(i) A hollow shaft having an inside diameter 50% of its outer diameter is to replace a solid shaft transmitting the same power at the same speed. Calculate the percentage saving in material if the material to be used is also the same.
(ii) A dose coiled spring has coil diameter to wire diameter ratio of 6. The spring deflects 30 rnm under a load of 500 N and the maximum shear stress is to exceed 350 MPa. Find the diameter and length of wire required modulus of rigidity of wire material = 80 GPa.