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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).
Analysis of spark ignition phenomena, including tension, pressure effects, and wire armouring.

Identifier  ExFiles\Box 58\2\  Scan158
Date  11th October 1934 guessed
  
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the arc phase, and sometimes by oscillations at a frequency rate of 10^-6 (fig.2).

Tension.- This shows great differences, according as to whether the distribution of the magneto is of the carbon (fig.4) or sparks (fig.5) type.

Figure 3 is an example of numerous disruptive discharges in a spark. Figure 6 is a similar example, studied more in detail.

Figures 3 and 5 are obtained with different plugs mounted on the same magneto.

Remark.- Observations made with a tube fed from a transformer containing air under pressures varying from 1/20 to 1/10 of atm, have resulted in finding again the disruptive and the arc phases (as a rule, without oscillations). The effluvium phase has disappeared, but the electrodes - of plane, parallel and circular surfaces - became polished and their edges well rounded. (fig.7: tension; fig.8: intensity).

Such are likely to be the main phenomena of an ignition spark produced by a magneto.

Rise of pressure.- If the magneto gives a sufficient tension, the sparks passes; but it does not last so long, and the disruptive discharges are less numerous.

Wire armouring.- The effect of armoured wire is comparable with that of an added capacity; the spark is produced if the magneto can charge the capacity at a disruptive tension. The total duration of the spark decreases, the disruptive
  
  


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