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).
The loss of spark length in a chassis battery ignition system due to a second variable gap.
| Identifier | WestWitteringFiles\D\January1920\ Scan37 | |
| Date | 5th January 1920 | |
| X.3129. CHASSIS BATTERY IGNITION A.{Mr Adams} Loss of spark length due to second variable gap using R.R. standard ignition coil and contact breaker. The H.T. lead of an R.R. ignition coil was connected to a spark gap with brass electrodes which was in turn connected to a gap with platinum point electrodes. The brass electrodes were set to various gaps, and the gap at the platinum electrodes adjusted so as just to allow even sparking. The following readings were taken :- Contact breaker speed = 500 R.P.M. running current = 1.00 amps. Length of H.T. cable - 1' 6". [Table Data] Brass electrode gap ("): O | .005 | .010 | .020 | .050 | .100 | .200 | .300 | .400 | .480 | .480 Platinum point gap ("): .480 | .480 | .480 | .475 | .425 | .350 | .175 | .025 | .020 | .014 | O Total gap ("): .480 | .485 | .490 | .495 | .475 | .450 | .375 | .325 | .420 | .494 | .480 -Conclusion- Provided one gap does not exceed .014" the larger gap is not noticeably affected. The total of the lengths of the two gaps appears to reach a maximum, when the smaller gap is in the region of .020" and a minimum when both gaps are nearly equal. R.C.S.J. | ||