front and rear suspension design for solar car
TRANSCRIPT
FRONT AND REAR SUSPENSION DESIGN FOR SOLAR CAR
MOH DZOHAIRY BIN MOHAMMAD MOHSAN
Report submitted in partial fulfillment of the
requirements for the award of the degree of
Bachelor of Mechanical Engineering with Automotive Engineering
Faculty of Mechanical Engineering
University Malaysia Pahang
DECEMBER 2010
ii
UNIVERSITI MALAYSIA PAHANG
FACULTY OF MECHANICAL ENGINEERING
I certify that the project entitled “Front and Rear Suspension Design for Solar Car“ is
written by Mohd Dzohairy Bin Mohammad Mohsan. I have examined the final copy of
this project and in our opinion; it is fully adequate in terms of scope and quality for the
award of the degree of Bachelor of Engineering. We herewith recommend that it be
accepted in partial fulfillment of the requirements for the degree of Bachelor of
Mechanical Engineering with Automotive Engineering.
DR. RIZALMAN BIN MAMAT
Examiner Signature
iii
SUPERVISOR’S DECLARATION
We hereby declare that we have checked this project report and in our opinion this
project is satisfactory in terms of scope and quality for the award of the degree of
Bachelor of Mechanical Engineering with Automotive Engineering.
Signature :
Name of Supervisor : ZAMRI BIN MOHAMED
Position : LECTURER
Date : 06 DECEMBER 2010
iv
STUDENT’S DECLARATION
I hereby declare that the work in this report is my own except for quotations and
summaries which have been duly acknowledged. The report has not been accepted for
any degree and is not concurrently submitted for award of other degree.
Signature :
Name : MOHD DZOHAIRY BIN MOHAMMAD MOHSAN
ID Number : MH08011
Date : 06 DECEMBER 2010
v
ACKNOWLEDGEMENT
First I would like to express my grateful to ALLAH S.W.T. as for the blessing
given that I can complete my final year project. In preparing this paper, I have engaged
with many people in helping me completing this project.
I am grateful and would like to express my sincere gratitude to my supervisor
Mr. Zamri Bin Mohamed for his germinal ideas, invaluable guidance, continuous
encouragement and constant support in making this research possible. I appreciate his
consistent support from the first day I applied to graduate program to these concluding
moments. I am truly grateful for his progressive vision about my training in science, his
tolerance of my naïve mistakes, and his commitment to my future career.
My sincere thanks go to all my labmates and members of the staff of the
Mechanical Engineering Department, UMP, who helped me in many ways and made
my stay at UMP pleasant and unforgettable. Many special thanks go to member engine
research group for their excellent co-operation, inspirations and supports during this
study.
I acknowledge my sincere indebtedness and gratitude to my parents for their
love, dream and sacrifice throughout my life. I acknowledge the sincerity of my parents-
in-law, who consistently encouraged me to carry on my higher studies. I cannot find the
appropriate words that could properly describe my appreciation for their devotion,
support and faith in my ability to attain my goals. Special thanks should be given to my
committee members. I would like to acknowledge their comments and suggestions,
which was crucial for the successful completion of this study.
The next category people who help me to grow further and influence in my
project are my colleagues who always help me in order to finish this project. I really
appreciate the idea and information given.
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ABSTRACT
Suspension is a necessary system for solar cars because it protects the frame and
other on-board components from large jolts encountered along highways. If the
suspension is too soft, energy is wasted by absorbing the motion of a car as it travels
over bumps. For increased efficiency, most solar cars use a suspension that is stiffer
than normal. For this project, the solar car has two front wheels and one rear wheel. The
front wheels provide turning, so the front suspension needs to let the wheels turn. The
suspension also allows the wheels to move up and down as the car runs over bumps.
