chassis braking 1

8/18/2019 Chassis Braking 1

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Chassis Technology 1

(FVB11303)PREPAPED BY: MOHD FAIZAL BIN JUSOH@SHAFIE

LECTURER

Automotive Engineering Section


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Course works distribution

Test 1 (20%)

Test 2 (20%)

Test 3 (20%)

FINAL (40%)


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• Functions of a steering system

• Basic steering systems

• Steering column assembly

• Steering gear principles

• Steering linkage (worm-type gearbox)

• Manual rack-and-pinion steering

(Continued)


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• Integral-piston power steering system (linkage

type)

• External cylinder power steering (linkage type)

• Power rack-and-pinion steering

• Electronic steering assist

• Four-wheel steering systems


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• Provide precise control of the wheel

direction

• Maintain correct steering effort

• Transmit road feel to the driver’s hands

• Absorb most of the road shock going to the

steering wheel

• Allow for suspension action


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• Two basic kinds of steering systems are in

use today:

– linkage (worm gear) steering systems

– rack-and-pinion steering systems

• Each may be operated manually or with

power assist


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Steering

Basic linkage

steering

Basic rack-and-

pinion steering


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• Consists of the steering wheel, steering

shaft, column, ignition key mechanism, andsometimes, a flexible coupling anduniversal joint

• Bolts to the underside of the dash

• Sticks through the firewall and fastens tothe steering gear


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Steering Column Components


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Locking Steering Wheel

• When the ignition is off, the steering wheelcannot be turned

• A rack and sector slide a steel pin into mesh

with a slotted disc that is splined to thesteering shaft

• The pin locks the steering shaft to the column,

preventing the steering wheel from beingturned


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Locking Steering Wheel


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Collapsible Steering Column

• Helps prevent driver chest and face injuryduring an auto accident

•

The column will crumple or slide togetherwhen forced forward during a collision

• Several types are used:

– steel mesh (crushing)

– tube-and-ball (sliding)

– shear capsule (break and slide)


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Collapsible Column Operation


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Tilt Steering Columns

• A flex joint, or U-joint, allows the top half ofthe column and the steering wheel to bepositioned at different angles

• Manual tilt column

– uses a lever on the steering column to unlockthe flex joint so the wheel can be moved up

and down


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Power Tilt Column

• Uses a small electric motor, a control switch,

and a gear mechanism to change the steering

wheel angle or height

• When the tilt switch is activated, current to

the motor spins the small gears to move the

steering column’s upper tube


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Memory Tilt Wheels

• Use a tilt control module to “remember”

more than one steering wheel position

• A steering column sensor provides

feedback so the module knows where thewheel is located

• When the driver selects a switch position,

the control module energizes the power tiltmotor until the wheel has moved to thepreprogrammed position


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Memory Tilt Wheel


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Power Tilt Gear Mechanism


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• Two basic types of gear mechanisms arefound in steering gearboxes:

– worm gears

–rack-and-pinion gears


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Gear Mechanisms


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Steering Gears

Rack-and-pinion gear

Worm steering gear


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Recirculating-Ball Gearbox

• Normally used with a linkage steering

system• Small steel balls circulate between the gear

members to reduce friction


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Recirculating-Ball Gearbox


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Gearbox Components

• Worm shaft

– the input gear connected to the steering shaft

• Sector shaft

– the output gear from the steering gearbox

• Ball nut

– rides on the ball bearings and the worm gear


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Gearbox Components

• Ball guides

– route extra balls in and out from between the

worm and ball nut

• Adjusting nut

– used to set worm shaft bearing preload

•

Adjusting screw – used to set the sector shaft clearance


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Gearbox Components


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Gearbox Ratio

• Comparison between steering wheel

rotation and sector shaft rotation

• Ratios range from 15:1 to 24:1

• Variable-ratio gearbox

– changes the internal gear ratio as the wheels

are turned away from center

• Constant-ratio gearbox

– has the same gear reduction from full left to

full right


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Worm-and-Roller Steering Gearbox

