CHAPTER 1

INTRODUCTION

1.1 Background of Study

The Shell Eco-Marathon is an educational project that challenges the student teams to
design and build the most energy-efficient vehicle to compete against other teams’
vehicles. The principle of the Shell Eco-Marathon is to design and build a vehicle
that uses least amount of fuel to travel to the farthest distance.

Malaysia will become the host for the Asian programme for 3 consecutive years from
2010, thereafter it will be brought to another Asian country for the subsequent 3 years.
For 2010 edition, the Shell Eco-marathon will be held on 8-10 July 2010 at the Sepang
International Circuit in Kuala Lumpur, Malaysia.

Figure 1.1: Sepang International Circuit where the race will take place.

In vehicle dynamic, some factors that influence fuel consumption of the vehicle are:
1. Engine performance
2. Drag force (effectively influence when vehicle at high speed)
3. Rolling force(vehicle at low speed)

Running chassis system is one of the most important parts in a vehicle to control the
movement and provide ride comfort of the vehicle on the road. The parts include in this

1
system are steering, brake, wheel and suspension. Running chassis system of vehicle will
increase the usage of fuel when the rolling force between tire and road is high. The
factor influences the rolling force are weight of the vehicle and the type of tire and wheel
used. The vehicle with larger weight will has higher rolling force.

The project will be designed and selection of the steering system will based on the rule
and regulation of the competition. The steering system also influences the ride comfort
of the vehicle during driving especially on bad road condition. The precision of the
steering also has to be considered in designing the steering system. After design and
select the steering system that will be used, the students together with other group
member have to fabricate the car. The car needs to be tested and analyzed to get the best
performance.

1.2 Problem Statement

The Shell Eco-marathon challenges students around the world to design, build, and test
vehicles that travel further using less energy. Steering system should be design as light
and simple as possible in order to reduce the weight of the vehicle. The requirement of
the Shell Eco-Marathon state the turning radius must be sufficient to enable safe
overtaking as well as negotiating the curvature of the track. During cornering, the
steering system determines whether the vehicle will have slipping or in case of oversteer
or understeer.

The crude oil in the earth is depleting from time to time and the price of fuel also
increases, this project is an innovation to design a vehicle that has low fuel consumption.
Since Malaysia will be the host for Shell Eco-marathon for the first time in 2010,
Universiti Teknologi PETRONAS has responsibility to ensure our country can compete
with other team from other country especially in Asia region.

2
1.3 Objective

The objective of this project is to design and fabricate the lightest and simplest steering
system in order to reduce the weight of the vehicle and meet the sufficient turning radius
to be participated in Shell Eco-marathon 2010.

1.4 Scope of study

The project focuses on one part of running chassis which is steering system. The steering
system has to be designed as light and simple as possible. The design should meets the
competition rule which is the vehicle has sufficient turning radius to enable safe
overtaking as well as negotiating the curvature of the track. The steering system is
considered as an assembly consisting of steering wheel, steering column, steering shaft,
steering gear box and steering linkages. After designing the steering system, the
simulation has to be done in order to ensure it can work and some steering behaviors will
be analyzed such as kinematic steering ratio and maximum front steer wheel angle. The
complete steering system has to be fabricated and installed on the complete car. The car
has to be tested whether it meets the requirement to participate in Shell Eco-Marathon
2010.

3
 CHAPTER 2
LITERATURE REVIEW

The current European Shell Eco-marathon record for a combustion engine entry was set
in 2004 by the team from Lycée La Joliverie (France) at 3,410 km on the equivalent of a
single liter of fuel. For prototype vehicles using fuel cells, the record is even more
impressive. In 2005, the hydrogen-powered vehicle built by Swiss team ETH Zurich
achieved a projected 3,836 km on the equivalent of a single liter of fuel. This is the
equivalent of driving from Paris to Moscow [1].

The top performing vehicles are specially designed for high efficiency. Some vehicles
use a coast or burn technique whereby they briefly accelerate from 16 to 32km/h and
then switch the engine off and coast for approximately 2 minutes until the speed drops
back down to 16 km/h. This process is repeated resulting in average speed of 24km/h for
the course [2]. Typically the vehicles have:
 Automobile drag coefficients (Cd) less than 0.1
 Rolling resistance coefficients less than 0.0015
 Weight without driver less than 45kg
 Engine efficiency less than 200 s.f.c. (cc/bhp/hr)

All the previous teams tried to fabricate the car including the steering system as light as
possible. They use light material such as aluminium and carbon fiber to minimize the
weight of the vehicle. The Dalhousie Supermileage team from Dalhousie University,
Canada fabricated the running chassis components from 6061 T6 Aluminium round and
square tubing [3]. Pac-Car ETH Zurich from Switzerland used advanced materials which
are polyurethane foam and carbon-epoxy sandwich as their running chassis material [4].

For steering system, the previous team used simple link-joint mechanism and rack and
pinion system. The example of teams was using simple link-joint mechanism are

4
Cal Poly Supermileage from California Polytechnic State University, USA[5], Dalhousie
Supermileage[3] and National University of Singapore[6]. The example of team was
using rack and pinion system is Northern Arizona University [7].

Figure 2.1: Rack and pinion system by Northern Arizona University

Figure 2.2: Simple link and joint mechanism by Cal Poly Supermileage

For steering wheel, the previous teams used joystick and handlebar. Most of the teams
used handlebar as their steering wheel such as National University of Singapore, Cal
Poly Supermileage and University of British Columbia[8]. Only Pac-Car from ETH
Zurich used joystick as the steering wheel [4].