The type of front suspension for this project is a double wishbone system. It has a pair
of an A-frames, one above the other, mounted to the top and bottom of the wheel hub. A
separate spring until then sits between either the hub itself or one of the wishbones and
the body to control the wheel movement. Lastly, this car uses a trailing arm on rear
suspension. This kind of suspension has only one link (arm) on each side which puts
greater structural requirements on it. Strong bending forces in all directions (especially
during cornering) must be withstood by this suspension and as well as breaking, camber
and steer torques. Nevertheless trailing arm suspension has been used in many vehicles
as a rear linkage, because it requires little space to be accommodated.
vii
ABSTRAK
Suspensi adalah sistem yang diperlukan untuk kereta solar kerana melindungi
frame dan bahagian-bahagian on-board lain dari goncangan besar ditemui di sepanjang
jalan raya. Jika suspensi terlalu lembut, tenaga terbuang dengan menyerap gerakan
mobil saat dihantar melalui benjolan. Untuk meningkatkan kecekapan, kebanyakan
kereta solar menggunakan suspensi yang lebih kaku dari biasanya. Untuk projek ini,
kereta suria mempunyai dua roda depan dan satu roda belakang. Roda depan
memberikan berputar, sehingga suspensi depan perlu membiarkan roda putar.Suspensi
juga membolehkan roda bergerak naik dan turun ketika kereta berjalan di atas
benjolan. Jenis suspensi depan untuk projek ini adalah sistem wishbone ganda. Ia
memiliki sepasang A-frame, satu di atas yang lain, mount ke atas dan bawah dari hub
roda. Sebuah pegas berasingan sampai kemudian duduk antara baik hub sendiri atau
salah satu wishbones dan tubuh untuk mengawal gerakan roda. Terkini, kereta ini
menggunakan lengan sisa pada suspensi belakang. Suspensi semacam ini hanya
memiliki satu link (lengan) di setiap sisi yang menempatkan keperluan struktur yang
lebih besar di atasnya. kekuatan bending yang kuat di segala penjuru (khususnya saat
menikung) harus bertahan dengan suspensi ini dan juga melanggar, camber dan
mengarahkan torsi. Namun demikian trailing suspensi lengan telah digunakan dalam
banyak kenderaan sebagai penghubung belakang, kerana memerlukan sedikit ruang
untuk diakomodasi.
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TABLE OF CONTENTS
Page
TITLE PAGE
EXAMINER DECLARATION
i
ii
SUPERVISOR DECLARATION
STUDENT DECLARATION
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
iii
iv
v
vi
vii
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF SYMBOLS
LIST OF ABBREVIATIONS
viii
xi
xii
xiv
xv
CHAPTER 1 INTRODUCTION
1.1 Project Synopsis 1
1.2 Problem Statement 2
1.3 Objective 2
1.4 Project Scope 2
1.5 Project Planning 2
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 4
2.2 Mechanical Systems of Solar Car 4
2.3 Suspension Alignment 5
2.3.1 Toe Setting 5
2.3.2 Camber Angle 6
2.3.3 Caster 7
2.3.4 Thrust Line 8
ix
2.3.5 Scrub Radius 9
2.3.6 Set-Back 10
2.3.7 Set Back By Design 11
2.3.8 Roll Centre 12
2.3.9 Roll Axis 13
2.3.10 Bump Steer Geometry 14
2.4 Suspension Systems 15
2.4.1 Active Suspension 15
2.4.2 Passive Suspension 16
2.4.3 Semi-Active Suspension 16
2.5 Suspension Types 17
2.5.1 Beam Axle 17
2.5.2 Trailing Arm 18
2.5.3 Split Beam 19
2.5.4 MacPherson Strut 20
2.5.5 Wishbones Suspension, Equal and Parallel 21
2.5.6 Wishbones Suspension, Non-Equal and Parallel 21
2.5.7 Double Wishbones Non-Equal and Non-Parallel Suspension 22
2.5.8 Multi-Link Suspension 23
CHAPTER 3 METHODOLOGY
3.1 Introduction 25
3.2 Summary of Suspension Selection 27
3.3 Material Selection 28
3.4 Computer Aided Design Drawing 29
3.5 Finite Element Analysis 33
3.5.1 A General Procedure for Finite Element Analysis 33
3.5.1.1 Preprocessing 34
3.5.1.2 Solution 34
3.5.1.3 Post Processing 34
3.6 Aluminum Welding 35
3.7 Suspension Bushes 36
x
3.8 Ball Joint Selection 37
CHAPTER 4 RESULT AND DISCUSSION
4.1 Introduction 41
4.2 Analysis of Natural Frequency 41
