Steering System In Automobile Engineering

Steering system-A basic understanding

It is not possible to run the vehicle always along straight road as road is made as per the topography. Therefore, it is necessary for driver to turn the vehicle now and then as per the road turning. It is purpose of steering wheel and steering column which transmits the rotational motion of steering to steering gears. This steering gear increases the rotational force in order to transmit greater torque to steering linkage which transmits the steering gear movement to front wheel through front axle. The steering system configuration used depends upon the type of vehicle as car or truck.

There are mainly 2 types of steering Rack and Pinion type and recirculating ball type  

The Function of Steering System: 

1. Is to convert rotary movement of steering wheel into angular turn of front wheel.
2. It helps in swinging the wheels to left and right as per requirements.
3. Absorb large part of the road shocks and prevent them being transmitted to the driver.
4. It provides directional stability
5. It helps in wear and tear of vehicle
6. It multiplies the effort of driver through linkage in order to make easy to turn the wheels.

Requirements of Steering System:

1. It should multiply the turning effort (torque) applied to steering wheel by the driver.
2. When the vehicle is cornering the steering system must turn the front wheels quickly but easily and smoothly.
3. The mechanism must have self righting mechanism so that when the driver releases the steering wheel after finishing the turn, the steering wheel should return to its original position.
4. Proper Steering effort(when vehicle is at rest or motion elastic deformation of the tire thread due to friction between tire and ground)should be provided otherwise steering effort will be greater when car is stopped and will decrease when car speed increases. Therefore in order to maintain easier steering and better feel it should be made lighter and at a low speed and heavier at high speeds.            

 Principle of Steering System Operation

• The wear of tire is minimum when the relative motion between the tires and read is completely rolling type. When the vehicle is moving in  a curved path the steering should be designed so that the path of points of contact of  each wheel to ground are concentric circular arcs.
• For correct steering, the axis of rotation of all the wheels should meet at one point which is the instantaneous center of rotation of the vehicle wheels.
• To make this happen, the inner front wheel should be turned through a greater angle than outer wheel angle.
• Here smaller angle is theta 1 and larger angle is theta 2

General Geometry  steering system

To maintain these angles properly the front wheels are mounted on short axles (known as stab axles) pivoted on chassis of vehicle. O is the point where these axles instantaneous center lies.

                 let AB=a

                      CD=b

                      l=AE (Wheel Base)

                      O is the point where these axles instantaneous center lies.

                  Draw OP Perpendicular from O to AB

                              now from figure - AP-BP:

This is the fundamental equation required for perfect steering. If this equation is satisfied then there will no lateral slip of wheels when vehicle is taking a turn. The Mechanisms used for automatically adjusting the values of theta1 and theta 2 for perfect steering at any turn is known as steering gear mechanism.

There are 2 types of steering gear mechanism 

• Davis Steering Gear
• Ackermann Steering Gear

With the detail explanation of these mechanisms let us meet in upcoming blog. Please stay connected with this blog for exciting updates on automobile engineering.