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).
Test report on the wear and performance of a magneto over an extended run, noting measurements and observations.
| Identifier | ExFiles\Box 36\1\ scan 110 | |
| Date | 30th June 1917 guessed | |
| Contd. 4. Diameter across cam fibres = .731" (average of two ends) Gap between points on either side of cam = .012" "It will be noticed that the gap was on the small side to start with, viz. .012" instead of .020", and that the diameter across cam fibres was small, viz .731" instead of about .740" as on a new machine. This was due to the considerable amount of running we had already given the magneto for the observation of the contact breaker motion). The magneto ran well at 6000 R.P.M. for 5 hours with quite regular firing, as far as could be judged, (occasional sparks at the contact points being visible. It only became slightly warm during this time. After this the sparking became irregular, due to the fibre block, having worn away sufficiently to make the break uncertain. It became more and more irregular up to the time the test was stopped. After 6 hours running the magneto could be described as "warm" but it did not attain at any time during the 12 hours run, such a temperature as to be called "hot". At the end of the test the platinum points were observed to remain in contact on rotating the machine by hand, and the diameter across the fibres was measured and found to be .698". Thus the wear on each block in 12 hours was about .015". Since the original gap on a new machine should be .020" we can estimate by proportion that the total number of hours run by a new machine before failing to give a spark would be about 84 hours. Results of tests of electrical phanomena to follow later. EFC. | ||