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).
Endurance, short circuit, and open circuit tests performed on two magnetos.
| Identifier | ExFiles\Box 40\2\ Scan206 | |
| Date | 13th June 1927 | |
| -5- Contd. (6) In an endurance test carried out on the two magnetos, in which they were run for 7 hours each at a speed of 2000 r.p.m. with timing lever fully advanced, sparking being caused to take place on a sequence of H.T. 3rd point spark gaps in air set to 5.5 mm., the observed results were quite O.K., but in the case of the Watford magneto, it was noticed that the bakelite distributor gear wheel had a high spot causing rather uneven meshing, necessitating rather more torque to drive the magneto. (7) On our routine short circuit test in which the magneto is run at 1500 r.p.m. for half an hour with timing lever central and with the primary and secondary windings short-circuited to the framework of the magneto, the performance of both machines were O.K. (8) In our routine open circuit test in which the magneto is run at 1500 r.p.m. for a quarter of an hour with timing lever fully advanced and H.T. terminal not connected to anything so that the secondary spark discharges take place on the safety gap of the magneto, it was noted that in the case of the Watford machine the sparking at the safety gap was uneven indicating that the maximum voltage which the magneto was capable of producing was not always sufficient for this length of gap. The Lucas was quite regular on the safety gap. The length of safety gap given in our standard specification is to be not less than 8.5 mm. As this Watford is 9.2 it could be reduced a little. We like, however, these magnetos to be capable of producing a very high voltage, one which corresponds to the minimum sparking safety gap of 8.5 mm. specified. | ||