SCOPE
This information sheet utilizes an analytical heat balance model to provide a means of calculating the thermal transmittable power of a single- or multiple-stage gear drive lubricated with mineral oil. The calculation is based on standard conditions of 25° C maximum ambient temperature and 95° C maximum oil sump temperature in a large indoor space, but provides modifiers for other conditions.

FOREWORD
[The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of AGMA ISO 14179-1, Gear Reducers - Thermal Capacity based on ISO/TR 14179-1.]

This thermal rating method was the American proposal to ISO/TR 14179. It utilizes an analytical heat balance model to calculate the thermal transmittable power for a single or multiple stage gear drive lubricated with mineral oil. Many of the factors in the analytical model can trace their roots to published works of various authors. The procedure is based on the calculation method presented in AGMA Technical Paper 96FTM9 by A.E. Phillips [1]. The bearing losses are calculated from catalogue information supplied by bearing manufacturers, which in turn can be traced to the work of Palmgren. The gear windage and churning loss formulations originally appeared in work presented by Dudley, and have been modified to account for the effects of changes in lubricant viscosity and amount of gear submergence. The gear load losses are derived from the early investigators of rolling and sliding friction who approximated gear tooth action by means of disk testers. The coefficients in the load loss equation were then developed from a multiple parameter regression analysis of experimental data from a large population of tests in typical industrial gear drives. These gear drives were subjected to testing which varied operating conditions over a wide range. Operating condition parameters in the test matrix included speed, power, direction of rotation and amount of lubricant. The formulation has been verified by cross checking predicted results to experimental data for various gear drive configurations from several manufacturers.

AGMA ISO 14179-1 is not identical to ISO/TR 14179-1:2001, Gears - Thermal capacity - Part 1: Rating gear drives with thermal equilibrium at 95° C sump temperature. Differences in this information sheet include:

• In table 2, the second equation for P1 for spherical roller bearings was changed to correctly indicate the condition (F_r /F_a) ≥ Y₂;
• Text and a figure were added to clause 6 to assist in illustrating Method A testing;
• Text and a figure were added to 7.1 to assist in illustrating the thermal calculation procedure;
• Figures A.1 and A.2 were revised to accurately reflect dimensions shown;
• An annex was added to provide example calculations.

The first draft of AGMA ISO 14179-1 was made in December, 2002. It was approved by the AGMA membership in March 2004.