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8/10/2019 CAR no. 53, Final PDR
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BAJA SAE INDIA 2014
DESIGN REPORT
TEAM EXERGY
TEAM ID: - 14117
VEHICLE NAME:- ARJUN MARK 1
MALWA INSTITUTE OF TECHNOLOGY
& MANAGEMENT, GWALIOR, MP
ABSTRACT
Baja SAE, the ATV design and Racing event which
provides a platform for the undergraduate student
to apply the universally known principles if the
engineering and physics to experience then
proficiency in the automobile sector. By fabricating
and designing a prototype vehicle that could be
used by consumer.
INTRODUCTION
Team “EXERGY” aim to design an ALL TERRAIN
VEHICLE with light weight, inexpensive, fun to
drive, safe and reliable, inexpensive for an off road
vehicle enthusiast.
In order to accomplish their task different designs
of SAE Baja vehicle analyzed and certain element of
the car were chosen for specific focus. There are
many facets of ATV such as, the chassis,
suspension, steering, drive train and braking. All of
which requires huge design concentration. The
points of the car that the team “EXERGY” decided
to specifically focus on were chassis, drive train,
suspension, and braking because of the most
dramatic effect of off road.
Team “EXERGY” began the task of designing ATV by
conducting extensive research and analysis of
components of the vehicle.
Team was divided into three groups namely X, Y,
and Z:
X: Designing group
Y: Research and analysis group
Z: Documentation group
VEHICLE SPECIACIFICATION
GOAL ACHIEVED: - (VEHICLE SPECIFICATION)
ENGINE:-
• Briggs & Stratton model
20s332 -0036 OHV intake 305.
POWER TRAIN:-
Gearbox: - constant synchromesh4-forward + 1 reverse sequential
type.
BRAKES:-
Type: - Front & Rear Hydraulic
Disc Brakes.
TIRES:-
Type:- front:- 25 ”
Rear: - 25 ”
SUSPENSION:-
Type:- independent
Geometry:- double A-arm.
Shocks: - coil spring with dampers.
STEERING:-
Type: - front wheel steer.
Geometry:- Ackermann geometry
OVERALL DIMENSIONS:-
Wheel base:- 1600 mm
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Wheel track:- 1300 mm.
TARGET WEIGHT:-
Kerb weight:- 280 kgs
Weight distribution:- 40:60
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1. CHASSIS: -
Purpose of Chassis is to serve various functions
like: Linking the Powertrain, Suspension,
Comfortable to operate, Driver ergonomics and
Safety issues and other design factors included
durability and maintainability of the frame.
Our team has taken a good consideration of 5
second escape and other clearances & tolerances
that are mentioned in rulebook.
The space frame is firstly drawn on paper to
accommodate the ease and behavior of design
aesthetics and only then modeled and analyzed in
‘SOLIDWORKS 2013’
The Cross-sectional property of the space frame
roll bars are 25.4 mm O.D. and 3 mm wall
thickness.
MATERIAL USED
Material Data - Steel – AISI 1018
COMPOSITION:
Element Weight %
Thickness 3mm
C 0.18
Mn 0.74
P 0.02
S 0.03
Si 0.16
DES
IGN
CO
NSIDER
ATI
ON
S:
1- Minimizing the weight of vehicle.
2- A compact vehicle.
3- Minimum cost of manufacturing.
4- Ease of maintenance and replacement of
parts.
5- Acceptable level of safety.
6- To have an energetic look of an off-road
vehicle.
DESIGN METHODOLOGY:The main objective of the frame is to provide a 3-
dimensional protected space around the driver
that will keep the driver safe. The space frame is
firstly drawn on paper to accommodate the ease
and behavior of design aesthetics and only then
modeled and analyzed in ‘SOLIDWORKS 2013’
Prototyping was also done using PVC Pipes to check
the driver ergonomics & accommodation of various
subsystems as shown in fig and further changeswere made in design by several iterations.