• Contains a roller that is mounted on the

pinion shaft and meshes with the worm

gear• The roller replaces the ball bearings and

the ball nut used in the recirculating-ball

gearbox


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•Series of arms, rods, and ball sockets thatconnect the steering gearbox to the

steering knuckles

•

Commonly called a parallelogram steeringlinkage


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Steering Linkage


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Steering Linkage

• Pitman arm

– transfers gearbox motion to the steering

linkage• Center link (relay rod)

– a steel bar that connects the right and left

sides of the steering linkage


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Steering Linkage

• Idler arm

– supports the end of the center link on the

passenger side

• Tie-rod assemblies

– fasten the center link to the steering knuckles

– ball sockets are used on both ends

– a toe adjustment sleeve allows length changefor alignment


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Ball Sockets

• Provide for motion in all directions

between two connected parts

• Some have a grease fitting, allowing

lubrication

• Others are sealed units

•

Used in pitman arms, idler arms, and tie-rods


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Ball Sockets

A. Idler arm

B. Tie-rod endC. Tie-rod inner

end

D. Tie-rod (rack-

and-pinion)


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Rack-and-Pinion Steering


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Steering Gear

• Consists of a pinion shaft, rack, thrust spring,

bearings, seals, and a gear housing

• Bolts to the frame or unibody structure

• Rubber bushing mounts help absorb road

shock


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Steering Gear


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Steering Gear

• When the pinion shaft turns, the pinion gear acts

on the rack gear

• The rack slides sideways, moving the tie-rods and

the front wheels


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Tie-Rod Assemblies

• Connect the ends of the rack with the steeringknuckles

• Rubber dust boots fit over the inner ball sockets

to keep out road dirt and water


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Power Steering Systems

• Most systems use an engine-driven pump

and a hydraulic system to assist steering

action

• An electric motor in the rack may be used

to provide power assist


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Basic Power Steering


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Basic Operation

• Pressure from the oil pump is used to

operate a piston-and-cylinder assembly

• When the control valve routes oil pressure

into one end of the piston, the piston slides

in its cylinder

• Piston movement helps move steering

system components


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Types of Power Steering

• There are three main types of power steering

systems:

– integral-piston linkage system

– rack-and-pinion system

– external cylinder power steering system


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Integral-Piston Linkage


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Rack-and-Pinion


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External Cylinder


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Power Rack-and-Pinion


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Power Steering Pump

• Engine-driven pump that produces thehydraulic pressure for steering systemoperation

•Driven by a belt or directly off the back of thecamshaft

• The power steering fluid reservoir may beformed as part of the body or as a separatecontainer


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Pump and System


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PumpTypes


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Slipper-Type Pump


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Vane-Type Pump Operation


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Pressure-Relief Valve

• Used in a power steering system to control

the maximum oil pressure

•Prevents system damage by limitingpressure

• A relief valve opens when the steering

wheel is turned to the full-left or full-rightposition


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Pressure-Relief Valve


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Power Steering Hoses

• High-pressure, hydraulic, rubber hoses that

connect the power steering pump and the

gearbox or power cylinder

• One line serves as the pressure feed line

• One line serves as a return line to the

reservoir

• Metal lines may be used where vibration or

movement is not a problem


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• The hydraulic piston is mounted in thesteering gearbox housing

• System components:

– power steering pump

– hydraulic lines

– integral power-assist gearbox


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Integral Power Steering Gearbox

• Contains a conventional worm-and-sector

gear, a hydraulic piston, and a flow-direction

valve

• Two valve designs are commonly used:

– spool valve

– rotary valve


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Spool Valve-Type Gear


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Spool Valve Operation

• When the steering wheel is turned, the

pivot lever moves the spool valve so

pressure enters a power chamber

• Pressure forces the power piston left orright, helping to turn the sector shaft

