Design and Analysis of Hypoid and Helical Gears for Modular Tandem Axle

Abstract

Rear axle is the last member of the power train which finally transfers the engine’s power to the driving wheels. In heavy duty trucks, we often use more than one driving axle which brings us to the need for tandem axle. A tandem axle divides the incoming power into two parts, each one going to different driving axle. Using tandem axle in a vehicle also improves road stability at highway speeds and usually has better suspensions. At VECV, a wide range of heavy duty vehicles employ tandem axle which makes it quite beneficial to develop a modular design which helps in achieving a simpler design. To achieve this modular design, critical components inside a tandem axle such as hypoid gear set, helical gear pair and differential gears are designed taking consideration of the specifications of the whole range of vehicles and then grouping them into similar groups. The design procedure followed for all components is taken from various publications studied during our literature survey. Most prominent reasons for the failure of automotive gears are bending stresses and contact stresses. Therefore, each gear set designed is rated for both pitting resistance (contact stresses) and bending strength with the help of standards developed by organizations such as AGMA. Hypoid gear geometry is one of the most complicated geometry in all of the gear types. A geometry design calculation sheet has also been developed to generate complete design specifications sheet which includes a program for an iterative process.