beat to death topic with a twist....cutting springs

Hawkeye_306 said:

Assuming the spring is not progressive, the spring constant for a helical spring is:

k=(d^4*G)/(8*D^3*N)

Where:
d = wire diameter
D = diameter of coil
G = Modulus of rigidity (a constant)
N = Number of coils

If you remove a coil you will raise the spring rate, because all else is constant. If you have 400lb/in springs with 10 coils, then

k = 4000/N

because,

k = constant/N

with,

k = 400 lb/in

N = 10

the constant must be,

constant = 4000 = (d^4*G)/(8*D^3)

If you remove one coil, N=9,

k = 4000/9 = 444 lb/in

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