PROPERTIES:
Material Properties used in Roll Cage
Density (×1000 kg/m3) : 7870
Poisson's Ratio : 0.30
Elastic Modulus (GPa) : 205
Tensile Strength (MPa : 634
Yield Strength (MPa) : 365
Elongation (%) : 27
Reduction in Area (%) : 48
Hardness (HB) : 197
FINITE ELEMENT ANALYSIS OF ROLLCAGE
DESIGN USING SOLIDWORKS 2013
All simulation of the space frame was done in the
SW2013 by considering a static structural analysis
of meshing type ‘beam mesh’ and stimulated load
were applied on the critical points of the roll cage
Before attempting to calculate the input loads, it
was necessary to determine what kind of obstacles
would be encountered during vehicle operation
AISI 1018
(M.S.)
AISI 4130
(Chromoly)
Availability 1 0
Modulus of
elasticity
205 GPa 205 GPa
Elongation 53.7 63.1
ElongationAt Break
15% 25.5%
Result Chosen For
Vehicle
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This was done by reviewing test and competition
videos of other SAE Baja vehicles on the internet.
This allowed the team to get a very broad sense of
what terrain the vehicle would be required to
overcome.
Force estimation for loading conditions
By Newton’s IInd Law of motion
F = m.a
Where,
F= Force, m = mass of vehicle, a = acceleration
For Front impact analysis (Assumed G factor = 3.6)
Ff = 280kg x 3.6 x 9.81 m/s2
Ff = 9888.48 N
Hence force was taken to be 9890 N for
FRONT IMPACT TEST.
Results
Name Min Max
Stress 0 N/mm^2 (MPa)
Element: 38
163.978
N/mm^2 (MPa)
Element: 506
Displacement 0 mm Node: 35 5.87726 mm
Node: 412
Factor of Safety 2.22591
Node: 516
1e+016
Node: 42
For Rear impact analysis (Assumed G factor
= 3.6)
F= 280kg x 3.6 x 9.81 m/s2
Fr= 9888.48 N
Hence force was taken to be 9890 N for
REAR IMPACT TEST.
Results
Name Min Max
Stress 0 N/mm^2
(MPa)
Element: 25
155.904 N/mm^2
(MPa)
Element: 566
Displacement 0 mm
Node: 27
8.67686 mm
Node: 39
Factor of
Safety
2.34119
Node: 119
1e+016
Node: 27
For Side impact analysis (Assumed G factor = 3.2)
F= 280kg x 3.2 x 9.81 m/s2
Fs= 8789.76 N
Hence force was taken to be 8790 N for
SIDE IMPACT TEST.
Results
Name Min Max
Stress 0 N/mm^2 (MPa)
Element: 571
190.862 N/mm^2
(MPa) Element: 492
Displacement 0 mm
Node: 60
4.61364 mm
Node: 454
Factor of Safety 1.91237
Node: 502
1e+016
Node: 581
TORSION TEST
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2.
SUSPENSION:-
An ATV is proposed to have a best of the suspension
system than the other categories of the vehicle. The
unpredictable nature of off road racing creates the need
for a reliable an efficient suspension system. It is a part
that gives a vehicle the ability to maneuver, the job of
the suspension is to maximize the friction between the
tire and road surface to provide steering ability with
good handling.
Designing of the car suspension is almost entirely a
matter of making efficient approximation. So, the
selection of the suspension system was the most
important task for the team.
DESIGNING GOALS:-
Not to use stiffer or softer spring.
Light weight suspension system.
Try to keep calculation as simple as possible.
Draw free body diagram for load on wishbone.
Ensures the free movement of wishbones.
Improve vehicle handling and stability.
Provide adequate wheel travel during jounce
and bumps and not to become solid on bumps
or jounce.
Serviceability.
Try to create an overall good performing
suspension system that could perform in all
terrains
PROCESS OF SUSPENSION DESIGNING /
CONSIDERATION:-
Selecting vehicle level target
Type of suspension.
Positioning hard points.
Loads in suspension
Calculate spring rate
DESIGN APPROACH:-
We decided to opt. independent suspension over
dependent suspension because of inconsistencies in the
track.
