CAR no. 53, Final PDR

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



Wheel track:- 1300 mm.

TARGET WEIGHT:-

Kerb weight:- 280 kgs

Weight distribution:- 40:60



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



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


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


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



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



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.



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



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.



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 powertrain 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.



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.

Documents

CAR no. 53, Final PDR