## Spring calculation

Basics of theory of coil springs

d – rod diameter, mm.

D1 – outer diameter of spring, mm.

D – average diameter of spring, mm.

n – number of working spring coils.

n1 – full number of spring coils.

l – length of spring in released condition, mm.

t – spring pitch in released condition, mm.

с – spring stiffness, N/mm.

G – modulus of shearing (for spring steel 78500 MPa).

**Stiffness analysis**** **

c – spring stiffness is the energy required for spring deformation.

c = Gd^{4}/8D^{3}n, N/mm

The wound cylindrical spring with constant pitch has linear stiffness, if the spring has a cylindrical shape. For instance, if it has a conical shape then a load-deformation curve is made by the formula:

Where,

R – internal radius of projection of the largest coil.

r – internal radius of projection of the smallest coil.