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STEERING SYSTEMS

FOUR WHEEL STEERING:

There are three types of 4 wheels steering system

Mechanical 4wS

Hydraulic 4ws Electro-hydraulic 4ws

The concept of four wheel steering is hardly and relatively new as four wheeldrives admittedly those systems were custom, typically controlled and separatelycontrolled from the front wheels.

The first production four wheels steering for the average,American automoile consumer was offered !" years ago. #n the $%&&, this systemwas entirely self-contained, automatic and mechanical' no electronic, no speed

sensors, no computers, no hydraulic, (ust two rac)s and a rod etween them.

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*our wheel steering +4ws is also called the rear wheels steering or all wheel steering.

The +4ws four wheel steering should not e confused with four wheel drive. 4wssystem improves handling and helps the vehicle at lighter turns. The front wheels dothe actual steering wor). The rear wheel turning is generally limited a " to !" "

during an opposite duration turn. uring the same direction turn rear wheel steeringis limited the aout $" to $. ". /n a +4ws system, the front and rear wheels steertowards same direction which is said to e in-phase at high speed, where as the frontand rear wheels turn in an opposite direction at slow speed which is called anti-phaseor opposite phase and it is produced at a sharper turn and tighter turn.

Steering system allows the driver to control the direction of the vehicle travel. This ismade possile y lin)age that connects the steering wheel to the steerale wheels andtires. The steering system may e either manual or power .0hen the energy sourcefor the steering system is the force, the drives applies to the steering wheel, then the

vehicle has manual steering .1ower steering used a hydraulic pump or in motor toassist the driver effects. /n the modern age most of the vehicles are manufacture witha power steering mechanism.

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The operation is same for oth manual and power steering .As the drive turnsthe steering where the movement is carried to the steering gear. /t chains the rotarymatron of the steering wheel, in to straight line or linear motion. The linear motionacts through steering lin)age 2tie rod attached to the steering )nuc)le .arms orsteering arms. The steering )nuc)le then turns the wheels in to left or right side.

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ADVANTAGE OF FOUR WHEEL STEERING:

The vehicle's cornering behaviour becomes more stable and controllable

at high speedways well as on wet or slippery road

surfaces.

The vehicle's response to steering input becomes quicker and more

precise throughout the vehicle's entire speed range. The vehicle' s

straight-line stability at high speeds is improved.

Negat ive effects of road irregularities and crosswinds on the vehicle's

stability are minimized. Stability in lane changing at high speeds is

improved.

The vehicle is less likely to going a spin even in situat ions in whichthe driver must make a sudden and relatively large change of

direction.

y steering the rear wheels in the direction opposite the front

wheels at low speeds! the vehicle's turning circle is greatly

reduced.

Therefore! vehicle manoeuvring on narrow-roads and during

parking becomes easier.

APPLICATION OF FOUR WHEEL STEERING:

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"t is used for easy parking of four wheelers! and can be implemented in monster

trucks! large farm vehicles and trucks.

FAIL OF SAFETY MEASURES:

#ll $%S systems have fail-safe measures. &or eample! with the

elector-hydraulic setup! the system automaticallycounteracts possible causes of fa i lur e( both e lect ronic and

hydraulic! and converts the entire steering system to a

conventional two-wheel steering type.

Specifically! if a hydraulic defect should reduce pressure level

)by a movement malfunction or a broken driving belt*! the rear-

wheel-steering mechanism is automatically locked in a neutral

position! activating a low-level warning light.

"n the event of an electrical failure! it would be detected by a self-

diagnostic circuit inte gr at ed in the fo ur wh ee l- st ee ri ng co nt ro l

uni t .

T he co nt ro l un it st im ul at es a so le no id valve! which neutralizes

hydraulic pressure! thereby alternating the system to two-wheel

steering.

The failure would be indicated by the system's warning light in

the main instrument display

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.+n any $%S system! there must be near-perfect compliance

between the posi tion of the steer ing wheel! the posi tion of the

front wheels! and the posi tion of the rear wheels. "t is usually

recommended that the car be driven about , feet ) meters* in a dead-

straight line.

Then! the position of the front/rear wheels is checked with

respect to steering wheel position.

The base reference point is a strip of masking tape on the steering wheel

hub and the steering column. %hen the wheel is posit ioned dead

centre! draw a line down the tape.

0un the car a short distance straight ahead to see if the reference line

holds. "f not! corrections are needed! such as repositioning the steeringwheel. 1ven severe imbalance of a rear wheel on a speed sensitive $%S

system can cause problems and make basic troubleshooting a bit

frustrating.

ZERO STEERING:

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2ero steering are those which has a minimum steering radius that is equal to zero!which rotates about its own some of the 3eeps comes with this type of steering. 4ou can see in

this picture that the turning radius is zero and this is known as zero steering.

A (eep named hurricane has this type of steering..

JEEP HURRICANE STEERING:

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The 5urricane's steering system is a marvel of engineering all by itself. There are multiple

steering modes using four-wheel independent steering. That means that each wheel can turn

separately from the others.

"n standard steering mode! the rear wheels turn in the opposite direction to the front wheels!

which tightens the turning radius and makes for more accurate steering.

"n a second mode! the rear wheels turn in the same direction as the front wheels! meaning the

5urricane can 6crab-steer6 -- move to the side without changing the direction that it faces.

# third mode! utilizing the 6T-o 2ero Steer6 mechanism! allows all four wheels to 6toe-in6

and changes the drive direction to each wheel so that they alternate. The result7 The 8eep

5urricane has a turning radius of zero. The 5urricane can actually rotate in place.

The cars with four wheel steering differ from that of ordinary one as shown inthe image aove.