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).
That hollow headed valves should be 45% filled with sodium.
| Identifier | ExFiles\Box 158\5\ scan0093 | |
| Date | 5th November 1940 | |
| To Rm{William Robotham - Chief Engineer}/HH. from Rm.{William Robotham - Chief Engineer} Rm.{William Robotham - Chief Engineer}7/ET.5.11.40. Please specify that 45% of the hollow headed valves should be filled with sodium. Rm.{William Robotham - Chief Engineer} | ||