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 Hoffmann Manufacturing Co. Ltd. regarding a recurring ball split failure attributed to material seaminess.
| Identifier | ExFiles\Box 153\1\ scan0317 | |
| Date | 27th June 1939 | |
| c. Rm.{William Robotham - Chief Engineer} c. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} 1B00. 27th. June 1939. BY.4/G.{Mr Griffiths - Chief Accountant / Mr Gnapp} Messrs. Hoffmann Manufacturing Co. Ltd., Chelmsford, Essex. For the attention of C.H. Smith, Esq., Dear Sirs, Further to our letter of June 19th. I regret to have to point out that we have had another ball split in exactly the same manner as the two referred to in Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}6/MH.{M. Huckerby} of the 19th inst., the failure appears to be due to central seaminess of the material. I am very disturbed at this new position, which appears to be developing. Prior to the failures of the three balls referred to we have been able to carry four times the maximum load, which is imposed on the balls by turning the front wheels from lock to lock with the car stationary. All three of these balls have failed with only 100% overload. I do not know what methods you adopt for checking the length of wire used for producing the balls to ensure that the material is internally sound, our own practice is to take a length from each end of each bar of material delivered, quench and fracture for the purpose of ensuring :- (a). It is the correct material as specified, and is within our hardness limits. (b). That the bar is internally sound. In producing our valve spring wire which is specified from the ingot to the last single operation; in the making of the spring by this Company, each end of each 50 ft. length of wire, into which length the wire is drawn, is again examined at both ends and etched to expose seams and similar defects. To-day we can say that our valve springs are 100%, failure of a chrome vanadium spring being unknown. | ||