Among the other independent suspension MacPherson
strut, double-wishbone, semi-trailing arm were our
main approach.Though having simple design and few components,
MacPherson struts used widely spaced anchor points
that reduce loads. This suspension system has high cost
of servicing the shock absorber.
Semi-trailing Arm has been ruled out due to difficulties
in packaging, so it cannot be used further. The rear
wheel track reduces the maneuverality of vehicle
therefore double A-arm wishbone suspension system in
front and rear was opted.
SUSPENSION SPEACIAFICATION:-
TYPE FRONT REAR
LOWER ARM LENGTH 255 mm 255mm
UPPER ARM LENGTH 240 mm 266 mm
SPRING WIRE DIA. 7 mm 8 mm
SPRING MEAN DIA. 50 mm 50 mm
SPRING LENGTH 270 mm 300 mm
NO. OF ACTIVE COILS 13 7
TOTAL LENGTH 395 mm 450 mm
ROLL CENTRE 57 mm 85 mm
MAX. TRAVEL 145 mm 145mm
STIFFNESS 14000 N/m 20000 N/m
MOTION RATIO 0.6 0.6
A-ARM DESIGN CONCEPT:-
Once wheel track and height of roll center is
calculated, it becomes easy to us to find out the
required length, angle of inclination (w.r.t. upright
and chassis) of A-arm by considering distance
between pivot points on the chassis and the
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dimensions of A-arm as well as geometric
configuration of each arm.
Design for optimal geometry of A-arm is done to
support both the race weight of the vehicle as well
as to provide optimal performance to stop.
Designing also includes maximum adjustability in
order to tune the suspension.
VIEW OF A-ARM:-
Load applied = 2 KN
Factor of safety =1.66
SHOCK ABSORBER AND MOUNTING POINTS:-
We are using shock absorber of splender in front
and rear shock absorber of pulsar 220 in rear.
REASONS:-
Reduce cost and time of manufacturing.
Become more reliable.
FRONT SHOCKER MOUNTED ON LOWER A-ARM:-
To Reduce The Vehicle Weight.
Increase the driver visibility.
Strengthen the upright on chassis.
REAR SHOCK ABSORBER:-
Can’t be mounted on lower as the axle shaft
between the upper and the lower arm.
Mounting shocker on the knuckle ensures
reliability and allows us to lighten A-arm
but wheel travel decrease which could
transfer load on mainframe of suspension
system.
MAIN FEATURES OF SUSPENSION SYSTEM:-
Front roll at 57 mm and rear roll at 85 mm
above the ground the value reduces jacking
forces with acceptable value of rol
angle=6°.
The ratio of rear roll Centre to front rol
Centre is 1.49 which is very close to idea
value 1.50.
Little bit nose dive type.
3. STEERING:-
A good steering mechanism is must for vehicle stability
at the time of turning. Steering of our vehicle is
designed in a manner so that it will not permit lateral
slip of front wheel during steering. We use rack and
pinion steering gear of Maruti 800(customized) with
some modification because it’s being compact,
economical and light package. Rack and pinion gearsystem is more stable as compare to worm and roller it
has involute teeth profile therefore the meshing teeth i
better as compare to worm and roller type of steering
gear system.
STEERING GEOMETRY:
When a four wheeler takes a turn, all its four wheels
should roll without slipping laterally. This is possible
only when the axis of four wheels intersect at one point
This point is the centre about which the vehicle turn at
that instant.
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ACKERMAN STEERING:
When a vehicle travels round a bend, the inside wheel
must follow a lighter curve than the outside wheel. To
achieve this, the geometry of the steering must be
arranged to turn the wheel.
STEERING CALCULATIONS:
Inner lock angle 40®
Outer lock angle 26®
Steering ratio 13:1
No. of steering wheel rotation 2.9
Turning radius 2.7m
Ackerman angle 31.38®
Ackerman % 108%
Toe-in 10mm
STEERING DESIGN METHODOLOGY:1. We use inner lock angle 40® to satisfy the
Ackerman steering condition.
2.
No. of steering wheel rotation is more to ease in
cornering in manual steering.
3.
