Chassis: The Backbone of an Automobile

Anik Hasan Badhon, ME (2020-21)

Chassis: The Backbone of an Automobile

In our everyday routines, we frequently require transportation to get from one location to another. To facilitate this mobility, we use a variety of automobiles. So, how does the automobile operate? How are the components such as power unit(engine), power transmission system integrated and arranged within the automobile? Let’s dive into the world of automobile to find out the answer.

Before diving into the chassis system, it’s essential to gain a comprehensive understanding about the entire automobile to grasp how it operates.

Components of Automobile

Basic structure, Power Unit, Transmission System and Controls all are parts of the chassis system or in other language these parts are mounted on the chassis. Superstructure and Auxiliaries are part of body of the automobile. So, we come to conclusion that,



The chassis can be defined as a fundamental component that bears the vehicle weight and its occupants, resists the stresses caused by road conditions and braking and provide capability to steer the vehicle.

Conventional Chassis

  • Consists of two long side members and 5 or 6 cross members joined together through rivets.

  • The whole engine is mounted in front of the driver’s cabin.

  • The problem with this type of chassis is that the driver can’t see in front of the front wheels (blind spot). So, the visibility is poor.

Fully Forward Chassis

  • The whole engine is mounted inside the driver’s cabin.

  • The driver can easily see the roads in front of the front wheels. So, the visibility is good.

Semi Forward Chassis

  • Half of the engine is mounted in front of the driver’s cabin and remaining half is mounted inside the driver’s cabin.

  • Visibility is moderate.

Chassis Frame

When designing a chassis frame, it is essential to thoroughly understand the loads that are acting on the chassis.

  1. Short duration loads: Vehicles while moving in rough road comes across broken patches and then the broken patches apply a reaction force, this reaction force is short duration load.

  2. Momentary duration loads: Vehicles while turning or cornering the side forces are acting and the frame needs to withstand it.

  3. Impact loads: When a vehicle comes across an accident than its chassis is subjected to tremendous impact force.

  4. Inertia loads: Due to own body weight of the automobile. Inertia force mainly acts due to two main reasons:

  5. Braking: During braking whole-body weight is shifted to the front side so the frame should be strong enough to withstand this load.

  6. Acceleration: During acceleration the whole-body weight is shifted to the back side of the frame and the frame should withstand this load.

  7. Static loads: Due to weight of chassis components like suspension system, steering system, transmission system etc.

Some very common types of chassis are discussed here:

Ladder Frame Chassis

Material: Steel Alloy.

Naming: Looks like a ladder with long and transverse members.

  • A ladder frame chassis provides excellent beam resistance because of its continuous rails from front to rear.

  • Resistance against torsion is very poor.

  • Employed in heavy vehicles.

Tubular Space Frame Chassis

Material: Carbon steel, AISI-SAE 4130(chrome-moly) or aluminum.

Naming: 3-dimensional design and that’s why named as space frame.

A tubular space frame chassis utilizes numerous circular section tubes arranged in various orientations to offer mechanical strength against forces from any direction. These tubes are welded together which forms a complex shape.

Employed in Race and sports car where torsional force is dominant.

Monocoque Frame Chassis

Material: Depending on material monocoque chassis is of two types

  • Metal monocoque chassis

  • Carbon fiber monocoque chassis

    Almost all the cars built around the world chooses monocoque frame.

    Monocoque chassis is one-piece structure made by welding of several parts (spot winding).