CCAS 3381 AUTOMOTIVE SKILL I - PowerPoint PPT Presentation

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CCAS 3381 AUTOMOTIVE SKILL I

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CCAS 3381 AUTOMOTIVE SKILL I SUSPENSION & STEERING SYSTEM OBJECTIVES To understand the operational principles and basic mechanisms of suspension & steering systems ... – PowerPoint PPT presentation

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Title: CCAS 3381 AUTOMOTIVE SKILL I


1
CCAS 3381 AUTOMOTIVE SKILL I
  • SUSPENSION
  • STEERING SYSTEM

2
OBJECTIVES
  • To understand the operational principles and
    basic mechanisms of suspension steering systems

Double-wishbone suspension on Honda Accord 2005
Coupe
Lecture 1 hour Workshop 1 hour
3
SUSPENSION SYSTEM (1)
  • Power of a car is useless if car cannot be
    controlled
  • Car suspension
  • maximizes friction between tires and road surface
  • provide steering stability with good handling
  • ensure the comfort of the passengers

4
SUSPENSION SYSTEM (2)
  • Vehicle dynamics
  • Ride - car's ability to smooth out bumpy road
  • Handling - car's ability to safely accelerate,
    brake corner
  • Road isolation - allow vehicle body to ride
    undisturbed while traveling over rough roads
  • Road holding - keep tires in contact with ground
    (friction between tires and road affects a
    vehicle's ability to steer, brake accelerate)
  • Cornering - minimize body roll

5
SUSPENSION SYSTEM (3)
  • Frame - structural, load-carrying component
    supporting car's engine body (supported by
    suspension )
  • Suspension system - setup supporting weight,
    absorbing dampening shock helps maintaining
    tire contact
  • Steering system - mechanism enabling driver to
    guide direct vehicle
  • Tires wheels - components making vehicle motion
    possible by way of grip /or friction with road

6
SUSPENSION SYSTEM (4)
  • Springs
  • Coil springs
  • Leaf spring
  • Torsion bars
  • Air springs
  • Sprung mass unsprung mass

7
SUSPENSION SYSTEM (5)
  • Sprung mass - mass of the vehicle supported on
    the springs
  • Unsprung mass - mass between the road and the
    suspension springs
  • Stiffness of springs affects how sprung mass
    responds while the car is being driven
  • Loosely sprung cars versus tightly sprung cars -
    balance passenger comfort with handling is a
    complex task

8
SUSPENSION SYSTEM (6)
  • Shock absorbers - controls unwanted spring motion
    through dampening
  • compression cycle
  • extension cycle

9
SUSPENSION SYSTEM (7)
  • Struts and Anti-sway Bars
  • Strut shock absorber inside a coil spring
  • provide dampening function
  • provide structural support for the vehicle
    suspension
  • critical safety feature - worn shocks struts
    allow excessive sway reducing tire grip, handling
    braking performance
  • Anti-sway or anti-roll bars
  • give moving stability
  • creates a more level ride reduces vehicle sway

Common strut design
Anti-sway bars
10
SUSPENSION SYSTEM (8)
  • Dependent front suspension - rigid front axle
    connecting the front wheels
  • Independent system - front wheels are allowed to
    move independently (MacPherson strut, double
    wishbone)

Double-wishbone suspension on Honda Accord 2005
Coupe
  • Double-wishbone allows for more control over
    camber angle of the wheel (degree to which the
    wheels tilt in and out) they also help minimize
    roll or sway and provide for a more consistent
    steering feel.

11
SUSPENSION SYSTEM (9)
  • Dependent rear suspension - solid axle connects
    the rear wheels
  • Independent rear suspension system both rear
    wheels are mounted sprung individually

Bose Suspension Front Module
12
SUSPENSION SYSTEM (10)
13
SUSPENSION SYSTEM (11)
14
STEERING SYSTEM (1)
  • During turning your front wheels are not pointing
    in the same direction
  • Geometry of steering linkage makes the inside
    wheel turn more than the outside wheel

15
STEERING SYSTEM (2)
  • Rack-and-pinion steering
  • most common
  • converts steering wheel rotation to linear
  • provides gear reduction to turn wheels
  • A steering wheel rotates 360o causing wheels
    turning 20o has steering ratio of 360/ 20 181
  • Variable-ratio steering
  • Power Rack-and-pinion

16
STEERING SYSTEM (3)
  • Recirculating-ball steering
  • Used on many trucks and SUVs today
  • contains a worm gear
  • Power steering in a recirculating-ball system
    works similarly to a rack-and-pinion system

17
STEERING SYSTEM (4)
  • Power Steering
  • Rotary-vane pump driven by car's engine via a
    belt and pulley - amount of flow provided by the
    pump depends on the car's engine speed
    (pressure-relief valve)
  • Rotary valvesenses steering wheel force assist
    driver only when necessary like during parking

18
STEERING SYSTEM (5)
  • Todays steering system runs constantly, pumping
    fluid all the time (wastes)
  • "drive-by-wire" system (like joysticks)
  • General Motors concept car (Hy-wire)

19
STEERING SYSTEM (6)
20
WHAT COULD GO WRONG (1)
  • Worn loose ball joints causing suspension noise
    (typically a "clunking" sound when hitting a
    bump)
  • Bent wheel (shimmy on steering wheel sideway
    movement of wheel)
  • Leaked shock absorbers (realignment after strut
    change)
  • Shocks too soft
  • Worn shocks (sway, dip, bounce)
  • Loose steering wheel (gt 0.25) tie rod ends,
    rack, wheel bearing)
  • Power steering morning sickness worn steering
    rack

21
WHAT COULD GO WRONG (2)
  • Steering wheel jerks to one side upon hitting
    bump misalignment in chassis bent steering
    arm
  • Car pulled to one side wheel misalignment
    (camber, toe-in), tire pressure, mismatched
    tires, sagging spring, dragging brake, unreleased
    parking brake, uneven load)
  • Unbalanced tires static dynamic
  • Most problems affecting the suspension and
    steering system develop gradually as a result of
    wear. Watch for the following warning signs.

22
WHAT COULD GO WRONG (3)
  • Theres too much play (free movement) in the
    steering wheel. With power steering, there should
    be virtually no play in the wheel. In a manual
    system, there should be no more than 2 inches of
    play.
  • The steering wheel vibrates or is difficult to
    turn.
  • The front end of the car wobbles or shimmies.
  • The car bumps as you turn the wheel while driving
    on a smooth road.

23
WHAT COULD GO WRONG (4)
  • The car pulls to one side as you drive.
  • The car bounces too much after hitting a bump.
  • Tread wear on the front tires is uneven.

24
THE END
IQ EQ SQ TQ
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