Sae Baja India 2011(Fdr)

5/24/2018 Sae Baja India 2011(Fdr)

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2011


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Every design aspect and parameter mentioned in the rule book serves as bench mark for the

design and selection of various components and subsystems of the vehicle.

The material used for the entire required roll cage members must be:

(i) Circular steel tubing with an outside diameter of 2.5 cm (1 inch) and a wall thickness of 3.05

mm (.120inch) and a carbon content of at least 0.18%.

(ii) Steel members with at least equal bending stiffness and bending strength to 1018 steel having

a circular cross section with a 2.54 cm (1 inch) outer diameter and a wall thickness of 3.05 mm

(.120 inch)

The following elements of the roll cage are designed based upon rules mentioned in

corresponding points.

(i)Rear Roll Hoop (RRH) Rule 31.2.2

(ii)Roll Hoop Overhead Members (RHO) Rule 31.2.4

(iii)Front Bracing Members (FBM) Rule 31.2.7

(iv)Lateral Cross Member (LC) Rules 31.2.4 and 31.2.5

The drivers helmet to be 15.24 cm (6 inches ) away from a straightedge applied to any two

points on the cockpit of the car, excluding the drivers seat and the rear driver safety supports

The drivers torso, knees, shoulders, elbows, hands, and arms must have a minimum of 7.62 cm

(3 in) of clearance from the envelope created by the structure of the car.

Driver must be able to exit from either side of the vehicle within 5 seconds.

A firewall between the cockpit and the engine and fuel tank compartment is mandatory. It must

cover the area between the lower and upper lateral cross member. This firewall must be metal, at

least .508 mm (.020inch) thick, and must completely separate the engine compartment and fuel

tank from the cockpit.

The vehicle must have at least two independent hydraulic braking systems that act on allwheels and is operated by a single foot and in case of a leak or failure at any point in the system;

effective braking power shall be maintained on at least two wheels.

Teams are free to use any transmission such that maximum speed of the vehicle on a plain

terrain is recommended to be no more than 60 km/hr in top gear

Any muffler whose back pressure does not exceed 450 mm of Water Column may be used.


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Roll cage design is an important parameter for the fabrication of an efficient buggy. The roll

cage is the frame which envelopes the driver and its design is of utmost importance considering

the safety of the driver design and analysis of the roll cage is done. The roll cage design consists

of the three different bays.

1. Front bay which serves as impact member and suspension A-arm mounting.

2. Center bay for driver cabin

3. Rear bay for the engine mounting.

Improvisation:

During the design of roll cage our design teams main concentration was on the loop holes of the

previous year design, driver ergonomics, aesthetic looks and weight reduction. Rule book servedas the basis for the design of the roll cage. The roll cage which was made for Baja 2010 used the

material mild steel seamless pipe with a carbon percentage of 0.18 which about the 55 kgs. For

the weight reduction factor this year we are going for a material with high strength and less

weight.

The geometry is also limited by industry standards. It is important to utilize commonly available

tubing sizes and materials. Tubing is available in standard fractional sizes to the 1/8th of an inch:

1 to 1.5 inch. Also the wall thicknesses available are: 0.035, 0.049, 0.058, 0.065, 0.083 and 0.120

inches.

The available materials for the tubing are 1018 Mild Steel and 4130 Chromyl Steel. The benefit

of the chromoly steel is that 17.5% stronger than the 1018 mild steel the modulus of elasticity

and density are same for both the materials. Keeping the weight reduction and strength factors in

mind chromoly is considered as the efficient material for the roll cage fabrication.

Material aggregates:

Outer diameter : 2.54 cm (1 inch)

Wall thickness : 0.305cm (0.120inch)

Yield stress : 360.6 M.pa

Youngs modulus : 190-210 G.pa

Impact strength : 61.7 J (izod)

Carbon percentage : 0.3%


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Structural analysis:

AutoCAD and ANSYS 10 workbench were used for the design and analysis. The structural

analysis consists of three impact scenarios which help in analysis of the stresses developed in theroll cage. They are

Front impact.

Side impact.

Rollover impact.

