baja 2013 final year project report
TRANSCRIPT
A
Final Design Report
on
“Design & Fabrication of an ALL TERRAIN VEHICLE”
Submitted in partial fulfilment of the requirements for the award of the degree of
BACHELOR OF TECHNOLOGY
in
MECHANICAL ENGINEERING
Submitted by:
KALYAN POTUKUCHI (11091007)
KANISHK RAJ (11091008)
KUNTAL BASU (11091014)
Under the supervision of
PROF. N. K. BATRA
ER. VISHAL GUPTA
DEPARTMENT OF MECHANICAL ENGINEERING
M. M. ENGINEERING COLLEGE
MAHARISHI MARKANDESHWAR UNIVERSITY,
MULLANA, AMBALA, HARYANA.
May 2013
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CERTIFICATE FROM GUIDE
This is to certify that the project “Design and Fabrication of an All Terrain
Vehicle” by KALYAN POTUKUCHI (11091007), KANISHK RAJ (11091008),
KUNTAL BASU (11091014), VIVEK SHARMA (11092366), ADITYA SAINI
(11092459), NITISH BENJWAL (11092484), HARPREET SINGH (11092375),
GURINDER SINGH (11090971), TALWINDER SINGH (11092390) is a bonafide
work that has been carried out under my guidance, for partial fulfilment of the
requirements for the award of the degree of Bachelor of Technology in
Mechanical Engineering by Maharishi Markandeshwar University, Mullana.
Prof. N. K. Batra
Project Guide
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ACKNOWLEDGEMENT
This is a heartfelt expression of indebtedness and gratitude to all those who are helping us to
successfully complete this project. It has been a very pleasurable learning experience where
we could put our theoretical knowledge to practical use and have learned a lot by working
hands-on, together in a team.
Foremost we are extremely grateful to Prof. N. K. Batra, Professor & Head, Mechanical
Engineering Department, MMEC and Er. Vishal Gupta, Asst. Prof., Mechanical engineering
Department, MMEC. Their never ending support and benevolent cooperation was a guiding
force to us. Their encouragement and valuable suggestions provided us the enthusiasm to
work harder in completing the project.
We thank the Society of Automotive Engineers for the concept of Mini BAJA, and for their
numerous publications based on which we have decided our design parameters. We also
salute the warm affection of the teaching and non-teaching staff of the Mechanical
Engineering Department of M. M. Engineering College, Mullana.
Last but not the least we thank the Almighty without whose countless blessing nothing is
complete.
Looking forward to further cooperation from all concerned,
KALYAN POTUKUCHI (11091007)
KANISHK RAJ (11091008)
KUNTAL BASU (11091014)
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PREFACE
This report presents a detailed objective summary of the process and parameters used
for designing and fabricating our project — an ALL TERRAIN VEHICLE.
The report is divided into several headings corresponding to the departments divided
for the purpose of executing the project, like Frame, Suspension, Braking, Steering and so on.
It describes a detail of the methodology adopted, the comparison of different parameters, etc.
Reasons for selecting the final specifications have been elaborated at every stage. The
combination of figures, graphs and detailed explanation will surely make it interesting in
reading the report. However, detailed calculations have not been added to avoid making the
report voluminous. Formulas and mathematical relations have been stated, where applicable.
Reports like Bill of Material and Cost Report have been summarized under broad heads.
All figures mentioned here have been referred to from publications and standards of
different professional societies like Society of Automotive Engineers (SAE), Society of
Indian Automobile Manufacturers (SIAM), Automotive Research Association of India
(ARAI), etc.
The figures shown here were either captured while fabrication work was being carried
out or generated from software. They are copies of original work.
Although, the report gives an exhaustive account of the project progress, any
omissions or mistakes noted are deeply regretted.
All figures mentioned here are authentic and true to the best of our knowledge.
KALYAN POTUKUCHI (11091007)
KANISHK RAJ (11091008)
KUNTAL BASU (11091014)
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CONTENTS
S No. Topic Page No.
Certificate from Guide ii
Acknowledgement iii
Preface iv
List of Figures and Tables v
1. Abstract 2
2. Introduction 3
3. Objective 5
4. Procedure 6
5. Frame Design & Analysis 7
5.1. Deciding Material properties
5.2. Ergonomics
5.3 Analysis of Frame
7
8
9
6. Suspension System 12
6.0.a. Basic Calculations in Spring Design
6.1. Design of Front and Rear Suspension
6.1.a. Calculation for Springs
6.1.b. Calculation for Spring Rate
6.1.c. Alternative Approach
6.2. Knuckles
14
14
14
15
16
18
7. Steering System 20
8. Braking System 22
9. Innovation 25
9.1. Mechanism
9.1.a. Hydraulic Mechanism
9.1.b. Gear Mechanism
9.1.c. Electric Mechanism
9.1.d. Computer Mechanism
9.1.e. Safety
25
25
25
26
26
26
10. Engine & Transmission 27
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10.1 Methodology for Selection of
Transmission Components 28
11. Wheels & Tire Assembly 30
11.1. Rim
11.2. Tyre
11.3. Hub
11.4. Stub Axle
11.5. Axle
11.6. Vibration Control
11.7. Coupling
11.7.a. Engine with primary pulley
11.7.b. Primary Pulley to Secondary Pulley
11.7.c. Secondary Pulley to gear box
11.7.d. Gear box to axle
11.7.e. Welding joint in axle
11.7.f. Stub axle with hub
11.7.f.i. Calculation for Key
11.8. Wheel Assembly
30
30
30
31
32
32
32
33
33
33
33
33
34
34
34
12. Safety Feature 36
13. Specifications of our vehicles 37
14. Bill Of Materials 38
15. Financial Outlay 39
16. Conclusion 40
16.1. Future Scope 40
17. Glimpses 41
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LIST of TABLES:
Table 1: Classification of Automobiles 3
Table 2: Properties of Roll Cage Material 7
Table 3: Final Analysis Data of Frame 10
Table 4: Parameters used in designing the suspension system: 13
Table 5: Final Specifications in Suspension Design 16
Table 6: Suspension Design Methodology 16
Table 7: Steering System Specifications 20
Table 8: Details of Project Costs 39
LIST of FIGURES:
