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).
Test report on ballast resistance with mileage readings over time.
| Identifier | ExFiles\Box 168a\5\ img050 | |
| Date | 3rd April 1929 | |
| X7720 ENGINE & CHASSIS-DATA SHEETS DEPT. Date:- 3-4-29. Ballast resistance of 1/2 value. | Date on. | Location | Date off. | Remarks. | Miles Reading Start. | Miles Reading Finish. | Miles covered | Total Miles. | |---|---|---|---|---|---|---|---| | 3-4-29 | 14 G4 | | Fitted to 14G4 | 346 | 1335 | 989 | 989 | | 17-4-29 | " | | | 1335 | 2061 | 726 | 1715 | | 8-5-29 | " | | . | 2061 | 2394 | 333 | 2048 | | 14-5-29 | " | | | 2394 | 5498 | 3104 | 5152 | | 6-7-29 | " | | | 5498 | 7285 | 1787 | 6939 | | 24-8-29 | " | | | 7285 | 9666 | 2381 | 9320 | | 25-10-29 | " | | | 9666 | 11019 | 1353 | 10673 | | 3-12-29 | " | | | 11019 | 13844 | 2825 | 13498 | | 3-2-30 | " | | | 13844 | 31888 | 18044 | 31542 | | 8-6-30 | " | | | 31888 | 33873 | 1985 | 33527 | | 8-7-30 | " | | This test proves that the present standard coil will not overheat with a 10% lower value ballast resistance. | | | | | | ||