1

Chapter 1

Introduction

1. Introduction

1.1 The basics: steering and suspension

There are many different systems in cars, but they can be broken down into 7 sub-

systems. Those systems are steering, suspension, drive train, emissions, brakes, electronics, and

safety. These can also be broken up into smaller sub systems, and i will go into greater detail with

later posts. This is part one: Steering and Suspension

Let’s start with steering, the system that allows your vehicle to turn. It consists of many parts,

which vary depending on what type of steering your vehicle has. Let’s start with the parts they all

have, which would be the steering wheel, the inner tie rods, and the outer tie rods. (Also known

as tie rod ends) Inner tie rods connect the power steering unit to the outer tie rod ends, which

directly connect to the wheel. The power steering unit, or rack, can be of differing types, it can be

hydraulic, which is traditional, electric, which is seen more on newer cars and hybrid cars, or not

Chapter 1

2

have one at all, manual steering on older cars and trucks. The steering wheel is connected to a

universal joint in the middle of two shafts. A universal joint allows the shaft to spin and be at an

angle at the same time, it acts kind of like your wrist, this allows the steering wheel to be tilted to

fit the driver properly and saves space. The other end of this would connect to the rack. Most

people have hydraulic power steering and those need to have fluid added to them occasionally,

especially if they whine.

The next system would be the suspension. There are many different types of

suspension setups for many different vehicles. I will go over two different types here, basic

suspension on a mid-size car, (Ford Taurus, Chevy Cavalier) and suspension on 4 wheel drive (or

4wd) trucks. On the mid-size cars there is less over all parts. The main part would be the strut

assembly. They consist of a spring, a strut, and an upper strut mount, the strut is a shock

absorber that has the spring mounted to it to save space. The upper strut mount bolts directly to

the body, and has a bearing in it to allow it to rotate when the wheel turns. The strut is bolted on

top to the body of the car and to the steering knuckle on the bottom. The steering knuckle is

where the wheel hub is located and the wheel is bolted on to. The wheel hub also has the brake

assembly bolted to it. The steering knuckle also has the outer tie rod end connected to it so the

wheel can turn. The bottom of the steering knuckle is bolted to a ball joint, which allows the

steering knuckle to rotate and move. And the ball joint is connected to the lower control arm,

which allows the suspension to go up and down. Before i start talking about truck suspension, let

me explain about shocks, struts, and springs. Shocks and struts serve the same purpose; keep the

tire in contact with the road. If cars did not have shocks, they would bounce every time the

smallest bump was hit. They slow down the movement up and down to give a smoother ride.

Springs are there to keep the vehicle up, to support it. They also absorb shock, to keep the car

ride smooth, but without the shocks there to slow them down, it would be a very bumpy bouncy

ride. Four wheel drive trucks have many different suspensions depending on how their drive train

is set up. The rear is the simplest on a solid axle rear end, which means the axle casing goes from

wheel to wheel. The springs are mounted on the casing, and the shocks are mounted to the casing

also. The axle is held on in differing ways depending on the manufacturer. In the front it is very

different from a car. The shocks and springs are separate, unlike a strut assembly. There is an

upper control arm and ball joint where the strut would have mounted. The tie rod end and the ball

Introduction

3

joints still connect to the steering knuckle. There may be a sway bar, which is a long metal rod

which goes from side to side and connects to the steering knuckle or strut with sway bar

links. This lessens the amount of body roll which allows for better handling and more safety.

4

5

Chapter 2

NEED OF PROJECT

2.1 NEED OF PROJECT

In today’s modern world there has been a great progress in the automobile industry.

Various innovations are done and use of high level technology has made it possible to improve

the various sections of automobile industry.

It has been observed that a lot of research and development is going on all the parts of the

automobile. This is done so as to improve the quality, comfort, service and overall performance

of the vehicle.

This project focuses on studying the steering and suspension system of the vehicles and

there analysis by practical application to increase the comfort and safety of the passengers.

6

7

Chapter 3

TYPES OF STEERING

3. TYPES OF STEERING

3.1 Rack and pinion, recirculating ball, worm and sector

Many modern cars use rack and pinion steering mechanisms, where the steering wheel turns the

pinion gear; the pinion moves the rack, which is a linear gear that meshes with the pinion,

converting circular motion into linear motion along the transverse axis of the car (side to side

motion). This motion applies steering torque to the swivel pin ball joints that replaced previously

used kingpins of the stub axle of the steered wheels via tie rods and a short lever arm called the

steering arm. The rack and pinion design has the advantages of a large degree of feedback and

direct steering "feel". A disadvantage is that it is not adjustable, so that when it does wear and

develop lash, the only cure is replacement. Older designs often use the recirculating ball

Chapter 3

8

mechanism, which is still found on trucks and utility vehicles. This is a variation on the older

worm and sector design; the steering column turns a large screw (the "worm gear") which

meshes with a sector of a gear, causing it to rotate about its axis as the worm gear is turned; an

arm attached to the axis of the sector moves the Pitman arm, which is connected to the steering

linkage and thus steers the wheels. The recirculating ball version of this apparatus reduces the

considerable friction by placing large ball bearings between the teeth of the worm and those of

the screw; at either end of the apparatus the balls exit from between the two pieces into a channel

internal to the box which connects them with the other end of the apparatus, thus they are

"recirculate".

