Team YUYUTSU SVNIT Surat Final Final

7/28/2019 Team YUYUTSU SVNIT Surat Final Final

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Car #46

Team YUYUTSU Baja SAE India 2009 Design Report

Ashwin MishraShreesh Shauraya

Murtaza MK

B.Tech(Mechanical),SVNIT,Surat.

[email protected]

ABSTRACT

Team Yuyutsu aims at developing a technically sound

vehicle which is backed by a very simple yet profound

design and healthy manufacturing practices. This report

describes in detail, the parameters included in the entire

design and the considerations made for zeroing in on

those parameters. First the issues and design approach is

discussed and then the resulting design procedure has

been explained. Due efforts have been put to validate our

design by theoretical calculations, simulations and

known facts.

INTRODUCTION

Baja SAE India Competition 09 is an inter-collegiate

design competition for Undergraduate engineeringstudents. The goal of the competition is to simulate real

world engineering design projects and their related

challenges.

The objective of the participating teams is to build a

single seated, rugged, off road, recreational vehicle

intended for sale to the non-professional, weekend, off

road enthusiast. The idea is to design an efficient vehicle

within a budget of Rs. 1.5 lakhs (including overheads) to

sustain a production run of 4000 vehicles annually.

Although the event sponsors do provide some basic

essentials like 340cc, 10 HP Lombardini engine,transmission (Mahindra Alfa), steering box (ZF steering)

and seat belts; the teams have to find their individual

sponsors for the rest of the expenses.

The vehicle should meet the necessary requirements of

performance which is manifested in terms of

maneuverability, driver comfort, acceleration, hill climb,

braking and endurance tests.

The track record of SAE-SVNIT in both national and

international BAJA events is a legacy in itself. The

institute has one of the largest SAE collegiate chapters

and it has previously produced three BAJA vehicles.

GARUNA intended to participate in SASOLMINIBAJA 2005 in South Africa and used as a test

vehicle for testing the track in BAJA SAE India07.

PUSHPAK participated in BAJA SAE-WEST2006 in Portland, USA and won the Chairmans

award.

ASHWAMEDH participated in BAJA SAEIndia07 and was ranked 7th overall with a cash prize

of Rs. 1lakh in acceleration and hill climbing.

This year we intend to continue the legacy, as our fourth

vehicle YUYUTSU prepares to exhibit a rich blend of

performance and efficiency at the BAJA SAE INDIA09

to be held at NATRAX facility of National Automotive

Testing and R&D Infrastructure Project (NATRIP) atPithampore, near Indore, Madhya Pradesh.

With about 59 other teams in the fray, team YUYUTSU

has decided to put utmost efforts into producing a design

that promises to bring out maximum performance and at

the same time abide by the indispensable rules and

regulations as laid in the BAJA SAE India rulebook for

the 2009 event.

DESIGN METHODOLOGY

The designing was started only after thorough study of

the aforementioned ATVs, which was followed by

system advantages and production costs. All the design

issues were studied and an attempt has been made to

solve them in the present design. In order to increase the

ease and speed of manufacturing, great care was taken to

ensure that every component of the vehicle was modeled

using Pro/Engineer CAD software. Using an accurate

master assembly of the digital car, we were able to

quickly and easily verify design ideas and ensure inter-

component compatibility. Also, most of the designed


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Side Impact Members (SIM) The SIM increases chassis

stiffness and is a major member that provides protection

to the driver in a side-on collision. In the discussed

design, the SIM member extends at a width of

36straight up to the drivers knee and then converges to

20 at the front. The LFS members are tapered by 3 on

both sides which reduces the structural weight of the

chassis without any considerable reduction in the cock-

pit space. The option of the Front-Fore Aft bracing was

decided in an attempt to keep the weight of the vehicle

to a minimum. The final design decision dealt with the

geometry of the Rear Bracing. The Rear Bracing

encloses the engine, transmission, and rear drive

assembly. The rear bracing also incorporates a new

independent rear suspension,

Once we finished the design of our roll cage and verified

that it adhered to the Rules and Regulations, we

designed the back half of our frame to fit the engine and

the rest of the drive train using the same material and

welding procedures used with the roll cage.