Figure 1: Analysis of Crumpled Zone 9
Figure 2: Front Impact Test Analysis 10
Figure 3: Isometric View of Roll Cage 11
Figure 4: Side View of Roll Cage 11
Figure 5: Front View of Roll Cage 12
Figure 6: Top View of Roll Cage 12
Figure 7: Front and Rear Wish-bones 15
Figure 8: Metal pieces used to fabricate front and rear knuckles 18
Figure 9: Front Knuckle 19
Figure 10: Rear Knuckle 19
Figure 11: Fabrication Process under-way 21
Figure 12: Steering Shaft 21
Figure 13: Steering Rack 21
Figure 14: Steering Wheel 21
Figure 15: Brake Disc 23
Figure 16: Front and Rear Brake Callipers Mounting 23
Figure 17: Front and Rear Brake Calliper 23
Figure 18: Virtual Model and Prototype of Rear knuckle welded with rear calliper
mounting (with housing for two callipers) 24
Figure 19: Dynamic Stabilised Steering System Layout 26
Figure 20: Left and Right View of the Engine. 27
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Figure 21: Cone Pulleys of the CVT 28
Figure 22: Rim 30
Figure 23: Hubs made of Aluminum alloy using VMC 30
Figure 24: Fabrication of stub axle (in-process) 31
Figure 25: Stub Axle 31
Figure 26: Press-fitted bush in CVT 32
Figure 27: Front Wheel Assembly 35
Figure 28: Rear Wheel Assembly 35
Figure 29: Bucket Seat 36
Figure 30: Final Assembly of the vehicle 37
Figures 31, 32 & 33: Complete ATV, while participating in SAE India BAJA 2013,
competition in Indore. 41
LIST OF GRAPHS
Graph 1: Suspension angles at bump
(a) Camber angle (b) Toe Angle (c) Castor Angle 17
Graph 2: Suspension angles at roll
(a) Camber angle (b) Toe Angle (c) Castor Angle 17
Graph 3: CVT Characteristics (rpm-velocity) 29
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Design & Fabrication of an All Terrain Vehicle
Final Design Report
Kalyan Potukuchi (11091007),
Kanishk Raj (11091008),
Kuntal Basu (11091014),
Aditya Saini (11092459)
Vivek Sharma (11092366)
Nitish Benjwal (11092484)
Gurinder Singh (11090971)
Harpreet Singh (11092375)
Talwinder Singh (11092390)
Final Year, 2009-2013,
Mechanical Engineering Department,
Maharishi Markandeshwar Engineering College,
Mullana, Ambala, Haryana.
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1. ABSTRACT
The objective of our project is to design and fabricate an ‘All Terrain Vehicle.’ It is
aimed to simulate a real world engineering design project and their challenges. It involves the
planning and manufacturing tasks found when introducing a new product to the consumer
industrial market. Our primary focus is to design a single-sitter high-performance off-road
vehicle that will take the ruggedness of rough roads with maximum safety and driver comfort.
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2. INTRODUCTION
An automobile, motor car or car is a wheeled motor vehicle used for transporting
passengers, which also carries its own engine or motor. The word automobile comes, via the
French automobile from the Ancient Greek word αὐτός (autós, "self") and the Latin mobilis
("movable"); meaning a vehicle that moves by itself.
Automobiles may be classified by a number of different criteria and objectives.
However, comprehensive classification is elusive, because a vehicle may fit into multiple
categories, or not completely satisfy the requirements for any. The most widely used general
categorisation is summarised in Table 1 below.
Table 1: Classification of Automobiles
HLDI classification Definition
Sports Those cars with significant high performance features
Luxury Higher-end cars that are not classified as sports
Large Length more than 495.3 cm (195 in) and wheelbase more than
279.4 cm (110 in)
Midsize Length 457.3–495.3 cm (180–195 in) and wheelbase 266.8–
279.4 cm (105–110 in)
Small Length less than 457.2 cm (180 in) and wheelbase less than
266.7 cm (105 in)
An all-terrain vehicle (ATV), also known as a quad, quad bike, three-wheeler, or four-
wheeler, is defined by the American National Standards Institute (ANSI) as a vehicle that
travels on low-pressure tyres, with a seat that is straddled by the operator, along with
handlebars for steering control. As the name implies, it is designed to handle a wider variety of
terrain than most other vehicles.
ATVs are intended for use by a single operator, the rider sits on and operates these
vehicles like a motorcycle, but the extra wheels give more stability at slower speeds. The first
three-wheeled ATV was the Sperry-Rand tri-cart. It was designed in 1967 as a graduate project
of John Plessinger at the Cranbrook Academy of Arts near Detroit. The Tri-cart was straddle-
ridden with a sit-in rather than sit-on style.
The primary aim of this project is to design and fabricate an All-Terrain Vehicle — a
four wheeler that will take on rugged non-motorable roads with ease and have paramount
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importance to driver safety. We have strived to self-design and manufacture most of our
components while some have been readily bought from the market and customised as per our
requirements. As a guideline, we have taken the rules and guidelines stipulated for SAEINDIA
BAJA 2013. (http://www.bajasaeindia.org/down/Rulebook%20Final.pdf). We shall use a
Briggs & Stratton 10 Hp OHV Model 205432 engine as our power source. All other
components selected have been elaborated in details.
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3. OBJECTIVE
The main objective of our project is to attain the following in our vehicle:
To have maximum ground clearance.
For thus we have used a double wish bone type independent suspension.
To have maximum traction in the roughest of roads.
Independent suspension ensures the wheels are always in touch with the ground,
the special treads of off-road tires provides good traction, use of cutting brakes
ensures that power can be transferred to the other wheel when one wheel skids
or is stuck.
To give maximum precedence to driver/rider safety.
For this strict conformance to SAE and ARAI designing norms have been
ensured. Further, an innovative and indigenously designed dynamically
stabilised steering system was being developed.
Reduce Vehicle weight.