We use toe-in to stabilize steering, prevent
slipping towards side out and prevent excessive
tire wear.
4.
Inner wheel through a larger angle than the
outside wheel. The Ackerman steering produces
a simple solution to this problem.
TOE-IN:
Purpose of toe-in is to ensure the wheels on rolling
parallel.
To stabilize steering and prevent slipping towards side
and to prevent excessive tire wear.
FORMULA FOR CALCULATIONS:
1). Ackerman condition:
Cot0 – cotI =Wt/Wb
Where,
o=turn angle of the wheel on the outside of the turn
=turn angle of the wheel on the inside of the turn
Wt=track width
Wb=wheel base.
2).Minimum radius of the turn:
R=B/tani+ Wb
3).Maximum radius of the turn:
R1=√
Where,
b=distance from rear axle to centre of mass
4).Steering movement ratio:
M.R=
=
5).Output load transfer to tie rod:
Fo= Fi ×M.R.
Where,
Fo=Force transmitted on tie rod
Fi=Force applied by each hand on steering wheel
6).Inner lock angle ()
=
7).Outer lock angle (:
cot - cot =Wb×b
8.) Ackerman angle:
Tan=
9). Ackerman %:
%Ackerman=
100
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4. POWER TRAIN DESIGN
OBJECTIVE
The power train is designed to transmit the power
of the engine to the wheels and tires. As a team we
wanted to do this as efficiently and reliable as
possible. We did this in a manner that would allowan efficient power-train system which would be
easy to operate, and reduce maintenance and its
maintenance cost.
EngineAll the teams participating in BAJA SAE INDIA
2014 have generously sponsored with a 305cc,
10Hp Briggs and Stratton engine. The specification
of engine is as follow.
ENGINE
SPECIAFICATION
Torque* (N-m) 18.6
EngineDisplacemen
(cc)
305
Number of
Cylinders
Single
Engine
Configuration
Horizontal Shaft
Engine Technology OHV
Length (in) 12.3Width (in) 15.4
Height (in) 16.4
Weight (lbs.) 50.4
Bore (in) 3.12
Stroke (in) 2.44
Engine Fuel petrol
Spark Plug RC12YC
Design methodologyThe drive train includes the engine, transmission
and axle for transmitting the power to the wheels.
The transmission should fulfill the conditions of the
Baja buggy like climbing steep grades, propelling
the buggy with a maximum speed in terrain and
provides the required torque in rough tracks as
efficiently as it can be done. We will be having a
rear wheel drive and the engine and the
transmission both will be placed such that Centre
of gravity of both of them lie more or less in the
Centre.
Selection of transmission type.
CVT is an automatic transmission which on one
hand provides comfort in drivability and handlingbut on the other hand is very expensive. Manua
transmission on one hand is cheap but it has some
complexity in its operation. The below mentioned
table is comparing both CVT and Manua
transmission feature.
Transmission Selection Criteria
PARAMETERS CVT MT
Weight 1 0
Performance 1 1
Drivability 1 1
Reliability 0 1
Simplicity 1 1
Cost 0 1
From the comparison made above, we suitably
choose Manual Transmission rather than CVT in
terms of cost, reliability, performance and fue
efficient in which the overall gear ratios are varying
from 7.66(top gear) to 55.08 in reverse. The below
matrices showing the gear ratios of the
transmission system:-
GEAR GEAR RATIO
FIRST 31.48
SECOND 18.70
THIRD 11.40
FOURTH 7.66
REVERSE 55.08
CALCULATIONS.
Max Velocity on road.
=
= 53.2 km/hr.
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Where,
G = gear ratio.
N = revolutions per minutes.
R = outer radius of tire in meter.First = 10 to 12 km/hr.
Second = 15 to 18 km/hr.
Third = 25 to 33 km/hr. Fourth = 40 to 55 km/hr.
Reverse = 8 to 11 km/hr.
Max possible acceleration.First gear = 4.91 .
Second gear = 1.8 .
Third gear = 1.49 .
Fourth gear = 0.90 .
Average acceleration of our vehicle = 1.8 m/. Max gradiability.Assuming no speed condition at rear wheels.
