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 performance results for Watford HC6 and Scintilla magnetos, including spark gaps, speeds, and resistances.
| Identifier | WestWitteringFiles\L\2April1924-June1924\ Scan71 | |
| Date | 15th May 1924 | |
| Contd. -2- EPC6/T15.5.24. (a) (b) (c) (d) 1st. machine. 6.7 6.15 4.80 2.65 2nd. " 6.2 5.1 4.2 2.4 -------------------------------- A comparison of these results with those recently issued in our EPC1/T9.5.24 for the Scintilla magnetos, shows that these figures are very similar to those of the Watford HC6 machine. The Scintilla magnetos on the other hand were capable of more H.T. voltage initially, but would misfire more easily on badly leaking plugs. The maximum regular spark gaps for highspeed running in advanced, central and retarded positions respectively were :- 1st machine 7.7, 7.3, 7.5 mm. 2nd machine 5.7, 5.6, 5.85 mm. The minimum speeds for low speed sparking on a 4.5 mm. gap in air were:- 1st machine 220 r.p.m. 190 r.p.m. 190 r.p.m. 2nd.machine 160 r.p.m. 125 r.p.m. 118 r.p.m. Both these are well within the figures given in the production test. The primary and secondary resistances of these machines were/.66 and .52 ohms at 19°C. Primary. Secondary 3350 ohms at 15°C and 2500 ohms at 22°C. The milliamperes taken by the secondary Contd. | ||