4.2.1 Result of Natural Frequency on Front Suspension 42
4.2.2 Result of Natural Frequency on Rear Suspension 49
4.3 Analysis of Material Model on Stress 54
4.3.1 Result of Stress on Front Suspension 54
4.3.2 Result of Stress on Rear Suspension 60
4.4 Final Design of Suspension 66
4.4.1 Front Suspension of Solar Car 66
4.4.2 Rear Suspension of Solar Car 67
CHAPTER 5 CONCLUSION AND RECOMMENDATION
5.1 Introduction 69
5.2 Conclusion 69
5.3 Recommendation 70
REFERENCES 71
APPENDICES 72
A Gantt Chart 72
B Designs of Front Suspension for Solar Car 73
C Designs of Rear Suspension for Solar Car 74
D Examples of Front Suspension 75
E Examples of Rear Suspension 76
xi
LIST OF TABLES
Table No. Title Page
3.1 Aluminums Alloy 6060-T5 Material Properties 29
4.1 Result Analysis of Natural Frequency on Front Suspension 48
4.2 Result Analysis of Natural Frequency on Rear Suspension 53
4.3 Result Analysis of Stress on Front Suspension 60
4.4 Result Analysis of Stress on Rear Suspension 66
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LIST OF FIGURES
Figure No. Title Page
2.1 Four wheel versus three wheel 5
2.2 Toe setting 6
2.3 Camber angle 7
2.4 Caster angle 8
2.5 Thrust line and angle 9
2.6 Scrub radius 10
2.7 Set back 11
2.8 Set back by design 11
2.9 Roll centre 12
2.10 Roll axis 13
2.11 Bumper steer 14
2.12 Active suspension 15
2.13 Passive suspension 16
2.14 Semi-active suspension 17
2.15 Beam axle suspension 18
2.16 Trailing arm 19
2.17 Split beam 19
2.18 MacPherson strut assembly 20
2.19 Equal and parallel A-arm 21
2.20 Non-equal and parallel A-arm 22
2.21 Non-equal and non-parallel A-arm 23
2.22 Multi-link suspension 24
3.1 Flow chart of the project methodology 26
3.2 Absorber 30
3.3 Bush tire 30
3.4 Front A-arm suspension (bottom) 30
3.5 Front A-arm suspension (upper) 31
3.6 Front suspension (vertical) 31
3.7 Rear suspension 31
xiii
3.8 Washer 32
3.9 Full assembly of front suspension (left) 32
3.10 Full assembly of front suspension (right) 32
3.11 Full assembly of rear suspension 33
3.12 Urethane bushes 37
3.13 Heim Joint 38
3.14 T-Pin Heim rod end 39
3.15 Ball joint 39
3.16 Tie rod end 40
4.1 The natural frequency of 1st design on front suspension 43
4.2 The natural frequency of 2nd design on front suspension 44
4.3 The natural frequency of 3rd design on front suspension 45
4.4 The natural frequency of 4th design on front suspension 46
4.5 The natural frequency of 5th design on front suspension 47
4.6 The natural frequency of 6th design on front suspension 48
4.7 The natural frequency of 1st design on rear suspension 49
4.8 The natural frequency of 2nd design on rear suspension 50
4.9 The natural frequency of 3rd design on rear suspension 51
4.10 The natural frequency of 4th design on rear suspension 52
4.11 The natural frequency of 5th design on rear suspension 53
4.12 The stress of 1st design on front suspension 55
4.13 The stress of 2nd design on front suspension 56
4.14 The stress of 3rd design on front suspension 57
4.15 The stress of 4th design on front suspension 58
4.16 The stress of 5th design on front suspension 59
4.17 The stress of 1st design on rear suspension 61
4.18 The stress of 2nd design on rear suspension 62
4.19 The stress of 3rd design on rear suspension 63
4.20 The stress of 4th design on rear suspension 64
4.21 The stress of 5th design on rear suspension 65
4.22 Final design of front suspension 67
4.23 Final design of rear suspension 68
xiv
LIST OF ABBREVIATIONS
CAD Computer Aided Design
CAE Computer Aided Education
FEA Finite Element Analysis
FYP Final Year Project
1
CHAPTER 1
INTRODUCTION
1.1 PROJECT SYNOPSIS
Suspension is a necessary system for solar cars because it protects the frame and
other on-board components from large jolts encountered along highways. If the
suspension is too soft, energy is wasted by absorbing the motion of a car as it travels
over bumps. For increased efficiency, most solar cars use a suspension that is stiffer
than normal.
