equivalent to the take off and see whether any harm is caused to the engine. contd. :- | ||