A helical compression spring prepared of oil tempered carbon steel is subjected to a load which lies between 400N to 1000N. The spring index is 6 and the design factor of safety is 1.25. If the yield stress in shear is 350 MPa Calculate:
(i) Size of the spring wire
(ii) Diameter of the spring
(iii) Number of turns of the spring and
(iv) Free length of the spring.
The compression of the spring at the maximum load is 30 mm. The modulus of rigidity for the spring material may be taken as 80kN/mm2.