4. CORRECT STEERING ANGLE
• The perfect steering is achieved when all the four
wheels are rolling perfectly under all conditions of
• 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
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
• 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'
• 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.
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.
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
• The Ackerman steering mechanism is mostly used because
the true rolling is achieved by the instantaneous center.