Wherever possible, light materials like aluminium and its alloys have been used.
Composite materials or plastics could also be used.
Augment performance by minimising power loss.
A continuously variable transmission (CVT) shall be used.
Basically our vehicle shall be a unique single-seat, off-road, rugged, recreational
and fun-to-drive vehicle which in intended for sale to weekend off-road enthusiasts.
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4. PROCEDURE
To achieve our goal we have completed the tasks under different sub-heads like —
Frame/Chassis, Suspension, Wheel & Tire Assembly, Steering, Brakes, Engine,
Transmission, Fabrication/Body-Work. For design, analysis and optimisation of various
vehicle components different CAD modelling and Analysis software like Solid-Works,
Pro-E, ANSYS, Lotus is being used.
Initially we went through different design manuals, SAE and other automotive
industry papers to know about the standards to be adopted and most commonly used
materials and fabrication processes.
Once material and component was finalised, each of them were modelled using
software. Some of our components like wheel hub and its assembly have been
indigenously designed and manufactured, while some components were purchased from
the market. All individual components were assembled to prepare a virtual model of the
car. Emphasis was laid on the ergonomics of the vehicle. The roll cage was tested at 10g-
force and found to have a factor of safety of 2.15.
Further extensive market survey was undertaken to ensure all material and
components chosen could be readily available when fabricating. We also prepared a
project budget based on the figures obtained from market survey. Necessary changes were
made if availability was a problem.
After fabrication, exhaustive test trails were conducted to ensure adept
performance. This was followed by body-work and painting.
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5. FRAME DESIGN The initial material chosen for fabricating the Roll cage was AISI 4130. The dimensions
of the chosen pipe were 1.25 inch outer diameter and 2mm thickness. Due to its high yield
strength we could make use of pipes with larger Outer Diameter and less thickness which
helped in reducing the weight of our Roll cage substantially. But, due to the unavailability of
material in small quantity (suitable for constructing a single vehicle) we were forced to use a
more commonly available material i.e., AISI 1018. Comparison of the properties of the two
materials is shown in Table 2. Circular pipes of 1 inch outer diameter and wall thickness of 3
mm were used and square pipes of 1.25 inch sides were used for the base.
Table 2: Properties of Roll Cage Material
Properties AISI 4130 AISI 1018
Category Steel Steel
Class Alloy Steel Carbon Steel
Composition (Weight %)
C : 0.28-0.33 Mn : 0.40-0.60 P : 0.035 (max) S : 0.04 (max) Cr : 0.80 - 1.10 Mo : 0.15-0.25
C : 0.15-0.20 Mn : 0.60-0.90 P : 0.04 (max) S : 0.05 (max)
Density (x1000 kg/m3) 7.7 - 8.03 7.7 - 8.03
Elastic Modulus (GPa) 190-210 190-210
Tensile Strength (MPa) 560.5 634
Yield Strength (MPa) 360.6 386
Hardness (HB) 156 197
MIG Welding was utilised as it provides better strength and clean welds.
The change in material and thickness, though reduced the manufacturing cost, posed a
serious problem of increase in mass which also decreased the FOS from 2.12 to 1.87 in a front
impact condition. Hence, the entire frame was re-analysed after taking into consideration the
new data that had been introduced.
5.1. Deciding Material Properties:-
Material Selection – 20% of the weight of our vehicle is of the roll cage. So we decided to use
alloy steel of high yield strength. This ensured that pipe of larger diameter and less thickness
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can be used thus reducing the overall weight of our roll cage. The most suitable for our
purpose was use of AISI 4130 steel. However, the cost of the material in small quantity was
not feasible for our project. Evaluating other options based on our requirements, the most
suitable next choice was AISI 1018.
Primary Members : O.D. – 1inch, Thickness – 3mm
Secondary Members : O.D. – 1inch, Thickness – 2mm
Secondary members of less thickness were used to reduce weight of our roll cage. Another
major design goal was to more effectively pack all components in order to decrease the length
of roll cage. This has been successfully obtained through our compact design.
Solid works was used for Modelling and analysis of our design, results of which are shown
below. Proper mounting points for engine, Gearbox and Suspension links are provided in roll
cage. Electric arc welding was used for welding roll cage.
First a prototype of PVC pipes before manufacturing roll cage was made in order to check
space as well as comfort for driver. After satisfactory ergonomics was tested, the final roll-cage
was fabricated.
5.2 ERGONOMICS:
It is very important for our vehicle to be driver friendly such that driver should not feel
fatigue in long endurance run. This part of vehicle designing was given proper care such that
fun to drive vehicle can be made.
In order to achieve this goal following techniques are used to make driver feel comfortable:-
1) All the controls of vehicle were kept as close as possible to driver.
2) Brake and Accelerator pedals were installed and removed many times to mount it to
proper position which can be comfortable to our driver.
3) Steering has been made adjustable so that both drivers can adjust it according to their
requirements.
4) As we will face different types of terrains as well as turns time and again so changing of
gears again and again will make driver feel fatigue in 4 hour long endurance run. To
tackle with this problem CVT was used which made driver free from pressing clutch
again and again and also shifting of gears is also not required.
5) Seat from Sparco has been used.
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5.3 ANALYSIS OF FRAME:
Figure 1: Analysis of Crumpled Zone
The frame was designed and analysed using SolidWorks (a design and analysis
software). As there are no fixed amounts of force that a vehicle can endure in a frontal collision
and by using entities such as mass (vehicle) and its presumed top speed; a maximum force of
only 18000 N was derived, but there may be even serious conditions of collision than the ones
that are projected. Hence, a benchmark (of maximum endurable force) was to be finalised at
which our vehicle could sustain a collision and still have an FOS of at least 2. According to
U.S.A. automotive industry norms, all vehicles must be tested at a force of 10G’s, since an
average human body can only endure a force of 9G’s. A force of 10G’s comes out to be around
29,345 N or 30,000 N. Hence, the frame was tested at a force of 30,000 N in front impact
producing a FOS of 2.1 was achieved, but the impact caused a huge displacement of the force
throughout the frame.
