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).
Report page continuing the comparison of ignition coils and discussing engine starting torque.
| Identifier | ExFiles\Box 164\3\ img140 | |
| Date | 18th February 1938 | |
| - 2 - (b). Coil. cont'd.{John DeLooze - Company Secretary} engine at 6.3 volts in one case, and started it at the same voltage in another test, while RR. failed with the ballast resistance in series. (2).When output is plotted the RR. curve is a better output throughout the range of engine speed at 12 volts. (3).The Delco carries all its resistance in its primary windings, which creates a higher coil temperature and incidentally if forgotten and left on will roast the coil. (4).The separate ballast resistance was forced on us by burnt out coils. It was this ballast resistance which prevented a start being obtained. The ballast can and should be automatically short circuited in the process of starting up, which can be done at negligible cost. (5).Conclusion. We should do a complete bench test and plot the results for both Delco and RR. coils, with same battery supply current at a controlled figure to represent car operation both for regular service and for cold conditions and plot results as Kilo-volts output, so that our decisions are based on accurately controlled tests. Engine Torque. The torque required to turn the Wraith engine as against the Bentley is evidently wrong, the high torque in question was undoubtedly required, but it was either due to the newness of the engine or to the use of highface pressure piston rings or both, as in other respects the Bentley and Wraith engines are similar, and no appreciable difference in cold turning torque should exist today, as we have abandoned the high ring pressure. The Lucas starter motor as judged by the output curves submitted will make a heavier demand on the battery for current, which will bring the available coil voltage down still further, and we should therefore give this scheme further consideration to eliminate this possibility before we spend money and time on the project as we must save the battery from any unnecessarily high discharge. BY.{R.W. Bailey - Chief Engineer} | ||