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).
Axle design, breakage issues, and recommendations against adopting certain types of axles.
| Identifier | ExFiles\Box 114\1\ scan0054 | |
| Date | 24th September 1936 guessed | |
| (sheet 5) of a very large overhang. This breakage always resulted from the hub being disturbed on the taper which would naturally be the point of maximum bending moment resulting from purely side loads. In Leyland's view it was only a matter of time before the axle shaft broke. We had laid down with our proposal that where a taper was used it was not necessary to disturb it for with-drawing the brake drums, and in any case the shaft was to be free from features such as threads at the point of maximum bending moment. Having regard to the difficulties surrounding the half and three quarter types of rear axle in connection with high duty work, we have not employed this principle on the main design, and moreover we think it would require very extensive testing before embodying it in place of the full floating axle. With regard to the question of reduction of slack in the drive, we know of no way of making this less than on our normal type of axle. Attempts to fix the driving shaft to the hub solidly by other makers have always resulted in fractures local to the attachment. We have however in the case of the Wraith arranged the shaft splines to be on the inner end at the differential instead of at the wheel hub, as we think the former position being lubricated and more remote from the outside will be more silent when the torque change occurs, and we are able to on this scheme to considerably stiffen up the shaft to reduce its flexibility. It should not be forgotten that both the Ford and the Lincoln Zephyr which are fitted with the half floating type of axle have been adjudged as being bad for chunking in the drive. In conclusion we cannot support the recommendation to carry out a bump test on a Ford rear axle or proceed with a 10,000 mile test on butt welded tubes adapted to our existing types of axles, as we do not think this is good enough to put on our products, and in effect is transplanting a practice which may be satisfactory under one set of conditions to a duty which is much more onerous. We cannot also recommend producing an axle to the design put forward by Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} for the reasons stated, but we do think some form of half floating or three quarter scheme | ||