Presentation on theme: "CCAS 3381 AUTOMOTIVE SKILL I"— Presentation transcript:
1 CCAS 3381 AUTOMOTIVE SKILL I SUSPENSION &STEERING SYSTEM
2 OBJECTIVESTo understand the operational principles and basic mechanisms of suspension & steering systemsDouble-wishbone suspension on Honda Accord 2005 CoupeLecture – 1 hourWorkshop – 1 hour
3 SUSPENSION SYSTEM (1)Power of a car is useless if car cannot be controlledCar suspension:maximizes friction between tires and road surfaceprovide steering stability with good handlingensure the comfort of the passengers
4 SUSPENSION SYSTEM (2) Vehicle dynamics Ride - car's ability to smooth out bumpy roadHandling - car's ability to safely accelerate, brake & cornerRoad isolation - allow vehicle body to ride undisturbed while traveling over rough roadsRoad 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 contactSteering system - mechanism enabling driver to guide & direct vehicleTires & 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 springsSprung mass & unsprung mass
7 SUSPENSION SYSTEM (5)Sprung mass - mass of the vehicle supported on the springsUnsprung mass - mass between the road and the suspension springsStiffness of springs affects how sprung mass responds while the car is being drivenLoosely 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 dampeningcompression cycleextension cycle
9 SUSPENSION SYSTEM (7) Struts and Anti-sway Bars Strut: shock absorber inside a coil springprovide dampening functionprovide structural support for the vehicle suspensioncritical safety feature - worn shocks & struts allow excessive sway reducing tire grip, handling & braking performanceAnti-sway or anti-roll barsgive moving stabilitycreates a more level ride & reduces vehicle swayCommon strut designAnti-sway bars
10 Double-wishbone suspension on SUSPENSION SYSTEM (8)Dependent front suspension - rigid front axle connecting the front wheelsIndependent system - front wheels are allowed to move independently (MacPherson strut, double wishbone)Double-wishbone suspension onHonda Accord 2005 CoupeDouble-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 wheelsIndependent rear suspension system – both rear wheels are mounted & sprung individuallyBose® Suspension Front Module
14 STEERING SYSTEM (1)During turning your front wheels are not pointing in the same directionGeometry 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 linearprovides gear reduction to turn wheelsA steering wheel rotates 360o causing wheels turning 20o has steering ratio of 360/ 20 = 18:1Variable-ratio steeringPower Rack-and-pinion
16 STEERING SYSTEM (3) Recirculating-ball steering Used on many trucks and SUVs todaycontains a worm gearPower 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 valve senses steering wheel force – assist driver only when necessary like during parking
18 STEERING SYSTEM (5)Today’s steering system runs constantly, pumping fluid all the time (wastes)"drive-by-wire" system (like joysticks)General Motors concept car (Hy-wire)
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 softWorn shocks (sway, dip, bounce)Loose steering wheel (> 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 armCar 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 & dynamicMost 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)There’s 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.