Vehicle will topple when reaction at front wheels
becomes zero.
First gear = 39.84°.
Second gear = 21.46°.
Third gear = 12.93°.
Fourth gear = 8.31°.
Reverse gear = 87.31°.
Theoretical max gradeability comes out to be =
42.29°.
5.
WHEEL AND TIRE SELECTION
The final components of the power- train are the
wheels and tires. The wheels and tires play an
important role in performance as well as reliability
and aesthetics. We wanted to choose tires and
wheels that would give our vehicle an aggressive
off road look. We also wanted to make changing
the tires easy and convenient for our customers.
Our research found that when riding rough terrain,
tire problems are common and many riders bring
spare tires along with them so they can overcome
these challenges in the field. We made this
convenient on our customers by using the same
bolt pattern all the way around our vehicle. This is
unique to what is found in the industry where the
front and rear tires and wheels are commonly
different. Since we are using axels of maruti 800 so
for our convenience we use maruti 800 hubs with
matching bolt patterns of 4j/12 on all wheels. For
our tires we choose Polaris 25×8×12 tires because
of their appearance and radial design and their
availability. The radial tires will be more reliable for
maintaining air pressure. We choose our tires to be
an inch wider than wheels so that track obstacles
will come into contact with our tires before our
wheels which will reduce damage to our wheels.
AXLES –
Axels are used to transfer power from thegear box to the tires. We had the option of getting
custom build axels or buying maruti 800 axels.
Since custom build axels are very expensive
because of machining that has to be done while
maruti 800 axels cost a lot less and easily available
in market.so we will use maruti 800 axels with two
half shafts connected to differential via CV joints.
6. BRAKES:-
An excellent braking system is the most important
safety feature of any vehicle. It goes without saying
that brakes are one of the most important contro
components of vehicle. They are required to stop
vehicle within the smallest possible distance and
this is done by converting the kinetic energy of
vehicle into the heat energy which dissipated in the
surroundings.
BRAKING CONSIDERATION:-
1. At least two hydraulic system, so that in the
failure of one, the other would continue to
provide adequate braking.
2. Ease of procurement, performance and
simplicity are the few criteria which are
considered and also be reliable.
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3. The brakes must be strong enough to stop
the vehicle within a minimum distance in an
emergency. But this should also be
consistent with safety. The driver must have
proper control over the vehicle during
emergency braking and the vehicle must
not skid.
4. The brakes must have good antifade
characteristics i.e. their effectiveness
should not decrease with constant
prolonged application e.g., while
descending hills. This requirement demands
that the cooling of the brakes should be
very efficient.
DESIGN APPROACH:The two main types of brakes which are considered
were: 1) drum brakes, and 2) disc brakes.
But, as we know that the terrain will full of mud
and sand, which can create a problem for drum
brakes by gathering inside space between shoe and
drum, hence, the selection of drum brakes was
ruled out.
In disc Brakes, mechanical disc brakes were ruled
out because as it is actuated through brake cableswhich is not possible to install in ATV or heavy
vehicles. Therefore, we opted hydraulic disc brakes
for both front and rear with two master cylinders
for both ends.
BRAKING FORCE:-
F= µmg
FRONT 791.1 N
REAR 1153.65 N
DEACCELERATION:-
Ff + Fr = ma
Ff = front braking force
Fr = rear braking force
m = mass of vehicle
a = deacceleration = 6.86 m/s2
STOPPING DISTANCE:-
At 45 km/h 11.40 m
At 54.2 km/h (top speed) 16.52 m
WEIGHT DISTRIBUTION:-
In plane:-
() ( )
(
) ( )
WEIGHT DISTRIBUTION %AGE:-
() ( )
7.
THE ELECTRICAL SYSTEM:-
The electrical system in our vehicle is similar as it is
in the other road vehicles. They are mainly
concerned with the brake light, horn, reverse light
and kill switches and are able to the communicate
with the outer world with its action.
KILL ACTION:-
We are provided with two kill switches, one near
the driver and other engine and it is so to save
energy and to get ride of any risk.