chassis braking 1
TRANSCRIPT
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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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Integral Gear Operation
Right turn
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Integral Gear Operation
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
Power Rack-and-Pinion
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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
Power Rack-and-Pinion
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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.
http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwisyeCCipDLAhVQ1I4KHdLuA4YQjRwIBw&url=http://www.bestmadeinkorea.com/showroom/neotec-co-ltd-/product-list.html&psig=AFQjCNHwdtaDTX5_Z__HpIcyHxuBbeXUaQ&ust=1456392240775299
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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
http://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwjf0aHxjJDLAhWOCo4KHb-dDesQjRwIBw&url=http://www.buildyourownracecar.com/race-car-powertrain-basics-and-design/2/&psig=AFQjCNHzOWGZbUEplRUMSVZeGhGvsoyfxw&ust=1456393009478505
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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
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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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