3 Steering System Updated

7/29/2019 3 Steering System Updated

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The steering system allows

the operator to guide thevehicle along the road andturn left or right as desired.



The steering system allows the driver tocontrol the direction of vehicle travel.

This is made possible by linkage that connectthe steering system may be either manual orpower.

When the only energy source for the steeringsystem is the force the drivers applies to thesteering wheel, the vehicle is manualsteering.



The system includes the steering wheel, whichthe operator controls the steering mechanism,

which changes the rotary motion of the steeringwheel into straight-line motion and the steeringlinkage.

Most systems were manual until a few yearsago. Then power steering became popular. It isnow installed in most vehicles manufacturedtoday.



Pitman Arm

The pitman arm transfers steering mechanism motion to the steering linkage. Thepitman arm is splined to the steeringmechanism output shaft (pitman arm shaft).



Center Link

The parallelogram steering linkage uses acenter link, otherwise known as anintermediate rod, track rod, or relay rod,which is simply a steel bar that connects thesteering arms (pitman arm, tie-rod ends,and idler arm) together.



Idler Arm

The center link is hinged on the opposite endof the pitman arm by means of an idler arm.



Ball Sockets Ball sockets are like small ball joints; they

provide for motion in all directions betweentwo connected components. Ball sockets areneeded so the steering linkage is NOTdamaged or bent when the wheels turn or

move up and down over rough roads.Ball sockets are filled with greaseto reduce friction and wear.



Tie-Rod Assemblies

Two tie-rod assemblies are used tofasten the center link to the steeringknuckles. Ball sockets are used on both endsof the tie-rod assembly. An adjustment sleeveconnects the inner and outer tie rods.



STEERING RATIO

The steering ratio is the ratio of how far you turn the

steering wheel to how far the wheels turn. For, instance if one complete revolution (360 degrees) of the steeringwheel results in the wheels of the car turning 20 degrees,

then the steering ratio is 360 divided by 20, or 18:1

With a 30:1 steering ratio, the steering wheel must turn30 degrees to pivot the front wheels 1 degree.

● Transmit road feel (slight steering wheel pull caused by road surface) to the operator’s hands



Maintain the correct amount of effort needed to turnthe front wheels.

Provide precise control of front- wheel direction.

Transmit road feel (slight steering wheel pullcaused by road surface) to the operator’s hands.

Absorb most of the shock going to the steeringwheel, as the tires hit bumps and holes in the road.

Allow for suspension action.

● Transmit road feel (slight steering wheel pull caused by road surface) to the operator s hands. ● Absorb most of the shock going to the steering wheel, as the tires hit bumps and holes in the road. ● Allow for suspension action.



STEERING RATIO

The steering ratio is a number of degrees that thesteering wheel must be turned to pivot the front

wheels 1 degree.

The higher the steering ratio (30:1 for example), the easier it is to steer the vehicle, all

other things being equal.

However, the higher steering ratio, the more the

steering wheel has to be turned to achieve steering.



Worm Gear



Rack



Pinion



There really are only two basic categories of steering system today; those that have

pitman arms with a steering 'box' and thosethat don't. Newer cars and unibody light-duty trucks

typically all use some derivative of rack andpinion steering.



Pitman arm mechanisms have a steering 'box'where the shaft from the steering wheel

comes in and a lever arm comes out - thepitman arm This pitman arm is linked to the track rod or

centre link, which is supported by idler arms.The tie rods connect to the track rod.



Types of manual steering gear box

● Worm and Sector / Gear

● Worm and Roller

● Cam and Lever

●

Worm and Nut (Re circulating Ball type).



In this type of steering box, the end of theshaft from the steering wheel has a wormgear attached to it

It meshes directly with a sector gear (socalled because it's a section of a full gearwheel)

When the steering wheel is turned, the shaft

turns the worm gear, and the sector gearpivots around its axis as its teeth are movedalong the worm gear.



The worm and roller steering box is similar indesign to the worm and sector box.

The difference here is that instead of having asector gear that meshes with the worm gear,there is a roller instead.



The roller is mounted on a roller bearing shaft and isheld captive on the end of the cross shaft.

As the worm gear turns, the roller is forced to movealong it but because it is held captive on the cross

shaft, it twists the cross shaft. Typically in these

designs, the worm gear is actually an hourglass

shape so that it is wider at the ends. Without thehourglass shape, the roller might disengage from it

at the extents of its travel.



This is by far the most common type of steering box for pitman arm systems. In a

recirculating ball steering box, the wormdrive has many more turns on it with a finerpitch.

A box or nut is clamped over the worm drivethat contains dozens of ball bearings.



These loop around the worm drive and thenout into a recirculating channel within the nut

where they are fed back into the worm driveagain. Hence recirculating. As the steering wheel is turned, the worm

drive turns and forces the ball bearings topress against the channel inside the nut



This forces the nut to move along the wormdrive. The nut itself has a couple of gear teeth

cast into the outside of it and these meshwith the teeth on a sector gear which isattached to the cross shaft just like in theworm and sector mechanism.



This system has much less free play or slackin it than the other designs, hence why it's

used the most. The example below shows arecirculating ball mechanism with the nutshown in cutaway so you can see the ballbearings and the recirculation channel.



Cam and lever steering boxes are very similarto worm and sector steering boxes.

The worm drive is known as a cam and has amuch shallower pitch and the sector gear isreplaced with two studs that sit in the camchannels.



As the worm gear is turned, the studs slidealong the cam channels which forces the

cross shaft to rotate, turning the pitman arm.One of the design features of this style is thatit turns the cross shaft 90° to the normal so itexits through the side of the steering box

instead of the bottom. This can result in avery compact design when necessary.



The manual rack-and-pinion steering gear

basically consists of a steering gear shaft, pinion

gear, rack. thrust spring, bearings, seals, and gear

housing. In the rack-and-pinion steering system theend of the steering gear shaft contains a piniongear, which meshes with a long rack. The rack

is connected to the steering arms by tie rods, which

are adjustable for maintaining proper toe angle



Hydraulic Power Steering (HPS)

Electric/electronic Power Steerin (EPS)



Reservoir pump hose

Return hose

Pump - controlvalve hose



For a right turn, the control valve routes oil tothe left side of the power piston. The piston ispushed to the right in the cylinder to aidpitman shaft rotation.

For a left turn, the control valve routes oil to

the right side of the power piston. The pistonis pushed to the left in the cylinder to aidpitman shaft rotation.



To bleed out any air, start the engine and turnthe steering wheel fully from side to side.Keep checking the fluid and add as needed.This will force the air into the reservoir andout of the system.

3 Steering System Updated

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