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).
New type of cracking failure on Bentley front axles, discussing testing and potential modifications.
| Identifier | ExFiles\Box 84\3\ scan0224 | |
| Date | 1st June 1934 | |
| X201 To WGR. from E.{Mr Elliott - Chief Engineer} c. Sg.{Arthur F. Sidgreaves - MD} Hs.{Lord Ernest Hives - Chair} Dy.{F R Danby} Bn.{W.O. Bentley / Mr Barrington} Mft. Hc. Bentley Front Axles. It should be clearly understood that the cracking of the boss surrounding the brake shaft on the Bentley front axle is a new type of failure not previously experienced. In this respect it has nothing to do with the previous weakness which caused bent axles, and for which the sections of the axle involved had already been suitably strengthened. The unstrengthened Bentley front axle which is really the original Peregrine design stood up to over 100 hours bump test with normal damper loads, and this test has always been a complete guarantee of freedom from failure on the road before, more so than the 10,000 mile runs in France. The Experimental Department, we understand, have been able to reproduce the cracking trouble on the bumper test only by increasing the damper loadings on the original weak axle, but the intermediate strengthened type stood up to this test. We think the axle at the point where the cracks have developed is relatively weaker than P.2. or 20/25 on account of the diameter of the brake operating shaft being relatively larger. With the modification now instructed the strength at the critical point will be increased many times and should be capable of dealing with the bigger proportion of front braking which is used on the Bentley chassis. At the same time we are examining P.2. and 20/25 axles, with a view to deciding whether we should not recommend adding a little metal around the brake shaft boss. A modification is also being made to the machining operation which fixes the length of the straight part of the axle (and is of general application) to avoid danger of notching at the present point of fracture. E.{Mr Elliott - Chief Engineer} | ||