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).
Comparative analysis table of rear axle half shafts for various car models.
| Identifier | ExFiles\Box 114\1\ scan0169 | |
| Date | 22th February 1939 | |
| 1075 To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c.c. Da.{Bernard Day - Chassis Design} c.c. Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} c.c. Da{Bernard Day - Chassis Design}/LV. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}1/MH.{M. Huckerby}22.2.39. REAR AXLE HALF SHAFTS. We think the following figures worthy of being circulated, as they show that the 8 1/2" crown wheel axle should be adequate for the light straight eight cars. It is surprising that there have been no P.III failures. The right hand column is a figure of merit, being the reciprocal of a stress. The same axle ratio is assumed in all cases. | Car. | Shaft dia. at root of splines. | D³ | Engine Torque | D³/T x 1000 | |---|---|---|---|---| | 3 1/2 Bentley | 1.000 | 1.00 | 175 lbs/ft | 5.7 | | 4 1/4 " L series | 1.000 | 1.00 | 200 | 5.0 | | 4 1/4 " M series | 1.140 | 1.48 | 200 | 7.4 | | P.III | 1.250 | 1.95 | 350 | 5.6 | | B.V. A (Semi-F) | 1.200 | 1.72 | 200 | 8.6 | | 8 cyl. (3 1/2 x 4 1/2) | 1.200 | 1.72 | 306 | 6.48 | | Buick | 1.150 | 1.52 | 266 | 5.7 | | ROVER 20 | .997 | .99 | 100 | 9.9 | | " 10 | " | " | 68 | 14.5 | Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} | ||