Caster Angle in wheel Alignment of Vehicle

Caster Angle in wheel Alignment of Vehicle

 

Abstract

        In the modern era, steerability and behavior features of the vehicle have become key aspects. Providing comfort to the driver by reducing steering effort without any negotiation in steerability and control of the vehicle with ride comfort may be a major concern for automakers. Assessing handling and steering features of a vehicle in a virtual environment with the help of multibody system packages saves product growth period and cost.  The steering exertion, steering wheel return aptitude, and the lateral forces produced by the tires were got in order to forecast the Performance of the vehicle for dissimilar wheel geometry parameters. It can be seen from the consequences that positive caster angles improve the steering wheel returnability but upsurge the steering effort. Higher steering axle inclination (Sai) angles help in improving the wheel return ability and decreasing the steering effort also. Negative camber angles help in producing higher lateral forces to enhance the cornering ability of the vehicle. Toe-in angles help in refining the straight-line constancy whereas toe-out angles help in refining the cornering

INTRODUCTION

        The turning ability of the vehicle is significant in improving the overall driving stability of the vehicle. By improving the cornering ability of the vehicle, the general driving stability will also improve thus giving the driver a safer driving experience and swifter control of the steering. The unequal and non-parallel double wishbone suspension system is a favorite choice by car manufacturers for the conventional vehicle due to the characteristic of the double-wishbone suspension system that allows the engineer to manipulate various parameters such as the camber angle, caster angle, toe pattern, scrub radius and lots of more to realize a better cornering limit and better cornering performance of the vehicle. However, when a cornering force is applied to the tire during a cornering motion, conventional double-wishbone the suspension will tilt the tire to the other side of the turning way, thus upsurges the cornering resistance that will touch the overall cornering performance.

 CONCEPT

        The caster angle can be defined as the side view inclination of the steering axis. Generally, the range of the caster angle is 0 to 6 degrees. This introduces a mechanical trial called caster trial which in conjunction with the pneumatic trial is very important in giving a steering a suitable feel and also has a significant effect on directional stability because of steering compliance. The steering feel is attuned to get the desired relationship amid lateral force and aligning torque. Adding a caster trial moves the point of maximum steering torque closer to the purpose of maximum lateral force, or even beyond it that is steering goes lighter. During cornering the steering must also support the centrifugal compensation forces on the steering mechanism. This is called centrifugal caste

 

What is a positive caster?

       The positive caster positions the lower ball joint in front of the upper ball joint or struts mount. This results in the tire contact patch hitting the ground in front of the steering system and suspension components.

Why is positive caster desirable?  

        The origins and numerous documented benefits of positive caster date all the way back to the late nineteenth century. (Discoveries of the French automotive engineering pioneer Arthur Constantine Krebs, for all you history buffs out there.) The positive caster creates two primary benefits:

Improved straight-line stability at speed.

       The front wheels positioned forward of the upper ball joint/strut mount produces a self-aligning torque on the front wheels and tires. This is a fairly complicated engineering concept, but the idea is that positive caster creates a tension that wants to return/keep the front wheels pointed straight ahead while at speed. You experience the benefits of positive caster and self-aligning torque every time the steering wheel naturally “unwinds” back to 12 o’clock when exiting a corner. And without positive caster and the resulting self-aligning torque, the vehicle would be very inclined to wander at highway speeds. (You’d feel that too! For a risk-free preview, send a shopping cart, which has negative caster at the front wheels, on its way. Just make sure there aren’t any cars or fellow shoppers around.)

Improved vehicle handling and cornering performance.

     Caster has a direct relationship to negative camber, which is fundamental to maximizing the tire’s contact patch when cornering, and therefore key to maximizing the available grip. Specifically, positive caster helps to create increased negative camber on the outside wheel during cornering. When cornering, the vehicle weight shift is met with a maximization of the tire contact patch on the outside front wheel that’s under maximum cornering load. In performance driving circles a caster increase –sometimes to the maximum available setting that the vehicle will accommodate –is credited with improvements in vehicle handling, maximum traction, and steering responsiveness

What is a negative caster?

        The negative caster positions the lower ball joint behind (rearward of) the upper ball joint or strut mount. Unlike in a positive caster arrangement, the wheel and tire contact patch hit the ground behind the steering system and suspension components. A negative caster angle isn’t a setting used by modern road cars. The self-aligning torque and straight-line stability that is characteristic of the positive caster are absent in a negative caster setting. In fact, a “loose” steering wheel and immense front-wheel instability would result from a negative caster setup. Caster’s influence on tire wears Caster settings is not a primary, direct factor in tire wear. However, excessive positive caster in association with other alignment maladjustments can exacerbate a tire wear issue. For example, a tire wear pattern called feathering can result from a combination of too much caster with incorrect toe settings. Tire featherings characterized by a high-low, smooth-sharp variation in the wear pattern of the tread blocks. Tire feathering of all of the alignment settings, however, the caster is the least likely to be a cause of uneven or abnormal tire wear. A holistic alignment approach involves verification of caster settings that are to your vehicle’s specifications. Caster might not get the headlines of the other alignment variables and adjustments, but it’s fundamental to vehicle performance and safety just the same

Conclusion

       The difference of wheel parameters with admiration to change in the caster angle.  Even if certain parameter shows the same value they have a dissimilar difference in frequency. Hence the above analysis shows that the caster angle between two to four degrees is a feasible solution for the prepared car model