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, Qv = 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, Qv = 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.