5
Most the previous teams were using front wheel steer. But there are some teams were
using rear wheel steer which are Cedarville University[9] and Pac-CarII from ETH
Zurich.

The Shell Eco-Marathon also become as an academic coursework for some academic
institution such as National University of Singapore. The Shell Eco-Marathon is
integrated into students’ coursework as an optional module, again for third- and fourth-
year students. The project is also a part of the studies programme at the Politecnico di
Torino Italy, where time spent on the project is taken into consideration as part of
students’ internship requirements [6].

6
 CHAPTER 3
THEORY

3.1 Ackermann Steering Geometry

The main conflicts entering into the design of steering systems concern the isolation
from feedback of road shocks, while retaining sufficient road fell for positive control and
striking an acceptable compromise between light steering efforts when parking and
sufficient weight at speed. Much of the dynamic effects attributed by customers to the
steering system are the result of suspension geometry and wheel control factors,
especially in regard to toe settings and dynamic toe changes occurring at the front, rear
or both [10].

The first approach to obtaining the best steering control and handling behavior might be
to attempt to design the steering system so that the two front wheels run with equal slip
angles during cornering. Initially, it might be assumed that the way to achieve this would
be to design the steering system with Ackermann geometry as shown in figure 3.1
below. Ackermann steering geometry is a geometric arrangement of linkages in the
steering of a vehicle designed to solve the problem of wheels on the inside and outside
of a turn needing to trace out circles of different radii. However, the principle of
Ackermann steering geometry assumes a vehicle cornering with its tires running at zero
slip angles [10].

l
tan  o 
t
R
2
Rs
l
tan  i  Figure 3.1: Ackermann
t
R steering geometry
2

7
In order to avoid skidding of tires when the vehicle is taking a turn, it is necessary that
both the inner and outside wheel turn on arc which has a common centre of turn [11].
Slip angle as shown in Figure 3.2 below is the angular difference between the direction
the tire contact patch with the road is pointing and the direction of the wheel.

Figure 3.2: Slip angle

Figure 3.3: Variations of the Ackermann steering geometry

In ideal no slip situations, Ackermann steering would make perfect sense, but with issues
such as slip angle and varying tire coefficients (due to temperature, vehicle speed,
steering angle, etc), several variations of the Ackermann steering geometry have been
used instead as shown in Figure 3.3 above. True Ackermann geometry would be a
situation as seen by Figure 3.3 (a) where both wheels turn on arcs parallel to one
another. As can been seen, the slip angle of the inner wheel is greater than the outside
wheel. Parallel Ackermann steering is defined by having the same slip angle on both the
inner and outside wheel (Figure 3.3 (b)). Reverse Ackermann is the exact opposite of

8
true Ackermann geometry as the outside wheel is at a higher slip angle than the inner
wheel.

At low speeds when the tires have minimal tire shear losses on dry, clean pavement, the
true Ackermann steering geometry is beneficial as the tires are in almost a perfect
situation of minute slip angle. Parallel or reverse Ackermann in this scenario would push
(or understeer) the front of the car away from the desired path. In both situations, the
inner tire contributes to this push similarly to a centrifugal force.

At high lateral accelerations, true Ackermann becomes disadvantageous as loads on the

outside wheel increase and the greater slip angle of the inner tire creates higher tire
temperatures and slows down the car due to tire drag. The inner tire has also surpassed
the maximum slip angle of grip assuming the outside tire is already at the optimum slip
angle. Parallel or reverse setups are more advantageous in this situation as both the inner
and outside tires still have lateral grip. Reverse Ackermann steering can even be more
beneficial than the parallel Ackermann geometry since the outside tire (which currently
has more loads due to weight transfer) is at the optimum slip angle and the inner is at a
lower slip angle with fewer grips. This in turn allows the inner tire to have grip but less
than the outside tire, decreasing the effects of understeer [12].

During the development of a vehicle, the understeer or oversteer characteristics typically

will be quantified in order to ensure the vehicle in safe condition during cornering. The
original definition of understeer and oversteer was proposed by Olley[10], was based on
relative sizes of front and rear slip angles. Understeer was defined as front wheel slip
angle being larger than rear wheel and oversteer was defined as front wheel slip angles
being smaller than rear wheel. The effect of slip angle on vehicle handlings that causes
the understeer or oversteer is shown in Figure 3.4.

9
 Figure 3.4: Effect of slip angle on vehicle handling

3.2 Steering Behaviour

The theoretical turning radius, Rs is the radius of circle which the outer wheel traces with
the largest steering angle. The turning radius of vehicle should be as small as possible to
make it easy to turn and park [13]. The formula:

l ………………….(3.1)
Rs  d
sin  o

Where δo is outer wheel angle, l is wheelbase and d is kingpin offset. Since kingpin
offset is very small compared to wheelbase, the equation 3.1 can be written as:

l ……………………(3.2)
Rs 
sin  o

A typical passenger car turning radius is normally between 5.5m and 6.5m with SUV
turning radius going out as much as 7.5m to 8.5m. In the record, the London taxi has a
tiny 4m turning radius to allow it to do U-turns in the narrow London streets [14].

The kinematic steering ratio, is is one of the important characteristic for steering system
that refers to the ratio of the steering wheel angle, δH to the mean steer angle, δm of a pair
of steered wheels.

