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).
Ignition testing regarding the length of spark gaps.
| Identifier | ExFiles\Box 33\3\ Scan001 | |
| Date | 25th January 1909 | |
| X-1812 C. 25.1.09 X-1812 IGNITION RE LENGTH OF SPARK GAP. With sparks gaps of battery plugs set at 35 thousands the engine missed five slightly. With the magneto plug gaps set at 25 thousands it sparked well on sudden acceleration. Magneto setting of 25 thousands plug gaps seemed to run better than if the plugs were set at 18 thousands. 25/1/09. | ||