Steering System AE

7/25/2019 Steering System AE

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Steering System

Syllabus: Requirement and steering geometry;castor action, camber and king pin angle, toe-in of

front wheels, Steering linkages and steering gears;wheel alignment, Manual and Power Steering.


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Functions of Steering System

Primary unction! "o achie#e angular motion of the front

wheels to negotiate a turn. "his is done through linkage

and steering gear which con#erts the rotary motion of

the steering wheel into the angular motion of the front

wheels.

Secondary Functions :

"o pro#ide directional stability of the #ehicle when going

straight ahead. "o pro#ide perfect steering condition, i.e. perfect rolling

motion of the road wheels at all times.

"o facilitate straight ahead reco#ery after completing a turn.

"o minimi$e tyre wear.


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Requirements of Steering System

"he steering mechanism should be #ery accurate andeasy to handle.

"he effort required to steer should be minimum and mustnot be tiresome to the dri#er.

"he steering mechanism should also pro#ide directional

stability i.e. the #ehicle should ha#e a tendency to return

to its straight ahead position after turning.


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Wheel Alignment

Positioning of the steered wheels to achieve the following is

termed Wheel Alignment:

%irectional Stability during straight ahead position.

Perfect rolling condition on steering.

Reco#ery after completing the turn.

Rear wheels should follow the front wheels properly.

"his would happen if all four wheels are parallel to the

frame. "his is called Tracking..


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Wheel Alignment

To have effective steering under all conditions and at all

loads the factors to !e considered are:

actors pertaining to wheels.

Steering &eometry.

Steering linkages. Suspension system.


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Factors pertaining to Wheels

"alance of Wheels : #f the wheels are not in dynamically!alance there would !e wheel wo!!le which influences

steering control.

#nflation of Tyres :"he steering system is designed fora particular rolling radius. 'ariation of air pressure

from the standard prescribed will change the rolling

radius.

"rake Ad$ustment : #f the !rake is not ad$usted %ro%erly

e.g. if it is dragging it can %ull the vehicle to one side

while !raking.


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Steering &eometry

&orrect Steering 'eometry Princi%le : The a(is of all thewheels of an automo!ile while taking a turn must intersect atthe common instantaneous centre of rotation %oint.

Steering Parameters : &am!er.

&astor. Steering A(is #nclination.

#ncluded Angle.

Steering )atio.

Toe #n* Toe out.

Scru! )adius.

Thrust Angle.

Turning radius.

Tracking.


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Camber

(amber is the tilt of the car wheels from the #ertical when#iewed from the front of the #ehicle.

(amber is positi#e if the tilt is outwards at the top and

negati#e if the tilt is inwards of the #ertical at the top.

(amber is also called )*heel Rake+. positi#e camber would ha#e the tendency to make the wheel

to "oe ut. negati#e camber would tend to "oe n.

n independent suspension usually the change of spring height

changes the camber. *hen the camber is $ero, slight irregularities on the road may

cause the wheel load to change from one bearing to another,

also changing the direction of the camber effect. "his situation

may thus cause a phenomenon called )*ander+.


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/ing Pin0 Steering 1is nclination

#nclination of the +ing Pin from vertical is called +ing Pin

#nclination or +ing Pin )ake.

#n modern vehicles where +ing Pin has !een re%laced !y !all

$oints it is called Steering A(is #nclination.

+P# * SA# hel%s the straight ahead recovery thus %roviding

directional sta!ility. When the vehicle takes a turn the

inclination of king %in causes the vehicle !ody to move u% inrelation to the wheels. So when the steering is left after the

turn is com%leted the weight of the vehicle tends to return the

wheels to the straight ahead %osition.


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#ncluded Angle,&om!ined Angle-

+P# when added to &am!er angle gives the #ncluded Angle

,&om!ined Angle-.

+P# %ositive cam!er / #ncluded Angle 0 +P#.

+P# negative cam!er / #ncluded angle 1 +P#.

The #ncluded Angle has to !e the same on !oth the sides

even if the cam!er is different. Scru! )adius : #t is the distance !etween where the +P# a(is

intersects the ground and the centre of the tyre.

#t is %ositive when the tyre centre line lies outside the +P# a(is

whereas it is negative when it lies inside the +P# a(is. Frontwheel drives generally have negative scru! radius.

The amount of Scru! )adius de%ends u%on the +P#* SA# the

wheel offset 2 sus%ension height.


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(astor

&astor is the angle of the line %assing through the

steering %ivots +P#* SA# a(is with res%ect to the verticalwhen viewed from the side of the vehicle.

#f king %in centre line meets the ground ahead of the

vertical centre line then it is Positive &astor while if it is

!ehind the vertical wheel centre line then it is negativecastor.

With %ositive castor the wheels tend to Toe3#n and with

negative castor they tend to Toe34ut.

When vehicle is taking a turn %ositive castor tends tohel% the centrifugal force to roll3out the vehicle whereas

negative castor counteracts the centrifugal force and

tend to roll3in the vehicle.


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Steering Ratio

Steering Ratiois the ratio of the angular mo#ement of

steering wheel to the actual mo#ement of the steered

wheels on the ground.

t is generally 23.4 ! 2.


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"oe n and "oe ut

Toe measurement is the difference in the distance

!etween the front of the tyres and rear of the tyres at thes%indle height.

Toe3#n means that the front of the tyres are closer to

each other than the rear.

Toe34ut means that the rear of the tyres are closer toeach other than the front.

The %ur%ose is to minimise tyre wear and reduce rolling

friction.