10
 o  i …………………….(3.3)
m 
2

H …………………….(3.4)
is 
m

In general, the steering ratio of the vehicles varies from 13:1 to 16:1. For racing cars, the
steering ratio is normally much smaller than for passenger cars that is closer to 1:1.This
is because the racing drivers need to get fuller deflection into the steering as quickly as
possible

In practice, a parallel steering-in of the front wheels (real layout) is targeted up to a

steering angle of about 20° and only with larger steering angles, an approximation of the
Ackermann condition is implemented [15].

Figure 3.5: Toe-out angle as a function of the mean steering angle for static and real
steering element layout

11
3.3 Self-Centering

The smooth operation of steering depends much upon the wheel alignment which means
the vehicle has self centering [12]. The important alignment factors are caster angle,
camber angle and kingpin inclination. The caster angle is the angle formed by the
forward or backward tilt of the kingpin centre line from vertical when viewed from the
side of the wheel. The purposes of caster angle are to maintain directional stability and
control, to increase steering return ability and to reduce the driver’s effort to turn the
vehicle.
,v

Figure 3.6: Caster angle

The chamber angle is the angle between the centre of the tire and the vertical line when
viewed from the front. Kingpin inclination is the angle between the centre line of the
kingpin and the vertical line. The purposes of kingpin inclination are to provide
directional stability along with the caster angle and helps in self-centering of wheels
after taking a turn.

λ
δ

d
Figure 3.7: Camber angle and kingpin inclination

12
3.4 Mechanical Linkage

A mechanical linkage is a series of rigid links connected with joints to form a closed
chain or a series of closed chains. Each link has two or more joints and the joints have
various degrees of freedom(DOF) to allow motion between the links. A linkage is called
a mechanism if two or more links are movable with respect to a fixed link. Mechanical
linkages are usually designed to take an input and produce a different output, altering the
motion, velocity, acceleration, and applying mechanical advantage.

The most common linkages have one degree of freedom(DOF), meaning that there is
one input motion that produces one output motion. Most linkages are also planar,
meaning all the motion takes place in one plane. Spatial linkages (non-planar) are more
difficult to design and therefore not as common.
Kutzbach-Gruebler's equation is used to calculate the degrees of freedom of linkages.
The number of degrees of freedom of a linkage is also called its mobility.

The general form of the Kutzbach-Gruebler equation for planar linkages involving more
complex joints:
……………………(3.5)

and for spatial linkages (linkages involving 3D motion):

…………………….(3.6)

Where:
= mobility (degrees of freedom)
= number of links (including a single ground link)
= number of total joints, regardless of connectivity or degree-of-freedom

= sum of each joint's individual degree of freedom

13
Mechanisms with one degree of freedom are termed constrained mechanisms. As
mentioned, most mechanisms used in machines are constrained. Mechanism with zero,
or negative degree of freedom are termed locked mechanisms. These mechanisms are
unable to move and form a structure. Mechanisms with more than one degree of freedom
are termed unconstrained mechanisms. These mechanisms need more than one driver to
precisely operate them [16].

14
 CHAPTER 4
METHADOLOGY

4.1 Overview

The methodology is formulated based on Morris Asimow’s morphology of design.

According to the scope of project, project activities will start from problem definition
until design communication. Final output of this project is detail design for prototype
fabrication. Fabrication of fully-working prototype is out of the project scope.
Project timeline is shown in the Gantt Chart attached in Appendix . Detail methodology
is shown in Figure 4.1 and 4.2.

Figure 4.1: Flow chart of methodology FYP I

15
Figure 4.2: Flow chart of methodology FYP II

16
As shown in the flow chart of methodology in figure 4.1 and 4.2, Table 4.1 below
indicates the expected output for each design phase:

Table 4.1: Expected output for each design phase

Project Phase Expected Output
Problem Definition  PDS document
 Literature review summaries
Conceptual Design
 Sketches / simple CAD models
 Geometric layout
 CAD model
Embodiment Design
 Simulation model
Development
 Simulation results
 Proof of concept model
 Detail drawings
Detail Design
 Bill of materials(BOM)
Development
 Detailed product specification
Design Fabrication  Final product
Design Analysis and
 Approval of model
Testing
 Presentation slideshow
Design Communication
 Report

4.2 Problem Identification

Understand the principle of Shell Eco-marathon and the rule and regulation about
steering system to participate in the competition. Identify the objective, problem
statement, job scope and the significant of the project to the student and university.

17
 Figure 4.3: Measuring the radius of turn in Sepang circuit

All the turn at Sepang circuit has been analyzed to know the radius in order to ensure the
steering system will be designed has sufficient turning radius. The data is tabulated in
table 4.2 below.

Table 4.2: Detail of turn in Sepang Circuit

Turn Length(m) Angle Radius(m)

1 125.2 200o 35.87
2 88.2 150 o 33.70
3 347.9 97 o 205.50
4 36.6 60 o 34.95
5 268.8 123 o 125.21
6 177.4 90 o 112.94
7 31.5 10 o 180.48
8 13.8 25 o 31.63
9 166.0 32 o 297.22

Based on the table 4.2 above, the smallest radius is approximately about 31.63m at turn
number 8.