STEERING SYSTEM

STEERING BOX

One of the many problems faced with previous year`s

steering was of the offset positioning of pinion. To

mitigate this problem WORM and ROLLER

STEERING BOX is used this time, which is sponsored

by ZF Steering India and hence helped us financially

as well. Its high turning ratio would be advantageous in

manoeuvring the vehicle in tight turns.

STEERING GEOMETRY

Though we started with pure Ackerman geometry, later

on it was realized that with the given steering box lots of

effort will be required from the driver. Keeping driver

comfort in mind, we decided to go for more than 100%

Ackerman which decreased the driver input to the wheel

and the steering response became much smoother. An

initial toe-in was also decided to be incorporated in the

front as with the toe angle set in and more Ackerman, it

will result with the outside tire being towed-in relative to

the circular path and the inside tire running parallel to

the circular path they are following.

The steering system included a worm and roller steering

box out of which only one driving link actuated the

whole system, hence after extending this link to the

bottom of the chassis a T joint was introduced to

regulate the two respective tie-rods.The T-joint used has

been taken from FIAT Padmini.

BRAKES

While designing the brake system, simplicity was given

prime importance and it was decided to use two pairs of

disc brakes that are used best suited for our vehicle. We

will be using double wall steel tubing with 3/16 O.D

as per the rules

Figure 1 Brake lines

The master cylinders mount directly to the custom made

brake pedal and are located above the drivers feet

allowing the driver to easily enter and exit the car.

Though last years design worked satisfactorily, we

could not incorporate differential braking in the design

Also the designed discs did not have good machinability

and had poor heat dissipation properties, this prompted

the use of Maruti800 discs which suited our braking

requirements, the design calculation have been given in

the appendix.

Absence of hand brakes created problems for many of

the teams during hill climbing and highlighted the utility

of the same, but the problem of actuating a mechanical

hand brake on disc brakes compelled us to connect hand

lever to the additional master cylinder we are using. The

line diagram has been given in the figure. In genera

brakes are used to control the speed of the vehicle, they

are seldom used for sudden braking which may cause the

vehicle to nose-dive. We have decided to increase the

CG height by around 5-6 inches to increase ground

clearance and improve driver comfort, hence greater

pitching tendency is expected in our design, we have

taken pro-active measures by using anti-dive geometry

in suspensions and are going to use proportioning valves

so that greater braking force is applied at the rear which

bears the majority of the load, this will also be

favourable for driver comfort. However, more braking

will be actuated in the front when sudden stops are

required.

TYRES

Tires were strictly subjected to availability. To have

larger tire at rear we procured pair of 25 and 22 ATV

tires from Trident International, Pune. The treads

ensured grip on slippery and sandy BAJA tracks and

their optimum depth made it sure that the tires did not

dig up loose sand. Light weight rims to decrease un-


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sprung mass were selected only after ensuring proper

packaging of knuckles and brakes.

WHEEL END

The wheel end is made up of the following parts- Rim,

Hub, Disc, Milled bearing, and knuckle in sequence

.Their compatibility with each other is a major design

issue as these parts have been taken from different

sources.

KNUCKLE:-

The dampers, A-arms and steering tie rod are connected

to this part. Every car needs a separate design to have the

required Caster and Kingpin angles set for the particular

car. It is also to be noted that all the load will be

transferred to the tires through the knuckle only. So, this

parts design is very critical for any cars performance.

Knuckle is mounted to the hub with a bearing with the

help of a hydraulic press and bolts are screwed to keep

the stud and brake disc together. The inner part of

bearing is milled which acts as a spline to transmit

power from the axle.

APPROACH I:-Fabricate the knuckle out of plates of

M.S by welding and mount it to a stud with a fabricated

matching plate to fix with the rim. This would give us

independence in selecting the geometry control the

dimensions. But this would take more time, cost and

would be compact.

APPROACH II:-Use the knuckle of an on-road vehicle

and modify it accordingly. This would involve

converting the Mc-Pherson type mountings to Double

wishbone type and no change in geometry possible. But

this approach would be cheap and reliable and also aid in

better packaging with our rim.

Knuckle manufacture can be done by casting, but since

our design may not be full proof any changes may later

create problems. Cost of the process is also a limiting

factor.

We have selected approach 2, because of the time

constraint and increased reliability of the system. The

compatibility issue have been minimized, as we will

construct our vehicle around this part with suspensions

and all other things can change at this stage.