The redundancies against this were chalked out and the frame was further optimized to
get an F.O.S. of 5.1, where a crumple zone was generated in the front part of the frame which
absorbed most of the damage leaving the cock-pit safe for the driver, was chosen as our final
design. Figure 1, shows the stress distribution in the frame (it may be noted that the entire stress
concentrates in the crumple zone) and figure 2, depicts the displacement of the frame in case of
front collision at 30,000 N.
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Figure 2: Front Impact Test Analysis
The frame was also tested under conditions of rear impact, bump impact, roll over, etc. The
related data is summarised in Table 3.
Table 3: Final Analysis Data of Frame
S.
No. Name of the Test FOS Max. stress Max. Displacement
1. Front impact (10G) 5.1 110,104,380 N/mm2 1.1720 mm
2. Rear impact (5G) 6.4 90,872,256 N/mm2 1.1388 mm
3. Roll over (2.5G) 3.0 151,804,816 N/mm2 0.4594 mm
4. Bump impact (6000N) 8.2 217,156 N/mm2 0.9631 mm
The drawings of the frame with necessary dimensions are shown in figures 3, 4, 5 and 6. The
frame was fabricated using the MIG welding set-up in Welding Shop of our College. It was
coated with red-oxide to prevent rusting. Further chainers were attached to the frame and holes
drilled wherever required. A few new braces were also added where physical satisfaction of the
frame was not achieved. Finally very thin sheet metal (mild steel) was welded to the surface
and was used to generate a characteristic body of the vehicle. Later the entire frame was spray
painted.
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Figure 3: Isometric View of Roll Cage
Figure 4: Side View of Roll Cage
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Figure 5: Front View of Roll Cage
Fig 6: Top View of Roll Cage
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6. SUSPENSION SYSTEM
Suspension is the term signifying the assemblage of the system of springs, shock
absorbers and linkages that connects a vehicle to its wheels and allows relative motion between
the two.
Suspension systems serve dual purposes —
i. Contributing to the vehicle's road-holding/handling and braking for good active safety
and driving pleasure, and
ii. Keeping vehicle occupants comfortable and reasonably well isolated from road noise,
bumps, and vibrations, etc.
For our vehicle we have used a Double Wishbone Independent Suspension system. This
is because of the following factors:
Wishbone suspension give more movement of the tyres and hence the vehicle, for the
same movement of the spring.
Independent suspension.
In double wishbone suspension, force is distributed at 5 points on the roll cage unlike in
Mac-Pherson strut where force acts at only one point.
It can be slightly adjusted for different parameters of suspension tuning like camber
angle, ground clearance at the time of testing.
Control movement at the wheel during vertical suspension travel and steering, both of
which influence handling and stability.
Table 4: Parameters used in designing the suspension system
Estimated weight of the vehicle 270 kg
Driver with accessories 80 kg
Overall weight of the vehicle 350 kg
Un-sprung mass 70 kg
Sprung mass (with driver) 280 kg
For designing the springs the sprung weight of the vehicle is considered.
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6.0.a. Basic Calculation in Spring Design:
Front lower wishbone length = 390.993mm
Damper mounting = 245.54mm
Motion ratio = 245.54/390.993 = 0.628
Natural frequency = 2 Hz
According to this motion ratio, natural frequency and taking 40% sprung mass for front,
spring rate is calculated as
Spring Constant = 24N/mm
Suspension travel = 10inch
Length of shock absorbers = 24inch
Similarly for rear taking 60% sprung mass, the spring rate is calculated as
Motion ratio = 0.712
Natural frequency = 2.4 Hz
Spring Constant = 32N/mm Travel = 10inch
Length of shock absorbers = 24inch
6.1. DESIGN OF FRONT AND REAR SUSPENSION SYSTEM
For the front, we are using unequal A-shaped Control Arm Double Wishbone System.
This was selected based on calculations for Roll Centre, Camber Angle, Caster Angle, King-pin
Inclination, Scrub Radius, etc. The design was tested under static analytical conditions and found
to be safe. The dynamic calculations were stimulated and analysed in LOTUS. Graphs plotted
justified design considerations.
On the rear side, we have used unequal H-shaped control arm for providing high
stability, at the same time to minimize the yaw motion without affecting the travel. Design
procedure adapted for the rear was similar to that of the front suspension.
Suspension arm was made of 1018 steel pipe of OD 1 inch with 3 mm wall thickness.
In front we have used ball joints of off road THAR jeep and in rear we have used bushes of 1
inch diameter and 2 inch length with the aim of minimizing the rear-yaw motion.
6.1.a. Calculation for Springs:
Analytical method is used in spring rate calculation and for that we had to take some parameters,
given in table 4.
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6.1.b. Calculation for spring rate:
We found that spring rate is depends upon motion ratio and wheel rate in the following way:
Front lower wishbone length = 409.423mm
Damper mount = 286.596mm
Motion ratio = = = 0.700
Natural frequency (f) = 2 Hz
According to this motion ratio, natural frequency and taking 40% of sprung mass for
front, spring rate is calculated as
K spring = 21 N/mm
Suspension travel = 10inch
Length of shock absorbers = 26inch
Similarly for rear taking 60% sprung mass, the spring rate is calculated as
Natural frequency (f) = 2.4 Hz
Motion ratio = 0.712
K spring = 30 N/mm
Figure 7: Front & Rear Wish-bones
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6.1.c Alternative approach:
We know that spring rate is calculated as:-
K spring = ,
where, G - Modulus of rigidity or shear modulus of spring material
d - Wire diameter
n - Number of active coils
D - Mean coil diameter
After considering all the above calculated data the suspension was designed and implemented
with the following specifications and dimensions.
