scope:

This information sheet provides a set of numerical examples which calculate the geometry factor for pitting resistance, I, and bending strength, J, for a variety of gearsets selected to demonstrate the various gear geometries analyzed in AGMA 908-B89, Geometry Factors for Determining the Pitting Resistance and Bending Strength of Spur, Helical and Herringbone Gear Teeth. A flow chart is also included to formalize the calculation procedures for the numerical examples and to assist in the practical application of AGMA 908-B89.

Numerical examples

Numerical examples were selected to demonstrate the following conditions: accurate and inaccurate spur gears, conventional and LACR (low axial contact ratio) helical gears, internal and external gears, double helical and herringbone (Sykes) gears and addendum modification. For simplification purposes and for demonstrating the effect on resulting geometry factors, similar examples were selected with different load locations (example 3.1.1 vs 3.1.2) and face widths (example 3.1.3 vs 3.1.4)

The results are presented in tabular form by providing the numerical results for each equation as presented in AGMA 908-B89 and appropriate to that gear geometry. Gear cutter data is presented for each component in each numerical example. All gearsets are functional and do not violate any of the exceptions stated in the scope of AGMA 908-B89. The examples used are for demonstration purposes only and are not intended to be recommendations for gearset design.

Flow chart

The flow chart provides a step by step procedure for calculating geometry factors, I and J, using the equations and instructions from AGMA 908-B89. The numerical value tables are formatted to coincide with the flow chart procedures.

Exceptions

A procedure for the calculation of bending strength geometry factor, J, for internal gears has not been established by AGMA. For this reason, numerical examples and flow chart procedures for such a calculation are not included.