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).
Tests comparing the heating of ignition coils in different positions on 20 HP and 40/50 chassis.
| Identifier | WestWitteringFiles\T\November1928\ Scan004 | |
| Date | 2nd November 1928 | |
| To R.{Sir Henry Royce} from EFC. c. PJ. E.{Mr Elliott - Chief Engineer} EX. ORIGINAL PHANTOM IGNITION COIL POSITION. XS-710 X8710 Further to our EFC1/T3.10.28 we have now completed a series of tests with a view to comparing the heating of the ignition coil, both externally (coil not working) and externally + internally (coil working) on both the 20 H.P. and 40/50 chassis, on which the coil positions are different and, we consider, somewhat more favourable to the satisfactory functioning of the coil in the 20 H.P. position. The actual difference in heating obtained is not great but we think from the evidence available that this is sufficient to make the difference between safety and the possibility of failure. We do not, for instance, consider that coil windings should show a higher temperature than 100°C. In the 20 H.P. case the temperature measured both by primary and secondary resistance has been less than this figure, whereas in the 40/50 H.P. case the temperature has, in the case of each winding, been greater. The following figures, which are all °C., actually obtained on chassis show the differences referred to. For the not operating temperatures the time allowed for the temp. to settle down was one hour in each case (20 H.P. and 40/50 H.P) To arrive at the final operating temp. an additional 1 1/2 hours was given with the coils operating. For the 20 H.P. chassis with battery ignition not operating, the final temperatures attained by the ignition coil were 56 as measured by increase of primary resistance, and 58 as measured by increase of secondary resistance. | ||