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"hrust ngle

Thrust angle is the direction that the rear wheels are

%ointing in relation to centre line of the vehicle.

#f the thrust angle is not 5ero then the vehicle will 67og

Track8 and the steering wheel will not !e centered.

Front Toe must !e set to com%ensate for the thrust

angle allowing for the steering to !e centered.


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"urning Radius

Turning )adius is the radius of the circle traced !y the

centre %oint of any vehicle when the wheels are

com%letely steered towards one side.

#t is an inde( of steering effectiveness.


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(ornering orce

*hile taking a turn the centrifugal force acts on the #ehicle which

produces a side thrust.

"he angle through which the wheel has to turn to sustain the side

force is called the Slip ngle.

"he force produced due to this 5at right angles to the plane of the

wheel6 which counters the side thrust, is known as the (ornering

orce.


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(ornering orce 'alue of slip angle depends upon the amount of side force, the

fle1ibility of tyre, load carried by the wheel, camber angle and

condition of the road surface.

"he magnitude of slip angle is small at low speeds 7 less sharp

cur#es. t increases at high speeds 7 sharp turns.

or the same slip angle, positi#e camber increases cornering force

while negati#e camber decreases it. "he alteration of cornering force,

due to camber is referred as )(amber orce+.

"he ratio of Side force sustained to the slip angle is )(ornering

Power+.


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Self 8 Righting "orque

&ornering force acts at a distance 9( ,%neumatic trail- from

the line of side thrust.

Self3)ighting Tor;ue ,/ cornering force ( %neumatic trail- has

the tendency to !ring !ack the wheel in the direction of

motion.


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9ndersteer 7 #ersteer

When the sli% angles of the front wheels are greater thanthose of rear wheels radius of turn is increased. This

means the vehicle will turn less shar%ly than it should for

a given rotation of a steering wheel. This is called

=ndersteer.

When the sli% angles of the front wheels are less than

the sli% angles of the rear wheels radius of turn is

decreased. This means the vehicle will turn more shar%lythan it should for a given rotation of the steering wheel.

This condition is called 4versteer.


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Steering System

>echanical Steering

Power Steering

>echanical steering : With mechanical linkages.

Power steering : >echanical steering assisted !y %ower.

a- ?ydraulic Power

!- @lectrical %ower.


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Steering System

STEERING GEOMETRY


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Steering System

>echanical steering : With mechanical linkages.

&om%onents of >echanical Steering:

a- Steering wheel

!- Steering &olumn

c- Steering 'ear

d- Tie rod ,eft and )ight-

e- )elay rod

f- #dler arm

g- Steering armh- Steering +nuckle and s%indle

This is called relay steering linkage.

'ears are mostly worm and roller ty%e.


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Steering System

Main Components

The manual steering system incorporates:

1.steering wheel and column,

2.a manual gearbox and pitman arm or a rack andpinion assembly,

.linkages! steering knuckles and ball "oints!#.the wheel spindle assemblies.


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Steering System

$t is the ratio o% the angular mo&ement o% steeringwheel to the actual mo&ement o% the steeredwheels 'enerally it is

1(.) : 1


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Steering System

Manual *orm and +ector +teering The manual worm and sector steering gear

assembly uses a steering sha%t with a threeturnworm gear supported and straddled by ball

bearing assemblies. The worm meshes with a 1#tooth sector attached to the top end o% thepitman arm sha%t. $n operation, a turn o% thesteering wheel causes the worm gear to rotate

the sector and the pitman arm sha%t. Thismo&ement is transmitted to the pitman arm andthroughout the steering train to the wheelspindles.


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Steering System


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Steering System

*orm - +ector Type +teering


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Steering System


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Steering System

Manual ack and /inion +teering

0 typical rack and pinion steering gear assemblyconsists o% a pinion sha%t and bearing assembly,rack gear, gear housing, two tie rod assemblies,an ad"uster assembly, dust boots and boot

clamps, and grommet mountings and bolts. *henthe steering wheel is turned, this manualmo&ement is relayed to the steering sha%t andsha%t "oint, and then to the pinion sha%t. +ince thepinion teeth mesh with the teeth on the rack gear,

the rotary motion is changed to trans&ersemo&ement o% the rack gear. The tie rods and tierod ends then transmit this mo&ement to thesteering knuckles and wheels.


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Steering System


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Steering System


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Steering System

Manual ecirculating all +teering

*ith the manual ecirculating ball steering gear,turning %orces are transmitted through ball bearings%rom a worm gear on the steering sha%t to a sectorgear on the pitman arm sha%t. 0 ball nut assembly is3lled with ball bearings, which roll along groo&es

between the worm teeth and groo&es inside the ballnut. *hen the steering wheel is turned, the worm gearon the end o% the steering sha%t rotates, and mo&emento% there circulating balls causes the ball nut to mo&e upand down along the worm. Mo&ement o% the ball nut is

carried to the sector gear by teeth on the side o% theball nut. The sector gear then mo&es with the ball nutto rotate the pitman arm sha%t and acti&ate thesteering linkage. The balls recirculate %rom one end o%the ball nut to the other through ball return guides.


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Steering System

ecirculating all 0ssembly


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Steering System


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Steering System

ecirculating all +teering +ystem


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Steering System


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Steering System


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Steering System

Hydraulic Power Steering


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Steering System

4ydraulic /ower +teering


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Steering System

5lectronic /ower +teering


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Steering System

6our *heel 7inkage +teering


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Steering System

6our *heel 4ydraulic /ower +teering


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Steering System

6our *heel 7inkage +teering


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Steering System


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Steering System


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Steering System

Documents

Steering System AE