A closely coiled helical spring is to carry a load of 500N. Its mean coil diameter is to be 10 times that of the wire diameter. Calculate these diameters if the maximum shear stress in the material of the string is to be 8OMN/mA2

. A helical compression spring is to be made of oil-tempered wire of 4 mm diameter with a spring index of C=10. The spring is to operate inside a hole, so buckling is not a problem, and the ends can be left plain. The free length of the spring should be 80 mm. A force of 50 N should deflect the spring 15 mm. (Take: G= 77 GPa) 1- Determine the minimum hole diameter for the spring to operate in. 2-Determine the solid length. 3-Determine a static factor of safety based on the yielding of the spring if it is compressed to its solid length.

Two helical coil springs are made from a steel bar radius of 20 mm. One spring has an outer and inner diameter of 10 cm and 6 cm respectively while the other one has a coil diameter of 12 cm. The springs have 20 turns each. What is the equivalent stiffness of the assembly if: a. the spring with the smaller coil diameter is placed inside the spring with the larger coil diameter; b. the spring with the smaller coil diameter is placed on top of the spring with the larger coil diameter. c. the spring rate equivalent at (a) is parallel with the spring rate equivalent at (b) d. the spring rate equivalent at (a) is in series with the spring rate equivalent at (b) e. the derived spring rate equivalent equation at (c) f. the derived spring rate equivalent equation at (d)

Two concentric plain helical springs of the same length are wound out of the same wire circular in cross section and supports a compressive load P. The inner spring consists of 20 turns of mean dimeter 160 mm and the outer spring has 18 turns of mean diameter 200 mm. Calculate the maximum stress induced in the spring if the diameter of wire is equal to 10 mm and Pis equal to 1000 N. (Take K,-1)