18
The output of problem definition process is a control document named as Product
Design Specification (PDS). The PDS for the steering system is as follows:
General Features:
a. It should be light weight
b. Steering geometry should not get affect by bad road conditions
c. It must be easily operateable
d. Minimum space needed

For the purpose of this project, the specific requirements are identified in order to
achieve the objective of this project. The requirements are:
a. Front wheel steer
b. Turning radius need to be smaller than radius of turn in Sepang circuit: 4.0-6.5m
c. Steering ratio is closer 1:1
d. Maximum angle for outer wheel 30 o. This value will be ensured the car will has
turning radius between 4.0m. See Appendix for calculation.
e. Follow the Ackermann steering geometry.
f. The difference between angle for inner wheel and outer wheel small as possible
g. Light to turn the wheel(kingpin inclination angle, castor angle and camber angle
is equal to zero)

4.3 Conceptual Design

Before producing the design concepts, the research was conducted to find out about
other teams that have been participated in Shell Eco-marathon and their design. The
research was conducted by reading and searching the previous teams and organizers’
website. The next of step of this phase is to produce design concepts that would perform
as required.

The morphological chart was used to uncover combination of ideas that comprise design
concept that might not normally be generated.

19
 Table 4.3: Morphological chart for design concept generation
Part Function Concept 1 Concept2 Concept 3 Concept 4

Steering wheel -Steer input

Steering column -Tansmit steer

input

Steering column -Hold the

holder steering cloumn

Tie rod -Connect

steering column
to spindle

Spindle -Steer the

wheel

20
By combining concepts from the morphological chart, four (4) conceptual designs are
generated as follows:

Design 1 Design 2

Figure 4.4: CAD model for Design 1 Figure 4.5: CAD model for Design 2

Design 3 Design 4

Figure 4.6: CAD model for Design 3 Figure 4.7: CAD model for Design 4

21
4.4 Embodiment Design Development

Use CATIA software to design the conceptual steering system. Overall four alternatives
steering system has been designed. Next, all the alternatives steering system was
simulated by using ADAMS software to analyze the mechanism and the steering
behavior. Based on the result obtained from ADAMS, only one alternative steering
system was selected by using weighted property index method to be used in the
competition. The design was selected has been optimized to increase the maximum angle
for inner and outer wheel in order to ensure the sufficient of turning radius. There are
three options of materials that can be used in fabricating all parts of steering system
which are aluminium, carbon fiber and steel and only one material was selected by using
weighted property index method.

4.5 Detail Design Development

Provide the detail drawing for selected steering system by using CATIA software. The
finalized drawing was simulated in ADAMS and the result has been reviewed in order to
ensure it is follow the Product Design Specification(PDS).

4.6 Design Fabrication

Fabricate the steering components together with the frame of the car. Tolerance is the
important criteria in machining process in order to ensure that the steering components
can be assembled with other part of the car.

4.7 Design Analysis and Testing

Test the steering system to control the movement of the complete vehicle. The problems
rose from the steering system such as mobility, convenience and workability has been
analyzed. The comparison between the actual results with the simulation result has been
made.

22
 CHAPTER 5
RESULTS AND DISCUSSION

5.1 Design Development

The basic of the steering system as shown in Figure 5.1 below:

Tie rod
arm/Spindle

Wheel

Steering wheel Steering column

Figure 5.1: Basic steering system

Base on the Figure 5.1 above, the parts of steering system includes steering wheel,
steering column, tie rod, steering rack, tie rod arm and spindle.

Four designs have been proposed in the beginning. After make some analysis, simulation
and comparison between all the designs, only one design will be selected. Table 5.1
shows the designs have been proposed.

23
 Table 5.1: Designs were proposed in the beginning for steering system

Design CAD Drawing Kinematic Drawing Validate Description

1 The mechanism has six Use simple link
links(n=6), three rotational mechanism. Four ball
joints(A, F, G) and four joint is used to connect
spherical joint(B, C, D, E). The steering column with
number of DOF for this spindle.
mechanism: j
m  6( n  j  1)   f i
n 1

 6(6  7  1)  (3  1  4  3)
3
Since DOF >0, the mechanisms
is unconstrained.
2 The mechanism has six Use simple link
links(n=6), three rotational mechanism. The
joints(A, F, G) and four mechanism almost
spherical joint(B, C, D, E which similar with go-kart
C and D is positioned at same steering system. The tie
place). The number of DOF for rod is connected
this mechanism: j directly to hub axle by
m  6( n  j  1)   f i using ball joint.
n 1

 6(6  7  1)  (3  1  4  3)
3
Since DOF >0, the mechanisms
is unconstrained.

24
3 The mechanism has six Use simple link
links(n=6), three rotational mechanism. Slightly
joints(A, F, G) and four similar with design1.
spherical joint(B, C, D, E). The But the connection
number of DOF for this position of the tie rod
mechanism: j below the steering
m  6( n  j  1)   f i column.
n 1

 6(6  7  1)  (3  1  4  3)
3
Since DOF >0, the mechanisms
is unconstrained.
4 The mechanism in has six Use simple link
links(n=6), three rotational mechanism. Four ball
joints(A, F, G) and four joint is used to connect
spherical joint(B, C, D, E). The steering column with
number of DOF for this spindle. Most of go-
mechanism is j kart use this design.
m  6( n  j  1)   f i
n 1

 6(6  7  1)  (3  1  4  3)
3
Since DOF >0, the mechanisms
is unconstrained.

25
5.2 Simulation

All the designs have been analyzed by using ADAMS to ensure that the design can
function well. The motion was set in the steering column to simulate the mechanism.
The simulation will show whether the design has functionally worked or not. By using
ADAMS Postprocessor, the data of simulation can be viewed in graph and worksheet.

