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 memo discussing research on valve springs, their permissible stress range, and performance comparisons.
| Identifier | ExFiles\Box 158\4\ scan0034 | |
| Date | 8th June 1936 | |
| x1360 To E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Smth.12/KW.8.6.36. Valve Springs. We have been reading a paper on valve springs by Zimmerli, Chief Engineer of Barnes, Gibson and Raymond Inc., of America. They have done an extensive research into the permissible stress range of springs made of various materials and with various set-up loads. We reproduce herewith their results for chrome-vanadium steel of the type we use. If the stress range for a spring, allowing for surge and correcting by Wahl's formula, lies within lines AB & OB and below the elastic limit, the spring may be considered safe. We have plotted on the curve calculated figures for a few of our springs and have expressed the working range as a percentage of the permissible range. It will be seen that the Bentley spring EB.175 is near the limit, as we suspect it to be, and that the Ph.III inner spring E.87951 is above the limit. We attach a reproduction and some figures for American springs. These average about 70% of the permissible range. Those of ours shown on the chart average 87%. The experimental Bentley spring Rm.{William Robotham - Chief Engineer}53 which we are running at Le Mans has a figure of 73% compared with 96% for the standard spring. We think these curves should prove a valuable aid to the design. Hs{Lord Ernest Hives - Chair}/Smth. | ||