Efficiency and Durability Predictions of High Performance Racing Transmissions

Abstract

Efficiency and durability are key areas of research and development in modern racing drivetrains. Stringent regulations necessitate the need for components capable of operating under highly loaded conditions whilst being efficient and reliable. Downsizing, increasing the powerto-weight ratio and modification of gear teeth geometry to reduce friction are some of the actions undertaken to achieve these objectives. These approaches can however result in reduced structural integrity and component durability. Achieving a balance between system reliability and optimal efficiency requires detailed integrated multidisciplinary analyses, with the consideration of system dynamics, contact mechanics/tribology and stress analysis/structural integrity.This paper presents an analytical model to predict quasi-static contact power losses in lubricated spur gear sets operating under the Elastohydrodynamic regime of lubrication. Tooth Contact Analysis (TCA) is used to predict variations in contact loads, local surface curvature and rolling and sliding velocities. This is combined with an extrapolated oil film thickness formula available in literature, to predict instantaneous lubricant film thickness and sub-surface stresses. Subsequently, viscous and boundary friction are estimated, enabling calculation of power losses.The presented methodology has been used to investigate the effects of parabolic tip relief on power loss and induced sub-surface stresses. The results of this investigation are also presented.

Multiscale Friction in Lubricant-Surface Systems for High-Performance Transmissions Under Mild Wear

“…In the case of meshing gear teeth, the value of W changes through the meshing cycle. This is obtained from an analysis of the same transmission, reported by Fatourehchi et al [3]. In the case of pin-on-disc tribometry, W is the applied contact load through the pin, and because of the hemispherical profile of the pin…”

“…Research and development in technologies, purporting to improve system efficiency, commonly occur through the 'track-to-road' concept [2]. High-performance transmissions are routinely subjected to extreme contact pressures, temperatures and kinematics of contacting teeth pairs [3]. Owing to these prevailing extreme contact conditions, it is critical to fundamentally understand the effect of governing operating parameters, before suitable remedial actions can be proposed.…”

Transient thermal analysis of mixed-elastohydrodynamic contact of high performance transmission in a dry sump environment

“…Therefore, an analytic predictive method is preferred due to its computational efficiency. Fatourehchi et al [2] introduced an analytical method with improved computation times, based on the analytical-experimental lubricant film behaviour reported by Evans and Johnson [8] in order to predict gear contact power loss in high performance transmission systems. The same method was used in [9] to perform a parametric study for the effect of tooth modification on planetary spur gear system efficiency.…”

“…Various numerical and experimental studies have investigated these frictional losses for different gearing systems, also taking into account the effect of gear teeth geometry, noise and vibration and fatigue performance [1][2][3][4][5]. The transmission of high performance race vehicles comprises a series of spur and bevel gear pairs.…”

“…The same method was used in [9] to perform a parametric study for the effect of tooth modification on planetary spur gear system efficiency. In both cases [2,9] tooth contact analysis was used to accurately represent the contact geometry, kinematics and load share per meshing teeth pairs in the analysis.…”