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 page discussing spring friction, comparing cantilever and flat spring designs and performance.
| Identifier | ExFiles\Box 173\2\ img032 | |
| Date | 14th February 1934 guessed | |
| -5- SPRING FRICTION - Continued: F = uWt(N-1) / l shows that the friction is approximately the same in both types. The other formulae give the same result. Suppose the more usual case, that the number of plates in the pivoted cantilever is the same as the flat spring. Plate thickness for piv cant / Plate thickness for flat spring = (4)^(1/3) = 1.588 Stress for piv cant / Stress for flat spring = 1/(4)^(1/6) = 1/1.26 The cantilever has approximately 60% more friction. Confirming this, Rolls-Royce at one time, before hydraulic shocks, made some "thick leaf" cantilever springs having about five leaves. I do not have full particulars of these but they were approximately a theoretical design like the one quoted above in which the stresses were kept the same as a flat spring. Every one of them had to be replaced for insufficient damping action. Springs with 10 to 12 thinner plates were fitted and were perfectly satisfactory. 15 plate springs with Cleveland graphite shoes might give better results than existing 10 plate springs with friction strips, and should certainly be tried. The Rolls-Royce car mentioned above had 45" front springs with 15 plates. Very truly yours, M.{Mr Moon / Mr Moore} Olley M Copies to Messrs: Parker, Wyeth, Fretz. | ||