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).
Specifications for ordering and stress calculations for compression springs.
| Identifier | ExFiles\Box 154\1\ scan0268 | |
| Date | 7th April 1936 guessed | |
| Compression Springs. Necessary Specifications for Ordering :- Material. Size and kind of stock. Diameter. Inside or outside. State if spring works over a rod or in a hole, giving dimensions. Length. Pitch or number of coils. Style of ends (see plate, page 13). Solid height: i.e., the greatest distance allowable with all coils closed. Calculation for Stress. The first fundamental of spring practice is contained in Hooke's law, which states that stress divided by strain is a constant within the elastic limit of the material used. This means that if a piece of metal is twisted 10 degrees by a certain load that a 20 degree twist would require twice the load. It will be noticed that no consideration is given to the hardness or other physical characteristics of the particular material in question. The stress to which a spring is subjected is very necessary to intelligent spring design. The fundamental formula given in most books on mechanics is: S = MV/J for material in torsion. Wherein M = moment of the force D {John DeLooze - Company Secretary} /2 x P V = distance from fibre under consideration, to center of gravity; usually the outside fibre. For wire then d {John DeLooze - Company Secretary} /2 J = polar moment of inertia; 3.1416 d^4 / 32 | ||