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).
Calculations for stress, radii, and load on back plates for a spring assembly.
| Identifier | ExFiles\Box 43\2\ Scan197 | |
| Date | 28th September 1937 guessed | |
| - 2 - Back Plates. Suppose we decide that 100,000 lbs/in² is a good max. stress for all plates and that the plates will be selected from three sizes of stock, .250", .218", and .187". Neglecting the effect of slight variations in radius through spring thickness, all these plates will be bent to the same radius R₁ (above) on max. bump. But they will have different initial radii Rₓ given by:- .250 plate 15,000,000 x .250 / Rx + 15,000,000 x .250 / R₂ = 100,000 (See (S) above) .218 plate 15,000,000 x .218 / Rx₂ + 15,000,000 x .218 / R₁ = 100,000 .187 plate 15,000,000 x .187 / Rx₃ + 15,000,000 x .187 / R₁ = 100,000 Hence Rx, Rx₂, Rx₃ are easily found. And for a given spring length these initial radii are held constant for each thickness of plate. This is considered essential to avoid local over-stressing. The only "nip" provided is due to the difference in internal and external radii and different thicknesses of plates. LOAD OF SPRING. It is necessary to find the force at the centre bolt produced by a given stress in plates of each thickness. [Diagram of a beam labelled L₁ and L₂ for length segments, with a central downward force W, and upward support forces W₁ and W₂ at the ends] Bending moment at "centre bolt" M = f bt{Capt. J. S. Burt - Engineer}²/6 where f = stress in spring. W₁L₁ = W₂L₂ = M | ||