# Helical spring

1. Sep 6, 2007

### linda123

how can we increase or decrease the stiffness of a spring

2. Sep 6, 2007

### DaveC426913

Thicker cross-section?

3. Sep 6, 2007

### AlephZero

The basic design formula is

Spring stiffness = $$\frac{Gd^4}{8nD^3}$$

G = shear modulus of material
d = wire diameter
D = spring diameter
n = number of coils.

$$G = \frac{E}{2(1 + \nu)}$$

where E is Young's Modulus, $\nu$ is Poisson's ratio.

You can change any or all of G, D, d or n.