Automobile is made up of hundred of different structures which can be broadly categorized into six components :

1 Basic structure

2 Power unit

3 Transmission system

4 Auxiliaries

5 Controls

6 Superstructure

The first five components are are collectively known as automobile chassis. Given below is brief description of each component :

(a) Basic Structure It is the automobile unit on which other automobile units like engine,transmission system etc., are attached.



It mainly comprises of

1) FRAME  It is the main structure of automobile that bears most of its weight. It is constructed in two ways

1)  Conventional frame   : A conventional steel frame is prepared and all the mechanical units are attached to it


2) Frameless construction :  The body is designed in such a way that the function of frame and body is combined

and all the mechanical units are directly attached to it.



It prevents road shocks from being transmitted to the vehicle.

> It maintains the stability of vehicle during pitching(rotation about x-axis ) and rolling(rotation about z axis).

They are of two types :

1) Conventional – The road springs are attached to rigid axle .

2) Independent – There is no rigid axle beam and each wheel is free to move vertically without affecting the other wheels

3) Axles : They are central shafts which connects the wheels to the frame. Depending upon use they are of two types:

  1. Live axle : It transfer the torque received from the engine to the driving wheel.   
  2. Dead axle : It connect the wheel to the frame but don’t transfer any power.   

We know that rotating rod is called shaft and non rotating rod is called axle. But in automobile rotating rod is called axle because it drive its name from bullock cart where axle used to be stationary.

Wheels : They are most important part of the vehicle. Without wheels vehicle cannot even be towed . They carry the weight of whole vehicle .They generally are of three types :

  1. Disk wheels

2. Wire wheels

3. Alloy wheels

Among them disk wheels are most commonly used .