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).
Comparison and stress analysis of a proposed half-floating rear axle for Bentley B.50 and Wraith models against a Cadillac axle.
| Identifier | ExFiles\Box 111\4\ scan0009 | |
| Date | 16th December 1937 | |
| BY (struck through) Mr. Dav. Rm.{William Robotham - Chief Engineer} De/Hdyc (struck through) 1044 DA{Bernard Day - Chassis Design}/HB.{C. E. Harcombe}27/C.16.12.37. 802 PROPOSED HALF FLOATING REAR AXLE, BENTLEY, B.50 and WRAITH. Recommendations have been made in Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}2/AP. 25.10.37. in connection with the axle shaft for this axle. We have now made a comparison between our proposed axle shaft, fitted to Wraith, and the Cadillac 60, an axle shaft and wheelswhich we have. The worst conditions appear to be :- (1). Full Torque, Top Gear. (2). Full Torque, 1st. Gear. (3). Cornering under extreme conditions, i.e. car about to overturn or skidding with µ = 1.0 The appended Table 1 gives the more important figures, showing how stresses have been derived. In the case of the Wraith the heaviest body and maximum loads have been used, whereas the Cadillac weight is estimated from available figures which it is probable do not represent the maximum body weight for this model, and it is thought that the same axle is also used on the larger Cadillac models up to the 85 (12 cyl.), although this cannot definitely be confirmed. The axle shaft fitted to the three quarter floating axle on the largest Cadillac 16 cyl. is 1.600" under the bearing, and 1.532" in the case of the Cadillac 60. As the difference in diameters is so little, it appears unlikely that an intermediate size would be used on the 85 (12 cyl.) and it is known that the latter is fitted with an axle and of the same type as the 60. The shear stress in the Wraith axle shaft under condition (1) compares favourably with that in the Cadillac Shaft, evenfor a dia. of 1.575" and is slightly higher than the Cadillac under condition (2). Under condition (3) the maximum principal stress on a shaft 1.625" dia. as recommended in Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}2/AP.28.10.37. is considerably in excess of the Cadillac figure, and appears to be too near the yield stress of the material. This stress is reduced by increasing the overhang, but this increases the stress under conditions (1) and (2). The effect is shown in Table 2. The axle as originally | ||