• As the power piston strokes, oil from the

other power chamber is vented throughthe spool valve back to the reservoir


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Rotary Valve Operation

• Rotary valve-type steering boxes have a

small torsion bar to detect steering wheel

turning direction and turning effort

• When the steering wheel is turned, the

torsion bar twists and turns the rotary valve

• Rotary valve directs pressure to the correct

side of the power piston


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Integral Gear Operation

Driving straight ahead


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Right turn


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Left turn


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• The power cylinder is commonly bolted to

the frame and the center link

• The control valve may be located in thegearbox or on the steering linkage


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External Cylinder Power Steering


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Uses hydraulic pressure to assist the driver in

moving the rack and

the front wheels


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Power Rack-and-Pinion Steering


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Power Cylinder and Piston

• Power cylinder

– precisely machined tube that accepts thepower piston

• Power piston – formed by attaching a hydraulic piston to the

center of the rack

•

Routing oil pressure into either end of thepower cylinder causes piston movement



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Power Rack-and-Pinion(Rotary Control Valve)


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Control Valves

• Rotary control valve

– operated by a torsion shaft connected to the

pinion gear

• Spool control valve

– operated by the thrust action of the pinion

shaft that occurs when the pinion gear is

rotated against the rack gear



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Power Rack-and-Pinion(Spool Control Valve)


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System Operation

• When the steering wheel is turned, vehicle weightcauses the front tires to resist turning, moving thecontrol valve

• Movement of the control valve aligns specific oil

passages internally

• Pump pressure forces oil through the control valve tothe power cylinder

• Pressure acts on the power piston, pushing the rackand the front wheels


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High Speed Operation

Little valve movement, low power assist


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Low Speed Operation

More valve movement, high power assist


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• Uses a small electric motor to help movethe rack-and-pinion gearbox

• The motor is mounted inside the rack

housing and acts on the steering rack

Electronic Assist


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Electronic Assist

Rack-and-Pinion

Lighter and more compact than a hydraulic

system

l i i O i


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Electronic Assist Operation

• A steering control module (computer)electronically reacts to steering pressure

• The module operates the electric motor in the

rack assembly to help the driver steer thewheels

• The module can reverse motor rotation andalter motor speed as needed

P i l P S i


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Proportional Power Steering

• Senses vehicle speed and steering load to

ensure adequate road feel

• Increases steering effort at higher speeds for

more road feel

• Lowers steering effort at lower speeds to ease

maneuvering

L S d O i


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Low Speed Operation

• A computer-controlled electromagnet isused to alter the operation of the stubshaft, torsion bar, and rotary control valve

•

At low speeds, the computer sends currentthrough the electromagnet in one directionto help attract and pull on the stub shaftand torsion bar, increasing valve output

pressure

Hi h S d O i


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High Speed Operation

• At high speeds, the computer reverses

electrical flow through the electromagnet

•

The valve output pressure decreases,reducing assist, and increasing steering

effort for better road feel

P ti l St i


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Proportional Steering

In this system, a computer, a vehicle speed

sensor, and a solenoid control hydraulic

pressure


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In a four-wheel steering system, allfour wheels change direction to

improve handling, stability, feel,

and maneuverability


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Four-WheelSteering System

F Wh l St i


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Four-Wheel Steering

In a gentle turn, the wheels pivot

in the same direction

F Wh l St i


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Four-Wheel Steering

In a sharp turn, the wheels pivot back and

then turn in opposite directions

M h i l S t


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Mechanical System

• Uses a special front rack-and-pinion gearboxwith a transfer box

• The transfer box operates a long shaft that

extends back to the rear rack

• When the front wheels are turned, the shaft

rotates to turn the rear wheels

H d li S t


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Hydraulic System

• Uses a conventional power rack-and-pinion

steering system up front

• Hydraulic lines extend back to a rear power

steering pump, which is driven by the

differential

• Depending on vehicle speed, the rear pump

forces fluid under pressure into a controlvalve

Hydraulic System


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Hydraulic System

• When a specific road speed is reached, the

control valve can then operate the rear

steering system

• The rear rack is connected by tie-rods to

the rear suspension trailing arms

• When activated, the rear rack shifts the

trailing arms to steer the rear wheels

Electronic System


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Electronic System

• An electronic system is speed-sensitive

• An electric-motor-driven power rack (rear

actuator) acts on the rear wheels using arecirculating-ball drive and mechanical links

