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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).
Report discussing engine firing irregularities, focusing on magneto performance, spark plugs, and carburation.

Identifier  ExFiles\Box 33\3\  Scan132
Date  5th May 1921
  
Contd. -2- R12/G10.5.21.

Kindly advise me if I have read your report incorrectly.

In conclusion, it seems that we require a magneto which will bear longer safety gap, and it is not a question of sparking at extremely slow speed, +and I doubt if it is a question of insufficient heat of a spark with the smaller magnetos. If you agree that this is certain, we should take the matter up with the Watford people, which I propose doing shortly.

My own impression of the irregular firing of our engine by the magneto is chiefly due to the intermediate position of the magneto ignition plugs. This can easily be proved or contradicted by changing the ignition wiring over and letting the magneto fire the pocket plugs. With the knowledge in hand this would tell you many things.

Also my impression is that hot working single pointed plugs fail through some oxidation of the plug points when used with our regular working carburettor and weak mixtures, chiefly observable with the better quality of motor fuels.

These were very old conclusions of mine which may require some modification, additions, or contradiction.

One feels also that proper carburation or distribution is also most likely to be giving trouble at the speeds to which you chiefly refer, i.e. full throttle slow speed directly after the throttle has been opened, or do you conclude this is continuous?

+ although this may also be desirable. R.{Sir Henry Royce}

[Handwritten note in left margin]: Naturally worse with modern lower grade spirit
  
  


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