A helical compression spring is to be made of oil-tempered wire of 4-mm diameter with a index of C 5 10. The spring is to operate inside a hole, so buckling is not a problem and the an be left plain. The free length of the spring should be 80 mm. A force of 50 should deflect ing 15 mm. Determine the spring rate. Determine the minimum hole diameter for the spring to operate in. Determine the total number of coils needed. 2010

A helical compression spring is required to provide a minimum force of 150 lb at installation and have a working deflection of 1 in. The spring rate is 75 lb/in. The coil must fit in a 2.1-in-dia hole with 0.1 in total clearance. Use 0.25-in diameter unpeened music wire and squared/ground ends. Use a 15% clash allowance, shear modulus G = 11.5 Mpsi, and weight density γ = 0.285 lb/in3. Assume Sys = 0.6Sut. Part A Find the shear stress at the initial deflection. Express your answer in pounds per square inch to three significant figures.         τiτi =       Part B Find the mean stress. Express your answer in pounds per square inch to three significant figures.     Part C Find the alternating stress in the coil. Express your answer in pounds per square inch to three significant figures.     Part D Find the fatigue safety factor for infinite life in shear. Express your answer using three significant figures.…