Parametric Study Of The Gear Blank Structure In Helicopter Transmission Design

A predictive methodology to determine the strength and the stiffness of the web and the rim structure (gear blank) in the gear design is presented in this paper. The deflection has significant influence on the error in the transmission and the smoothness of the gear meshing. The study of the rim deflection will improve the design of a helicopter transmission to its optimal weight and size. Closed-form solutions for a few simplified gear blank structures under concentrated edges load are examined. Determining the maximum deflection for the more general gear blanks is not a straight:-forward calculation. Parametric studies have been conducted using threedimensional finite element analyses. The results are summarized as design charts as well as empirical equations in terms of a few design parameters such as the plate thickness, the conical angle, the ratio of inner radius to outer radius and the rim thickness. A conical box configuration has been recognized as a stiffer gear blank structure in both vertical and tangential directions. It is believed that this study provides not only a convient tool for design but also demonstrates an accurate and efficient method in gear blank deflection and stress analysis.