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).
Comparison of low-speed sparking performance for various magnetos.
| Identifier | WestWitteringFiles\F\February1921\ Scan83 | |
| Date | 10th December 1920 | |
| Contd. -8- EFC4/T3.2121. Magneto. Lowest speeds for 5.5 mm. Adv. Cent. Retd. Watford E.6 95 175 210 " E.6 150 220 320 " E.O.6 160 140 136 R.{Sir Henry Royce} Bosch Z.R.6. 260 190 250 U.S.A. Bosch ZR6 125 220 320 " " B6 150 280 530 Considerable differences in the low speed sparking will be seen. In investigating this matter on further magnetos, we propose not working on the makers ranges as this method is not properly comparative for magnetos with different ranges. Instead of this we propose to adopt a similar range for all machines, viz. 34° as an average, and to fix the top of this range so as to make a position which will give regular sparking on 5.5 mm. gaps at 3500 R.P.M. and the fully retarded position as 34° back from this. The lowest speed for 5.5mm. sparking will then be found for the retarded position in this way, which gives a fair comparison of various magnetos. At the present moment we understand that we are using a 30° range on the car, as this is the range of the standard Watford magneto as set by the makers, but other machines have been allowed a range of perhaps 40° by the makers. It is assumed that slightly more range than 30° would be desirable although we understand that really not much more is required. We have accordingly fixed the required range at 34° and will compare the magnetos in their retarded position at 34° back from the Contd. W'H' 532Y (100 J.{Mr Johnson W.M.}) (W'H' 388 10-12-20) C' 3891 | ||