- The formulas below give good results for moderately stressed springs.
- A constant factor of 26.4 is used to compensate for cross curvature occurring in the extension form.
- The spring obeys Hooke's Law as an increment is deflected from curved to straight.
- The spring is usually not attached to storage drum and at least 1.5 turns should remain on storage drum at full deflection.
- Caution must be used while using a highly stressed spring like constant force spring as it has an inherently limited fatigue life and its failure can result in harm to equipment or personnel.
Constant Force Spring Nomenclature:
P = Load, lbs
E = Modulus of elasticity, psi
S = Stress, psi
b = Material width, in.
t = Material thickness, in.
Rn= Natural radius, in (Rn= Natural Inside Diameter ÷ 2)
R2 = Storage drum radius, in.
Sf= Stress factor