Problem # $2$

A static service music wire helical compression spring is needed to support a $20-1$bf load after being compressed $2$ in $.$ The solid height of the spring cannot exceed $\frac{11}{2}-in.$ The free length must not exceed $4$ in $.$ The static factor of safety must equal or exceed $1\mathrm{.}2.$ For robust linearity use a fractional overrun to closure $$ of $0\mathrm{.}15.$ There are two springs to be designed. Start with a wire diameter of $0\mathrm{.}075$ in$.$

a$)$ The spring must operate over a $\frac{3}{4}-$in rod. A $0\mathrm{.}050-$in diametral clearance allowance should be adequate to avoid interference between the rod and the spring due to out$-$of$-$round coils. Design the spring.

b$)$ The spring must operate in a $1-$in$-$diameter hole. A $0\mathrm{.}050-$in diametral clearance allowance should be adequate to avoid interference between the spring and the hole due to swelling of the spring diameter as the spring is compressed and out$-$of$-$round coils. Design the spring.