An Experimental Study of the Influence of Manufacturing Errors on the Planetary Gear Stresses and Planet Load Sharing

In this paper, results of an experimental study are presented to describe the impact of certain types of manufacturing errors on gear stresses and the individual planet loads of an n-planet planetary gear set (n=3-6). The experimental setup includes a specialized test apparatus to operate a planetary gear set under typical speed and load conditions and gear sets having tightly controlled intentional manufacturing errors. The instrumentation system consists of multiple strain gauges mounted on the ring gear and a multichannel data collection and analysis system. A method for computing the planet load-sharing factors from root strain-time histories is proposed. Influence of carrier pinhole position errors on gear root stresses is quantified for various error and torque values applied to gear sets having three to six planets. The results clearly indicate that manufacturing errors influence gear stresses and planet load sharing significantly. Gear sets having larger number of planets are more sensitive to manufacturing errors in terms of planet load-sharing behavior.