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).
Continued testing of coil windings, including temperature, insulation, and sparking gap performance.
| Identifier | WestWitteringFiles\J\December1922\ Scan52 | |
| Date | 29th November 1922 guessed | |
| -2- Contd. The temperature results of the windings of the coils are rather lower than were anticipated, considering that the coils were heated up for half an hour on the engine, during the greater part of which the water in the radiator was boiling and the temperature under the bonnet must have been in the neighbourhood of 90°C. Half an hour was considered long enough as the same coil running in the ordinary way in that temperature would have ceased to function in less than that time, but apparently the heat was slow in penetrating to the winding. This is somewhat borne out by the SB{Mr Bull/Mr Bannister} coil which had been warned a little from the inside whilst firing the engine and for which a higher temperature was found. Test 2. For this test a direct E.M.F. of 198 volts obtained by means of a number of batteries connected in series and an alternating E.M.F. obtained from the lighting mains, and transformed up to 260 volts, were used. Each supply in turn was applied to all the current carrying parts of the H.T. circuit, simultaneously, on one side through D.C. and A.C. milliammeters respectively, while the other side was connected to the chassis frame. Tests were made with the engine cold and hot but only once could an appreciable flow of current be detected. Volt: Current Insulation Current Insulation COLD. COLD. HOT. HOT. D.C. 198 M.A. 1.394 No .142 megohms. reading. - A.C. 260 No reading - - - The one reading obtained was perhaps more of the nature of surface leakage due to moisture. (3) In this test, coil G.II. 18 was used. The maximum regular sparking gaps for medium and low speeds were obtained with the coil cold. It was then gently heated up to 100°C and again run on the same gaps. There was no appreciable difference in the sparking at very low speeds; it appearing as regular as that at the higher speeds. (4) In connection with this experiment, a coil (SB.{Mr Bull/Mr Bannister}9) for which we had no further use, was taken and the inductances of the primary and secondary windings obtained. It was then run at 700 r.p.m. on eight volts and twelve volts respectively, the max. regular sparking gaps, and the Contd. | ||