Methodology & Experimental study to reduce steering effort and improve directional stability in 3 wheeler vehicle

Abstract With an intense competitive automotive environment, it becomes imperative for any OEM to launch their products into the market in a short span of time & with a 'First Time Right' approach. Within the current scenario in the Automotive Industry, the selection of optimum set of hard points and wheel geometry often becomes an iterative or a trial and error process which is both time consuming and involves higher development cost as there may be instances where 2 to 3 sets of iterations are needed before specification is finalized for production. Through this paper, an attempt has been made to develop a methodology for deciding wheel geometry parameters (covered in the later section of this paper like Caster, Camber, Mechanical trail, etc.) for a three wheeled vehicle as a First Time Right (FTR) approach to cut down on conventional, expensive & time-consuming iterative approach. In this paper, we have studied the parameters which affects the directional stability and steering effort using a multi body dynamics (MBD) model and validated it with a series of experiments on prototype three wheeled vehicles. In a three wheeled vehicle the design of front suspension system is very critical as the steering system or the handle bar is often an integral part attached to the same front wheel. The problem definition was approached by carrying out a literature review and identifying the parameters affecting steering effort. Parametric studies were carried out through simulation to understand the effect on handle bar steering effort. The primary objective of this dissertation is to highlight the systematic approach carried out during full vehicle dynamics analysis to identify key wheel geometry hardpoints which influence the steering effort and ride feel for the customer. Similarly, the impact of the above listed parameters can be gauged by the fact that it directly effects the directional stability of the vehicle. The outcome of this study was validated on the actual test vehicle to confirm its universal applicability. Through this paper we have attempted to bring forth new design considerations for a suspension steering linkage geometry in a three-wheeler vehicle which, we feel, will be useful for future reference of similar system architecture. Key words: Three wheeled vehicle, Steering effort, Shimmy, Directional stability.