chasis frame and body

CHASSIS, FRAME & AND BODY

1Chassis, Frame and Body

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Chassis, Frame & Body: Syllabus

Types of frames, engine location, Comparison of front and rear mounting of engine, arrangement of clutch assembly, gearbox, propeller shaft with universal joints, front and rear differentials, rear, front and four wheel drives, their relative merits, types of chassis, pre requirements of body, types of bodies & their construction, aerodynamic considerations in body profiling, ergonomical considerations, defects in frames and body.


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Automotive SystemsBroadly an automobile can be divided in to following

main systems.

1. Body & Chassis

2. Engine and related Systems

3. Transmission

4. Braking System

5. Steering System

6. Suspension System

7. Heating and Air Conditioning System

8. Safety Systems


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CHASSIS


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Chassis consists of the following systems suitably mounted:

1. Frame.

2. Suspension system.

3. Axles

4. Engine.

5. Steering.

6. Electrical system. (Part of both chassis and body.)

Vehicle without body is Chassis.5

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Main Components of Chassis


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1. Conventional Construction.

1. Body and frame are separate.

2. Eg. Trucks.

2. Frameless or Unitary Construction.

1. No separate frame.

2. Eg. Cars.


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CLASSIFICATION OF CHASSIS

Based on Control

1. Conventional Chassis.

Engine is in front, driver sits behind the engine.

2. Semi forward chassis.

Portion of the engine is within the drivers cabin and portion is outside.

3. Full – Forward Chassis

Complete engine is mounted within the driver cabin.


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Conventional Chassis


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SEMI FORWARD CHASSIS

SPRINTER - MERCEDES


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FULL FORWARDCHASSIS


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FRAME


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TYPES OF FRAMES

1.Conventional frame

2.Integral frame

3.Semi integral frame


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Conventional Frame

It has two long side members and 5 to 6 cross members joined together with the help of rivets and bolts.

Frame sections used:

a. Solid round or rectangular cross section.b. Enclosed thin wall hollow round or rectangular

box type.c. Open Channeling such as ‘C’, ‘I’ or ‘top hat’

sections. 15Chassis, Frame and Body

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Conventional Frame


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Integral Frame

1. Used in most of the cars.

2. There is no frame and all the assembly units are attached to the body.

3. All the functions of the frame carried out by the body itself.

4. Due to elimination of long frame it is cheaper and less weight.

5. Disadvantage: Repairing is difficult.


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Integral Frame


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Semi - Integral Frame

1. In some vehicles half frame is fixed in the front end on which engine gear box and front suspension is mounted.

2. It has the advantage when the vehicle is met with accident the front frame can be taken easily to replace the damaged chassis frame.

3. This type of frame is used in FIAT cars and some of the European and American cars.


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LOADS ACTING ON FRAME

1. Vertical Bending.

Due to weight of vehicle.

2. Longitudinal Torsion.

Due to action of diagonally opposite forces.

Due to road irregularities, bumps.


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LOADS ACTING ON FRAME

3. Lateral Bending.

While turning.

Centrifugal forces. Wind effects.

4. Horizontal Lozenging.

Due to road obstacles

Cause the rectangular frame to distort to a parallelogram.


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CHASIS SIDE AND CROSS MEMBER FASTENING

1. Riveted Joints. Provides compressive force between the

plates.2. Bolted Joints. For heavy duty applications and if additional

components are to be fastned. Nuts can become loose leading to noise,

vibration, corrosion and fatigue failure.3. Welded Joints. Lap welding. High stress concentration on the joints,

Destroys previous heat treatment done.


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Frame constructionA – Longitudinal

member

B – Cross Member.

C – Brackets supporting body.

E – Brackets supporting springs.


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BODY


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Body Construction

There exists 2 main ways of automobile construction

1. The Chassis and Body method &

2. The Monocoque method.

The Chassis and Body method 1. Body is separate unit joined with ladder type chassis.

2. All other parts like steering, suspension etc. are attached to the chassis.

3. The benefits are higher load capacity and strength.

4. Disadvantages are vibrations less refined handling

5. Used mostly for MUVs, SUVs and bigger vehicles. 27


Body Construction

The Monocoque method.

No ladder frame

Suspension, steering etc. are all bolted directly to the body, the body is thus made sturdier.

Makes vehicle solid

Less rattles and squeaks

Handling is better

lesser load carrying capacity

Highly suitable for passenger cars


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No hard & fast rules for classification as new segments and sub segments keep emerging

Broad classifications of the vehicles.

SUV

MUV/MPV

Pik Up

Hatchback

Sedan/Notchback

Station Wagon/Estate

3 Wheeler

Body Shapes


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1. The engine area is separate and the passenger and boot area are enclosed together.