Table 5: Final Specifications in Suspension Design
Specifications FRONT REAR
Roll Centre (Static) 175.62 mm 197.5 mm
Static Camber 2 degree
Static Caster 3 degree NA
King pin Inclination 12 degree 8 degree
Scrub Radius 26.5 mm 18.034 mm
Table 6: Suspension Design Methodology
Page | 17
Graph 1: Angles at BUMP Graph 2: Angles at ROLL
Graph 1(a) Graph 2(a)
Graph 1(b) Graph 2(b)
Graph 1(c) Graph 2(c)
Page | 18
6.2 KNUCKLES:
For the purpose of attaining desired configuration of the assemblies of braking system
to tyres and axles, the knuckles were self-fabricated. The front knuckle was fabricated as per
the requirements of the steering system, suspension system, braking system and tyres, whereas,
the rear knuckle was fabricated as per the requirements of the transmission system, suspension
system, braking system and tyres.
These knuckles were designed through the process of stress analysis and tested on
software. Firstly, the blueprint was designed using information obtained from the suspension
system specifications calculated, brake calliper positions and the inner diameter of the rim and
other adjacent components. Then, the design was tested with the amount of stresses the vehicle
had to endure during its running life and conditions; wherein a FOS of more than 3 was attained
for front and rear knuckles.
After the design was finalised, a prototype was fabricated to test the durability of the
designed knuckle. Further, the knuckles were modified to allow calliper mountings to be
welded upon them.
Figure 8: Metal pieces used to fabricate front and rear knuckles
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Figure 9: Front Knuckle
Figure 10: Rear Knuckle
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7. STEERING SYSTEM
Steering is the term applied to the collection of components, linkages, etc. which will
allow a vessel or vehicle to follow its desired course. The basic aim for us is to reduce the
steering effort to minimum with maximum steering response.
Design Methodology
Type of Steering System Decided
↓
Lightest Assembly of that system found
↓
Rack Length Measured
↓
Steering Arm Length and Angle decided
↓
Maximum Turning Angle Found
Table 7: Steering System Specifications
Steering Ratio 11:1
Maximum Turning
Angle
45 Degree (Inner)
30.23 Degree (Outer)
Turning Radius 2.5meter
Steering Arm Length 4”
Steering Arm angle 15 Degree
Tie rod length 12”
Rack Length 13”
Ackerman Geometry is adhered to in our steering system. Over steering is used to
decrease the steering ratio. Rack and Pinion arrangement has been chosen for its simplicity,
light weight, easy to assemble. Steering system of Maruti 800 is modified to make it centre
steering. A modified steering rack of Maruti 800 vehicle is used.
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Figure 11: Fabrication process under-way
Figure 12: Steering Shaft
Figure 13: Steering Rack
Figure 14: Steering Wheel
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8. BRAKING SYSTEM
A brake is a mechanical device which slows or stops motion. The purpose of braking
system is to increase the manoeuvrability by locking all the wheels in the shortest possible
time span. Our aim was to design a braking system which is easy to operate and light in
weight. Hydraulically actuated disc brakes have been used. Disc as well as calliper of
APACHE RTR 180 is used. Cutting brakes with hand operated master cylinder has been
employed at rear wheels to augment efficiency and safety of the vehicle by:
1) increasing the steering efficiency at corners by locking a single wheel by using cutting
brakes.
2) moving our vehicle out from the situation when one of the wheels is slipping and the
whole power is being transferred to the slipping wheel so by locking that wheel we can
transfer the power to the wheel in contact with the ground
Disc brakes of Apache RTR180 were used due to their small size which can
easily fit in rim. Also disc brakes of APACHE are of petal type which makes them more
efficient. Tandem master cylinder of Maruti 800 was used because of its separate braking
circuit at front and rear.
Modified pedal of Maruti 800 is used with leverage ratio of 6:1. Cutting brakes are
used in order to remove the drawbacks of open differential. Thus two separate levers are
installed and two separate callipers have been used. Both levers are connected to calliper
independently. Hand brake levers of Maruti 800 are used because of its availability in market.
Now we need master cylinder with one point delivery valve for cutting brakes. As no master
cylinder of single delivery point is available so Clutch cylinder of Tata Sumo is used as master
cylinder for cutting brake system with a modified fluid having low viscosity.
Stopping distance, as calculated theoretically, is 1.2 m.
Cutting brakes are a system of levers, switches, or pedals that allows the driver to lock
up individual brakes in order to stop one wheel and then use the other wheels to drive the
vehicle, thus pivoting around that locked wheel. This results in a tremendously tight turning
radius, and they can be implemented in a variety of ways. Cutting brakes operate by using
levers to actuate small master cylinders that apply each rear brake independently. It is placed
in open mode. One wheel is locked and vehicle pivots on the locked corner.
Weight distribution is approximated to be 60:40. If we stop our vehicle within 16
meters weight transfer of 55 kg from rear to front will take place.
During turning, bump and rebound of a vehicle, the centre of gravity of the vehicle
Page | 23
shifts according to forces acting on the chassis. In our innovation, we try to stop this shifting
of C.O.G by implying counter forces responsible for C.O.G shifting.
Figure 15: Brake Disc
Figure 16: Front and Rear Brake Callipers Mounting
Figure 17: Front and Rear Brake Callipers
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The entire calliper mounting was designed from the data acquired from the internal
diameter of the rim, the dimensions of the brake calliper and the dimensions of the knuckle
being used (front or rear knuckle). The calliper mountings once designed were tested for any
dimensional discrepancies while being attached to the brake calliper. Then the callipers were
fabricated using Laser Beam cutting machine to obtain impeccable dimensional tolerances.
Then these calliper mountings were welded to the knuckle to form a single body. The design
of knuckle and its analysis was done separately before welding the calliper mountings to it.
Figure 18: Virtual Model and Prototype of Rear knuckle welded with rear calliper
mounting (with housing for two callipers)
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9. INNOVATION
During turning, bump or rebound of a vehicle, centre of gravity of vehicle shifts
according to forces acting on chassis. In our innovation, we try to stop this shifting of C.O.G
by implying counter forces responsible for C.O.G shifting.
9.1. Mechanism
There are four sections in innovation:-
A. Hydraulic mechanism
B. Gear mechanism
C. Electrical mechanism
D. Computer Section
9.1.A. Hydraulic mechanism:
Components used for innovation:
1) Piston (For front wheel) - 2
2) Piston (For rear wheel) - 2
3) Pipes - According to size
4) Pipe joints
5) Safety valves
6) Safety lever
9.1.B. Gear mechanism:
In this, the power from the motor to the piston is transferred. There are two pairs if
piston is used. Each pair contains two piston and these pairs are connect with each other to
a rack.
