Elementary rate + bending stress
Helical torsion spring
Inputs
Nominal round-wire diameter.
Mean coil diameter; must be positive.
User-entered active turns excluding inactive end effects.
User-entered Young’s modulus; no material selection is implied.
Applied spring angle in degrees.
Results
Ideal angular spring rateMRR
21.701
N·mm/degApplied spring moment
976.56
N·mmNominal wire bending stressσ
368.41
Spring index
8
—k_360 = E·d⁴/(10.8·D·n); kθ = k_360/360; M = kθ·θ; σnom = 32M/(πd³)
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Axial response · Beam deflection & reactions · Elastic stability · Solid-shaft torsion
Method
Formula, when it applies, and when it does not
Calculate ideal angular rate, moment, and nominal wire bending stress from spring geometry and modulus.
k_360 = E·d⁴/(10.8·D·n); kθ = k_360/360; M = kθ·θ; σnom = 32M/(πd³)
When
- Round wire
- Active coils stated
- Elastic response
- Nominal stress only
Don’t
- This is an elementary round-wire torsion-spring screen using stated modulus, geometry, and angle. The 10.8 coefficient is a per-turn (360°) rate; it is divided by 360 so the displayed rate is per degree. It excludes leg geometry, coil contact, set, stress correction factors, fatigue, material heat treatment, residual stress, winding direction, coil clearance, tolerances, mounting, and design approval.