• The rear-wheel steering angles arecomputer controlled

Electronic System


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Electronic System

Electronic System Operation


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Electronic System Operation

• The computer analyzes signals from anglesensors in the front steering and signals from

wheel speed sensors in the anti-lock brake

system• The rear actuator is energized by the

computer to move the rear wheels as needed

Rear Actuator


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Rear Actuator

Chassis


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Objectives

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Objectives

• Define the most important parts of a vehicle• Explain body design and frame variations

• Compare unibody and body-over-frame

construction• Identify the major structural parts, sections,

and assemblies of body-over-frame vehicles

Objectives (continued)


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Objectives (continued)

• Identify the major structural parts, sectionsand assemblies of unibody vehicles

• Summarize how to classify vehicles by body,

engine, and drivetrain configurations

Introduction


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Introduction

• Vehicle construction refers to how a vehicle ismade

• Vehicles are a maze of interacting mechanical-electrical systems

• Over 15,000 parts are used in a typical vehicle

• Damage to one part can affect the operationof another seemingly unrelated part

•Different types of construction requiredifferent methods repair frame/unibodydamage

Crash Testing


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Crash Testing

• Vehicles must be light, aerodynamic, and yetstrong and safe

• Computer-simulated crash testing is used beforebuilding a prototype to find weak structural areas

• Critical that passenger compartment is strongenough to prevent injury

• Certified crash tests are done with a real vehicleand sensor equipped-dummies

• Crush zones are built into the frame or body toabsorb some of the energy of a collision

Vehicle Classifications


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Vehicle Classifications

• Vehicle classification relates to theconstruction, size, shape, number of doors,

type of roof, and other criteria of a motor

vehicle• To communicate properly in collision repair,

you must understand these basic terms

Vehicle Construction


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Vehicle Construction

• Part or component refers to the smallest unitson a vehicle

• An assembly is several parts that fit together

• Panel refers to a large removable body part

• Pan refers to a floor-related component

• Chassis includes everything under the body,

consisting of the mechanical systems that

support and power the car


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(B) With body-over-frame construction, a thick gauge steel frame provides the foundation for holding

other parts. This type of construction is commonly used on large trucks and SUVs.

Figure 9-4. Two very different methods used to construct modern vehicles: unibody and body-over-

frame construction

(A) Unibody construction welds major body panels together to form the frame for attaching the

engine, drivetrain, suspension, and other parts. This type of construction is commonly used on cars.

Full Frames


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Full Frames

• Body-over-frame vehicles have separate bodyand chassis parts bolted to the frame

• Full frame vehicle is heavier - high amounts of

energy are absorbed by the frame in a collision• Torque boxes allow some twisting to absorb road

shock and collision impact

•

Crossmembers extend sideways across frame railsto support the engine, suspension, chassis

• Full- or partial-frame construction is used on

most full-size and some small pickup trucks

Full Frames (continued)


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Full Frames (continued)

• Frame is an independent separate part

• Perimeter frame has a frame rail near the outside

of the vehicle, and is the most common

• Ladder frame has long frame rails with a series ofstraight crossmembers, and is seldom used

