Coiled Spring
Compute spring index c, Wahl factor k, torsional stress τ, deflection δ and spring rate κ for helical coil springs.
Inputs
Formula
c=D/d; k=(4c−1)/(4c−4)+0.615/c; τ=k·8WD/(πd³); δ=8NeD³W/(Gd⁴); κ=Gd⁴/(8NeD³)
G≈80 GPa for steel; N = Ne+2 for ground-end compression springs.
How to use
- Fill in Applied load W, Mean coil dia. D, Wire dia. d, Active coils Ne, Shear mod. G in the Inputs section (watch the unit on each field).
- Click Calculate; the tool evaluates the formula shown above.
- Read Spring index c, Wahl factor k, Torsional stress τ, Deflection δ, Spring rate κ in the results area.
Formula notesHelical spring: wire dia d = 1.6·∛(F·C/τ); spring index C = D/d; Wahl K = (4C−1)/(4C−4) + 0.615/C.