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title MEE342 Homework 5 2026
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Instructions

  1. This homework is DUE on Apr 11.
  2. Please submit this homework in class.

Problem 1 (10 Points)

A 17-tooth spur pinion has a diametral pitch of 8 teeth/in, runs at 1120rpm, and drives a gear at a speed of 544rpm. Find the number of teeth on the gear and the theoretical center-to-center distance.

Problem 2 (10 Points)

For a spur gearset with $$\phi$$ = 20 deg, while avoiding interference, find: the smallest pinion tooth count at a ratio $$m = N_G/N_P = 2.5$$, and the largest gear tooth count possible with this pinion.

Problem 3 (20 Points)

A compound reverted gear train is to be designed as a speed increaser to provide a total increase of speed of exactly 45 to 1. With a 20 deg pressure angle, specify appropriate numbers of teeth to minimize the gearbox size while avoiding the interference problem in the teeth.

Problem 4 (20 Points)

A commercial enclosed gear drive consists of a 20 deg spur pinion having 16 teeth driving a 48-tooth gear. The pinion speed is 300rev/min, the face width 2in, and the diametral pitch 6 teeth/in. The gears are grade 1 steel, through-hardened at 200 Brinell, made to No. 6 quality standards, uncrowned, and are to be accurately and rigidly mounted. Assume a pinion life of $$10^8$$ cycles and a reliability of 0.90. Determine the AGMA bending and contact stresses and the corresponding factors of safety if 5hp is to be transmitted.

Problem 5 (20 Points)

A 57-tooth spur gear is in mesh with a 23-tooth pinion. It is known that $$\phi$$ = 20 deg. The gearset transmits 125hp at 1000rpm pinion speed. Size the spur gears for a bending failure safety factor of at least 2 assuming a steady torque, full-depth teeth, $$Q_y = 9$$, an AISI 4140 steel pinion ($$S_t$$ = 40ksi), and a class 40 cast iron gear ($$S_t$$ = 13ksi). The desired reliability is $$99.9%$$ with a life of $$10^5$$. Take $$K_o = 1$$, $$(Y_N)_P = 3.517N^{-0.0817}$$ and $$(Y_N)_G = 6.1514N^{-0.1192} $$.

Problem 6 (20 Points)

Size the spur gears from problem 5 for a surface failure safety factor of at least 2. It is known that $$Z_N = 2.466N^{-0.056}$$ for both the pinion and the gear. The pinion material has $$S_c = 165ksi$$, $$H_B = 230$$ and gear material has $$S_c = 80ksi$$ and $$H_B = 200$$.