2. Equipped with 4 wheel drive or has as an option of 4 wheel drive.

3. Highly performance oriented. (Powerful Engine)

4. Designed for off road usage.

5. Are generally equipped with technologically advanced & luxury features.

Examples in India: Scorpio, Tucson, Pajero, Safari, CR-V

Sport Utility Vehicle (SUV)


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1. Two versions

1. Engine, passenger area and boot area enclosed together.

2. Passenger and boot area enclosed with separate engine

area

2. Can also have third row of seating.

3. Taller and generally more spacious as they are people carriers.

4. Not feature rich hence cost is usually on the lower side.

Examples in India: Tavera, Innova, Sumo

MPV / MUV


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Pick Up

1. They have a separate engine area, a passenger area and a large loading area.

2. Large tyres

3. High load carrying capacity

4. Good ground clearance.

Examples in India: Bolero Pik-Up, Bolero Camper Maxx Maxi Truck, 207 DI,


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Hatchback

1. Separate engine area, and passenger area

2. Luggage area merged the passenger area behind the rear seats.

3. The luggage area is generally smaller than notchback.

4. 5 doors (4 passenger doors + hatchback) or 3 doors (2 passenger doors + hatchback)

Examples in India: Santro, Getz, Palio, Indica etc.33


Sedan / Notchback

1. Separate engine area, passenger area, and boot area,

2. 4 doors.

Examples in India :Logan, Elantra, Sonata, Corolla, Camry etc.


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Estate / Station Wagon

1. Much like hatchback

2. Large luggage area extended till the roof

Examples in India: Indigo Marina, Adventure


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• Generally employed as rickshaws or goods carriers

• Separate area for driver with a comparatively larger area for passengers or goods

Examples in India: Alfa, Champion & Ape

3 Wheelers


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Basic Terminologies


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• Distance between the ground and lowest portion of the bottom of a vehicle

• Can also be measured at other points on the vehicle.

• Avoids scraping the bottom of the vehicle body on rough roads and terrain.

Ground Clearance


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• Distance between the front or rear wheels measured from the tyres center point.

• A wider tread generally gives more stability.

Front Tread

Tread

Rear Tread


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• Distance between the center of the front wheels and the center of the rear wheels.

• A longer wheel base generally leads to more passenger space, and results in enhanced vehicle stability at high speeds

Wheel Base

Wheel Base


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• Smallest Radius in which car can turn.

• Lower turning radius improves the maneuverability of the car

• Definite advantage in city driving.

• It is usually measured from the center point of the outer most wheel (kerb to kerb)

Turning Radius

Turning Radius


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ENGINE MOUNTING


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CHASIS DESIGN VARIATIONS: COMPARISON OF VARIOUS LAYOUTS


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LOCATION OF ENGINE

1. FRONT MOUNTED ENGINE WITH

REAR WHEEL DRIVE.

2. FRONT MOUNTED ENGINE WITH

FRONT WHEEL DRIVE.

3. REAR MOUNTED ENGINE WITH REAR

WHEEL DRIVE.


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FRONT MOUNTED ENGINE WITH REAR WHEEL DRIVE

1. Most common.

2. Engine crank shaft is parallel to axis of vehicle

3. Rear axle is live, front axle is dead.

4. Single reduction or multiple stage reduction.


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FRONT MOUNTED ENGINE WITH REAR

WHEEL DRIVE :ADVANTAGES1. Forward center of gravity gives higher stability in

handling at higher speeds.2. Safety.3. Location of radiator and use of air stream ramming

effect.4. While climbing a hill, a partial weight transfer to the rear

wheels takes place improving tyre – road grip.5. Control linkages to the driver cabin can be simple and

short.6. Engine is easily accessible for maintenance.7. Steering gear mechanism is easy to design, install and

operate8. Better weight distribution.9. More luggage space


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FRONT MOUNTED ENGINE WITH REAR WHEEL DRIVE

DIS-ADVANTAGES1. Long propeller shaft. Vibration, drumming and howl.

2. Higher ground clearance required to provide space for propeller shaft.

3. Car body space is taken up by gear box, tunnel for propeller shaft.

4. Weight transfer during braking to front wheels – decreased braking effort

5. When stuck in mud, difficult to drive away. 67


FRONT MOUNTED ENGINE WITH FRONT WHEEL DRIVE

1. Combined drive an steering to front wheels.


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FRONT MOUNTED ENGINE WITH FRONT WHEEL DRIVE: ADVANTAGES

1. Maximum body space; Flat and lower floor line.

2. Road adhesion and acceleration are improved due to concentration of engine and transmission on the front driving wheels.

3. Elimination of propeller shafts provide use of low floor profile; lower CG of veh.

4. Capable of driving out of pot holes and loose soil more easily.

5. Due to forward C of G, handling of vehicle is more stable.


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FRONT MOUNTED ENGINE WITH FRONT WHEEL DRIVE

DIS- ADVANTAGES1. To drive the live stub axles, constant –

velocity universal joints are required to be built into the front suspension and steering system.

2. Gradability is less.3. Heavier steering.4. More noise and vibration to the

passengers.


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REAR MOUNTED ENGINE WITH REAR WHEEL DRIVE

Advantages.

1. Due to concentration of weight on the rear driving wheels, traction is improved.

2. More effective braking.

3. Passengers do not experience excessive, noise, smoke, heat etc due to engine.

4. The exhaust system can be short, direct and compact.

5. Lower flat floors; suitable for buses and coaches.


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REAR MOUNTED ENGINE WITH REAR WHEEL DRIVE

Dis - Advantages.

1. Extended control linkages for engine, clutch and gearbox required.

2. Ride relatively unstable at higher speed due to C of G is moved back.

3. Engine cooling is more difficult.

4. Accessibility for maintenance is less.

5. Driver may not hear/ feel engine sound and may affect his judgement.


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chasis frame and body

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