//(Springs) Example 10.21
//Grade of the patented and cold-drawn steel gr
gr = 4
//Yield strength of the material is r% of the Sut
r = 60
//Factor of safety fs
fs = 2
//Mean coil diameter D (mm)
D = 18
//Maximum bending moment on the spring Mb (N-mm)
Mb = 250
//Modulus of elasticity of the spring E (N/mm2)
E = 207000
//Stiffness of the spring k (N-mm/rad)
k = 3