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).
Results of various tests on a magneto, including armature flux, platinum point gap settings, and endurance trials.
| Identifier | WestWitteringFiles\F\March1921\ Scan48 | |
| Date | 18th March 1921 | |
| Contd. -2- 6. Referring to the position of maximum armature flux at dead slow as datum position, we found that the make occurred 27.5° before and 18° after this position, for the advanced and retarded positions respectively. The makers' range we found to be 45.5°. The points of break for the advanced and retarded positions were 72.5° and 118° in relation to the same datum, thus the make ratio is .556, the cams being of intermediate length between those of the R.{Sir Henry Royce} Bosch and U.S.A. Bosch, which are long and short respectively. These figures are averages of the two sides which differed by amounts of the order of 2 or 3° due to the use of continuous cams, whereas in other magnetos we have tried, the difference in the two sides has been immaterial. The platinum point gap we found to be .012" initially. This gap was reduced to .011" by our running tests, causing the points of break to become later by about 5°, the differences in the two sides of the magneto not becoming worse. A reduction in the platinum point gap to .008" retarded the points of break a further 5° approx., and also render the timing unequal by about 9°. On the contrary, an increase in the platinum point gap advanced the points of break to a rather less extent, but did not increase the inequality of the two sides. 7. Results of short endurance test (12 hours) at 2000 R.P.M. sparking on a set of 5.5 mm. gaps in air with timing lever central:- Platinum points slightly burred. Some oxidisation on brass distributor points. Accumulation of carbon dust at point of contact between frame earthing brush and condenser housing. A loud grating noise emanated from gears towards end of test. 8 & 9. Open circuit volt-speed and short circuit ampere-speed curves of the magneto primary are given on the accompanying photostat. (To follow) 10. A short circuit test in which the magneto is run at 1500 R.P.M. for half a minute with timing lever central and secondary winding short circuited went through O.K. 11. The open circuit test in which the machine was again run at 1500 R.P.M. for half a minute with timing lever central and with the high tension terminal not connected to anything, so that the secondary spark took place on the safety gap of the magneto, was also O.K. Contd. | ||