HARCOURT BUTLER TECHNICAL UNIVERSITY PRESENTATION ON “REQUIREMENTS OF GOOD STEERING SYSTEM” Submitted toMr. R.K. Ambikesh Assistant Professor ME Department HBTU Submitted bySandeep Kumar (1404540044) Final B.Tech Mechanical Engineering CONTENTS • Introduction • Wheel Alignment • Camber angle • Castor angle • Kingpin Inclination • Toe-In Toe-Out • Included angle • Scrub Radius INTRODUCTION • The steering system allow the driver to control the direction of vehicle travel. • The following are the secondary function of steering system: (1) It provides directional stability of vehicle when going straight ahead. (2) It provides straight ahead recovery after completing a turn. (3) It helps in controlling wear and tear of tyres. (4) It converts the rotary movement of the steering wheel into an angular turn of the front wheels THE FOLLOWING ARE THE REQUIREMENTS OF A GOOD STEERING SYSTEM • The steering mechanism should be very accurate and easy to handle. • The vehicle should be steered with a minimum of effort so that the driver does not feel driving fatigue. • The steering mechanism should be affected by the side thrusts, cornering forces and wind effects. • The mechanism should have a tendency to regain the straight ahead configuration after steering need is over. WHEEL ALIGNMENT • Wheel alignment is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification • The purpose of these adjustments is to reduce tire wear, and to ensure that vehicle travel is straight and true (without "pulling" to one side). • Alignment angles can also be altered beyond the maker's specifications to obtain a specific handling characteristic. Motorsport and off road applications may call for angles to be adjusted well beyond "normal" for a variety of reasons. CAMBER ANGLE • Camber is the tilt of the car wheel from the vertical. • The tyre life will be maximum when camber angle is zero. • Camber angle alters the handling qualities of a particular suspension design; in particular, negative camber improves grip when cornering. This is because it places the tire at a more optimal angle to the road, transmitting the forces through the vertical plane of the tire, rather than through a shear force across it. Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the contact patch would begin to lift off of the ground, thereby reducing the area of the contact patch. By applying negative camber, this effect is reduced, thereby maximizing the contact patch area. Note that this is only true for the outside tire during the turn the inside tire would benefit most from positive camber. • Effect: Excessive camber causes improper contact of the wheel. Positive Camber Angle If tiles outward it is positive camber angle. Positive camber angle Primarily used on front wheels. Reasons to use Positive Camber Creates more stability. Carry more weight. Negative Camber Angle If tiled inward it is negative camber angle. Negative camber angle Primarily used on rear wheels. Reasons to use Negative Camber Increased cornering ability. Increases road shock & component wear. CASTER ANGLE • The angle between the king pin Centre line and the vertical, in the plane of the wheel is called caster angle. • Caster angle or castor angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car, bicycle or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (in a car - an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical. Car racers sometimes adjust caster angle to optimize their car's handling characteristics in particular driving situations. • When an automotive vehicle's front suspension is aligned, caster is adjusted to achieve the self-centering action of steering, which affects the vehicle's straight-line stability. Improper caster settings will cause the driver to move the steering wheel both into and out of each turn, making it difficult to maintain a straight line. • Effect: Incorrect caster can produce Difficulties like hard steering, Pulling to one side when brakes are Applied. • Positive Caster Angle The caster is called positive when the top of the king pin axis is inclined to the rear of the wheel. • Benefits of positive caster Helps to maintain directional stability. Helps to return wheels to straight ahead after being steered. • Negative Caster Angle If toping of the king pin axis is incline to the front of the vehicle, it is called negative caster angle. • Benefits of negative caster wheel is easier to turn. Positive Caster angle Negative Caster angle KING PIN INCLINATION • The angle between the vertical line and center of the king pin or steering axle, when view from front vehicle, is known as king pin inclination. • KPI is the angle at which the center line of the kingpin or the axis of the steering swivels leans inwards from the vertical. • Effect : It is reduces steering effort particularly when vehicle is stationary. It reduces tyre wear also. • Amount: The king pin inclination in vehicles ranges from 6°to 8°.It must be equal to both sides. • On most modern designs, the kingpin is set at an angle relative to the true vertical line, as viewed from the front or back of the vehicle. This is the kingpin inclination or KPI (also called steering axis inclination, or SAI). TOE-IN • Toe-in is the amount by which the front wheels are set closer together at the front than at the rear when the vehicle is stationary. • Excessive toe in wear outside of the tire. TOE OUT • The wheel may be set closer at the rear than at the front in which case the difference of the distance between the front wheels at the front and at the rear is called toe-out. • Excessive toe out wear down inside of the tire. • Advantage of proper Alignment Vehicle Shows Better mileage. Tires last for a long time. Increases Performance of steering INCLUDED ANGLE • Combined Angle or Included Angle is defined as the angle between the wheel Central line and the king pin center line. Combined angle is equal to camber plus kingpin inclination. Included angle is not directly measurable. To determine the Included angle, you add the SAI to the Camber. If the Camber is negative, then the Included angle will be less than the SAI, if the Camber is positive, it will be greater. The Included angle must be the same from side to side even if camber is different. If it is not the same, then something is bent, most likely the steering knuckle. SCRUB RADIUS • Scrub radius is the distance between where the SAI intersects the ground and the center of the tire. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Scrub Radius may be positive, zero or negative. Positive Scrub Radius : Scrub radius is Positive if king pin Axis meets the tyre center line below the ground. In this case wheel tend to toe out. Zero Scrub Radius : Scrub radius is Zero when king pin axis meets the tyre center line on the ground. In this case wheel keep straight position without any tendency to toe and toe out. In this position steering is called center point steering. Negative Scrub Radius : Scrub radius is Negative when king pin Axis meets the tyre center line above the ground. In this case, wheel tend to toe in. BENEFITS OF WHEEL ALIGNMENT • Reduce wear on tires • Better gas mileage, due to less work on the engine • Smoother driving, lack of vibration at high speeds • Straighter driving with no pulling to one side or the other • Improved safety • Shorter stopping distance • Safer driving • Save money and Environment • Improve fuel consumption, break & Steering condition REFERENCES 1. Brabec P, Maly M and Vpzenilek R (2004), “Control System of Vehicle Model with Four Wheel Steering”, International Scientific Meeting Motor Vehicles & Engines, Kragujevac. 2. Jack Erjavee (2009), “Automotive Technology–A System Approach”, Cengage Learning, 5th Edition. 3. Kirpal Singh (2011), Automobile Engineering, 12th Edition, pp. 207-229, Standard Publication Distributors. 4. Shibahata Y, Irie N, Itoh H and Nakamura K (1986), “The Development of an Experimental Four-Wheel–Steering Vehicle”, SAE 860623. 5. Thomas W Birch (1987), “Automotive Suspension and Steering System”.