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).
Experiments with a 'Radamax' spark plug tester, analyzing spark characteristics under various conditions.
| Identifier | WestWitteringFiles\F\January1921\ Scan7 | |
| Date | 7th January 1921 | |
| Contd. -2- EFC1/T7.1.21. progressively until no spark appears. Hence the brightness of the spark seen through the sight-hole is an indication of the extent to which the voltage rises at the sparking plug terminal before breakdown of the sparking plug gap occurs, it being remembered as we have previously pointed out, that the higher the initial voltage kick, the greater is the amplitude of the oscillatory current and voltage constituting the initial spark at the sparking plug gap. It will readily be appreciated that if the sparking plug is leaky so that the voltage does not have the same chance of rising on the plug to a high value, the discharge at the plug points will be less of the nature of an oscillation and more of the nature of an arc or burning discharge. In these circumstances the spark indicated by the instrument will be reduced in intensity or even non-existent, according to conditions. We have experimented with this plug tester on the bench. We find that on a magneto gap slightly too large for normal sparking, the "Radamax" will cause sparks to pass almost regularly, showing also at the sight hole. Placed across a 6.5 mm. gap of an R.R. standard battery ignition on the bench it extinguishes the spark and does not show at the sight hole. The maximum gap for regular sparking with the Radamax on the battery ignition is 4.6 mm. at 500 R.P.M. of the distributor. For 300 R.P.M. it is also 4.6 mm. and for 900 R.P.M. 3.8 mm. With a small gap of .003" sparking ceases at the sight hole at all the above speeds. The spark at the main gap is always louder and more intense with the tester in Contd. | ||