Figure 5.2: Simulation of the design for steering system in ADAMS view

5.2.1 Simulation Result

Design1

Figure 5.3: Graph of the front steer wheel angle versus steering wheel angle for design 1

26
Design 2

Figure 5.4: Graph of the front steer wheel angle versus steering wheel angle for design 2

Design 3

Figure 5.5: Graph of the front steer wheel angle versus steering wheel angle for design 3

27
Design 4

Figure 5.6: Graph of the front steer wheel angle versus steering wheel angle for design 4

The result of ADAMS simulation for all design is tabulated in Table 5.2 below:

Table 5.2: Result of ADAMS simulation for all design

Design 1 2 3 4
Angle outer 30 30 30 30
wheel, δo
Inner wheel, δi 18.8 Disable Disable 23.6
Steering wheel 48 Disable Disable 49.5
angle, δH
‫׀‬δi -δo‫׀‬ 11.2o - - 6.4 o
Steering ratio 1.97 - - 2.00
Turning 4.0 - - 4.0
radius(m)
Direction Same Same Opposite Same
orientation with orientation with orientation of orientation with
steering wheel steering wheel steering wheel steering wheel
Ackermann Reverse True Reverse Reverse

28
 5.2.2 Selection of The Steering System

Design Selection by using weighted property index and weight factor for steering design
selection as shown in Table 5.3 below.

Table 5.3: Weight Factor for steering design selection

Criteria Weight factor

Functionality 0.40
Steering ratio 0.25
Difference between angle for 0.15
inner wheel and outer wheel,
‫׀‬δi -δo‫׀‬
Ackermann geometry 0.10
Space 0.10

The weight factor is determined based on Product Design Specification(PDS). The

highest weight factor is functionality, followed by the steering ratio, the difference
between angle for inner wheel and outer wheel, the type of Ackermann geometry and the
lowest weight factor is the space required.

Table 5.4: Weight property index for steering design selection

Design 1 Design 2 Design 3 Design 4

Score Rating Score Rating Score Rating Score Rating
Functionality 8 3.20 5 2.00 3 1.20 8 3.20
Steering ratio 9 2.25 2 0.50 2 0.50 8 2.00
Difference between 8 1.20 2 0.30 2 0.30 9 1.35
angle for inner
wheel and outer
wheel, ‫׀‬δi -δo‫׀‬
Ackermann 7 0.70 9 0.90 7 0.70 7 0.70
geometry
Space 9 0.90 8 0.80 8 0.80 7 0.70
Weight property 8.25 4.50 3.50 7.95
index

29
The weighted property matrix as shown in Table 5.4 is applied to compare the design 1,
2, 3 and 4. Since the Table 5.4 shows the design 1 has the highest weight property index,
it will be chosen. After the selection of the steering system design, the optimizations of
the steering system have been done to ensure that the difference between angle for inner
wheel and outer wheel is smaller as possible and the steering ratio is closer to 1.

5.3.Material Selection

Material selection is important in order to produce the new product. There are
many materials in this world and every materials exist has their own properties and
characteristic. In general, each new product is invented to satisfy the functions they
need.

In order for the steering system to be light as possible and be able to perform well,
several properties of the steering system’s part have to be considered. In the selected
design, the steering system consists of three main parts which are steering column, tie
rod and spindle. The properties which will be needed in the three main parts are as
below:

Table 5.5: Properties for all steering system parts must have

Part Steering Column Tie Rod Spindle

Properties  Lightweight  Lightweight  Lightweight but
 Can absorb a great  Can absorb a great strong and sturdy
amount of impact amount of impact  Have high value of
 Machinable  Machinable hardness
 Low cost  Low cost  Weldable
 Long lifetime  Long lifetime  Machinable
 Long lifetime and
durable
 Able to absorb
huge pressure and
vibrations
 Low cost

30
With all the properties listed out, the further research is conducted on the materials
which will be used to produce all the parts. In order to shorten the list of materials,
several mechanical properties have to be met as shown in Table 5.6 below.

Table 5.6: Essential mechanical properties that the materials must have
Part Steering Column Tie Rod Spindle
Mechanical  Low density  Low density  Low density
Properties  High modulus of  High modulus of  High modulus of
elasticity elasticity elasticity
 Non-corrosive  Non-corrosive  High ductility
 High ductility  High ductility  High toughness
 High toughness  High toughness  Weldability
 Non-corrosive

Based on several aspects and observations, the best three materials that can be used to
produced all the parts have narrowed down. The materials with its mechanical properties
are mentioned in the Table 5.7 below.

Table 5.7: Mechanical properties for Carbon Fiber, Aluminium Alloy and Stainless Steel

Material Carbon Fiber Aluminium Stainless Steel

Alloy
Density (kg/m3) 1780 2600-2800 6920-9130
Elastic Modulus(GPa) 230 69-79 190-200
Yield Strength(MPa) - 35-124 107-415
Tensile Strength(MPa) 2500-4500 90-228 415-725
Ductility(%elongation) 0.6-2.0 6-40 5-40
Fracture 1.6-9.0 24-44 76
Toughness(MPa√m)

Machinability Very abrasive, Very easy to Depend on

difficult to machine, tend to ductility and
machine. Require has poor surface hardness. If too
careful handling finish ductile, chip
and removal of formation can
debris to avoid produce built-up

31
 contact with edge, leading to
inhaling of the poor surface finish,
fibers if too hard, it can
cause abrasive
wear of the tool
Weldability Cannot be welded, Need special skill Easy to be welded
can be joined to and equipment to
other parts by be welded
using screw.
Price Expensive Moderate Cheap

5.3.1 Weighted Decision Matrix for steering column and tie rod

Since the properties which will be needed to produce steering column and tie rod almost
same, the material will be used is same.

