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).
Specification sheet outlining formulas and constants for calculating extension springs.
| Identifier | ExFiles\Box 158\4\ scan0047 | |
| Date | 12th June 1936 guessed | |
| -8- EXTENSION SPRINGS - Specifications when ordering. Material - size and kind of stock. Length -overall. Diameter. Number of coils. Style of ends (see plate page 17) Formulas for Calculation. Extension springs follow exactly the same laws as compression springs and can be calculated from tables on page 5. There is one additional possibility in extension springs known as initial tension. This initial tension can be defined as the load necessary to just separate the coils of the spring. This load is controlled by the tightness of winding the wire and can be increased or decreased. Manifestly, the formula for rate does not hold until after the load has reached a figure great enough to overcome the spring, behave exactly as a compression spring does with increases in loading. As a usual thing springs are wound with some initial tension unless otherwise specified. The amount will vary to suit the requirements of the spring. Ordinarily it is unwise to specify an initial tension greater than a load which stress the wire over 10,000 to 15,000 lbs.per.sq.in We suggest that the design of such springs be worked out with the spring manufacturer. It is possible to solve spring problems from the point of view of energy involved. If we take ordinary formulas and remove the constants we find all springs have a similar set up of equations. A list of formulas and constants is as follows: Helical spring Extension or Compression Constant K Round wire .50 Square wire .31 Helical spring used in torsion Constant K Round wire .25 Square wire .33 Rectangular wire .33 The modulus of resilience for springs with wire in torsion is : | ||