Technical english for automotive engineering chapter 4 suspension

The damping properties of the shock absorbers are affected by spring bellow pressure depending on the load Fig 4.5 Fig 4.4: Torsion bars in suspension system Fig 4.3: Leaf spring assem

system is to isolate the car body from the vertical motion of the wheels as they travel over the rough road surface The suspension system can be understood with reference to Figure 4.1, which illustrates the major components

Fig 4.1: Major components of suspension system

1 SPRINGS

Notice that the wheel assembly is connected through a movable assembly to the body The weight

of the car is supported by SPRINGS Today's springing systems are based on one of four basic

designs:

1.1 Coil springs: this is the most common type of spring and is, in essence, a heavy-duty torsion

bar coiled around an axis Coil springs compress and expand to absorb the motion of the wheels (Fig 4.1)

1.2 Leaf springs: this

type of spring consists of

several layers of metal

(called "leaves") bound

together to act as a single

unit Leaf springs were

first used on horse-drawn

carriages and were found

on most American

automobiles until 1985

They are still used today

on most trucks and

1.3 Torsion bars: torsion bars

use the twisting properties of a steel bar to provide coil-spring-like performance The short torsion bar

springs grip into the guide tubes 2 and

3 in the centre of the vehicle (Fig 4.4) Parts 2, 3 and 4 are jointly subjected

to torsional stresses and so the torsional stiffness of the transverse tubes contributes to the spring rate On

the outside, the cast trailing arms 1 are welded to the transverse tubes,

which (pushed into each other) support

each other on the torsionally elastic

bearings 5 and 6 This creates a

sufficiently long bearing basis, which largely prevents camber and toe-in changes when forces are generated The entire assembly is fixed by the

brackets 7 which permits better force

transfer on the body side sill Guide tubes 2 and 3 are mounted in the brackets and can rotate, as well

as the outer sides of the two torsion bars 4 The two arms thus transfer all vertical forces plus the entire springing moment to the body The anti-roll bar 8 is connected to the two trailing arms via two

U-shaped tabs The two rubber bearings 5 and 6 located between the tubes 2 and 3 also contribute

to the stabilizing effect The bump and rebound travel stops are fitted into the shock absorber 9 1.4 Air springs: The air-spring bellows

are supplied by an electrically powered

compressor The individual wheel

adjustment permits the lowering or lifting of

the vehicle as well as a constant vehicle

height, regardless of – even onesided –

loading It is also possible to counteract

body tilt during cornering The damping

properties of the shock absorbers are

affected by spring bellow pressure

depending on the load (Fig 4.5)

Fig 4.4: Torsion bars in suspension system

Fig 4.3: Leaf spring assembly

Fig 4.5: Air springs in suspension system

energy that can be dissipated through hydraulic fluid

A shock absorber is basically an oil pump placed between the frame of the car and the wheels The upper mount of the shock connects

to the frame (i.e., the sprung weight), while the lower mount connects to the axle, near the wheel (i.e., the unsprung weight) In a twin-tube

design, one of the most common types of shock absorbers, the upper mount is connected to a piston rod, which in turn is connected to a piston, which in turn sits in a tube filled with hydraulic fluid The inner tube is known as the pressure tube, and the outer tube is known as the reserve tube The reserve tube stores excess hydraulic fluid

When the car wheel encounters a bump in the road and causes the spring to coil and uncoil, the energy of the spring is transferred to the shock absorber through the upper mount, down through the piston rod and into the piston Orifices perforate the piston and allow fluid

to leak through as the piston moves up and down in the pressure tube Because the orifices are relatively tiny, only a small amount of fluid, under great pressure, passes through This slows down the piston, which in turn slows down the spring

Shock absorbers work in two cycles the compression cycle and the extension cycle

The compression cycle occurs as the piston moves downward, compressing the hydraulic fluid in the chamber below the piston The extension cycle occurs as the piston moves toward the top of the pressure tube, compressing the fluid in the chamber above the piston A typical car or light truck will have more resistance during its extension cycle than its compression cycle With that in mind, the compression cycle controls the motion of the vehicle's unsprung weight, while extension controls the heavier, sprung weight

