Repeat Problem 14-20, part (a), using helical gears each with a 20° normal pitch angle and a helix angle of 30° and a normal diametral pitch of 6 teeth/in. Problem 14-20 A commercial enclosed gear...

Repeat Problem 14-20, part (a), using helical gears each with a 20° normal pitch angle and a helix angle of 30° and a normal diametral pitch of 6 teeth/in.

Problem 14-20

A commercial enclosed gear drive is to be designed. Initially, the following is specified. The drive is to transmit 5 hp with an input pinion speed of 300 rev/min. The drive is to consist of two spur gears, with a 20° pressure angle, and the pinion is to have 16 teeth driving a 48-tooth gear. The gears are to be grade 1 steel, throughhardened at 200 Brinell, made to No. 6 quality standards. The gears will be uncrowned, centered on their shafts between bearings. A pinion life of 10 8 cycles is desired, with a 90 percent reliability. Use a trial value of diametral pitch of 6 teeth/in and a face width of 2 in. For the pinion, determine the bending stress, allowable bending stress, and bending factor of safety. determine the contact stress, allowable contact stress, and contact factor of safety. Assume gears are readily available in face-width increments of 0.5 in, with face widths in the range of three to five times the circular pitch. Specify a diametral pitch and face width such that the minimum factor of safety for the pinion is equal to 2.