Design of a Helical Extension Spring

coil material

Fe

Cu

Al

Cr

Ti

Ni

Mg

number of active windings

16

wire radius (mm) (not to scale)

1.5

coil radius (mm)

14

According to Hooke's law,

F=kΔL

, the restoring force

F

of an extension spring is proportional to its linear extension

ΔL

.

The value

k

is the spring constant and depends on the design parameters as follows:

k=

μ

4

d

8

3

D

n

[1]. Here

D

is the diameter of the coil,

d

is the diameter of the wire,

n

is the number of active windings, and

μ

is the shear modulus of the material.