Question

Using the AGMA refined approach, design a high-precision (Qv =11) single-reduction straight spur gear unit to operate from a 50 -hp electric motor running at 5100rpm to drive a rotating machine operating at 1700rpm. The motor operates steadily at full rated power. A life of 108

pinion revolutions is desired, and a reliability of 99 percent is required. The gear material proposed is grade 1 steel and the Brinell hardness of the pinion and gear is 240 . Assume 20∘ pressure angle spur pinion with 20 teeth. The module of the gears is 3 and face width is 50 mm.
a. The Gear ratio
b. The pitch diameters of pinion and gear
c. Estimate the safety factor against bending fatigue failure for the pinion.
d. Estimate the safety factor against surface fatigue failure for the pinion.

Answer 1

The AGMA refined approach for designing a straight spur gear unit involves calculating the gear ratio, pitch diameters, and estimating safety factors against bending and surface fatigue failure for the pinion, which would use AGMA formulas and factors for material properties, hardness, quality number, and operating conditions.

Step-by-step explanation:

Design of a Straight Spur Gear Unit

To design a high-precision single-reduction straight spur gear unit using the AGMA refined approach, we need to calculate several key aspects of the gear system:

• The gear ratio required to reduce the motor speed of 5100rpm to the machine speed of 1700rpm.
• The pitch diameters of the pinion and gear based on the given module and number of teeth.
• The safety factor against bending fatigue failure for the pinion, which involves analyzing the gear tooth stresses and comparing them to the endurance limits for the gear material.
• The safety factor against surface fatigue failure for the pinion, which considers the contact stresses and compares them to material limits accounting for desired life and reliability.

Note that detailed calculations would require the use of specific AGMA formulas and factors, which would take into account the gear material properties, hardness, quality number, and operating conditions.

The specific details for these calculations are beyond the scope of this brief outline, but they would typically be performed using standardized formulas and tables provided in gear design handbooks or using gear design software that complies with AGMA standards.