For this project, the solar car has two front wheels and one rear wheel. The front
wheels provide turning, so the front suspension needs to let the wheels turn. The
suspension also allows the wheels to move up and down as the car runs over bumps.
The type of front suspension for this project is a double wishbone system. It has
a pair of an A-frames, one above the other, mounted to the top and bottom of the wheel
hub. A separate spring until then sits between either the hub itself or one of the
wishbones and the body to control the wheel movement.
Lastly, this car uses a trailing arm on rear suspension. This kind of suspension
has only one link (arm) on each side which puts greater structural requirements on it.
Strong bending forces in all directions (especially during cornering) must be withstood
by this suspension and as well as breaking, camber and steer torques. Nevertheless
trailing arm suspension has been used in many vehicles as a rear linkage, because it
requires little space to be accommodated.
2
1.2 PROBLEM STATEMENT
If the suspension is too soft, energy is wasted by absorbing the motion of a car as
it travels over bumps. For increase efficiency, most solar cars use a suspension that is
stiffer than normal.
1.3 OBJECTIVE
There are two main objectives to achieve in this research which are to design
front and rear suspension of solar car and for analysis a suspension of solar car.
1.4 PROJECT SCOPE
In order to reach the objectives, there is the scope of project which is a
benchmarking, a concept generation, to design of suspension structure using force
balance calculation and CAD, to analysis of suspension parts and a lastly, to make a
fabrication availability of components.
1.5 PROJECT PLANNING
This project started with made a research and literature review. It is from
internet, books and my supervisor that related to my project title. All of this literature
review takes about three week. I also do my schedule management for my project. This
is done by using Microsoft Excel Worksheet using Gantt chart system. The next week I
have been submit my project title acceptance form and continue detail research on
suspension and it takes a week to be done.
After all of literature review done, I must find out what is the suitable type of
suspension that matching with solar car’s body. After that, I sketch a design of the
suspension. The sketching of the suspension takes about 2 weeks to be done. The
sketching done using manual sketched at A4 size paper. Lastly, I transfer the design into
SolidWorks software because I want to analyze it by using ALGOR software.
3
The fabrication process is started on next semester. For the first fabrication is
must fabricate the part of suspension using a CNC machining. After done the fabrication
process, next process is assembly, testing, correction and finishing. This task scheduled
takes several weeks to finish. The next task is preparation of progress presentation and
progress report writing, both of these tasks takes one week to be done. After that, the
progress presentation week and progress report submission. On this week I have to
prepare the speech for the presentation and double checked the report that has to be
submitted.
Lastly, the final report has been written and prepared for presentation. This will
take about one week to prepared and accomplish. A report is guided by UMP thesis
format and also guidance from supervisor. Due to any problems that student face, the
management has agreed to extend the time of submission of the report and presentation.
All task scheduled takes around 28 weeks to complete.
4
CHAPTER 2
LITERATURE REVIEW
2.1 INTRODUCTION
The purpose of this chapter is to give the reader necessary background
information to understand the research presented in this paper. There are a few very
important fundamentals such as wheel alignment, weight transfer and suspension
configuration, which influence the design of vehicle suspension. This chapter gives
current knowledge which will introduce the reader to comprehensive suspension design
and development.
2.2 MECHANICAL SYSTEMS OF SOLAR CAR
The mechanical systems are designed to keep friction and weight to a minimum
while maintaining strength and stiffness. Designers normally use aluminum, titanium
and composites to provide a structure that meets strength and stiffness requirements
whilst being fairly light. Steel is used for some suspension parts on many cars.
Solar cars usually have three wheels, but some have four. Three wheelers
usually have two front wheels and one rear wheel: the front wheels steer and the rear
wheel follows. Four wheel vehicles are set up like normal cars or similarly to three
wheeled vehicles with the two rear wheels close together (see Figure 2.1).
Solar cars have a wide range of suspensions because of varying bodies and
chassis. The most common front suspension is the double wishbone suspension. The
rear suspension is often a trailing-arm suspension as found in motor cycles.
