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Spring Calculators
Online design calculations for compression, extension, torsion, disc and leaf springs
Extension Spring Calculator
Inputs
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Body and hook stresses are within allowable values.
Load–extension
Free length (inside hooks) estimated per GB/T 2088 hook types; F = F₀ + k·(H − H₀). Body allowable = 80% of compression value (0.40·Rm); hook bending per Shigley σ = F·[K_b·16D/(πd³) + 4/(πd²)], allowable 0.625·Rm; suggested F₀ from Shigley's preferred initial-stress range. For reference only.
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View related products →Formulas
Spring rate
k = G·d⁴ / (8·D³·n)
All body coils are active
Load
F = F₀ + k·(H − H₀)
F₀ = initial tension
Free length
H₀ = (n+1)d + D₁ / + 2D₁
Half loop / full loop, inside hooks
Initial stress
τ₀ = 231/e^(0.105C) ± 6.9(4 − (C−3)/6.5)
MPa, Shigley preferred range; F₀ = πd³τ₀/(8D)
Body stress
τ = K·8FD/(πd³)
Allowable = 80% of compression springs
Hook bending
σ = F·[K_b·16D/(πd³) + 4/(πd²)]
K_b = (4C²−C−1)/(4C(C−1))
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