To approximate the worst case scenario that the vehicle will see, research into the forces the

human body can endure was completed. The literature survey that the human body will pass out

at loads much higher than 9 times the force of gravity or 9 Gs. A value of 10 Gs was set as the

goal point for an extreme worst case collision.

In this case, a deceleration of 10 G was the assumed loading which is equivalent to 30KN by

assuming the weight of the complete buggy about 300kgs. After the analysis of impact the value

of deflection, with proper bracing & the FACTOR OF SAFETY comes to be > 1.5 which is

acceptable. Fig. 2 show the loads applied on the impact member of the roll cage and the

constraints given.


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Fig.2

Fig 3(a) and Fig3 (b). Shows the stresses developed in the members during the impact.


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Fig. 3(b)

Side impact:

As a side impact is most likely to occur with the vehicle being hit by another vehicle, the force

was assumed to be half that of head on collision with a fixed object of deceleration of 5 Gs. This

value is an extreme overestimation, but will allow the ability to account for a blown shock

absorber. The next step in the analysis was to analyze a side impact with a 5 G load which is

equivalent to 15kN as shown in fig 4.

Fig.4

After the analysis of impact the value of deflection, with proper bracing & the FOS comes to be

> 2.5 which is acceptable which is shown is fig 5.


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Fig.5

Roll over impact:

The final step in the analysis was to analyze the stress on the roll cage caused by roll over with a

2.5 G load on the cage. This is equivalent to a loading force of 7.5 KN. The fig.6 shows the point

of application for the loading on the roll cage the load was chosen to be on a single corner as this

would be the worst case scenario roll over.

Fig .6

After the analysis it is found out that the factor of safety is > 2.5 which is acceptable. Hence the

design is left unaltered as shown in fig .7


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Fig.7

Necessary bracing is done to the roll cage depending upon the stress formation in the members.

The bracing member gives adequate strength to the roll cage and reduces the stress developed in

the members. The final 3d vies of the roll cage with bracing members is shown in Fig.8 andFig.9

Fig : 8 Fig :9


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Ergonomics considered to be important for BAJA vehicle were drivers visibility, easy access

and view of the instrument cluster and controls, a comfortable seat with side rests with foam

padding and seat inclination with good back support. For a good comfort in the vehicle the

seating area of the seat should be slightly inclined at an angle of 4-5degrees with the horizontal

with the backrest at an angle of 110 degrees with it, this slight elevation of the seating area

provides adequate thigh support. The complete seat is at a height of seat adjustable between 25 to

35 cm from the floor. The steering wheel should be at an angle of 40-45degrees with the

horizontal, facing the neck area of the driver at a safe distance of 40-45cm from the drivers head

and 5-8cm above the drivers knees. The pedals are at a distance of 75 to 80 cms from the seat

(varies with seat being adjustable) from the front end of the seat and are spaced at 7-7.5cm from

each other.


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The suspension system suspends the automobile's body a short distance above the ground and

maintains the body at a relatively constant height to prevent it from pitching, swaying, or

leaning. In order to maintain effective acceleration, braking, and cornering, the components of

good handling, the suspension system must also keep all four tires firmly in contact with the

ground to maintain maximum possible contact patch. And lastly, since the power that is

produced by the engine is transmitted to the tires through the suspension system, to attain the

required performance level it should transmit maximum possible power to the tires without

absorbing much of it. The two main components of a suspension system are:

Comfort

Performance

Which are inversely proportional to each other. Therefore the primary aspect

of suspension design is to optimize these two parameters.

For a perfect off-roader it is required to have all the four wheels at four different heights and at

four different angles at an instance keeping the body of the vehicle parallel to the ground, for

which we need to have independent suspension at the both ends i.e. front and rear. There are

different types of systems available such as

Macphersons strut, semi trailing arms, multilink

suspension, double wishbones (equal and

parallel, non equal and parallel, non equal andnon parallel) etc. Depending on the technical

parameters and the previous year experience,

NON PARALLEL NON EQUAL DOUBLE

WISHBONE is the best suitable both at the front

and rear side of the vehicle which is compatible

with other sub systems design. It provides

perfect camber control and the camber angle

hardly changes under body roll. It also provides

lower roll center which gives minimal weight

transfer and it keeps the centre of gravity low

which is very desirable. Since the CG of the

vehicle is closer to ground it will minimize both the lateral and longitudinal weight transfer

during braking, accelerating and when the vehicle hits a bump. For a design of a suspension

system of an ATV all these parameters serve as a primary guidelines, which are very well

satisfied by the non equal non parallel double wishbones both at the front and rear sides.


