Springs

Spring Design

Helical compression, extension and torsion springs by the method of Shigley's Mechanical Engineering Design, Chapter 10: wire tensile strength from the ASTM wire-size relation S_ut = A/d^m with the Table 10-4 constants, E and G by material and diameter, the Bergsträsser and Wahl curvature factors, spring rate, lengths and pitch from the end-condition table, the yield check at solid height, clash allowance, buckling by the end-condition constant, the surge frequency against the forcing frequency, fatigue by Zimmerli's endurance data with the Gerber, Goodman and Sines criteria, and the figure of merit; extension springs add the preferred initial-tension range and the hook bending and torsion stresses, torsion springs the inner-fibre bending factor, the moment per turn, the coil diameter under load and the pin clearance. A drawing of the spring and the load-deflection chart. The default case is Example 10-1 of Shigley (No. 16 music wire, mean coil diameter 0.400 in from the 7/16 in OD, 12.5 squared coils), whose printed values the page reproduces, with an assumed working load of 3 to 5 lbf for the fatigue section.

1 worked example reproduced, listed on the tool page.

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