Influence of Root Clearance on Helical Gear Pocketing Power Loss

Abstract An experimental study is conducted to investigate individual contributions of components to the total spin power loss of a high-speed, gearbox operating under realistic lubricant flow conditions. An experimental test setup capable of operating the test gearbox containing helical gears at desired speeds, temperatures and lubrication conditions is designed and fabricated. Dedicated measurement systems to monitor bearing and oil temperatures as well as the torque loss of the gearbox are devised, and accompanying data analysis systems are developed. A test matrix consisting of two different lubricant flow conditions is defined, each covering a wide range of input speed. These tests are performed with the gearbox having variations of hardware content to separate gear drag, gear mesh pocketing, and bearing power losses from each other. These tests show that the power losses increase with increased lubricant flow rates. They further demonstrate that all three power losses are comparable to each other, and hence, must be considered in evaluating spin power loss of such systems. A parametric study is conducted to investigate the effect of the trapped volume in the gear mesh on pocketing power loss. A family of gears having different addendum coefficients are meshed with the same gear forming different root clearance values. The results of these tests are compared to quantify the influence of root clearance on resultant pocketing power loss.