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).
Letter to the Hoffmann Manufacturing Co. about ball failures in steering follower rollers, proposing experiments with cold versus hot forming.
| Identifier | ExFiles\Box 153\4\ scan0002 | |
| Date | 18th July 1939 | |
| 1300 Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} 18th. July 1939. BY.5/G.{Mr Griffiths - Chief Accountant / Mr Gnapp} The Hoffmann Manufacturing Co. Ltd., Chelmsford, For the attention of Mr. C.H. Smith. Dear Sirs, With reference to your letter of the 11th inst. (ref. CHS/AMB.1339) and further to ours of the 19th and 27th June, I must say I still feel very perturbed in regard to the ability of the ball to resist the type of load imposed upon it in carrying out its duty in a steering follower roller. It appears to me that whilst odd balls have failed under an overload test, that the overload test does not clear the rest of the balls in the race, as obviously only one or two balls come under the direct load, and furthermore the ball which successfully carries this load might only be carrying it because of the orientation of the fibre line in the ball relative to the load, in other words, if the fibre lines were at right angle to the load the ball would stand, but if the same ball were twisted through 90° so that the load fell along the same general direction as the fibre lines, it is quite probable the ball would split. In considering this problem, it occurs to me that where you change over from cold forming of the ball to hot forming of the ball, is a very suitable size of ball to try and interest an experiment, viz. to take the last size of ball which you would normally cold form, and form the slugs by the hot process, and then test balls from the same bar of material, some of them cold formed and some hot formed, arranging, if practicable, for the load to fall generally speaking parallel with the fibre lines.of the material There is still another method by which I believe the quality of the cold formed ball could be improved, and that is the experimental lines upon which I succeeded and improved the production of valve spring wire. By the method arrived at, it was possible to take wire which used in certain sizes would fail in even two hours testing on an engine, and from the same wire by further drawing work to produce wire which would run indefinitely, and by indefinitely I mean 2,000 hours inservice and then still be replaced for further work. The basis of the idea was that it would | ||