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 testing and comparison of ignition coils, their performance, specifications, and fitting to a specific chassis.
| Identifier | WestWitteringFiles\D\April1920\ Scan2 | |
| Date | 13th April 1920 | |
| Contd. -2- EFC2/T13.4.20. 10,000 mile run, and as reported in HSL/LG9.4.20, this coil has given no trouble. It is wound with 16,000 turns of standard secondary wire allowing of more liberal insulation than standard. Coil S.R.14 was fitted to 7 CA temporarily on the water pump in a position close to the distributor when this position was being tried out in the first instance, and gave ordinarily good results, although it was not considered by Mr. Hives to be quite as good as the standard coil with 21,000 turns. This coil has now been fitted to Hawk - Northcliffe chassis 3FX. We sent you under cover of our Ck{Mr Clark}3/T20.1.20, curves showing the spark length and average current at various speeds of the R.R. standard chassis battery ignition. We have now taken further similar curves, in the first instance making comparison between coil S.R.14, an average standard coil and a rather poor standard coil, and in the second instance, making a comparison between coils S.10, S.12, E.14, E.18, and another average standard coil, the particulars of this being the same in each instance, namely, that the high tension terminal was connected through 18" of high tension cable but no distributor to a single platinum point gap in air. Further the polarity used was always that giving the better regularity of sparking on the bench but the worse regularity of firing on the car. In this second instance, we also give a copy of curves showing the relation between the Contd. | ||