The recirculating ball mechanism has the advantage of a much greater mechanical

advantage, so that it was found on larger, heavier vehicles while the rack and pinion was

originally limited to smaller and lighter ones; due to the almost universal adoption of power

steering, however, this is no longer an important advantage, leading to the increasing use of rack

and pinion on newer cars. The recirculating ball design also has a perceptible lash, or "dead spot"

on centre, where a minute turn of the steering wheel in either direction does not move the

steering apparatus; this is easily adjustable via a screw on the end of the steering box to account

for wear, but it cannot be entirely eliminated because it will create excessive internal forces at

other positions and the mechanism will wear very rapidly. This design is still in use in trucks and

other large vehicles, where rapidity of steering and direct feel are less important than robustness,

maintainability, and mechanical advantage.

Other systems for steering exist, but are uncommon on road vehicles. Children's toys and

go-karts often use a very direct linkage in the form of a bell crank (also commonly known as a

Pitman arm) attached directly between the steering column and the steering arms, and the use of

cable-operated steering linkages (e.g. the Capstan and Bowstring mechanism) is also found on

some home-built vehicles such as soapbox cars and recumbent tricycles.

Types Of Steering

9

3.2 Power steering

Power steering helps the driver of a vehicle to steer by directing some of the power to

assist in swivelling the steered road wheels about their steering axes. As vehicles have become

heavier and switched to front wheel drive, particularly using negative offset geometry, along

with increases in tire width and diameter, the effort needed to turn the wheels about their steering

axis has increased, often to the point where major physical exertion would be needed were it not

for power assistance. To alleviate this auto makers have developed power steering systems: or

more correctly power-assisted steering—on road going vehicles there has to be a mechanical

linkage as a fail-safe. There are two types of power steering systems; hydraulic and

electric/electronic. A hydraulic-electric hybrid system is also possible.

3.3 Hydraulic power steering

A hydraulic power steering (HPS) uses hydraulic pressure supplied by an engine-driven pump to

assist the motion of turning the steering wheel. Electric power steering (EPS) is more efficient

than the hydraulic power steering, since the electric power steering motor only needs to provide

Chapter 3

10

assistance when the steering wheel is turned, whereas the hydraulic pump must run constantly. In

EPS, the amount of assistance is easily tunable to the vehicle type, road speed, and even driver

preference. An added benefit is the elimination of environmental hazard posed by leakage and

disposal of hydraulic power steering fluid. In addition, electrical assistance is not lost when the

engine fails or stalls, whereas hydraulic assistance stops working if the engine stops, making the

steering doubly heavy as the driver must now turn not only the very heavy steering—without any

help—but also the power-assistance system itself.

3.4 Speed Sensitive Steering

An outgrowth of power steering is speed sensitive steering, where the steering is heavily

assisted at low speed and lightly assisted at high speed. The auto makers perceive that motorists

might need to make large steering inputs while manoeuvring for parking, but not while traveling

at high speed. The first vehicle with this feature was the Citroën SM with its Diravi

layout[citation needed], although rather than altering the amount of assistance as in modern

power steering systems, it altered the pressure on a centring cam which made the steering wheel

try to "spring" back to the straight-ahead position. Modern speed-sensitive power steering

systems reduce the mechanical or electrical assistance as the vehicle speed increases, giving a

more direct feel. This feature is gradually becoming more common.

3.5 Four-wheel steering

Four-wheel steering (or all-wheel steering) is a system employed by some vehicles to

improve steering response, increase vehicle stability while manoeuvring at high speed, or to

decrease turning radius at low speed.

Types Of Steering

11

3.6 Active four-wheel steering

In an active four-wheel steering system, all four wheels turn at the same time when the

driver steers. In most active four-wheel steering systems, the rear wheels are steered by a

computer and actuators. The rear wheels generally cannot turn as far as the front wheels. There

can be controls to switch off the rear steer and options to steer only the rear wheel independent of

the front wheels. At low speed (e.g. parking) the rear wheels turn opposite of the front wheels,

reducing the turning radius by up to twenty-five percent, sometimes critical for large trucks or

tractors and vehicles with trailers, while at higher speeds both front and rear wheels turn alike

(electronically controlled), so that the vehicle may change position with less yaw, enhancing

straight-line stability. The "Snaking effect" experienced during motorway drives while towing a

travel trailer is thus largely nullified.

Four-wheel steering found its most widespread use in monster trucks, where

manoeuvrability in small arenas is critical, and it is also popular in large farm vehicles and

trucks. Some of the modern European Intercity buses also utilize four-wheel steering to assist

manoeuvrability in bus terminals, and also to improve road stability.

