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).
Final conclusions of tests on coil leakage and performance with earthed shields.
| Identifier | ExFiles\Box 69\1\ scan0125 | |
| Date | 6th July 1928 | |
| EFC3/T6.7.28. -4- Contd. "Tests carried out under (b) shewed that the leakage effect due to the earthed plate on the base was negligible, the length of series gap obtained for the various temp-eratures with both coils being approximately the same as for standard coils. With the earthed shield round the coil, however, as described in Test (c) we found that coil Y began to misfire on 5.5 mm. gaps after 2 hours running and the coil X, although better, only permitted a gap of .030" placed in series without irregularities as compared with about .275" normally running. We also tested two standard coils for two hours at 17.5 volts under normal conditions, and at the end of the run a gap of .285" could be inserted in series with the H.T. supply before any irregular firing commenced on 5.5 mm. gaps." It is clear from the above that the old phenomenon is still present with these coils that are packed out to the case, though only in a comparatively small degree when the coil is only fastened to an earthed plate. The effect of placing the hand on the coil, i.e. earthing shield, is much the same as it was previously, viz. that it seriously upsets the performance of the coil, whereas in the case of the stabalite cases no effect was observable. Our final conclusion is that in view of the fact that the advantage from a temperature is point of view is not very definite, and that the disadvantage from the leakage phenomenon point of view appears to be quite definite, we should not attempt to dispense with a small air space, but retain it to approximately the same amount, or only very slightly less, than we have latterly been doing. EFC. | ||