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).
Engine revolutions at specific speeds with a higher axle ratio.
| Identifier | ExFiles\Box 109\5\ scan0026 | |
| Date | 25th March 1938 | |
| 664. Sg.{Arthur F. Sidgreaves - MD} from Rm.{William Robotham - Chief Engineer} Rm{William Robotham - Chief Engineer}4/R.25.3.38. Replying to Sg{Arthur F. Sidgreaves - MD}25/E25.3.38., the engine revs. @ 80 m.p.h. with a higher axle ratio are 3,900; at 85 m.p.h. they are 4,150. Rm.{William Robotham - Chief Engineer} | ||