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).
Weaknesses observed in magnetos on 'R' engines, caused by the use of magnesium alloy.
| Identifier | ExFiles\Box 43\4\ Scan181 | |
| Date | 20th September 1929 guessed | |
| -2- this alloy in the case of their machines. Until about three weeks before the Race the behaviour of these magnetos on "R" engines was very good, the machines giving no trouble with the exception, in one instance, of a slight seizure of the advance and retard bearing surface. Even during the last three weeks there was no actual failure of a magneto to function. One of the two engines selected for the Race namely the R.9 having been dismantled for inspection previous to re-assembling for its final 15 minutes run, on inspection of the magnetos being made two weaknesses were observed, both of these being the result of the use of magnesium alloy. (1) Excessive wear mainly on the radial, but partly on the circumferential surface of the magnesium alloy of the advance and retard bearing was observed. The wear on the radial surface was obviously largely due to the sharp cutting edge of the advance and retard lever, accordingly steps were taken to round off these edges in all further cases. (2) A seizure of the rotor was noted which, on examination, proved to be due to the cast in laminated limbs of the magnetic circuit carrying the flux from the rotor to the armature, having worked loose in the magnesium alloy. This would be very largely due to vibration effects on the overhanging mass of the armature supported by these limbs. | ||