16.23 A 1200-rpm electric motor drives a belt conveyor (which imposes moderate shock loading to the drive train) through a straight-tooth bevel gear reduction unit. N = 20, N = 50, P = 10, b = 1 in., and = 20°. Both gears are made of steel having a hardness of 300 Bhn. The gear is straddle-mounted and the pinion is overhung, providing a mounting considered to be reasonably good from the standpoint of rigidity. The gears are manufactured to standards corresponding to curve B of Chapter 15, Figure 15.24. The design life is 7 years of 1500 hours/year operation. Estimate the horsepower that can be transmitted at 99% gear reliability. [Ans.: About 1.6 hp] A Pitch line velocity V (m/s) 0 10 20 30 5 E D Velocity factor K 2 st 3 Hobs, form cutters* Hobs, shaping cutters* Precision, shaved and ground C B High precision, shaved and ground 1000 2000 3000 * Limited to about 350 Bhn FIGURE 15.24 Velocity factor Kv. Highest precision, shaved and ground 4000 5000 Pitch line velocity V (ft/min) 6000 7000 A