This document discusses steering mechanisms for vehicles. It describes the condition for true rolling as having an instantaneous center where the front wheel axes meet the rear axis when turning. This requires the inner wheel to turn through a greater angle than the outer wheel. The main types of steering mechanisms are the Ackerman and Davis systems. The Ackerman mechanism is most widely used due to its simplicity and ability to achieve true rolling through an instantaneous center point between the wheel axes. It has turning pairs behind the wheels while the Davis mechanism has sliding pairs in front of the wheels and is more prone to wear.

1. STEERING MECHANISMS

2. • CONDITION FOR TRUE ROLLING (or)
CORRECT STEERING ANGLE
• STEERING MECHANISM
• TYPES OF STEERING MECHANISM
CONTENTS

3. CONDITION FOR TRUE ROLLING
(or)
CORRECT STEERING ANGLE

4. CORRECT STEERING ANGLE
• The perfect steering is achieved when all the four
wheels are rolling perfectly under all conditions of
running.
• While taking turns ,the condition of perfect rolling
is satisfied if the axes of the front wheels when
produced meet the rear wheel axis at one point.
• Then this point is the instantaneous centre of the
vehicle.

6. a
It is seen that the inside wheel is required to turn
through a greater angle than the outer wheel.

7. • The larger is the steering angle, the smaller is the turning
circle.
• There is however, a maximum to which we can go as regards
the steering angle.
• It has been found that steering angle (of the inner wheel) can
have a maximum value of about 440.
• The extreme positions on either side are called 'lock'
positions.
• The diameter of the smallest circle which the outer front
wheel of the car can traverse and obtained when the wheels
are at their extreme positions is known as the turning circle.

9. STEERING MECHANISMS

10. STEERING MECHANISMS
• We have already seen that for perfect steering we
must always have an instantaneous centre about
which all the wheels must rotate.
• For this purpose inner wheel has to turn more than
the outer wheel.
• To achieve this condition, two types of
mechanisms, have been devised.

11. TYPES OF STEERING MECHANISMS
1. Ackerman steering mechanisms.
2. Davis steering mechanisms.
• Out of these Ackerman mechanism is almost
universally used because of its simplicity.

12. Ackerman steering mechanism

14. This is known as Ackerman steering mechanism

15. DAVIS STEERING MECHANISM
• The Davis Steering gear has sliding pair, it has
more friction than the turning pair, there fore
the Davis Steering Gear wear out earlier and
become inaccurate after certain time.
• This type is mathematically Accurate.

18. Ackerman Vs Davis
• The whole mechanism of Ackerman steering mechanism is on
the back of the front wheels.(Turning pair)
• Where as in Davis steering mechanism, it is in front of the
wheels.(Sliding pair)
• The Ackerman steering mechanism is mostly used because
the true rolling is achieved by the instantaneous center.

20. Note:-backlash, sometimes called lash or play, is clearance or lost motion in a mechanism
caused by gaps between the parts