Question

The accessory drive unit of a large aircraft engine involves an identical pair of 200 full-depth spur gears. The gears have 70 teeth and rotate together at 8000 rpm. The diametral pitch is 12 and the face width 1.0 in. The gears are made of alloy steel, case-hardened to 62RC (680 Bhn). Although the case extends throughout the fillet, it is conservatively decided to use the core hardness of 500 Bhn for calculating fatigue strengths. The tooth profiles are finished with a fine-grinding operation that gives a degree of precision justifying the use of curve A of Figure 15.24 and the assumption that teeth share the load. The loading involves only very mild shock, justifying the use o Ko1.1. Also, assume the gear under analysis is an idler gear. a. Estimate the horsepower that can be transmitted with 99% reliability based on tooth bending fatigue. b. Estimate the horsepower that can be transmitted with 99% reliability based on tooth surface durability fatigue for 106 cycles.

Answer 1

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CG2. 122 11.1