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).
Ignition voltage measuring apparatus and comparison of different ignition coils.
| Identifier | ExFiles\Box 179b\2\ img170 | |
| Date | 1st November 1932 | |
| To R.{Sir Henry Royce} from Re/Est. ORIGINAL. Re/Est.1/AMGB.11.32 c. Bg. PM. c. Hiv. c. Mor. Da.{Bernard Day - Chassis Design} c. L. Rdy. c. Ry. X6103 IGNITION VOLTAGE MEASURING APPARATUS We have perfected a rig in the electrical laboratory for measuring ignition coil and magneto H.T. voltages. The rig consists of a high tension rectifying valve, condenser and calibrated ball gap. The high tension supply to be measured is led to the rectifying valve and condenser, the supply then being fed to the high tension condenser. From the top of the high tension condenser the rectified current is fed to the calibrated ball gap which is then adjusted to just spark over. The distance measured on the calibrated gap is transferred to a curve showing gap distance plotted against voltage and the voltage immediately ascertained. This rig is the same as that used by R.A.E. at Farnborough and by Messrs. Lucas at their Research Laboratories in Birmingham. This rig has been working for 3 or 4 months quite satisfactorily and we have been able to obtain some interesting comparisons between our ignition system and those of other makers. We give you herewith the following results obtained on different ignition coils. (a) R.R. L.72503 (present standard coil) This coil, under its maximum temperature working conditions, gives a voltage with 1/2 megohm leak across its terminals of 6400 with battery voltage of 16. (b) Lucas (outside primary type) This coil gave, under exactly the same conditions, a voltage of 6800. (c) Delco Remy (outside primary type) This coil gave, under exactly the same conditions, a voltage of 7800. It will be seen, therefore, that our present standard coil is giving a satisfactory high tension output. It should be remembered that the coil has a relatively larger number of secondary turns than either Lucas or Delco Remy and we feel sure that with the R.R. outside primary coil we are at present developing in the laboratory, owing to its more efficient design, the same voltage with less number of secondary turns will be obtained. This will have to be determined by experiment. | ||