A spur gearset has 17 teeth on the pinioni and 51 teeth on the gear. The pressure angle is 20° and the overload factor K, = 1. The diametral pitch is 6 teeth/in and the face width is 2 in. The pinion speed is 1120 rev/min and its cycle life is to be 10° revolu- tions at a reliability R = 0.99. The quality number is 5. The material is a through- hardened steel, grade 1, with Brinell hardnesses of 232 core and case of both gears. For a design factor of 2, rate the gearset for these conditions using the AGMA method.

Compute the contact stress number for the gear fain pair driven directly by an electrical motor. The driven machthe is concrete mixture with moderate shock, the other data are given below. Ks= 1.00, Km 1.21, Vt =1527 St/min, Av-11 Pd= 6, np= 1750rp.m, Np 20, No= 70, F=2.00/n Tp = 900ib, Dp= 3:333 in The material used for pioin an gear is Steel

There are two pairs of closed soft tooth surface spur gears A and B,Parameters of A: modulus m = 2mm, number of teeth Z1 = 40, Z2 = 90 , width of teeth b = 60mm.Parameters of B : modulus m = 4mm, number of teeth Z1 = 20, Z2 = 45 , width of teeth b = 60mm.The accuracy of the two pairs of gears is grade8, and other conditions are the same. Try to compare the contact fatigue strength and bending fatigue strength of the two pairs of gears? And explain the reason.

p sa 15. A straight bevel gear pair has the following data: 50; P¿ 10; and 20° pressure angle. If the gear pair is transmitting 3.5 hp, compute the fore- es on both the pinion and the gear. The pinion speed is 1250 rpm. The face width is 0.70 in. Compute the bend- ing stress and the contact stress for the teeth, and specify a suitable material and heat treatment. The gears are driven by a gasoline engine, and the load is a conveyor provid- ing moderate shock. Assume that neither gear is straddle nounted. N₂ No = 25; No J (M