Prepared by,

Prof. Santosh Kailas Chandole

ME (Design Engineering)

BE (Automobile Engineering)

Unit No.03

Suspension & Brake system

Function Suspension System •Supports the weight.

•Provides a smooth ride.

•Allows rapid cornering without extreme

body roll.

•Keeps tires in firm contact with the road.

•Prevents excessive body squat.

•Prevents excessive body dive.

•Allows front wheels to turn side-to-side for steering.

•Works with the steering system to keep the wheels in correct alignment.

Comparison of Rigid And Independent

Suspension System

Types of Suspension System

1.Non-independent/Rigid suspension has both right and left wheel attached to th

same solid axle. When one wheel hits a bump in the road, its upward movement causes

a slight tilt of the other wheel.

2.Independent suspension allows one wheel to move up and down with minimal

effect to the other.

Suspensions

Independent

Nonindependent

Suspension System

Coil spring is the most common type of spring found on modern vehicles.

Leaf springs are now limited to the rear of some cars.

Types of Springs

A. Coil spring

B. Leaf spring

C. Air spring

D. Torsion bar

Suspension System Basic Parts

Control arm – movable lever that fastens

the steering knuckle to the vehicle’s

body or frame.

Steering Knuckle – provides a spindle or

bearing support for the wheel hub, bearings

and wheel assembly.

Lower wishbone

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1 Wishbone Suspension

The suspension must be

designed in such a way as to

keep the wheel upright for

maximum tyre contact

(vehicle control) and to

minimize tyre wear.

The upper wishbone is short

and the lower wishbone is

longer.

Both wishbones pivot points

and lengths are calculated to

provide the best operating

angle for a given suspension

movement.

Upper wishbone

Advantages & Disadvantages of

Wishbone type independent suspension

Advantages

•Ride quality is good.

•Improve the steering

preciseness since the

wheel movement are not

link

•Ground clearance

increase

Applications:-SUV,CARS

Disadvantages

•Initial cost is more •Maintenance cost is

more. •Required frequent

wheel alignment

otherwise increase

tyre wear.

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2 MacPherson Strut

This is a very popular and efficient form of

suspension. It has one control arm and a strut

assembly. A coil spring and shock absorber

will normally form parts of the strut assembly.

Coil springs may be mounted on

the control arm instead of being

around the strut. On this type,

the shock absorber connects the

knuckle to the frame.

This type of suspension strut is

often also used on rear

suspension systems.

Coil spring

Strut

assembly

Frame

Shock

absorber

Control

arm

Knuckle

Front Suspension (MacPherson Strut)

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MacPherson Strut Suspension

The top of the strut is bolted to

a reinforced section of the

frame structure.

The lower end of the strut is

attached to a steering knuckle.

The control arm is also attached

to the steering knuckle.

The control arms are mounted on

a cradle section of the frame.

An anti-roll bar links the two

control arms together to reduce

sway (body roll).

Steering knuckle

Control

arm

Cradle

Anti-roll bar

Frame

Strut

Advantages & Disadvantages of

Macpherson strut suspension

Advantages

•Light in weight.

•Camber does not

change due to up &

movement of wheels

•Maximum Engine

compartment available.

•Maintenance cost is

less.

•Initial cost is less.

•Ride comfort is more.

•Improve road safety.

Disadvantages •Not suitable for Heavy

motor vehicle. •Load caring capacity is

less.

Applications:-CARS

Trailing arms, or links, hold the rear axle in position.

A stabilizer bar and track bar are included to add vehicle stability. 16 of 12

Solid Rear Axle Suspension

This type of rear suspension

is typical for a rear-wheel

drive vehicle.

The axle is inside a

solid housing.

The shock absorbers

are

mounted between the

solid axle and the frame.

The springs are arranged between the

axle housing and the frame of the vehicle.

Axle housing

Shock absorber

Coil

springs

Stabilizer bar

Trailing arm

Independent Suspension System Parts

Basic Parts

Ball Joints – swivel joints that allow

control arm and steering knuckle to move

up and down and side to side.

Springs – supports the weight of the

vehicle; permits the control arm and

Wheel to move up and down.

Shock absorbers or dampeners – keeps

the suspension from continuing to bounce

after spring compression and extension.

Control arm bushing – sleeves that

allows the control arm to swing

up and down on the frame.

Coil Springs

Leaf Spring Assembly

Air Springs

Layout of Air Suspension

System

Schematic view of Air Suspension System

Location of Air bellows

Advantages & Disadvantages of Air

suspension Advantages

• Variable space for wheel

deflection is put for optimum use for automatic height control.

Head light alignment does not

vary due to different loading

condition.

•It improve the ride comfort.

•Reduce noise in suspension

system.

Disadvantages

* Higher initial cost

* Occupies more space

* Maintenance cost is more

* Due lack of friction damping is

necessary due road shock

Applications:- Volvo Buses

Torsion Bar

The bar resists twisting action and acts

like a conventional spring

Torsion bar (large spring rod)

•One end is attached to the frame and the other to the lower control arm.

•Up and down of the suspension system twists the torsion bar. •It will then try to return to its original shape, moving the control arm to its

original place.

Advantages & Disadvantages of Torsion

bar suspension

Advantages

•Light in weight.

•Less space occupies .

•Its maintenance cost is less.

•Initial cost is less.

•Ride comfort is more.

