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).
Suitability of a one-piece cast aluminum axle casing compared to the existing design.
| Identifier | ExFiles\Box 111\4\ scan0029 | |
| Date | 16th February 1938 | |
| Per (crossed out) Rm{William Robotham - Chief Engineer}/Ady. (crossed out) Rm.{William Robotham - Chief Engineer} (crossed out) Ds/--- (crossed out) 1044 BY.1/G.16.2.38. 802 FJH{Fred J. Hardy - Chief Dev. Engineer} BENTLEY 50. RE: AXLE CASING. As the result of studying the three memos on the above subject, Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}2/AP.9.2.38. which made the proposal for a centre casing which incorporated the offside side webs in the casting, Da{Bernard Day - Chassis Design}/HB.{C. E. Harcombe}20/N.10.12.38. which considered the proposal from a stress point of view, and Ds.2/G.11.2.38. which examined it from a design stand point, I am satisfied that the one piece casting is not as good as our present design for our purpose. It is as Ds. remarks difficult to give convincing reasons for my view, but I think they can be expressed as follows :- (a). Cast aluminium is lacking in ductility, where strictly defined and controlled loads are dealt with which have reasonable maximum and minimum values, the material is dependable, but if occasionally exposed to a force much above the average it will fail. (b). The modulus of elasticity for aluminium is about ten million pounds, its ultimate tensile is about 12 tons per square inch, a safe working stress for conditions outlined in a/- is about 6000 lbs. sq.inch. Nickel steel for end plate and bolts will have a modulus of elasticity of thirty million, an ultimate tensile of 55 tons per square inch, and a safe working stress of 24,000 lbs. square inch, but in addition isolated forces, such as impacts which will double the stress will be absorbed by plastic flow without detriment. (c). The bolts necessarily concentrate the stresses, a condition of things which cast aluminium is not really suitable for, as overstress will spell failure owing to absence of real ductility. (d). The ability to "set up" the tensile load in the through bolts is a definite gain in rigidity in the structure. BY.{R.W. Bailey - Chief Engineer} | ||