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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).
Oxidising trouble with ignition plugs, its causes, and potential solutions.

Identifier  ExFiles\Box 33\3\  Scan006
Date  8th July 1916
  
X.1812.b
COPY
To EP.{G. Eric Platford - Chief Quality Engineer} from R.{Sir Henry Royce}
c. to By.{R.W. Bailey - Chief Engineer}
c. to EH. - 10/7/16
c. to J.{Mr Johnson W.M.}
R1/W8716.
July 8th, 1916.

RE OXIDISING TROUBLE WITH IGNITION PLUGS.

Regarding the trouble with the ignition plugs, you will remember that this phenomenon first made itself manifest in some attempts of mine many years ago to run a car over a long distance with a very weak mixture, and we found it was necessary to have ignition plugs that would work cooler that had points of platinum or nickel and many points.

We also found that either an excess of petrol or a small quantity of oil in the neighbourhood of the points would de-oxidise them.

Now it would appear that this trouble has commenced since we fitted smaller jets so as to prevent the engine becoming over-rich at high altitudes. It would therefore appear that outside the possibility of getting better plugs and assuming that extra lubricating oil is inadmissible for other reasons the most promising solution of the difficulty is the fitting of the mixture strength control to existing carburetters, so that it will not at any time be necessary to run with an abnormally weak mixture, and therefore, an oxidising flame inside the combustion chamber, and should any missing occur due to accidentally doing so it can be cured by giving a strong starting mixture for a short period by putting the hand control fully over to strong.

It would be interesting to find out whether we had the same trouble when using the Zenith carburetter, wherein we have not only the mixture control but probably other peculiarities of carburation.
  
  


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