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).
Proposal and stress analysis for a B.50 rear axle centre casing, comparing an aluminium casing to a steel tube.
| Identifier | ExFiles\Box 111\4\ scan0027 | |
| Date | 10th February 1938 | |
| To. By.{R.W. Bailey - Chief Engineer} and Da.{Bernard Day - Chassis Design} ... from Da{Bernard Day - Chassis Design}/HB.{C. E. Harcombe} c. Rm.{William Robotham - Chief Engineer} Da{Bernard Day - Chassis Design}/Hdy.{William Hardy} 10AM Da{Bernard Day - Chassis Design}/HB.{C. E. Harcombe}20/N.10.2.38. 802 FTH B.50 Rear Axle - PD's 90 to 92. Proposed Centre Casing incorporating R.H. side End Plate. It has been suggested in Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}2/AP.9.2.38, that it would be cheaper to make the R.H. End Plate, which is at present a S/M forging, in one with the A/C Centre Casing. DAH An estimate has been made of the relative strength of the aluminium centre casing constructed in this manner, and the steel axle tube, under the worst conditions. These conditions have been taken as occurring on full bump e.g. after passing over a bad hump-backed bridge, the loads on the axle being due to:- 1. Tyre compressed 4". 2. Axle in full bump position, rubber buffer fully compressed. +3. Inertia load due to an upward acceleration of approx. 20g on the axle. The stress in the steel axle tube increases progressively towards the outer end and the maximum stress given in the table below is that at the beginning of the parallel portion towards the outer end. The stress in the aluminium casing has been calculated from the dimensions of the casing which is being roughly schemed out.. Alum. casing. Steel tube Maximum stress lbs/sq.in. 6580 58,000 Yield stress 19000 70,000 Ratio Max.stress/Yield stress. .346 .83 It will be seen that the stress in the aluminium is a considerably smaller proportion of its yield than is the case in the steel tube. It would appear, therefore, that the aluminium casing will be stronger than the steel tube. These stresses are greater than those due to jacking at the centre. Da{Bernard Day - Chassis Design}/HB.{C. E. Harcombe} | ||