5
Figure 2.1: Four wheel versus three wheel
2.3 SUSPENSION ALIGNMENT
2.3.1 Toe Setting
Toe setting strongly affects the handling characteristics and transitional
cornering of the vehicle. It is the difference between the front and rear edges of the
wheels as shown in Figure 2.2. Toe-in means the front edges are closer together than the
rear edges and the wheels point inward. Toe-out means the front edges are farther apart
than the rear edges and the wheels point outward. Extreme toe-in or toe-out will cause
excessive tire wear and steering instability, especially at high speeds. Most vehicles
need a small amount of toe in for strait-line steering stability. Toe setting is adjusted by
lengthening or shortening the steering system’s tie-rods and it usually varies between ±
3 mm. An example of this is the Daihatsu Charade, model G100, where the toe setting
specification is between 1 mm toe out-3 mm toe in (Gregory’ s Automotive 1991, p
196).
6
Figure 1.2: Toe setting
Source: http://www.specprod.com
2.3.2 Camber Angle
Camber angle is measured in degrees. It is the angle at which the wheels are
angled i.e. the angle between the centreline of the tyre and a vertical line. Extreme
positive camber causes wear on the outside of the tyre. Extreme negative camber causes
wear on the inside of the tyre. Excess negative camber will also tend to increase straight
line stopping distances. The camber angle should be optimized to minimize dynamic
side forces acting on the wheel and decreasing steering imbalance caused by lateral
forces. The drawback of camber angle is increased rolling resistance and tyre wear. This
explanation is visualized in Figure 2.3.
7
Figure 2.3: Camber angle
Source: http://www.allwheelalignment.com
2.3.3 Caster
Caster is the backward or forward slope of the steering axis when viewed from
the side. Caster angles are used to alter the directional stability of the wheels. Hence
caster angle is a very dynamic setting. It changes as the suspension moves. As a result
the difference between caster angles of the left and right front wheels should be as small
as possible to avoid steering imbalance. Proper caster angle provides the self-centre
action to pull the front wheels back to a straight ahead position after coming out of a
corner. Proper caster will also help to keep the vehicle in a straight line at high speeds.
Caster angle is mostly adjustable on suspensions arms for normal wear in suspension
and steering. Negative caster can cause hard steering when returning out of a turn and
reduced straight line stability. Also vehicles with a negative caster tend to pull from side
to side. Most cars are designed with a positive caster setting which is from + ½ degree
to + 4 degrees, but there are some cars such as Mercedes which have specified caster
angle up to +10 degrees (Kerr 2003). The caster angle is shown in Figure 2.4.
8
Figure 2.4: Caster angle
Source: http://www.allwheelalignment.com
2.3.4 Thrust Line
Thrust line is defined by the rear suspension’s relationship to the centreline of
the car i.e. direction in which the rear wheels are pointed. Thrust angle refers to the
relationship of all four wheels to each other with respect to the centre line. If the thrust
line is to the right of the centreline, the angle is said to be positive. If the thrust line is to
the left of centreline, the angle is negative. Excessive thrust angle can cause tyre wear,
steering wheel misalignment, or pulling to one side. Figure 2.5 displayed the
relationship between the thrust line and the thrust angle.
9
Figure 2.5: Thrust line and angle
Source: http://www.specprod.com
2.3.5 Scrub Radius
Scrub radius is the distance between the projected steering axis indication (SAI)
and the tyre tread centreline at the road surface. This distance must be exactly the same
from side to side or the vehicle will pull strongly to one side at high speeds. The Scrub
Radius provides the driver with better driving stability. In conjunction with toe setting
the correct scrub radius helps to bring the running toe to zero. Different wheels or tyres
from side to side will cause differences in scrub radius as well as a tyre that is low on
air. Scrub Radius is set by the designer and it is not adjustable. Figure 2.6 displays the
scrub radius.
10
Figure 2.6: Scrub radius
Source: http://206.117.169.65/alignment.htm
2.3.6 Set-Back
Set-Back occurs when front and rear axles (which should be perpendicular to the
centerline) are not parallel to each other. This means that one front wheel is set farther
back than the other wheel. This is usually the result of a collision, different regulation of
caster of the right and left wheels and sometimes by the car manufacture (sees Figure
2.7, Set Back by design). Positive setback means the right front wheel is set back further
than the left. Excessive set back might affect steering system which can be indicated by
pulling the vehicle to one side. However, small amounts of setback usually won’t cause
any problems.