15.33 A spur gear reducer has an 18-tooth pinion driven 1500 rpmby an electric motor and a 36-tooth gear that drives a loadinvolving “moderate shock.†A life of 106 pinion revolutions isrequired, and the transmitted load, Ft, is 100 lb (this figureincludes a
safety factor of 2). Conditions are such that Km = 1.8 and kt = 1.It is proposed that standard 20° full-depth gears be used, withboth pinion and gear teeth being cut with a low-cost,average-quality, form-cutting process from steel of 235 Bhn for thegear and 260 Bhn for the pinion. Diametral pitch is to be 10, andface width 1.0 in. Estimate the reliability with respect to bendingfatigue failure.
