Estimate the fatigue stress concentration factor for the tension-side root fillet of the driving pinion.

1. A 10-pitch 20 full-depth involute gearset with a face width of 1.25 inches is being proposed to provide a 2:1 speed reduction for a conveyor drive unit. The 18-tooth pinion is to be driven by a 15-hp, 1725-rpm electric motor operating steadily at full rated power. A very long life is desired for this gearset, and a reliability of 99 percent is required. Do the following:

a. Using the simplified approach, estimate the nominal bending stress at the tension-side root fillet of the driving pinion.

b. Estimate the fatigue stress concentration factor for the tension-side root fillet of the driving pinion.

c. Calculate the actual bending stress at the tension-side root fillet of the driving pinion.

d. Repeat (c) for the tension-side root fillet of the driven gear.

e. Based on the recommendation of an in-house materials specialist, Grade 1 AISI 4620 hot-rolled steel is to be used for both the pinion and the gear and the value of [see (2-27)] has been estimated for this application to be 0.75, including the 99 percent reliability requirement but not including stress concentration effects. Estimate the existing safety factor at the tensionside root fillet of whichever of the gears is more critical, based on tooth bending fatigue.