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).
Comparing two different propeller shaft specifications for the 'Myth' chassis, including a table of whirling speeds.
| Identifier | ExFiles\Box 109\3\ scan0200 | |
| Date | 1st September 1941 | |
| To Rm.{William Robotham - Chief Engineer} c. to Ev.{Ivan Evernden - coachwork} [text crossed out] c. to Rm{William Robotham - Chief Engineer}/HH. [text crossed out] c. to Rm{William Robotham - Chief Engineer}/GB. [text crossed out] c. to Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} [text crossed out] c. to Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager} [text crossed out] 700 SECRET. Ev{Ivan Evernden - coachwork}/JD.{J. Draper - Frames}1/JH.1.9.41. Myth - Propellor Shaft. Rm{William Robotham - Chief Engineer}/GB. has written to Hardy Spicers to order two propeller shafts for the above chassis, they would prefer us to use a 2.000 dia. propeller shaft .064 thick tube, although we have called for propeller shaft 2.125 dia. thick tube. From the following comparison of the propeller shaft whirling speeds, we believe it will be O.K. to accept the propeller shafts at 2.000 dia. for the first 2 Myths at least. Will Rm{William Robotham - Chief Engineer}/HH. please modify the details to agree. | Prop. shaft dia. | Thickness. | Centres between joints. | r.p.m. whirling speed. | 70% revs. per min. safe whirling speed. | Engine revs. | Ratio safe speed max. speed. | |------------------|------------|-------------------------|------------------------|-----------------------------------------|--------------|-----------------------------| | 2.000 | .064 | 42.750 | 7.160 | 5.025 | 5.000 | 1.005 | | 2.125 | .064 | 42.750 | 7.620 | 5.340 | 5.000 | 1.069 | Ev{Ivan Evernden - coachwork}/JD.{J. Draper - Frames} | ||