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 ignition system waveforms, voltage peaks, misfiring, and spark energy measurements.
| Identifier | ExFiles\Box 164\5\ img420 | |
| Date | 19th April 1939 guessed | |
| - 2 - The waveform showed a peak of about 7000 volts followed by one or more smaller peaks of about 2000 to 4000 volts. These curves were taken with the horizontal scale enlarged to about six times that of the primary curves. The subsidiary peaks are probably caused by the oscillations in the primary circuit. The number of peaks is limited because the later oscillations in the primary do not induce a sufficient secondary voltage for a spark to cross the distributor rotor gap. At 55 lbs. the spark passes and there is only a single peak on the curve, of about 4000 volts. It is noticeable that the maximum voltage across the plug varies as much as 30% for different cycles. On one photograph two successive cycles were recorded, showing this variation. Occasional misfiring is very easily detected by the appearance of the oscillatory secondary voltage curve. This occasional misfiring at a pressure of about 60 lbs. was more pronounced with the R.R. distributor than with the Delco-Remy. Apart from this there appears to be very little difference in the secondary voltage curves for the two distributors. It was difficult to obtain satisfactory secondary current curves in the Laboratory owing to the presence of a lot of interference from neighbouring electrical apparatus. However an attempt was made to obtain current curves from a Wraith car engine. The value of the current was about the same for both the distributors. It is difficult to obtain a satisfactory waveform because of the very short duration of the current. The exact time of duration of the spark has not yet been measured, it is impossible to give a fair comparison of spark energies by the oscillograph method. Some accurate measurements of spark energy have been carried out using a calorimetric method. The method only takes about 20 minutes and gives very reasonable results. Work has been done on the effect of widening the rotor gap, on the secondary voltage curves, but no conclusive results were obtained. It might be of interest to repeat this, and to observe the effect of widening the gap on the heat | ||