Table 5.8: Weight property index for material selection for steering column and tie rod

Carbon Fiber Aluminium Alloy Stainless Steel

Factor Weight Score Rating Score Rating Score Rating

Density 0.30 9 2.70 8 2.40 7 2.10

Machinable 0.20 5 1.00 9 1.80 8 1.60

Non- 0.15 9 1.35 9 1.35 3 0.45

corrosive

Ductility 0.15 9 1.35 7 1.05 8 1.20

Toughness 0.15 4 0.60 7 1.05 8 1.20

Cost 0.05 2 0.10 8 0.40 9 0.45

7.10 8.05 7.00

32
The weighted property matrix is applied to compare the materials which are carbon
fiber, aluminium alloy and stainless steel that is possible to be used for fabricating
steering column and tie rod. Since the table 5.8 shows that aluminium alloy has the
highest weight property index, aluminium alloy will be chosen as the material for the
steering column and tie rod.

5.3.2 Weighted Decision Matrix for spindle

Table 5.9: Weight property index for material selection for spindle

Carbon Fiber Aluminium Alloy Stainless Steel

Factor Weight Score Rating Score Rating Score Rating

Density 0.25 9 2.25 8 2.00 7 1.75

Ductility 0.20 9 1.80 7 1.40 8 1.60

Toughness 0.20 9 1.80 7 1.80 8 1.60

Weldable 0.10 0 0.00 5 0.50 9 0.90

Machinable 0.10 5 0.50 9 0.50 8 0.80

Non- 0.10 9 0.90 9 0.90 6 0.60

corrosive

Cost 0.05 2 0.20 8 0.40 9 0.45

Weight property index 7.45 7.50 7.60

The weighted property matrix is applied to compare the materials which are carbon
fiber, aluminium alloy and stainless steel that is possible to be used for fabricating
spindle. Since the Table 5.9 shown that stainless steel has the highest weight property
index, stainless steel will be chosen as the material for the spindle.

33
5.4 Optimization

Design 1 will be optimized in order to ensure that the steering system meet the product
design specification (PDS) which are steering ratio is closer to 1 and the difference
between angle for inner wheel and outer wheel small as possible

Figure 5.7: Optimization of the design

The equation for arc length, s=rθ ……………….(5.1)

Where r is radius and θ is angle in radian. By varying r, the arc length will change.
Hence position of the tie rod also changes.

2
From Figure 5.7: r  k 2   L  …..…………..(5.2)
2

Where k is perpendicular distance between tie rod with axis of steering column’s
rotation and L is distance between two tie rods. In order to meet the requirements, some
value for k and L were choose in designing the steering column and will be going to
simulation.

34
 Table 5.10: The result of ADAMS simulation for various value of k and L
k(mm) L(mm) Outer Inner Steering Difference between Steering ratio, i
angle, angle, wheel angle for inner
δo δi angle, δH wheel and outer
wheel, ‫׀‬δi -δo‫׀‬
35 30 30.0 o 18.9 o 48.0 o 11.1 o 1.963190184
35 35 30.0 o 18.9 o 47.6 o 11.1 o 1.946830266
35 40 30.0 o 17.7 o 47.0 o 12.3 o 1.970649895
35 45 30.0 o 17.0 o 47.0 o 13.0 o 2.000000000
35 50 30.0 o 15.0 o 44.0 o 15.0 o 1.955555556
40 30 30.0 o 21.0 o 41.2 o 9.0 o 1.615686275
40 35 30.0 o 19.8 o 41.0 o 10.2 o 1.646586345
40 40 30.0 o 19.2 o 40.5 o 10.8 o 1.646341463
40 45 30.0 o 18.1 o 40.0 o 11.9 o 1.663201663
40 50 30.0 o 17.5 o 40.0 o 12.5 o 1.684210526
45 30 30.0 o 23.0 o 40.0 o 7.0 o 1.509433962
45 35 30.0 o 22.3 o 38.0 o 7.7 o 1.453154876
45 40 30.0 o 21.6 o 37.3 o 8.4 o 1.445736434
45 45 30.0 o 21.0 o 37.3 o 9.0 o 1.462745098
45 50 30.0 o 20.4 o 37.2 o 9.6 o 1.476190476
50 30 30.0 o 24.2 o 35.0 o 5.8 o 1.291512915
50 35 30.0 o 23.8 o 34.5 o 6.2 o 1.282527881
50 40 30.0 o 22.3 o 33.6 o 7.7 o 1.284894837
50 45 30.0 o 21.5 o 33.6 o 8.5 o 1.304854369
50 50 30.0 o 20.8 o 32.5 o 9.2 o 1.279527559
55 30 30.0 o 24.7 o 31.8 o 5.3 o 1.162705667
55 35 30.0 o 24.2 o 31.6 o 5.8 o 1.166051661
55 40 30.0 o 23.8 o 31.2 o 6.2 o 1.159851301
55 45 30.0 o 23.5 o 31.0 o 6.5 o 1.158878505
55 50 30.0 o 23.0 o 31.0 o 7.0 o 1.169811321

From the Table 5.10 above, by increasing the k value with maintaining the value of L,
the maximum inner angle is increasing. But when increasing L value with maintaining
the value of k, the maximum inner angle is decreasing. By changing the k and L value, it
will affect the difference between angle for inner wheel and outer wheel and also
steering ratio. Based on the table above, the best value of k is 55mm and L is 30mm.