SUSPENSION TYPES

3.1 Dependent Suspensions

3.1.1 Dependent front suspensions: have a

rigid front axle that connects the front

wheels Basically, this looks like a solid bar

under the front of the car, kept in place by leaf

springs and shock absorbers Common on

trucks, dependent front suspensions haven't

been used in mainstream cars for years

Fig 4.6: Shock Absorber

Fig 4.7: Dependent front

3.1.2 Dependent rear suspensions

Contrary to the front version of

this system, many cars are still

designed and built with

dependant (linked) rear

suspension systems

3.2 Independent Suspensions

3.2.1 Independent front Suspensions

So-named because the front wheel's

suspension systems are independant of

each other (except where joined by an

anti-roll bar) These came into existance

around 1930 and have been in use in one

Fig 4.8: Solid-axle, leaf-spring Fig 4.9: Solid-axle, coil-spring

Fig 4.10: Beam Axle

Fig 4.11: Macpherson strut

Fig 4.12: Coil Spring type 1

Fig 4.13: Coil Spring type 2

3.2.2 Independent rear Suspensions

III. NEW WORDS

leaf spring bound horse-drawn carriages torsion bars

stiffness transverse tube trailing arms air springs

orifice perforate dependent suspensions rigid front axle

mainstream contrary independent suspensions so-named

existance wishbone multi-link suspension antiroll bar

Fig 4.14: Double Wishbone Fig 4.15: Multi-link suspension

Fig 4.16: The rear axle on Mitsubishi Pajero

IV. COMPREHENSION QUESTION

1 What system connects each wheel to the car body?

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2 What is/are the primary purpose(s) of the suspension system?

-

3 How to support the weight of the car?

-

4 What are the four basic designs of the springing systems?

-

5 How do coil springs absorb the motion of the wheels?

-

6 How to constitute the leaf springs?

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7 What is/are the property(ies) of the Torsion bars for supplying coil-spring-like performance?

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8 Are the air springs possible to counteract body tilt during cornering?

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9 Is it the same kind of shock absorber assembly at each wheel in a car?

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10 How do the shock absorbers slow down and reduce the magnitude of vibratory motions?

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V. TRUE/FALSE

1 Suspension system connects each wheel to the car body ( True False)

2 The primary purpose of the suspension system is to isolate the car body from the horizontal motion of the wheels as they travel over the rough road surface ( True False)

3 The springs in suspension system support the weight of the car ( True False)

4 Coil springs compress and expand to absorb the motion of the wheels ( True False)

5 Leaf springs consist of several layers of metal bound together to act as a single unit ( True False)

13 A shock absorber is basically an oil source placed between the frame of the car and the wheels ( True False)

14 The sprung weight is the upper mount of the shock connects to the frame ( True False)

15 The unsprung weight is the lower mount connects to the axle, near the wheel ( True False)

16 Shock absorbers work in the compression cycle and the extension cycle ( True False)

17 Dependent Suspensions have a rigid axle that connects the front wheels ( True False)

18 Independent suspensions is named because the wheel's suspension systems are independant of each other ( True False)

19 Engine, clutch, transmission, drive shaft, differential and driven wheels are elements of drivetrain system ( True False)

VI. WORD(S) SELECTIONS

Select ONE word(s) in the below box and fill in the gap in column B with its meaning word in column A

a One type of

spring is

supplied by an

electrically

powered

compressor

c One type of spring consists of several layers of metal bound together to act as

a single unit

e The upper mount of the shock connects

to the frame

g link

i The lower mount

connects to the axle, near the wheel

b A device

controls

wanted spring

motion through

a process

dampening

performance

connects each wheel to the car body

h One type of spring uses twisting properties of a steel bar to provide coil-spring-like

performance

j frustrate