A double reduction gearbox design has developed to the point that the general layout and axial dimensions of the countershaft carrying two spur gears has been proposed, as shown in Fig. 7-10. The gears and bearings are located and supported by shoulders, and held in place by retaining rings. The gears transmit torque through keys. Gears have been specified as shown, allowing the tangential and radial forces transmitted through the gears to the shaft to be determined as follows. W=5401bf W = 197 lbf W=2431 lbf W885 lbf where the superscripts t and r represent tangential and radial directions, respectively; and, the subscripts 23 and 54 represent the forces exerted by gears 2 and 5 (not shown) on gears 3 and 4, respectively. Proceed with the next phase of the design, in which a suitable material is selected, and appropriate diameters for each section of the shaft are estimated, based on providing sufficient fatigue and static stress capacity for infinite life of the shaft, with minimum safety factors of 1.5. Bearing A Gear 3 dj-12 Pa CADEF G Н Example 7-2 (continued) Da ' Fig. 7-10 Solution Example 7-2 (continued) Perform free body diagram analysis to get reaction forces at the bearings. RA: 115.01bf RAY=356.71bf Raz=1776.0 lbf Ray 725.31bf R W Bearing B Gear 4 d-2.67 -20 उटण 10.75 SE112 KL MB N 11.50