A countershaft carrying two V-belt pulleys is shown in the figure. Pulley A receives power from a motor through a belt with the belt tensions shown. The power is transmitted through the shaft and delivered to the belt on pulley B. Assume the belt tension on the loose side, T at B is 17% of the tension on the tight side, T2. The shaft rotates at a constant speed, has a constant diameter, and is made from cold-drawn AISI 1018 steel. Calculate the minimum factor of safety, n for fatigue based on infinite life, using the modified Goodman criterion. Give your answer to 3 significant figures. Hints: Look for the maximum bending moment (need to draw shear and bending moment diagrams) Calculate the maximum bending stress and torsional stress Determine oa, Om, Ta and Tm (note that bending is completely reversed and torsion is steady) Obtain the Von Mises stresses for alternating and mean stresses (oa', Om') Calculate the endurance limit, Se Finally, find out the Modified Goodman factor of safety for fatigue Fo 01 500 lbf 75 lbf 18 in 8-in dia. 1-in dia. T B 12 in 10-in dia.