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).
Investigating the problem of magneto contact breaker rocker 'flinging' at high speeds on the Watford machine.
| Identifier | ExFiles\Box 36\1\ scan 089 | |
| Date | 16th February 1916 guessed | |
| To EFC. from Oy. C O P Y c. to EH. Oyl/B6217. c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to Wor.{Arthur Wormald - General Works Manager} for Mr. Ellis. c. to J.{Mr Johnson W.M.} X 2918 RE MAGNETOS. I have seen Mr. Watson of the M.L. Magneto Syndicate at the Admiralty recently, and he has pointed out that the trouble on the Bosch type of contact breaker, as for example, that fitted on the Watford machine, is that above a certain critical speed flinging of the rocker occurs, that is to say, it ceases to follow the cam and flies up into the air, finally rebounding and striking a heavy blow on the platinum contact points. This flinging is dependent on the speed. Below a certain critical speed it does not occur! The force of the blow in dependent upon the inertia of the rocker and the height to which it is flung, which latter is dependent upon the speed of rotation and the gap. If the blow is sufficiently powerful to hammer out the platinum to the slightest extent, it tends to increase the break or angular movement of the rocker, which, in its turn tends to increase the force of the blow. Therefore, the tendency to breakage is cumulative, and the contact breaker may be described as unstable. We do not know what is the critical speed on the Watford above which flinging occurs, and it is important that we should finish at the earliest possible moment the instantaneous vision apparatus which I described to Mr. Hives on his recent visit and of which I attach a sketch. This will be most useful in investigating the behaviour of these contacts breakers. The apparatus can be seen dn work at the M L Magneto Syndicate | ||