• Partial frame is a cross between a solid frame and

a unibody – Sub-frame assemblies are used at the front and rear

while the unibody supports the middle area

Unibody Construction


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Unibody Construction

• Unibody construction uses body parts weldedand bolted together

– Uses lighter, thinner, high-strength steel alloys

•

Body shell is formed by welding sheet metalinto a box- or egg-like configuration

– Strength is achieved through shape and designinstead of mass and weight

• Stressed hull structure disperses force overthe entire body shell

Space Frame


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Space Frame

• Space frame vehicle has a metal body structurecovered with an outer skin of plastic or composite

panels

•Roof and quarter panels may be attached withmechanical fasteners or adhesives

• After a collision a space frame is more likely to

have hidden damage, or hidden corrosion

• Support members are bolted to unibody bottom

– Needed in high-stress areas to reduce body flex


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Figure 9-7. The suspension and braking systems bolt directly to

the body on a vehicle with unitized construction.

Joining Parts


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Joining Parts

• Fastened parts are held together with fasteners• Welded parts are permanently joined by welding

• Press-fit or snap-fit parts use clips or an interfaceto fit parts together

• Adhesive-bonded parts use high-strength epoxyor special glue to hold parts together

• Composite unibody is made of plastics and othermaterials – Keeping metal parts to a minimum cuts weight while

increasing strength and performance


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Figure 9-8. Note the space frame construction. Composite (plastic) panels fasten to a metal

inner body structure. Composite panels can be made flexible to resist door dings and small

dents.

Major Body Sections


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Major Body Sections

• Vehicle is divided into three sections – Front, center and rear

• Front section includes everything betweenfront bumper and fire wall – Also called nose section, front clip, “doghouse”

• Center section or midsection includes bodyparts that form passenger compartment –

Also called a “greenhouse” • Rear section also called tail section, rear clip,

“cathouse”

Panel and Assembly Nomenclature


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Panel and Assembly Nomenclature

• Panel is a stamped steel or molded plasticsheet that forms a body part

• When panels are joined with other

components, the result is an assembly• Vehicles built for (example for American)

roads

– Left side is steering wheel side

– Right side is passenger side

Front Section Parts


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Front Section Parts

• Cowl is near rear of front section, right in frontof the windshield

• Shock towers or strut towers are reinforced

body areas for holding upper parts ofsuspension

• Dash panel, firewall, or front bulkhead is paneldividing front and center sections

• Bumper assembly bolts to front frame hornsor rails to absorb minor impacts


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Figure 9-12. This top view of unibody construction shows how structural

members are added to support the engine suspension and other

mechanical systems.

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Center Section Parts

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Center Section Parts

• Floor pan is main structural section in bottom ofpassenger compartment

• Tunnel is formed in floor pan for transmission anddrive shaft

•

Pillars are vertical body members that hold roofpanel in place and protect in case of rollover

• Front pillars extend next to windshield edges – Must be strong; also called A-pillars

•

Center pillars or B-pillars, are roof supportsbetween front and rear doors

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Center Section Parts (continued)

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Center Section Parts (continued)

• Rear pillars, or C-pillars, extend up fromquarter panels to hold rear of roof

• Rocker panels or door sills are strong beamsthat fit at bottom of door openings

• Rear shelf, or package tray, is a thin panelbehind rear seat in front of back glass

• Window regulator is a gear mechanism thatallows you to raise and lower door glass

• Side impact beams are metal bars orcorrugated panels that bolt or weld insidedoor assemblies


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Figure 9-15. Doors normally have strong steel beams under the door skin to

protect people during side impact collisions.

