1.       Size the second-stage spur gears in Problem 12-27 for a bending safety factor of at least 3.0 and a surface safety factor of at least 1.7 assuming a steady torque, 25° pressure angle, full-depth teeth, Q_v = 8, and AISI 4140 steel for all gears.

2.       Size the third-stage spur gears in Problem 12-27 for a bending safety factor of at least 3.0 and a surface safety factor of at least 1.7 assuming a steady torque, 25° pressure angle, full-depth teeth, Q_v = 8, and AISI 4140 steel for all gears.

3.       Design a two-stage compound spur-gear train for an overall ratio of approximately 78:1. Specify tooth numbers for each spur gear in the train.