REAR :- At the rear the 12inch rim can accommodate the

whole assembly of Maruti 800. However, coupling of

stud with rim was a problem as we have got rim of PCD

4inches. So we needed a matching plate for this. The

exploded view has been given in Figure 8.

FRONT:- Smaller rim needs a smaller disc. We selected

HONDA AVIATOR having 190mm of disc diameter

plus around 20-30mm for caliper. After comparison with

Maruti disc assembly, it was discovered that aviator

caliper took more space and could not be accommodated

in the rim unless the disc is machined. Hence Maruti

800`s caliper was used in the front as well

SUSPENSION SYSTEM

DESIGN APPROACH

The suspension not only dictates the path of the relative

motion but also controls forces transmitted by sprung

and un-sprung mass. However, suspensions have strong

non-linear parameters and many design variables tha

ostensibly, make it difficult to design. Selection ofsuspensions was based on the criteria of their degree of

freedom, roll-centre adjustability, ease in whee

alignment parameters etc. The suspension system is

tuned according to the actual needs, keeping in mind the

manufacturing aspects and the nature of loading it will

have to suffer. We will also study the nature of forces

acting on the suspension links and the ways to minimize

their effect on ride characteristics and component life.

Both the front and rear suspension systems are

independent double wishbone suspension having

unequal control arm/a-arm. The double wishbone system

was selected, owing to the uneven terrain. The a-arms at

the front are pinned to the chassis while at the knuckle

end the arms are attached using ball and socket joints

While at the rear as there is no cornering requirement

the a-arms are pinned both to the chassis as well as the

knuckle. An initial camber of -2 degrees has been

elected as for the front wheels so as to maintain adequate

ground contact at all the times during operation and

attain good off-road stability. Curved A-arms have been

used as they can sustain more bending stresses than their

straight counter-parts, no thermal stresses are produced

as the tubes will be cold bent. A perspective view has

been showed in Figure 2.

Figure 2. Suspension A-arm

MATERIAL

The material for A-arms is same as that used for rol

cage i.e. ASME 106/B grade carbon steel with O.D

=26.mm and wall thickness= 2.87mm.


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SHOCK ABSORBER SELECTION

In the previous year`s vehicle, three different type of

shock absorbers were used which was neither design

friendly nor suited for mass production. Wrong shocker

selection had proved fatal to last year`s teams

performance in the endurance event. This time due

consideration were given to proper selection of shockers.

GABREIL dealer from Lamington road, Mumbai

helped us procure the shockers suitable for our

magnitude and nature of loading. The rear shocker is

commercially used in ATV`s of desert lands and had

load carrying capacity of 300kgs. Since our major load is

concentrated on the rear, this shocker proved fruitful.

For front section spring in spring type shockers were

procured. This would be mounted side by side in parallel

(two on each side). These shockers, in spite of being

stiffer than those used in motorcycles provide greater

travel.

Dampers of numerous specifications were available in

market, but coupling of springs seemed to be

cumbersome and though we had found spring

manufactures willing to do the job, the damper did not

sport any scope for mounting.

One of the major drawback of last year`s design was the

mounting point of dampers and the knuckle. This year

both of them had been specially manufactured to get

flexibility in design and eliminate any compromise on

the suspension geometry design. Manufacturing cost lots

considerable amount of time and money, still it doesnt

ensure full reliability, not to mention the added un-

sprung mass.

This year customised Maruti 800 knuckles were used,

though they reduced the flexibility of the design.

However they ensured reliability with decreased un-

sprung mass. The Maruti 800 knuckle has been modified

to accommodate our Double A-arm suspensions.

Another decision critical to our design was the mounting

of suspension shockers. Mounting the shockers on the

knuckle ensured reliability and allowed us to have

lighter A-arms, but wheel travel was decreased which

could result in transfer of shocks to the main frame.

Length of the shocker was also a limiting factor. In the

light of these observations, lower mounting was kept on

the lower A-arm a front and on the upper A-arm at the

rear. Mounting the dampers on the front lower arm

allowed us to decrease the font vehicle height whichadded to the driver visibility and strengthened the

upright on the chassis. This concept however couldnt be

followed on the rear because of the driver axle running

between the upper and lower arms.

VEHICLE DIMENSIONS

A wider track width at the front than at the rear will

provide more stability in turning the car into corners

decreasing the tendency of the car to trip over itself on

corner entry and more resistance to diagonal load

transfer. Base to track ratio is kept 1.11 to ensure

straight-line stability. This also created ample space for

the driver and other systems.

