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).
Valve spring materials, testing procedures, and manufacturing processes for the Vulture engine.
| Identifier | ExFiles\Box 158\5\ scan0051 | |
| Date | 23th January 1940 | |
| Oy., R-R.{Sir Henry Royce} Inc., Room 2-251, General Motors Building, Detroit...Michigan. c to Rm.{William Robotham - Chief Engineer} [struck through] c to Hs.{Lord Ernest Hives - Chair} BY.2/HR.23.1.40. re VALVE SPRINGS. With reference to your memo, reference Oy.5/DS.22.12.39., the major difference in our experiences with valve springs in U.S.A. and at Derby is undoubtedly that the shot blasting works upon the decarburised skin of the carbon steel wire. I am arranging for Rm.{William Robotham - Chief Engineer}, to order 5,000 valve springs for the Vulture, to A.54031, on the understanding that the makers you select pass a 200-hour test. The spring length with valve closed is 1.500, and with valve fully open the length is .950. The makers WILL have to run a test covering these conditions. I would like to have 200 in advance, which we will run on our rig. For your test purpose, a cam constant acceleration for one third of the lift with valve spring decelerating for two thirds, would meet the case. Carbon steel is very susceptible to decarburisation - even the best hard drawn wire we have has at least .002 to .003 of completely decarburised material, whilst chrome Vanadium is not susceptible in this manner. Chrome Vanadium will scale and oxidise but will not re-act to cause decarburisation, even if a muffle is used which permits oxidation. Taking Swedish produced wire, there is a 15% to 20% advantage over springs made from this material as against similar springs in Chrome Vanadium steel. My experience in regard to shot blasting only extends to the use of small shot in conjunction with a high pressure air blast, for whilst we use Wheelabrator for scale removal on forgings and other -continued- | ||