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).
Tests on alternative valve spring materials and designs for Bentley and Phantom III engines to reduce cost.
| Identifier | ExFiles\Box 96\2\ scan0196 | |
| Date | 24th December 1936 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell} c. to Hs.{Lord Ernest Hives - Chair} c. to E.{Mr Elliott - Chief Engineer} c. to RHC.{R. H. Coverley - Production Engineer} 354. VALVE SPRINGS. Tests have recently been carried out both on the Bentley and Phantom III. with springs in "Swedish low carbon wire" and Brunton's piano wire in comparison with our standard S/CV. material. One of the main reasons for trying the alternate materials, is to reduce the cost, S/CV. springs relatively being expensive. With regard to Brunton's wire, there has been no encouragement both by the Laboratory and our own results to try any further than our latest effort, in which six springs broke in 2 hours on Phantom III. The springs in "Swedish low carbon wire" have as far as we have gone, proved very promising both on Phantom III. and Bentley. Some of the springs were made by Barnes, Gibson, Raymond of America, and others by The Tempered Spring Company, Sheffield. Of the American springs tried on Phantom III., some were replicas of our own design E.86364 and others were their version of the same spring. In the latter, .176" dia. wire was used in place of our .192" dia. wire, the first 3 coils at the spring base having a close pitch, which has been copied by us and is shewn on Rm.{William Robotham - Chief Engineer}260 for a Bentley spring. The end coils are ground square with the axis of the spring such that almost the whole circumference is a facing. The latter we have found to be a failure in that several of these type of springs have broken off on the last coil (90º approximately), where the wire is ground to a very thin section. The apparent reason for the Americans going to a thinner gauge wire and close coiling at the base, is to infer that they attach more importance to the natural periodicity and anti-surge characteristic rather than the actual calculated static stress in the springs. continued | ||