Rack: Rack has teeth on double sides.
Pinion Gears: Pinion is attached to rack. It is used to convert its rotary motion into
rack’s reciprocating motion.
Worm: Worm is attached to the pinion. It is used to restrict the motion in one direction.
1. Vehicle can easily be turn at high speed avoiding the problem of rolling and hard
turn.
2. Effect of bumper, bound, dive and squat is minimizing to extreme level.
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3. Now shifting of C.O.G is being controlled, so the drive is more comfortable
for the driver.
4. Skidding is also controlled. We maximize the limit of tire’s traction by counter the
forces.
9.1.C. Electrical Mechanism:
In electrical mechanism, a pre-programmed electronic circuit is used to determine how
much power has to be transferred to motor on the basis of shifting of Centre of Gravity.
9.1.D. Computer Mechanism:
In this mechanism basic input of signal from sensors are converted into
useful coding. it is used to control amount of current control transfer and coding
and decoding of sensor is done.
9.1.E. Safety:
We would use safety valves, so that in case of fluid leakage then valves will be
automatically closed and suspension acts like ordinary suspension. We would use safety lever
for the convenience of the driver. If driver feels any problem in suspension then he can stop or
disengage all mechanisms.
Figure 19: Dynamically Stabilised Steering System Layout
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10. ENGINE & TRANSMISSION
A lot of emphasis has been placed on the design of power train. Our objective is to
harness the power of 10 HP engine and efficiently deliver this power to the tires for peak
performance. In design of the drive train the optimization of several desired
characteristics are being kept in mind including towing capacity, acceleration, top
speed, and durability. Every internal combustion engine have a power band (range of
speed) at which the engine produces the maximum torque, below or above this power band
the engine does not provide enough torque to overcome the resistance torque and
accelerate the vehicle. Such a small amount of power within the power band is not sufficient
for the performance required.
Therefore we either have many gear speeds or we use a CVT (Continuously Variable
Transmission). Continuously variable transmission (CVT) belt drive is a device that is much
smoother than a conventional transmission and also has the ability to harness peak engine
power during operation. The CVT transmits power from the engine to drive train in place of a
conventional clutch dependent multi-gear transmission that requires constant shifting to
change reduction ratios. It consists of two variable pitch pulleys, the drive and the driven, that
semi-dependently change their ratios depending on the RPM at which they spin and the
amount of torque required.
The goal of the design for driveline is to eliminate as many losses, in transfer of
power from engine to the wheels, as possible. To accomplish this goal the drive train
consists of CVT, chain and sprocket and differential.
Figure 20: Left and Right View of the Engine.
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We are using a BRIGGS & STRATTON 10 Hp OHV Model 205432 Engine. The
CVT we are using is of POIARIS P90 with low gear ratio 0.75:1 and high gear ratio 3.83:1.
The differential used is of MAHINDRA ALPHA with gear ratio 4.173: 1. We will couple the
axles of MAHINDRA ALPHA CHAMPION & MARUTI 800. The custom made stub axle of
material EN-119 is to be used.
The size of tyres to be used is 23 x 8 x 12. As the engine reaches its governed rpm
limit 3800 rpm, the gear reduction across the CVT have been determined to be 0.75:1
and thus serving as an "overdrive" for the car. At low engine speeds the CVT produces a
reduction of 3.83:1 providing necessary torque considered for the half shafts because of their
ability to transmit torque through a higher range of suspension articulation. These features will
create a vehicle that utilizes all of its power in a smooth, quick transition from rest to top
speed, and ensures minimal maintenance. We plan to restrict our top speed to 45 kmph, the
vehicle being an off-roader.
Figure 21: Cone Pulleys of the CVT
10.1. Methodology for selection of Transmission Components:
A study on comparison between different transmission systems was done. CVT was best suited
for our application due to:-
1. Efficient power transmission capability
Page | 29
2. Simplicity in Setting up the system
3. Automatic Gear Ratio Selection thus reducing Human Errors.
4. Elimination of Clutch Assembly
Based on the study and discussions with old
teams regarding off road conditions at Pithampur
track top speed of 45-50kph was decided. Data
provided by Briggs and Stratton states maximum
rpm of engine as 3800 which can be considered
as constant. Finally gear ratio of 8.5-9.5 was
required to achieve top speed. Polaris P90 model
of CVT was selected due to its wide range of gear
ratios i.e. 0.76:1 to 3.83:1. Graph 3: CVT characteristics
There was a doubt regarding selection of type of differential to be used for which
benchmarking was done for different types considering various factors.
Open Differential was used based on above result. But problem of power loss during
slipping were considered as serious one so a proper solution was to be found. Cutting brakes
were used to remove the flaws of open differential system .Now with the help of cutting
brakes it is possible for us to lock slipping tyre and thus proper power transmission to the tyre
in contact with ground.
Now, due to overdrive of CVT setup final drive ratio of 11-12 was required. Reverse
gear was also a necessity for our vehicle so based on all these requirements, market survey
was done from which we came to know that Mahindra Alpha Champion gearbox comes with
two types of differentials (Open). Gear ratios of both differentials were 2.32:1 and 4.16:1.
Gearbox was dismantled and was found that if its 3rd gear is used in reverse with differential
having final drive of 4.16:1 then we get Top Speed of 50.54kph. Using Mahindra Alpha
Champion gearbox all the requirements were fulfilled i.e.
1) Required Gear Ratio
2) Reverse Gear
3) Open Differential.
To reduce the rotating mass a little modification was done with gearbox. All
other except third and fourth gears were removed from the gearbox.
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11. WHEELS & TYRE ASSEMBLY
11.1. Rim: Selection of Rim was the most
crucial factor to be decided as knuckle,
Disc and Calipers were to be placed
inside the rim, so, proper space must be
allocated there, to do so. Also, the
weight of rim must be less in order to
decrease rotational inertia of moving
parts. So, selection of rim size was done
by design, suspension and braking
department which had been discussed in
their respective departments. Figure 22: Rim
Rim from Polaris of Diameter – 12inch and width – 6inch were finalized for use, as
they are light in weight.
