An Analytical Method to Predict Skidding in High Speed Roller Bearings

Abstract

Skidding which occurs in high speed roller bearings frequently causes wear and incipient failure of bearing inner ring and roller surfaces. To eliminate skidding, aircraft gas turbine designers, historically, have employed out-of-round outer rings and other preloading devices. Prior to testing of the full-scale bearings at engine speeds, however, the designers have not, heretofore, been able to determine (a) the extent of skidding which occurs and (b) the effectiveness of means employed to eliminate skidding. The analytical method which is presented by this discussion is based upon recently developed elastohydrodynamic lubrication theory and can be used in lieu of expensive testing procedures to adequately predict bearing cage speed, and therefore the extent of skidding, under any condition of radial load and shaft speed. Moreover, the analysis can be used to determine how much radial preloading or outer ring out-of-roundness is necessary to minimize skidding. The analytical data of this study are compared against experimental data to establish the adequacy of the analysis.