STEERING MECHANISMS

• CONDITION FOR TRUE ROLLING (or) CORRECT STEERING ANGLE

• STEERING MECHANISM

• TYPES OF STEERING MECHANISM

CONTENTS

CONDITION FOR TRUE ROLLING

(or)

CORRECT STEERING ANGLE

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.

a

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

• 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.

STEERING MECHANISMS

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.

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.

Ackerman steering mechanism

This is known as Ackerman steering mechanism

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.

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.

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