For the problem specified in the table, build upon the results of the original problem to determine the minimum factor of safety for fatigue based on infinite life. The shaft rotates at a constant speed, has a constant diameter, and is made from cold-drawn AISI 1018 steel.
Problem 3€“72, A gear reduction unit uses the countershaft shown in the figure. Gear A receives power from another gear with the transmitted force FA applied at the 20_ pressure angle as shown. The power is transmitted through the shaft and delivered through gear B through a transmitted force FB at the pressure angle shown.
(a) Determine the force FB, assuming the shaft is running at a constant speed.
(b) Find the magnitudes of the bearing reaction forces, assuming the bearings act as simple supports.
(c) Draw shear-force and bending-moment diagrams for the shaft. If needed, make one set for the horizontal plane and another set for the vertical plane.
(d) At the point of maximum bending moment, determine the bending stress and the torsional shear stress.

(e) At the point of maximum bending moment, determine the principal stresses and the maximum shearstress.

16 in 0 14 in 9 in 20 1.25-in dia. Gear A 20-in dia. Gear B 8-in dia FA 300 lbf 20