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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).
Spark plug development at Farnborough, discussing overheating issues and proposing a cooling solution.

Identifier  ExFiles\Box 33\3\  Scan265
Date  1st October 1928
  
To R.{Sir Henry Royce} from Lr.{Mr Ellor}
c. to BJ. Hor. [BJ is struck through]
c. to NG. E.{Mr Elliott - Chief Engineer}
c. to BY.{R.W. Bailey - Chief Engineer} EP.{G. Eric Platford - Chief Quality Engineer} [BY is struck through]

Y1872A

Hs{Lord Ernest Hives - Chair}

Lr{Mr Ellor}5/LG4.10.28.

SPARKING PLUGS.
--------------

As regards plug development at Farnborough, there is nothing further to report, but a considerable amount of single cylinder test work on plugs has been carried out under ground boost conditions.

The cylinders used were the Bristol 'mercury' air cooled and the 'Liberty'.

As with our experiments, so they find the hot plugs to be the limiting factors.

Overheated central electrodes cause slight pre-ignition which is followed by mass detonation and burning of the insulation follows.

In my opinion we could go much further without the accompanying pre-ignition if the central electrodes had a little external cooling.

In the present case of plugs, the heat is conducted from the electrode through the insulation to the plug body. I think that if the wiring nut was converted into a radiator with fins exposed to the air stream, there would be sufficient heat extracted to prevent the tip temperature exceeding the critical point.

Lr.{Mr Ellor}
  
  


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