FRAME AND CHASSIS

Chassis is a French term which is now denotes the whole vehicle except body in case of heavy

vehicles. In case of light vehicles of mono construction, it denotes the whole vehicle except

additional fittings in the body. “Chassis consists of engine, power train, brakes,

steering system and wheels mounted on a frame”.

Front-Engine Front Wheel Drive

Front-Engine Rear-Wheel-Drive

Rear-Engine Rear-Wheel-Drive

Four Wheel Drive

FRAME

• The frame is the main part of the chassis on which remaining parts of chassis are mounted. The frame should be extremely rigid and strong so that it can withstand shocks, twists, stresses and vibrations to which it is subjected while vehicle is moving on road. It is also called underbody.

• The frame is supported on the wheels and tyre assemblies. The frame is narrow in the front for providing short turning radius to front wheels. It widens out at the rear side to provide larger space in the body

TYPES OF FRAME

• Conventional frame, • (b) Semi-integral frame, and • (c) Integral frame (or unit frame).

Conventional Frame

• It is non-load carrying frame. The loads of the vehicle are transferred to the suspensions by the frame. This suspension in the main skeleton of the vehicle which is supported on the axles through springs. The body is made of flexible material like wood and isolated frame by inserting rubber mountings in between. The frame is made of channel section or tubular section of box section.

• Example : This type of frame is used for trucks.

• It has two long side members and 5 to 6 cross members joined together with the help of rivets and bolts. The frame sections are used generally.

• a. Channel Section - Good resistance to bending• b. Tabular Section - Good resistance to Torsion• c. Box Section - Good resistance to both bending and Torsion

Semi-integral Frame

• In this case the rubber mountings used in conventional frame between frame and suspension are replaced by more stiff mountings. Because of this some of the vehicle load is shared by the frame also. This type of frame is heavier in construction.

• Example : Popular in European and American car.

• Semi - Integral Frame: In some vehicles half frame is fixed in the front end on which engine gear box and front suspension is mounted. It has the advantage when the vehicle is met with accident the front frame can be taken easily to replace the damaged chassis frame. This type of frame is used in FIAT cars and some of the European and American cars.

Integral Frame or Frame-less Construction

• In this type of construction, there is no frame. It is also called unitized frame-body construction. In this case, the body shell and underbody are welded into single unit. The underbody is made of floor plates and channel and box sections welded into single unit. This assembly replaces the frame. This decreases the overall weight compared to conventional separate frame and body construction.

• Integral Frame: This frame is used now a days in most of the cars. There is no frame and all the assembly units are attached to the body. All the functions of the frame carried out by the body itself. Due to elimination of long frame it is cheaper and due to less weight most economical also. Only disadvantage is repairing is difficult.

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TYPES OF SECTIONS USED IN FRAMES

• Channel section, • (b) Tubular section, and • (c) Box section

• Various loads acting on the frame are• 1. Short duration Load - While crossing a

broken patch. • 2. Momentary duration Load - While taking a

curve.• 3. Impact Loads - Due to the collision of the

vehicle.• 4. Inertia Load - While applying brakes.• 5. Static Loads - Loads due to chassis parts.• 6. Over Loads - Beyond Design capacity.

STATE THE DIFFERENT BODIES USED IN AUTOMOBILES

• The Automobile bodies are divided in two groups

• Body

1. Passenger Body 2. Commercial body