Q$7)$ a$)$ Design a close coiled helical compression spring for a service load ranging from $2250$ N to $2750$ N $.$ The axial deflection of the spring for the load range is $6$ mm $.$ Assume a spring index of $5.$ The permissible shear stress intensity is $420$ MPa and wodulus of rigidity, $G=84k\frac{N}{m}{m}^2.$ Neglect the effect of stress concentration. Draw a fully dimensioned sketch of the spring, showing details of the finish of the end coils.

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