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).
Technical memo discussing the pros and cons of an aluminium banjo type axle proposed for the Bentley 50.
| Identifier | ExFiles\Box 111\4\ scan0028 | |
| Date | 11th February 1938 | |
| <del>BY.{R.W. Bailey - Chief Engineer}</del> c. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. Hdy.{William Hardy} 1044 ---802--- DA.{Bernard Day - Chassis Design}2/G.11.2.38. [Handwritten: FJH{Fred J. Hardy - Chief Dev. Engineer}] BENTLEY 50. AXLE. PD.91. Re: Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}2/AP.9.2.38. Though it is difficult to give a convincing technical objection to this proposal, I am rather nervous about it. [Handwritten: AK] The P.11 axle construction was devised to avoid alum. in tension, though the 20/25 has had a complete alum. centre for years, in conjunction with a tie bar below. I know of one case in which an owner bumped his car against the curb (when the tie bar <del>obviously does not</del> function) and cracked the centre casing. The casing was thickened up to its present dimensions as a result of this, and I have heard of no further failures. I understand in accidents the casing has been found cracked, but the severity of the accidents is not known. Against this is the complete aluminium banjo type axle on the 3½ litre Alvis. I suggest we should see that we do not introduce into the axle beam a weak or flexible spot when the relative fatigue strength of the tubes and axle casing are taken into account. I understand that when the areas of the new alum. casing and the present through bolts are compared, there is a ratio of about 32 to 4 in the stresses, which may be about right, but the bolts are not subjected to the full fatigue effect, being wound up to a fairly high stress on tightening up and not again altered in stress except that if the alum. casing further compresses, the load on the bolts is slightly relieved. We have large diameter tubes in the new axle. The suggestion is that we should see that these tubes are not unduly strong or stiff compared with the part of the alum. casing in tension. The 20/25 had tubes more flexible than our new tubes. DA.{Bernard Day - Chassis Design} | ||