Chassis is a major component of a vehicle system. It is the back bone of the vehicle and is also called Carrying Unit. The main components of the Chassis are -
Frame: It is made up of long two members called side members riveted together with the help of number of cross members. It is the main part of the chassis on which remaining parts of chassis are mounted.
Engine or Power plant: It provides the source of power
Clutch: It connects and disconnects the power from the engine fly wheel to the transmission system
Classification of chassis:
According to its control
According to engine location
According to Chassis Frames
In this type of chassis, the body is made as a separate unit and then joined with frame. It supports all the components of vehicle.
It has 2 long side members and some cross members joint together with the help of bolts and rivets. Some joints used in conventional frame are X-joint, K-joint, Y-joint.
Section used in conventional frame:
To calculate Bending and Torsional Stress:
It is used in truck and bus due to higher load capacity
It is used in SUVs because ladder on frame chassis allows better suspension travel than its other counterpart, enables us to have a wide range of customizations to extract the most potential out of the vehicle and a higher center of gravity allows the vehicle to have a higher ground clearance to tackle the worst possible terrains.
It has higher load capacity and strength
Easy to design and manufacture
Easy to repair after accident
It consumes much fuel due the heavier weight it added to the vehicle
These chassis possess a higher center of gravity that negatively impacts the cornering abilities
This type of frame is not suited to resist torsion.
Integral Frame or Frameless:
In this type of construction, there is no frame. The body shell and underbody are welded into single unit.
Used mostly in hatchback and sedan cars.
Due to elimination of long frame, it is cheaper
Due to less weight, it is most economical also because puts less load on the engine, making the motor more efficient.
Frameless chassis offers a calm and composed ride quality.
Repairing is difficult and costly.
This type of chassis cannot be heavily customized due to lack of individual parts.
The load carrying capacity is lower
In some vehicles, half frame is fixed at the front end on which engine, gear box and front suspension is mounted and in this type of frame load is transferred to the body structure also.
This type of frame is used in FIAT cars and some of the European & American cars
For any kind of damage, the front frame can be taken easily to replace the damaged chassis frame.
This Frame however is heavier than integral frame.
Tubular Space Frame:
These types of frame chassis consist of tubes positioned in different direction in 3D to provide mechanical strength against force from anywhere.
A true space frame has small tubes that are only in tension or compression - and has no bending or twisting loads in those tubes. That means that each load bearing point must be supported in three dimensions.
It is used in some SUVs.
Stronger in any direction than ladder or monocoque chassis.
Its structure is complex and production cost is higher
Impossible for robotized production.
According to Drive
Front Wheel Drive:
Same as front engine and drive is given to rear wheels
Rear Wheel Drive:
Same as front engine rear wheel drive and rear engine front wheel drive
To increase maneuverability of the vehicle required to travel on rough unconstructed roads and tracks another arrangement known as four-wheel drive is provided.
Due to all the four wheels getting driven, whole of the weight of the vehicle is available for traction. The system is provided in some jeeps
Left- and Right-hand Drive:
In different countries, the automobiles are driven on different sides of the road
Left hand drive: The steering is fitted on the left-hand side of the automobile and such vehicles are convenient to drive in countries following right hand drive rules, e.g. U.S.A., Russia, European countries.
Right hand drive: The steering is fitted on the right-hand side of the automobile and such vehicles are convenient to drive in countries following left hand drive rules, e.g. U.K., India.
The cruciform frame is made of two straight beams placed perpendicular to each other.
Max bending moment occurs in joint.
Cross beams at front and back at suspension points are used to carry lateral loads.
It overcomes the weak torsional stiffness of ladder frame
When combined with a ladder frame, it can effectively take bending and torsional loads
The cross beams at the front and rear not only assist in carrying the torsion moment but also assist in carrying the lateral loads from the suspension mounting points.
The maximum bending occurs at the joint hence joint design becomes critical.
Since cruciform frame is used along with a ladder frame, it shares some of the disadvantages of ladder frame such as increased vehicle's overall height.
Back Bone Frame:
Similar to body frame design
Consists of strong tubular backbone (main backbone is a closed box section)
Transverse beams resist lateral loads
Back bone frame resists bending and torsion
Splayed beams resists bending
Transverse beams resist tension or compression
The vulnerable parts of the drive shaft are covered by a thick tube. The whole system is extremely reliable.
Manufacturing is more complicated and costly.
It is heavier for a given torsional stiffness than a unibody.
This type of chassis used in numerous sports cars.
Its frame is like conventional frame and can transform to fit various cars.