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WHEEL ALIGNMENT

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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”.
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