# Steering System PPT

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## Full text

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### Automobile Steering System

Course: Automobile Engineering Class: B.E. (Mech. Engg.)

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### Functions of Steering System

• To achieve angular motion of •the front wheels to make a turn

•To provide perfect rolling motion of the road wheels at all the time. •To provide directional stability of the

of the road wheels at all the time.

•Absorb most of the shock going to the steering wheel as the tire hits holes

and bumps in the road. • To facilitate straight ahead recovery after completing a turn

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## Functions of Steering System

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### in Inclination

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Combined angle is the angle formed between the wheel centre line and the king pin inclination (or steering axis).

Scrub radius is the distance between the wheel contact point through which road resistance acts and the other point where the steering axis touches the road surface.

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### Castor angle

The angle between the king pin centre line (or steering axis) and the vertical, in the plane of wheel is called caster angle

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### Caster angle

If the king pin centre line meets the ground at a point ahead of the

vertical wheel centre line, it is called positive caster.

Positive caster is preferred in

Automoble Steering System: S J Madki

Positive caster is preferred in automobiles.

If the king pin centre line meets the ground at a point behind the vertical wheel centre line, it is called positive caster.

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### in or Toe out

Toe-in is the amount by which the front wheels are set closer together at the front when it is stationary.

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### STEERING SYSTEM

The correct steering depends upon a sutable selection of cross arm angle α

Α = b/l where b= AB (dist. between pivots)

L= wheel base (centre distance between front and rear axle)

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C

D

A B

K

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### Slip Angle & Cornering Force

While taking a turn, the centrifugal force acts on the vehicle which produces a side thrust. To sustain the force, the plane of the wheel must make some angle with the direction of motion of the vehicle. This is achieved by the distortion of the tire which is flexible.

The angle through which the wheel has to tilt to sustain the side force is called the slip angle and the force produced due to this (at right angles to the plane of the wheel) which counters the side thrust, is known as cornering force.

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### Slip Angle & Cornering Force

The value of slip angle depends upon

- Amount of side force - Flexibility of tire

- Load carried by the wheel - Camber angle

Magnitude of slip angle is small at low speeds and at less sharp curves It is more, at high speeds and at sharp curves

Automoble Steering System: S J Madki

It is more, at high speeds and at sharp curves For same slip

angle-Cornering force increases for positive camber Cornering force decreases for negative camber

The alteration in the cornering force due to camber is known as camber force

Cornering Power = Side force sustained Slip Angle

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### Oversteer

Understeer: When the slip angles of the front wheels are greater than those for the rear wheels, radius of the turn increases. The vehicle turns less sharply than it is expected. Therefore to keep it on right path we have to steer more.

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### Oversteer

Oversteering: When slip angles of the front wheels are less than those of the rear wheels, the radius of the turn decreases. The vehicle turns more sharply than it is expected. Therefore to keep it on right path we have to steer a little less than needed.

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### Linkage Steering System (Worm Gear) Parts

•Steering Wheel – used by the driver to rotate a steering shaft that passes through the steering column.

•Steering Shaft – transfers turning motion from the steering wheel to the steering gearbox.

•Steering Column – supports the steering shaft.

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### Linkage Steering System (Worm Gear) Parts

•Steering Gearbox – changes turning motion into a straight-line motion to the left or right. •Steering gear box ratios range from 15:1 to

24:1 (with 15:1, the worm gear turns 15 times to turn the selector shaft once).

•Steering linkage – connects the steering gearbox to the steering knuckles and wheels.

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Pitman Arm transfers gearbox motion to

•Pitman arm is splined to the gearbox.

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### Steering Linkage for Independent Suspension

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Center Link (Relay Rod) steel bar connects the

right and left side of the steering linkage.

•Connects to Pitman arm, Tie rod ends, and Idler arm.

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### link on the passenger side of the vehicle.

•Bolts to the vehicle’s frame.

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### Basic Rack-and-Pinion Steering

•Pinion Gear- rotated by the steering wheel and steering shaft; it’s teeth mesh with the teeth on the rack.

•Rack- long steel bar with teeth along one section; slides sideways as the pinion gear turns.

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### Power Steering

normally use an engine driven pump and a hydraulic system to assist steering action.

Three major types of power steering systems: •Integral-piston linkage system.

•External power steering system. •External power steering system.

•Rack-and-pinion system •Integral power piston.

•External power piston.

Integral Rack-and-pinion system is the most common.

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### POWER STEERING

The slight movement of the steering wheel actuates a valve so that the fluid under pressure from the reservoir enters on the appropriate side of the cylinder, thereby applying the pressure on one side of the piston to operate the steering linkage, which steers the wheel in the appropriate direction.

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