12

13

Chapter 4

ACKERMAN STEERING MECHANISM

4. MECHANISM

Consider a front steering vehicle that is turning left as shown in the fig below. When the

vehicle is moving very slowly there is a kinematic condition between the inner and the outer

wheel that allows them to turn slip free. This condition is called the Ackerman condition and is

expressed by

Cot(outer wheel angle)-cot(inner wheel angle)=w/l

Where w-track width 1 -wheelbase

Chapter 4

14

A device that provides steering to the Ackerman condition is called as Ackerman

steering,Ackerman mechanism or Ackerman geometry.

15

Chapter 5

SUSPENSION

5. SUSPENSION

Suspension system is the term given to the system of springs, shock absorbers and

linkages that connect a vehicle to its wheels. When a tire hits an obstruction, there is a reaction

force and the suspension system tries to reduce this force. The size of this reaction force depends

on the unsprang mass at each wheel assembly. In general, the larger the ratio of sprung weight to

unspring weight, the less the body and vehicle occupants are affected by bumps, dips, and other

surface imperfections such as small bridges. A large sprung weight to unsprings weight ratio can

also impact vehicle control. The main role of suspension system is as follows:

• It supports the weight of the vehicle

• Provides a smoother ride for the passengers

• Protects the vehicle from damage

16

17

Chapter 6

PARTS OF SUSPENSION AND THE SYSTEMS

6. PARTS OF SUSPENSION AND THE SYSTEMS

6.1Parts of suspension

There are three basic components in any suspension system:

• Springs

• Dampers

• Anti-sway bars

We are not using Anti-sway bar in our car since we don’t require it.

Chapter 6

18

6.2 Available suspension systems in the market

1 Mechanical Suspension System:

i) Independent Suspension

• Leaf Spring Suspension

• MacPherson Suspension

• Wishbone Suspension

ii) Dependent Suspension

• Rigid Axle Suspension

2. Electric Suspension System

3. Magnetic Suspension System

19

Chapter 7

SELECTION OF SUITABLE SUSPENSION SYSTEM

7. SELECTION OF SUITABLE SUSPENSION SYSTEM

The selection of the suspension system which will best satisfy the requirements of an

ATV was carried out. Out of the many available suspension systems in the market, the Double

Wishbone Suspension System was selected for the ATV. This selection was done based on the

following basic parameters:

1. Load bearing capacity

2. Flexibility

3. Cost

4. Technical aspects: Camber, Stiffness, Rolling

5. Availability of parts and components

Chapter 7

20

III. DESIGN

The design procedure for the chosen suspension system is divided into two stages:

1. Primary design:

• Basic design and development of Suspension System components

• Modified design parameters based on approximation of Dynamic

Conditions

• Static testing and analysis

2. Secondary design

• Mathematical modeling of finalized concept ATV

• Dynamic testing and analysis

• Modification of Design Parameters based on Dynamic Testing

results

The following components are to be designed:

• Knuckle

• Wishbones

• Suspension spring.

MAJOR TYPES OF SUSPENSION SYSTEM

7.1Passive suspension

Passive suspensions as shown in Fig.2.a. can only achieve good ride comfort or good road

holding since these two criteria conflict each other and necessitate different spring and damper

characteristics. While semi-active suspense with their variable damping characteristics and low

power consumption, on systems offer a considerable improvement, (see Fig.2.b.)

Selection Of Suitable Suspension System

21

A significant improvement can be achieved by using of an active suspension system, (see

Fig.2.c.) which supplied a higher power from an external source to generate suspension forces to

achieve the desired performance. The force may be a function of several variables which can be

measured or remotely sensed by various sensors, so the flexibility can be greatly increased.

Fig.2.a. Passive suspension system

7.2 Semi active suspension system

With rapid advances in electronic technologies , The development of design techniques

for the synthesis of active vehicle suspension systems has been an active area of research over the

last two decades to achieve a better compromise during various driving conditions.

7.3 Active suspension system

Automotive companies are competing to make more developed cars, while comfort of

passengers is an important demand and everyone expects from industries to improve it day by

day. Therefore, in order to provide a smooth ride and satisfy passengers comfort, designing a

modern suspension system is mandatory. A good and efficient suspension system must rapidly

Chapter 7

22

absorb road shocks and then return to its normal position, slowly. However, in a passive

suspension system with a soft spring, movements will be high, while using hard springs causes

hard moves due to road roughness [12-18]. Therefore, it’s difficult to achieve good performance

with a passive suspension system.

23

Chapter 8

CONCLUSION

Our aim to design a system to steer and help to absorb shock on uneven and dangerous

roads is fulfilled by The Design and Analysis of the Steering and Suspension for the ATV.

We are glad to design and also Analyze our design for various forces and successfully be

able to implement the same in our project, giving in return a safe mechanism for off roads.

24

References

25

REFERENCES

Theory Of Machines by R.S. Khurmi, J.K. Gupta

En.wikipedia.org/automotive suspension

En.wikipedia.org/vehicle dynamics

Pdf report on design and analysis from www.calvin.edu/academic

Design and Fabrication of a Go Kart vehicle with improved suspension

dynamics

A textbook of Theory Of machines – J.S. Brar, R.K. Bansal.

The Theory of machines : McKay, Robert Ferrier.