Design and fabrication of variable steering ratio mechanism for light Motor vehicle

Abstract

To facilitate easy and proper steering of the vehicle while negotiating a turn, as per the requirements of driver in different situations like hair pin bends in hilly regions, sudden turns in highways and city streets or in sports car during race events an improved steering system is needed to address these problems. The steering arrangement used in a normal automobile was investigated and to solve the above problems a variable steering ratio mechanism was designed and fabricated, with the aim to determine if incorporation of variable steering ratio mechanism will make an improvement in the steady and transient state handling of the automobile. The size of the pinion gear and the number of teeth on the gear determine the rack-and-pinion steering ratio. The steering wheel must be turned one revolution to turn the front wheels one sixteenth of a turn, the steering ratio is 1 to 1/16. Reversing the numbers gives a ratio of 16 to 1, or 16:1. This steering ratio is always fixed. A variable steering ratio mechanism was fabricated by using constant mesh type gears from Bajaj-Super and steering mechanism from Tata-Nano. Gear housing using wood is created and gear shifting arrangement incorporated. It was observed that on engaging the 1st gear steering ratio is increased to 9.92:1. On engaging the 2nd gear steering ratio is increased to 7.20:1, On engaging the 3rd gear steering ratio is increased to 4.96:1 On engaging the 4th gear steering ratio is increased to 3.52:1. The effort required for steering is increased due to these ratios as energy is lost due to friction. This mechanism can only be practical if used in conjugation with power assist.

Keywords: - Variable Steering Ratio Mechanism, Constant Mesh Gear Box, Steering Wheel, Power Assist