11.2 TYRES: Tyres were decided on the basis of final drive at axle and top speed required.
It was also required to choose the tyre of less weight in order to decrease the rotating mass.
So LOW INERTIA BKT tyres of size 24 x 8 -12 were used.
11.3. HUB: Hub had to be self-manufactured as PCD of Polaris Rims did not match with
available standard. The hub had to be bolted to the rim at one end and to the disc rotor of
Apache RTR 180’s rear brake on the other.
Figure 23: Hubs made of Aluminum alloy using VMC
Page | 31
So, a hub was designed and fabricated according to the required dimensions & special
needs such as strength, structural integrity, etc. and also an effort was made to reduce the
weight of the hub, by using Aluminum alloy as the material for HUB.
Figure 24: Fabrication of stub axle (in-process)
T6 6061Grade is used due to its following properties:-
1. Ultimate high tensile strength.
2. Light weight
The hub fabrication also created a problem of locking the axle, which was
rectified by the use of grooves cut inside the hub where locks were placed to hold the axle
and stub axle sub-assembly.
11.4. STUB AXLE: Stub axle, as we know,
plays a crucial role in transmission of power
form the axle to the wheels through the
knuckle. Stub Axle of Maruti 800 has been
used in the manufacturing of this ATV. The
stub axle is very difficult to design as
precision is required so as to achieve the
proper meshing of stub axle to the power
transmission. In Maruti, stub axle and hub is
a single unit as they are manufactured by, Figure 25: Stub Axle
Page | 32
casting process so, cutting off of the hub until its stub-axle or required dimensions have
been achieved was the way to go. So, the stub axle was acquired from the MARUTI 800
hub. The only reason to take Maruti 800’s stub axle is that it has proper meshing with the
axle of Maruti 800 and this meshing must be kept as smooth as possible for better
transmission of torque.
11.5. AXLE: Axle of Alpha champion is used on the differential side as differential of alpha
champion has been used. Further, the axle is welded to Maruti 800 axle as stub axle of
Maruti has been used on the hub side, as the internal and external splines of stub axle and
axle mesh properly thus resulting in proper power transmission. Hence, both the different
axles were welded together to form one body, then they were machined (surface grinding)
for crack removal and also heat-treated to remove any residual stresses introduced.
11.6. Vibration Control: To control the vibration of Engine and Gear box we installed
three dampers of Maruti 800 engine and placed the entire assembly of Engine, CVT,
Gearbox and axles over these three dampers. The entire assembly of the transmission
system was then in connection with the vehicle through only these three dampers and
hence all the vibrations from the assembly were isolated to the transmission system itself.
This also reduced the slipping of the CVT belt as the engine and gearbox were now in a
synchronized vibrational state.
11.7 COUPLINGS: Coupling of different components in transmission system is to be
done with utmost care, using best efficient system and reducing weight of components.
Maximum loss of power occurs at couplings.
Figure 26: Press-fitted bush in CVT & Key fitted in Engine shaft
Page | 33
Coupling of different components has been done as follows:
11.7.a. Engine with Primary Pulley: - Outer diameter of Engine shaft is 25.4 mm and Inner
diameter of CVT where shaft is to be inserted is 30mm. Keyway is provided on Engine
shaft. So a method was selected such that modification of Engine Shaft and CVT need not
be required. Bush of Outer diameter- 30mm and Inner Diameter-25.4mm was made and
press fitted in CVT.
A little weld joints were provided to avoid slipping of bush on CVT. A keyway is
made on bush. Key of material EN31was made.
EN31 material was used because of following properties:-
a. High resisting nature against wear.
b. Ability to bear high surface loads.
Key was press-fitted on Engine shaft and finally CVT coupled with Engine.
11.7.b. Primary Pulley to Secondary Pulley – through V- Belt
11.7.c. Secondary Pulley to Gearbox: There are internal splines on gearbox as well as CVT
so a shaft is made according to those splines with uttermost care such that power loss as
well as wearing of splines due to play is reduced. EN19 Material was used for making
shaft due to following reasons:
a. Shock resisting.
b. Resistance to wear.
c. Ability to bear high stress.
11.7.d. Gearbox to Axle: Gearbox and Axle of same vehicle i.e. Mahindra Alpha Champion
is used so no need to make coupling.
11.7.e. Alpha Champion Axle welded to Maruti 800: Done with utmost care as improper
welding may lead to vibrations in shaft or failure may take place which can be fatal for
driver.
Page | 34
11.7.f. Stub Axle with Hub: A keyway was made on Stub axle and inside hub. A key was
placed in keyway of stub axle and press-fitted inside hub. Same material of key was used as
was used in Engine.
11.7.f.i. Calculation for key:-
Shear strength ( s) = 202.5 MPa
Compressive strength (Cs) = 585 MPa
Torque (T) = 350 N-m
Width of key (b) = 6.6 mm
Height of key (h) = 4.8 mm
Length of key (L) = 63.5 mm
Mean diameter of bush (Do) = Diameter of bush – Depth of groove
= 30 – 2.42 = 27.58 mm
Tmax =
= 1161.8N-m
(Factor of safety = 1161.8/350 = 3.32)
T’max =
=
= 1220.52 N-m
(Factor of safety = 1220.52/350 = 3.49)
11.8. WHEEL ASSEMBLY: When all the necessary component assembly are
fabricated, the wheel assembly is completed. The components of rear wheel assembly are
Rear knuckle, rear calliper mounting, 2 brake callipers, disc rotor, hub, stub axle, locks on
both sides to keep the axle from sliding, etc. . The front wheel assembly consists of the
components such as Front knuckle, front calliper mounting, brake calliper, disc rotor, hub,
stub axle, locks on both sides to keep the hub and knuckle locked to each other, etc. All the
components of the wheel assembly are assembled and tested again and again, so, as to
check for errors.