Disadvantages •It does not take

accelerate & Braking

thrust so required

additional linkages •Due lack of friction

damping is necessary

due road shock

Applications:-SUV Tata Safari, Tempo Trax

Suspension System Shock absorbers

•Limits spring compression-extension

movements to smooth the vehicle’s ride.

•Without shock absorbers, the vehicle

would continue to bounce up and down

long after striking dip or hump in the road.

Shock Absorber Action

Introduction of Brake

A drum brake is a brake in which the friction

is caused by a set of shoes or pads that press

against a rotating drum-shaped part called a brake

drum.

The term "drum brake" usually means a brake in

which shoes press on the inner surface of the

drum. When shoes press on the outside of the

drum, it is usually called a clasp brake.

Main functions of braking system

To stop the vehicle safely in shortest possible distance in case of emergency.

To control the vehicle when it is descending along the hills

To keep the vehicle in desired position after bringing in at rest

CONSTRUCTION

The Break Drum consist of

following components..

Back Plate

Brake drum

Wheel cylinder

Brake shoe

Brake lining

Return spring

Piston

WORKING

The drum brake stops the tire

from rotating by using the hydraulic

pressure transmitted from the master

cylinder to the wheel cylinder

to press the brake shoe against

that brake drum, which is

rotating together with the tire.

When the hydraulic pressure to

the wheel cylinder disappears, the

force of the return spring pushes the

shoe away from the inner surface of

the drum and returns it to is original

position.

Drum brakes are smaller for the same brake force.

Drum brakes don't need a hydraulic system for activation.

Due to simple in construction it can be easiliy repair.

Due to the fact that a drum brake's friction contact area is at

the circumference of the brake, a drum brake can provide more

braking force than an equal diameter disc brake.

The use of many clips and springs makes overhaul of the brake drum assembly

very time-consuming.3

Another problem with drum brakes is that if a vehicle is driven through water,

it takes longer to get the brakes working effectively.

When the drums are heated by hard braking, the diameter of the drum

increases slightly due to thermal expansion, this means the brakes shoes have

to move farther and the brake pedal has to be depressed further.

DISADVANTAGES

Applications: trucks, cars and in other automobiles.

ADV ANTAGES

Disc Type Brake

CONSTRUCTION DISC Brake consist of cat iron disc bolted to the wheel hub and an stationary

housing called “caliper”. The caliper is connected with some stationary part of position of vehicle, like stub or axle on of wheel of connecting rod .

The piston rod is connected in between which has friction pad is being held by an piston pins, springs etc.

Working of Disc brake

The brakes are operated when friction is being created on friction pads by forced applying on it against the disc .the forces created on its is hydraulic pressure from master cylinder, thereby an engaging the braking system.

When the hydraulic braking pressure is applied on piston will engaged an released bar due to pressure.

When pressure is released piston will regain its original position. Here friction pad works on main fundamental working process.

“CALIPER “ is added on system to balanced two calipers by diagrammatically opposite to each to other. In this way braking torque is reduced.

Advantages of Disc Brake Better heat dissipation as braking torque on surface of exposed air.

Adjustment of pads is automatic

Renewal of pad is quick and easy.

Disadvantages of Disc Brake.

In comparison of brake drum of similar capacity, rate pad wear is

more.

The HAND BRAKE MECHANISM IS NOT SO CONVINENT.

ANTILOCKING BRAKING SYSTEM {abs} SOURCE: Internet

Anti-lock braking system (ABS) is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding. It is an automated system that uses the principles of threshold braking and cadence braking which were practiced by skillful drivers with previous generation braking systems. It does this at a much faster rate and with better control than a driver could manage

ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or snow-covered pavement, ABS can significantly increase braking distance, although still improving vehicle control.

Working of Anti Braking System

The anti-lock brake controller is also known as the CAB (Controller Anti-lock Brake).

Typically ABS includes a central electronic control unit (ECU),

four wheel speed sensors, and at least two hydraulic valves within the brake hydraulics. The ECU constantly monitors the rotational speed of each wheel; if it detects a wheel rotating significantly slower than the others, a condition indicative of impending wheel lock, it actuates the valves to reduce hydraulic pressure to the brake at the affected wheel, thus reducing the braking force on that wheel; the wheel then turns faster. Conversely, if the ECU detects a wheel turning significantly faster than the others, brake hydraulic pressure to the wheel is increased so the braking force is reapplied, slowing down the wheel. This process is repeated continuously and can be detected by the driver via brake pedal pulsation. Some anti-lock systems can apply or release braking pressure 15 times per second. Because of this, the wheels of cars equipped with ABS are practically impossible to lock even during panic braking in extreme conditions

Modern ABS applies individual brake pressure to all four wheels

through a control system of hub-mounted sensors and a dedicated micro-controller. ABS is offered or comes standard on most road vehicles produced today and is the foundation for electronic stability control systems, which are rapidly increasing in popularity due to the vast reduction in price of vehicle electronics over the years

Construction of Anti Braking System

There are four main components of ABS: speed sensors, valves, a pump, and a controller.

Speed sensors The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information.

Valves There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions:

In position one, the valve is open; pressure from the master cylinder is passed right through to the brake.

In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder.

In position three, the valve releases some of the pressure from the brake.

Pump When the ABS system operates the brake lines lose pressure. The pump re-pressurizes the system.

Controller The controller is an ECU type unit in the car which receives information from each individual wheel speed sensor, in turn if a wheel loses traction the signal is sent to the controller, the controller will then limit the brakeforce (EBD) and activate the ABS modulator which actuates the braking valves on and off.