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).
Laboratory test results for a modified aero battery ignition changeover switch.
| Identifier | ExFiles\Box 163\7\ img303 | |
| Date | 1st December 1936 | |
| Rm{William Robotham - Chief Engineer}/Wat.10/JH.1.12.36. R.R. Aero Battery Ignition. Laboratory tests of changeover switch to R.R.Sch. 895 with modifications to D.7475/6/7/8/9. These modifications were designed to reduce the lag in the operation of the switch when changing back to the battery on a glide and they have been successful as the switch is a great improvement over the original design. Before commencing the test the switch was adjusted as follows :- Ignition contact gap .022". Battery negative contact gap .040". " posative " .040". Air gap in the off position .125". Tests were carried out with the equivalent of two and four coil loadings representing the Merlin Vulture and Exe engine conditions respectively. Two coil loading :- Temperature of switch 20°C. Changeover from battery to dynamo occurs at 12.4 volts. Reversion to battery occurs at 10.25 volts showing a volt lag of 2.15 volts. Temperature of switch. 40°C. Changeover from battery to dynamo 13.8 volts. Reversion to battery 10.5 volts. Volt lag 3.3 volts. | ||