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 memorandum discussing the properties and use of different valve spring materials.
| Identifier | ExFiles\Box 93\5\ scan0037 | |
| Date | 12th November 1936 guessed | |
| VALVE SPRING MATERIALS. As a result of the enquiries and discussions we have had recently on the above matter, the situation with respect to valve spring materials is as follows:- (1) CHROME VANADIUM STEEL. This is our present material. It is produced from rods which are ground and subsequently drawn down to size by cold working followed by annealing and is supplied in the soft state. It requires to be hardened and tempered after coiling. It has been found by long experience to be quite satisfactory for stresses up to 85000 lbs. using Wahls correction. (2) HARD DRAWN PIANO WIRE. This material is used by a number of firms in the Aero Engine Industry with varying success. It is produced by a method of heat treatment known as "Patenting" and is then cold drawn to give the necessary physical properties. We have made a number of attempts to use this material and have never succeeded. This in our opinion is due to certain inherent defects in this material caused through the patenting operation. It is now suggested that if this material could be ground in the coil after patenting, these defects would largely be removed and a reasonably sound wire result. We are at present in touch with Messrs. Samuel Fox & Co, Limited, Stockbridge, who are producing for us some wire ground after patenting for examination and test. The difficulty here may be the grinding operation as it is somewhat doubtful whether there is any grinding machine available to produce the material in economical lengths for coiling. In all our discussions on this type of material spring makers are definite that the maximum stress should not exceed 75000 lbs. whilst actually other aero engine makers do not use this material over 60000 lbs. stress. (3) CARBON STEEL WIRE NEEDING HEAT TREATMENT. In our recent investigation it has been shown quite clearly that certain firms whom we assumed were using Piano Wire are as a matter of fact using a Carbon Steel Wire of similar composition to the piano wire, but has definitely been heat treated and not cold drawn. This is applicable both to the American springs which were fitted to the Bentley car taken to America by Rm.{William Robotham - Chief Engineer} and also to springs used by Vauxhall. Cont'd.{John DeLooze - Company Secretary} | ||