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).
Experiments to standardize a 'leak' component for testing magneto performance under simulated sparking plug conditions.
| Identifier | ExFiles\Box 4\5\ 05-page308 | |
| Date | 20th October 1924 | |
| Contd. -2- EFC3/T20.10.24. variation of conductivity with temperature, and it has been finally decided that the leak forming an integral part of the combination supplied by the Lucas Co. is the most satisfactory, having the least variation of temperature. The liquid used in this leak is a solution of rose-bengal, an alkaline die, in alcohol; the variation is obtained by raising and lowering a suspended electrode in a vertical tubular column of this liquid. The object of these experiments has been to arrive at a standardised gap with shunted leak which is representative of a condition of the sparking plugs of the engine rather worse than the average. Magnetos will then be compared on their performances on the standardised gap with shunted leak at various speeds and degrees of advance, and it can readily be appreciated that such performances of the magnetos can be expressed as closed curves (loops) on a Cartesian diagram, one axis of which is the speed base (vertical) and the other of which is the degrees of advance base from some suitable datum, which datum is best taken to be the position (dead slow) of the armature in which it is threaded by the maximum, i.e. undistorted, flux. The standardised value of the leak fixed upon has a conductance of 3 micromhos - this corresponds to a resistance (non-inductive) of 333,000 ohms. Regarding the fixing of the standard annular gap, upon testing on the H.T. transformer the two annular gaps whose dimensions were given above, it was found that they Contd. | ||