35
The detail result of design 1 with k=55mm and L=30mm is shown in Figure 5.8 and
Table 5.11 below.

Figure 5.8: Graph of the front steer wheel angle versus steering wheel angle for
design 1 with k=55mm and L=30mm

Table 5.11: The simulation result for design 1 with k=55mm and L=30mm
Steering Outer Inner Mean wheel Difference between angle
wheel angle, angle, δo angle, δi angle. δmean for inner wheel and outer
δH wheel, ‫׀‬δi -δo‫׀‬
0o 0o 0o 0o 0o
5o 4.4 o 4.4 o 4.40 o 0o
10 o 9.4 o 9.2 o 9.30 o 0.2 o
15 o 13.6 o 12.6 o 13.10 o 1.0 o
20 o 18.8 o 16.8 o 17.80 o 2.0 o
25 o 23.0 o 20.0 o 21.50 o 3.0 o
30 o 28.2 o 23.7 o 25.95 o 4.5 o
33 o 30.0 o 24.7 o 27.35 o 5.3 o

36
5.5 Design Analysis

When all the steering system’s parts are completely fabricated, it has been assembled to
complete vehicle. The actual result as shown in Table 5.12 and Figure 5.9 below

Table 5.12: The actual result

Steering Outer Inner Mean wheel Difference between angle
angle, δH angle, δo angle, δi angle. δmean for inner wheel and outer
wheel, ‫׀‬δi -δo‫׀‬
0o 0o 0o 0o 0o
5o 3o 3o 3.00 o 0o
10 o 7o 6o 6.50 o 1.0 o
15 o 11 o 9o 10.00 o 2.0 o
20 o 16 o 12 o 14.00 o 4.0 o
25 o 20 o 15 o 17.50 o 5.0 o
30 o 25 o 19 o 22.00 o 6.0 o
35 o 30 o 23 o 26.50 o 7.0 o

Figure 5.9: Graph for the actual result of the front steer wheel angle versus steering
wheel angle

Steering ratio=1.32 (see appendix for calculation)

Turning radius=4.0m

37
 Table 5.13: Comparison between the simulation result with the actual result
Simulation Actual
Inner wheel angle, δi 24.7o 23.0 o
Outer wheel angle, δo 30.0 o 30.0 o
Steering wheel angle, δH 31.8 o 35.0 o
Steering ratio 1.16 1.32
Turning radius, m 4 4

There are differences between the actual and simulation result as shown in Table 5.13
above due to several factors such as misalignment of the matching part, tolerances of
each parts and limitation of manufacturing process.

Figure 5.10: Toe-out angle as a function of the mean steering angle based on simulation
result and actual result

By comparing Figure 5.10 with Figure 3.5 in theory, the pattern of graph is similar. It
can be concluded that the final design of the steering system is validate.

38
Base on the Table 5.11 and 5.12, the outer wheel angle is greater than the inner wheel
angle. The result is totally different with the true Ackermann steering geometry.

At low speeds when the tires have minimal tire shear losses on dry, clean pavement, the
design causes the car experience understeer. This scenario would push the front of the
car away from the desired path. In this situation, the inner tire contributes to this push
similarly to a centrifugal force.

At high lateral accelerations, the design is beneficial since the inner and outer wheel still
have lateral grip. The inner wheel has also surpassed the maximum slip angle of grip
assuming the outer wheel is already at the optimum slip angle. The outer wheel (which
currently has more loads due to weight transfer) is at the optimum slip angle and the
inner wheel is at a lower slip angle with fewer grips. As the result, it allows the inner
wheel to have grip but less than the outer wheel and also decreasing the effects of
understeer during taking the turn.

39
 CHAPTER 6
CONCLUSION AND RECOMMENDATION

In order to design and select steering system as light and simple as possible and meet the
sufficient turning radius to be participated in Shell Eco-marathon 2010, the comparison
and information about the teams that already participated in Shell Eco-marathon is
needed. The experience from team such as Pac-Car ETH Zurich from Switzerland and
Cal Poly Supermileage from California Polytechnic State University, USA become
guidance in designing the steering system. Their experience in the selection of steering
system is very useful.

Generally, the specifications of steering system are light, the steering geometry should
not get affect by bad road conditions, equipped with self-centering, easily operateable
and front wheel steer. For the purpose of this project, the Product Design
Specification(PDS) was determined in order to achieve the objective of this project. The
PDS of the steering system are the maximum angle for inner wheel and outer wheel is
high as possible, small turning radius, small steering ratio, follows true Ackermann
steering geometry, the difference between angle for inner wheel and outer wheel small
as possible and lastly, the steering system should be light to turn the wheel.

The material selection for steering system components has been done by using weight
property index method. From this method, the aluminium alloy is most reliable to use in
fabricating the tie rod and the steering column and stainless steel is most reliable to use
in fabricating the spindle. Four design of steering system were proposed in the
beginning, after do some analysis, simulation in ADAMS and weight property index,
design 1 was selected. This steering system has used simple link mechanism and the
mechanism almost similar with go-kart steering system. The design does not consist of
the tie rod arm and the tie rod is connected directly to spindle by using ball joint.

40
In the optimization step, some of the parameters have been changed when designing the
steering column in order to ensure that the steering system meet the product design
specification (PDS). The optimize design has been simulated in ADAMS again. The
result of simulation indicates the inner wheel angle and outer wheel angle of final design
of steering system are 24.7o and 30.0 o at steering wheel angle of 31.8 o. The turning
radius is 4m and the steering ratio is 1.16.

