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).
Page of calculations for determining the stress and wire size for springs, including formulas and worked examples.
| Identifier | ExFiles\Box 158\4\ scan0039 | |
| Date | 12th June 1936 guessed | |
| -2- Substituting values and simplifying the expression we get - S = (P x D x 2.55) / ((dia. of wire)³ or d³) P = Load in lbs. D = Pitch diameter which is the O.D. of spring minus the wire size in inches. d = dia.of wire in inches. S = Stress in lbs/sq.in. Examples of this equation are:- Desired, the stress on 1.1/16" O.D. spring from 1/16" wire under a 5 lbs. load. Substituting, we find: S = (5 x 1 x 2.55) / ((0625)³) = 52,250 lbs/sq.in. If we wish wire size, we can then take the desired fibre stress (say 60,000 for most steel springs) and calculate: 60,000 = (5 x 1 x 2.55) / d³ d³ = 12.7 / 60,000 = .00021 d = .05944 = the nearest commercial size being 1/16 or .0625. | ||