ABSTRACT
The rating of a gearbox is determined by the loads the gearbox components are capable of transmitting. In some cases where a system is operating continuously at a uniform load such as an electric motor driving a fan, the loading is simple to predict and component analysis can be based on a continuous horsepower transmitted at steady speed. Organizations such as the American Gear Manufacturers Association (AGMA) and the American Petroleum Institute (API) issue Standards that define gear rating procedures. This chapter discusses rating methods used in these standards: gear tooth rating, bearing rating, thermal rating and shaft rating. It illustrates the numerical values of service factors for high-speed units. The AGMA and API standards are good basic guidelines which, when followed, result in gearboxes that perform successfully. They provide a baseline with which to judge competing designs. High-speed gearing operating with low-viscosity lubricants is prone to a failure mode called scoring.
