C-gears in Rotorcraft Transmissions: a Novel Design Paradigm

摘要

This paper focuses on the final reduction stage of heavy-lift rotorcraft transmissions, typically constructed as a double-helical bull gear surrounded by several slender pinions in split-power paths from each engine. These gears are herein suggested to be re-conceived as curved-tooth gears, C-gears for short. An enumeration and a classification of the C-gear types are presented, the more promising ones are singled out, and an example is chosen to explain the mechanism of self-alignment. The inherent, omni-directional yet limited self-aligning capability, hence the alleviation of the localized edge-loading, and the absence of a center recess are the major advantages of C-gears, which are expected to not only improve the reliability, but also yield an appreciable weight saving of the transmission. This is due to the closer-to-unity load-distribution factor that can be used in the design calculations, as well as the smaller face width, hence all the associated dimensions.