) Find the factor of safety of the gears in bending. (b) Find the factor of safety of the gears in wear. (c) By examining the factors of safety, identify the threat to each gear and to the mesh.
A 17-tooth 20° pressure angle spur pinion rotates at 1800 rev/min and transmits 4 hp to a 52-tooth disk gear. The diametral pitch is 10 teeth/in, the face width 1.5 in, and the quality standard is No. 6. The gears are straddle-mounted with bearings immediately adjacent. The pinion is a grade 1 steel with a hardness of 240 Brinell tooth surface and through-hardened core. The gear is steel, through-hardened also, grade 1 material, with a Brinell hardness of 200, tooth surface and core. Poisson's ratio is 0.30, Jp = 0.30, JG = 0.40, and Young's modulus is 30(10°) psi. The loading is smooth because of motor and load. Assume a pinion life of 108 cycles and a reliability of 0.90, and use YN = 1.3558N-0.0178, ZN = 1.4488N-0.023. The tooth profile is uncrowned. This is a commercial enclosed gear unit. (a) Find the factor of safety of the gears in bending. (b) Find the factor of safety of the gears in wear. (c) By examining the factors of safety, identify the threat to each gear and to the mesh.
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