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).
Inter-office letter discussing induction pipes, thermometers, and preignition in engines.
| Identifier | ExFiles\Box 75\2\ scan0239 | |
| Date | 2nd August 1921 | |
| R.R.A. 25 25m. 12-20-20 40849 X2758 INTER-OFFICE CORRESPONDENCE ROLLS-ROYCE OF AMERICA, INC SPRINGFIELD, MASS. CC Mr. Belnap Mr. Nadin Oy2 - G 2821 Aug. 2, 1921 Dear Hives:- Re: Induction Pipes Replying to Hs{Lord Ernest Hives - Chair}/Lg 12.7.21: (1) Thermometers: Many thanks for your tip on not trusting to thermometers in the inlet manifold because of the "wet bulb" effect. This information is useful to us and has been circulated. (2) Preignition: My explanation of the preignition we got with the old pipe is that it was caused by the battery plugs being raised above the "critical temperature" which you found on aero engine tests. I wrote you about this yesterday. I believe you found on these tests that the sort of burning caused by an over hot plug was much more rapid than the legitimate burning caused by a proper spark, and reached much higher temperatures. Other experimenters have found that auto-ignition of the charge is much more rapid than legitimate ignition. Therefore, even if the charge ignited in this way only 50° before dead centre it might cause a bad knock in the engine, although legitimate ignition 50° before dead centre would not. This preignition was met with when pulling full throttle at about 15 m.p.h. with the brake on, to test for loading up. The effect of one hot preignition is cumulative of course, because it heats the plug still more. I think your statement that the hot spot increases the tendency for detonation should make you suspect a greater tendency for preignition, since we know that the things which produce the first (high temperature and pressure) will in the end produce the second. | ||