A steel spur gear and mating pinion similar to those you have seen in class have 67 and 24 teeth respectively. The pitch, P, is 12 and the pressure angle is 20°. The face width is 7/8 inch. The gears are to be used in conveyer drive. The gears operate continuously with a pinion speed of 1760 rpm. They must be 99% reliable over a period of 2 years while continuously transmitting 6 hp. In this application we know or assume: • The gears are machined.
• The velocity factor can be determined from Curve D in Figure 15.24 in J&M.
• The power source (electric motor) is uniform.
• The load is uniform.
• The gear mountings are not very rigid or accurate but contact across the full face of the gears will be obtained.
• The gear accuracy is not sufficient to assume that gear loads are shared among teeth.
• The gears operate at room temperature
a) What core hardness of the pinion is required in light of pinion tooth bending fatigue requirements?
b) What core hardness of the gear is required in light of gear tooth bending fatigue requirements?
c) What surface hardness of the pinion is required in light of pinion tooth surface fatigue requirements?
d) What surface hardness of the gear is required in light of gear tooth surface fatigue requirements?