AERODYANAMICS AND BODYPANELS

Though the ATV is meant for low speeds, their

aerodynamic study can reveal interesting facts which can

help in saving fuel consumption and it can also help in

easy handling. There also remains a scope to have a

more powerful engine. The vehicle has been simulated

for 70 Kmph speed and the effects of air flow have been

studied. As expected, the firewall/RRH is a major

contributor of drag and very strong vortices have

originated behind the RRH. A strong wake region is

developed in the space between engine and RRH and

this space is minimized to reduce their effect. To make

the simulation simpler wheel rotation has not been

considered. The rear portion of the chassis will be

tapered inside which not only decreases the drag force

but also leads to some weight reduction in the engine

supporting structure. Apart from eliminating sharp edges

in the front, the cockpit area over the pedals will be

covered to give the driver feel of a real car. The inherent

three dimensionality of the wake region makes it

difficult to suppress and giving priority to safety we

have not attempted any further modifications in the

chassis.

The material for paneling will be Aluminium sheets for

the firewall and the base of roll cage, but for the side

panels we are looking for lighter and cheaper

alternatives, one of the options is the use of steel mesh

coated by plastic sheets. Carbon fibres though suitable

are too costly for our use.

SAFETY

As per the rules, we have securely layered all tubing

members in the cockpit with a shock absorbing foam to

protect the driver during an event. 4-POINT SAFETY

BELTS sponsored by Autoliv India and SAE rated brake

lights have been installed to maintain highest safety

standards. The remaining standard safety equipmentincluding fire extinguisher, and two kill switches were

all placed for easy access and use, as well as maximum

optimization of their functions during an emergency

Apart from this arm restrains, neck collar, moto-cross

type helmet and fire extinguishers have also been

procured.

DESIGN SPECIFICATIONS


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Overall length 2.11 m

Track width

1.52 m (Front)

1.44 m (Rear)

Overall weight350 Kgs (inclusive of

Driver)

Engine10 HP LombardiniLGA 340

TransmissionMahindra Alfa

(modified)

Tires

&

Rims

22 x 8 inches (Front)

10 x 6 inches

25 x 8 inches (Rear)

12 x 6 inches

Wheel base 1.67 m

Roll CageASME 106/B grade

carbon steel

Suspension(front and

rear)

Double Wishbone

suspension (Parallel

and unequal arms)

Steering System Worm and Screw type

Braking (front and

rear)Hydraulic Disc brakes

Maximum Torque 19 Nm @ 3000 rpm

Maximum Speed 72 KMPH

Camber 2 degrees (negative)

Castor 3 degrees (positive)

CONCLUSION

The prototype that the team intends to submit for

entrance in the Baja SAE India competition was a

collaborative design effort among students from several

engineering disciplines. The teams goal was to produce

a design that met or exceeded the SAE criteria for safety,

durability and maintainability as well as provide features

that would have mass market appeal to the general off-

road enthusiast such as performance, comfort and

aesthetics. Design decisions were made with each of

these parameters in mind.

The team relied on individual members knowledge and

experience with off-road vehicles as a tool for

developing many of the initial subassembly designs for

the prototype. Several team members attended the 2007

SAE competition to gather ideas and information about

what design choices were successful and how they could

be incorporated into the prototype design.

Where applicable, selection of components for each

subassembly of the prototype was based on engineering

knowledge gained through undergraduate level course

work. Reliance upon engineering intuition governed

the selection of the remaining components

Computational design and analysis software were used

to verify that each part of a subassembly design met or

exceeded its stated objective. Use of these design tools

also allowed the team to address and rectify conflicts

between interfacing subassemblies before fabrication

saving both time and cost.