Then, the steering system has been fabricated based on the modeling in CATIA. The
actual result indicates the inner wheel angle and outer wheel angle of final design of
steering system are 23.0 o and 30.0o at steering wheel angle of 35.0o. The turning radius is
4m and the steering ratio is 1.32.

Since the final design does not followed true Ackermann steering geometry, the car has
experienced understeer that this scenario would push the front of the car away from the
desired path. For the improvement, the steering system should be designed properly that
will follow true Ackermann steering geometry. The true Ackermann steering geometry
is beneficial as the tires are in almost a perfect situation of minute slip angle especially at
low speeds when the tires have minimal tire shear losses on dry clean and pavement.

Although the design does not follow Ackermann steering geometry, the steering system
can be used safely in order to be participated in Shell Eco-Marathon 2010.

41
 REFERENCES

[1] Shell Eco-marathon. <http://www.shell.com/home/content/eco-marathon-

en/about/about.html>

[2] Wikipedia. < http://en.wikipedia.org/wiki/Eco-marathon>

[3] Dalhousie Supermileage Team. <http://poisson.me.dal.ca/~dp_08_14/Frame.html>

[4] Pac-Car. <http://www.paccar.ethz.ch/technics/pac_I_vs_II>

[5] Cal Poly Supermileage California Polytechnic State University USA, 22 May 2006.
<http://cpsmv.blogspot.com/search/label/Photo>

[6] Shell Eco-Marathon Europe 2009, Bringing Energy into the future, Germany, Shell
Eco-Marathon.

[7] Northern Arizona University. <http://nausupermileage.blogspot.com/>

[8] University of British Columbia Supermileage.

<http://www.mech.ubc.ca/~supermileage/2005/photos.htm>

[9] Cedarville University. <http://cusupermileage.blogspot.com/>

[10] Donald Bastow, Geoffrey Howard, John P. Whitehead 2004, Car Suspension and
Handling, SAE International Warrendale PA USA, Professional Engineering
Publishing.

[11] S. Selvaraj, S. Dhanushkodi and P. Jayapraksan 2006, Automobile Technology,

Selangor, IBS BUKU SDN. BHD.

42
[12] Milliken, William F. & Douglas L 1995. Race Car Vehicle Dynamics, Warrendale:
SAE.

[13] J. Reimpell, H. Stoll, J.W. Betzler 2001, The Automotive Chassis, SAE
International Warrendale PA USA, Reed Educational and Professional Publishing Ltd .

[14] The steering, <http://www.carbibles.com/steering_bible.html#ixzz0ihNDhWn3 >

[15] Dr. Vu Trieu Minh 2008, Textbook: Advanced Vehicle Dynamics, Universiti
Teknologi PETRONAS, Malaysia.

[16] David H. Myszka 2005, Machines & Mechanism Applied Kinematic Analysis,
Pearson Prentice Hall.

Chad Batterton, Matthew Harding, Liam Jeffery and Brad Marcus 2008. December
report. Dalhousie Supermileage Team, Dalhousie University, Canada

S Srinivasan 2003, Automotive Mechanics, New Delhi, Tata McGraw-Hill

43
 APPENDIX I
FYP Gantt Chart
FYP I Gantt Chart

Week Number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Activities/Milestone
Selection of topic
Brain Storming of ideas
Develop scope of project
Develop PDS
Submission preliminary
21/8
report
Produce conceptual
decomposition,
Develop and validate
concept design
Develop product 1 Mid-
architecture week sem
Submission of progress break break
10/9
report
Seminar 15/9
Develop CAD design
Validate design by using
ADAMS
Selection of design and
materials
Submission of interim 5/11
report final draft
Oral presentation

44
FYP II Gantt Chart

Week Number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Activities/Milestone

Produce detail drawing

Validate final design:

-Simulation
-PDS
Submission of progress
report 1
Clarification of machining
process, tolerance
Preparation of material,
machine, tool, equipment
Manufacture
Mid-
Installation the steering
sem
system to complete car
break
Submission of progress
report 2
Seminar
Validate/comparison with
PDS and simulation result
Poster exhibition
Submission of dissertation
final draft
Oral presentation
Submission of
dissertation(Hard bound)

45
 APPENDIX II
Sample of Calculation

R s=4m, l=2m
l
Rs 
sin  o
 l 
 o sin 1  
 Rs 
 2 
 sin 1  
 4.0 
 30 o

Design 1
Wheelbase, l=2m
Outer wheel angle, δo = 30o inner wheel angle, δi = 18.8o
Steering wheel angle, δH = 48 o
  i
m  o
2
30  18.8 o
o

2
o
 24.4
H
is  d i  d o  18.8o  30 o
m
 11.2 o
48 o

24.4 o
 1.97

Final design
Outer wheel angle, δo = 30o inner wheel angle, δi = 23o
Steering wheel angle, δH = 35 o
  i 
m  o is  H
2 m
o o
30  23 35.0o
 
2 26.5o
o
 26.5  1.32

46
 APPENDIX III
Alternative Designs

47
48
49
50
 APPENDIX IV
Final Design
Projection View of Final Design

51
Final Design with Label

52
Exploded View of Final Design

53
 APPENDIX V
Pictures of Real Design of Steering System

Front view of spindle

Bearing holder

Steering system

Top view of spindle Tie rod

54