Rear Section Parts


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Rear Section Parts

• Rear hatch is a larger panel and glass assemblyhinged for more access to the rear

• Quarter panels are large side body sections

that extend from side doors back to rearbumper

• Lower rear panel fits between trunkcompartment and rear bumper

• Rear shock towers hold rear suspension

• Inner wheel housings surround rear wheels

Gaskets and Seals


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Gaskets and Seals

• Various gaskets and rubber seals prevent airand water leakage between body parts

• Seals or weatherstripping are often used

around doors and the rear deck lid• Rubber seal is partially compressed when

door or lid is closed to form a leakproofconnection

• Rubber gasket often seals stationary glasswhere it fits into body

Anticorrosion Materials


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• Anticorrosion materials prevent rusting ofmetal parts

• Undercoating is often a thick tar or synthetic

rubber-based material sprayed ontounderbody

• After performing repairs, you must restore all

corrosion protection

Sound-Deadening Materials


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g

• Sound-deadening materials help quietpassenger compartment

– Insulation that prevents engine and road noise

from entering passenger area

Engine Locations, Drivelines


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g ,

•Longitudinal engine mounts to crankshaftcenterline front-to-rear – Used by front-engine RWD vehicles

• Transverse engine mounts sideways in engine

compartment, its crankshaft centerlineextends toward right and left

• Front-engine, front-wheel drive (FWD) hasboth engine and transaxle in front – Constant velocity (CV) axles extend out from

transaxle to power front wheels

Engine Locations, Drivelines

( ti d)


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(continued)

• Front-engine, rear-wheel drive (RWD) has engine infront and drive axel in rear

• Rear-engine, rear-wheel drive (RRD) has engine in

back – Transaxle transfers power to rear drive wheels

• Mid-engine, rear-wheel drive (MRD) has engine

behind front seat

• All-wheel drive uses two differentials for all wheels

• Four-wheel drive uses a transfer case to send power

to two differentials and all wheels


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Vehicle Sizes

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• Compact car is smallest body classification – Normally uses a 4-cynlinder engine

– Lightweight, gets the highest gas mileage

•

Intermediate car is medium in size – Uses a 4-, 6- or 8-cylinder engine

– Usually has a unibody construction

• Full-size car is large, heavy and often has ahigh performance V8 engine

– Either unibody or body-over-frame construction

Roof Designs


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g

• Sedan is a body design with a center pillar thatsupports roof

• Hardtop does not have a center pillar to supportroof

• Hatchback has a large third door at back,commonly found on small compact cars

• Convertible has a retractable canvas roof with asteel tube framework, or a removable hardtop

•

Station wagon extends roof straight back to rearof body with a rear hatch or tailgate

Vans and Trucks


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• Van has a large box-shaped body to increaseinterior volume or space

• Full-size van normally is front-engine, RWD

• Minivan is smaller and often uses front-engineFWD with unibody construction

• Pickup truck normally has a separate cab and

bed, typically with front-engine, RWD

Summary


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y• Vehicle classification relates to construction,

size, shape, number of doors, type of roof, etc.

• Three main types of frame construction

– Body-over-frame, unibody, and space frame

• Vehicle commonly divided into 3 body sections

– Front section, or nose section

– Center section, or midsection

– Rear section, tail section, or rear clip

• Vehicle sizes: compact, intermediate, full size

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj8iqGljZDLAhVPBo4KHTfFB_IQjRwIBw&url=http://www.gapingvoidart.com/gallery/any-questions/&psig=AFQjCNFGO2SoD6kg7mtVlxEmbjy0SyLfYQ&ust=1456393105032736


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Reference:

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj8iqGljZDLAhVPBo4KHTfFB_IQjRwIBw&url=http://www.gapingvoidart.com/gallery/any-questions/&psig=AFQjCNFGO2SoD6kg7mtVlxEmbjy0SyLfYQ&ust=1456393105032736http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj8iqGljZDLAhVPBo4KHTfFB_IQjRwIBw&url=http://www.gapingvoidart.com/gallery/any-questions/&psig=AFQjCNFGO2SoD6kg7mtVlxEmbjy0SyLfYQ&ust=1456393105032736http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj8iqGljZDLAhVPBo4KHTfFB_IQjRwIBw&url=http://www.gapingvoidart.com/gallery/any-questions/&psig=AFQjCNFGO2SoD6kg7mtVlxEmbjy0SyLfYQ&ust=1456393105032736


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chassis braking 1

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