REFERENCES

1. An Introduction to Modern Vehicle Design,Edited byJ ulian Happian-Smith Reed Educational andProfessional Publishing Ltd 2002

2. Consolidated Rules for 2009 Baja SAE, India,Society of Automotive Engineers, Inc.,

3. Design report SVNIT, Surat Baja SAE India07Indore, India

4. Thomas D. Gillespe, Fundamentals of vehicle

dynamics5. Milliken, W. F., Milliken, D. L., and Metz, L. D., RaceCar Vehicle Dynamics, SAE

APPENDIX A

CALCULATIONS

Approximate total weight (Including driver) = 350kgs

W = 3433.5 N

Location of center of gravity is 26 inches from rear

wheel and 40 inches from wheel axle line.

weight applied in rear60

405.3433 rW

= 2080.9 N

Assuming this weight to be equally shared by both tyres

NW

Wt

t 45.10402

Let the force exerted be F = 100 N


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xd = 7.61 m/s2

stopping distance,

m

d

VS

x

09.262

2max

CASE II: When tyre slides on surface, work done by

frictional force, between road and tyre, is responsible for

change in kinetic energy of vehicle.

05.0 2 VMW Frictional force acting on wheels f = Mg

m

g

Vdst 14.31

2

2max

SUSPENSION STIFFNESS

REAR

Modulus of rigidity of spring G = 80000 N/mm2

Diameter of spring = 12mm

Radius of coil = 50 mm

No. of coils = 7

Hence stiffnessnR

dK

3

4

64

= 26.62 N/mm

Static load on each rear wheel = 1038.80 N

for a load of 1038.8 N

Travel cm67.4256.22

8.1038

Hence travel while mounting = 35.1 mm

Weight transfer calculations

Due to braking, weight transfer occurs and this depends

on the deceleration of the vehicle. During maximum

deceleration, weight on the front wheels is more

compared to rear wheels.

Total weight of the wheel, Kgswtotal 350

Static weight on the front axle, frontw = Kgs105

Height of C.G of the vehicle, h = 467.5 mm

Wheel base, l = 1676 mm

Maximum deceleration of the vehicle during braking,

dx = 7.61 m/s2

Similarly, totalx

rearrear wl

h

g

aww

'

Static weight on the rear axle, rearw = Kg245

18.1693501676

5.467

8.9

61.7245'

rearw

Percentage of Weight transfer,

66.211001676

5.467

8.9

61.7%

weight

Therefore 21.66% of weight transfer occurs at maximum

acceleration of the vehicle

FOR MAXIMUM INCLINATION THE VEHICLE

CAN CLIMB IN STATIC CONDITION

Assume no speed condition at rear wheel; vehicle wil

topple when reaction at front axle will become zero.

When R0

h

btan distance of C.G from rear axle/ height

of C.G

467.0

508.0

= 47.380

MAXIMUM POSSIBLE ACCELERATION

uH-L

guaxa =5.428 m/s

2

CALCULATION FOR DISC BRAKE DIMENSION

Ro = Outer disc radii

RI = Inner disc radii

=0.3

T= torque acting on single wheel

P = pressure applied by brake fluid.

totalx

frontfront wl

h

g

aww

'

kgw front 81.1803501676

5.467

8.9

61.7105'


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= included angle of caliper disc contact

T= 333

2 iRRP o ...(1)

45.1R

R

i

o ..(2)

Substituting (2) in (1)

12.69cmRand

8.78cmR

3.04375.2253R

o

i

i3

The torque produced is calculated from the maximum

deceleration the vehicle can achieve while braking. The

resultant dimensions of the disc were a close

approximation to the disc size of Maruti800 and hence it

was selected for our vehicle.

LIMITING VALUE OF INCLINATION FOR

ABOVE ACCELERATION

sinmax ga

5.428+9.8sin =0.4675

)sin-(10.5089.81 2

207.8756 2sin + 106.497 sin = 84.1726

sin = 0.43, - 0.94

sin = 0.43

= 25.47 0

Hence the vehicle can safely climb a hill of more than 25

degrees with maximum acceleration. However the actual

inclination that could be climbed(with less than

maximum acceleration) will be much more than the

given value.


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APPENDIX B

VIEWS OF FINAL VEHICLE

Figure 3(A) Top view Figure 3(B) Front view

Figure 3(C) Side view

Figure 4 Isometric view


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APPENDIX CRESULTS OF CFD SIMULATIONS

Figure 5 contours of static pressure on car body and road

Figure 6 Pathlines emitted from the car body showing turbulent flow field aorund the vehicle


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APPENDIX D

Figure 7 Exploded view of wheel end(A) Rear (B) Front

To pedal brake On/Off valve

Front

Master cylinder

Oil reservoir To hand brake

Figure 8 Circuit diagram of hydraulic brake

Team YUYUTSU SVNIT Surat Final Final

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