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 performed on a magneto.
| Identifier | WestWitteringFiles\F\March1921\ Scan51 | |
| Date | 19th March 1921 | |
| Contd. -2- EFC2/T19.3.21. 6. Referring to the position of maximum armature flux at dead slow as datum position, we found that the make occurred 14.5° and 63° after this position for the advanced and retarded positions respectively. The makers' range we found to be 48.5°, so that the points of break for the advanced and retarded positions were 92.5° and 141°, in relation to same datum, thus the make ratio was .433 corresponding to the long cams. The platinum point gap we found to be .010". We found the above gap and timing not to be unreasonably affected by our running tests and by varying the platinum point gap - .004". 7. Results of short endurance test (12 hour) at 2000 R.P.M. sparking on a set of 5.5 mm. gaps in air with timing lever central :- slight signs of tracking and marks on segments which appeared to have been due to small arcs. Platinum points slightly blackened. Slight deposit of grey dust on sides of high tension collector slip ring insulating cheeks and collector brush holder. 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. The short 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. 12. The short test at 1500 R.P.M. for 15 minutes with timing lever central and the discharges taking place on 5.5 mm. gaps in air, with standard length, 2 ft. high tension cable as usual, was now taken to see if the machine was normal or correct after open circuit test. It was found to be O.K. 13. Utility Test. Maximum gaps obtained on this magneto on the utility test were as follows :- (a) 9.5 mm. (b) 8.6 mm. (c) 5.4 mm. (d) 3.6 mm. Contd. | ||