Page | 35
Figure 27: Front Wheel Assembly
Figure 28: Rear Wheel Assembly
Page | 36
12. SAFETY FEATURES OF OUR VEHICLE
Safe Roll cage design.
Evacuation - Easy entry & quick exit possible.
Proper firewall & body panels.
Firewall insulated with asbestos sheets.
Removable steering wheel.
Driver gears- helmet, goggles, suit, neck collar, restraints
Tube Padding – The minimum required thickness is ½”.
Kill Switches – 2 required, cockpit and external.
Safety Harness – 5 strap system, 3” lap belt, quick release connecters
Fire extinguisher – 2 required, 1 liter, ISI rated. One mounted in cockpit and one for
accessories.
Figure 29: Bucket Seat
Page | 37
13. THE SPECIFICATIONS OF OUR VEHICLE
Overall Length: 94”
Wheelbase: 72”
Track Widths: Front - 51” Rear - 49”
Weight without Driver: 270 Kgs;
Frame Weight with Brackets: 45 Kgs
Weight Distribution of 42:58
Wheels: BKT; Front & Rear: 24 x 8 - 12
Ground Clearance: 10”
Suspension and Steering:
Front Suspension: Double wishbone equal length, non-parallel (A-arms)
Rear Suspension: Double wishbone equal length, non-parallel (A-arms)
Centre of Gravity Design Height: 482.6 mm
Centered Rack and pinion, Steering Ratio of 11:1
Engine: Briggs & Stratton 305cc, 10Hp
Transmission:
Polaris P90 CVT giving drive to Differential.
Braking system
Tandem master cylinder, Apache RTR 180 rear disc
Cutting brakes with hand operated master cylinder
Figure 30: Final Assembly of the vehicle
Page | 38
S No. Item Quantity
1 Steering Wheel 1
2 Steering Column 1
3 Pinion Assembly 1
4 Rack Rod 1
5 Tie Rods 2
6 Ball Joint 4
7 Rack Ends 2
8 Bushes 4
9 Clampers 4
10 Steering Gaiter 3
14. BILL OF MATERIALS
DRIVE TRAIN
STEERING SYSTEM
BRAKING SYSTEM
ENGINE
FRAME
SUSPENSION
S No. Item Quantity
1 Primary Pulley 1
2 Secondary Pulley 1
3 Spring 1
4 Flyweight 3
5 Belt 1
6 Driving Sprocket 1
7 Driven Sprocket 1
8 Chain 1
9 Differential 1
10 Axle 4
11 Stub Axle 4
12 CVT Cover 1
13 Tires 5
14 Rim 4
15 Hub 4
16 Bearings 4
17 Shift Mechanism 1
S No. Item
Quantity 1 Brake Pedal 1
2 Master Cylinder 1
3 Brake Linings (Rubber) 4
4 Brake Linings (Metallic) 4
5 Disc Rotor 4
6 Brake Calliper 4
7 Brake Fluid 1
8 Disc Mounting 4
9 Hand Operated Lever 1
10 Brake Calliper
(cutting 10 brakes)
2
11 Brake Lining
(cutting brakes) 4
S No. Item Quantity
1 Engine 1
2 Choke 1
3 Accelerator 1
4 Pedal Cables 2
6 Spill Prevention 1
S No. Item Quantity
1 Structural Members 68
2 Roll Cage 1
3 Mounts 58
4 Firewall 1
5 Seat 1
Sl No. Item Quantity
1 Rear lower control arm 2
2 Rear upper control arm 2
3 Front Lower control arm 2
4 Front upper control arm 2
5 Rear Knuckle 2
6 Front Knuckle 2
7 Ball Joints 4
8 Bushes 24
9 Shock Absorbers 4
10 Shackles 8
11 Innovation 1
Page | 39
15. FINANCIAL OUTLAY
Table 8: Details of Project Costs
CATEGORY ITEMS CATEGORY COST (RS.)
Frame Steel Tubing, Sheet Metal
Welding Supplies
30,000
Power Train Gearbox, Rear Axle, Joints,
Chain, Sprocket & Bearings
1,30,000
Electronic Systems Pedal shifters, tachometer,
ECU etc.
10,000
Suspension Shocks, Springs, A-Arms, 20,000
Wheels and Tires Polaris Wheels & Tires
(4 + 1 spares)
90,000
Steering Rack & Pinion, Steering Arm,
Steering Wheel, Steering
Column etc.
15,000
Braking Callipers Pedal + Lever
Cylinders + Cables
20,000
Body Fibreglass, Pads, Ply Boards 20,000
Safety Equipment Driver Suit, fire extinguisher
Seat belt, goggles, Helmet etc.
50,000
Miscellaneous Travel, transportation, 50,000
Engine 30,000
Total: 4,65,000
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16. CONCLUSION
The fabricated vehicle has performed more than satisfactorily at SAEINDIA BAJA 2013 held
at National Automotive Testing Tracks (NATRAX), Pithampura, Madhya Pradesh. The vehicle
successfully cleared all the strict technical inspections conducted by the team of engineers from
Mahindra & Mahindra and Automotive Research Association of India (ARAI). In fact, we received
rich praises for the effort put in designing and fabricating the vehicle.
The tests endured by our vehicle include Break Test (all four wheels lock simultaneously),
Acceleration Test, Figure of Eight Test (the vehicle moved in a 8 shaped track with radius of 3 meters
without reversing and at considerable speed), Hill Climb Test (220 slope for 100 meters),
Manoeuvrability Test (the vehicle was made to go through L-turns, hair-pin bends, mud-pits, sand,
over logs, etc.) and most importantly the 4-hour long endurance run, which we successfully completed
in the top 15!
16.1 Future-scope:
However, the vehicle still has a scope of improvement. The innovative dynamic stabilised
steering system being developed can be very helpful in reducing driver fatigue. Extensive studies may
be undertaken in the areas of emission and engine efficiency with an aim to develop a greener vehicle.
Page | 41
Figures 31, 32 & 33: Complete
ATV, while participating in SAE
India BAJA 2013, competition in
Indore.