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Suspension hard points are determined using Susprog3d. (However these values will be cross

verified with the use of MSC ADAMS). The results after analysis are found to be:


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Engine: Lombardini LGA 340

Specifications:

Bore x Stroke : 84 mm x 64 mm, Single cylinder, Air Cooled

Swept Volume : 338 cc

Compression ratio : 8:1

Rated Power : 8 kW @ 4400 rpm

Max Torque : 19 Nm @ 3000 rpm

Transmission: To meet the peak performance, Mahindra & Mahindra Alfa transmission is chosendepending on the observance and experience of the previous participation. The transmission

facilitates direct coupling, eliminating use of chain/rope drives, thereby eliminating the power

loss due to coupling.

Gear Gear ratio Speed (kmph)

First gear 31.48:1 16

Second gear 18.70:1 27

Third gear 11.40:1 44.3

Fourth gear 7.35:1 68.7

Reverse gear 55.08:1 9.1

Constant-velocity joint: CV joints allow a rotating shaft to transmit power through a

variable angle, at constant rotational speed, without an appreciable increase in friction.


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The steering system as we all know becomes the most important part of the vehicle as it is

responsible for moving the vehicle in right direction. While proper suspension can give the car a

smooth ride, complete proper handling cannot be achieved without a properly designed steering

system. So the steering aggregates selected must satisfy the suspension system, the engine power

available which is responsible for the ground wheel rotation, the type of tire and many such

features. An improper steering geometry can cause additional expenses to the user in the form of

reduced tire life, increased fuel consumption and also wear of the suspension system. The

steering system employed is RACK AND PINION steering system. This system is a very sturdy

for the kind of terrain on which the vehicle will run and simple to design and use. The stub axle

will be designed such that it can accommodate the steering arms and also the independent

suspension arms. The geometry of any steering system comprise of the camber, castor, king pin

inclination and wheel offset. These aggregates can be calculated by considering the suspension

aggregates and also the type of road wheels and tires on it.

The track rod of the steering was to be designed such that it can also change its inclinations with

the change in the suspension angles. This is very important in order to avoid the contact between

the suspension arms and the track rod. By applying the castor principle, the self centering action

of the steering was maximized in order to ease the steering efforts after turning.

Calculations:

Cot cot = (track width / wheel base) = (b/l)

= inner wheel angle, = outer wheel angle

Turning radius(R) = (b/2) + (l / sin (avvg. steering angle)


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As mentioned in preliminary design report our braking system has two independent hydraulic

systems, one for Front disc brakes and other for rear disc brakes. Disc brakes provide a number

of important advantages over drums, including better cooling, better fade resistance, little or no

wet fading due to road splash, and reduced weight and complexity. Steel braided hoses are used

for braking system. . A DOT3 braking fluid is used, which is quite good enough for efficient

braking. Disc brakes are 2030% lighter than the drum brakes. By making certain changes,

braking system can contribute to overall weight reduction.

Functionality:

A tandem master cylinder with two separate cylinders and reservoirs, one operating

front brakes and the other cylinder operating the rear brakes. This master cylinder avoids

the possibility of all the brakes of a vehicle being put out of order by a leak or fracture in

the brake hoses.

Bleeding Procedure: Bleeding procedure will ensure a better braking performance,

leaving no chance of brake fading due to air in the hoses.

Braking calculations:

The Brake Pedal

The brake pedal exists to multiply the force exerted by the drivers foot. From elementary statics,the force increase will be equal to the drivers applied force multiplied by the lever ratio of the

brake pedal assembly:

Fig: Tandem master cylinder


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Where Fbp = the force output of the brake pedal assembly

Where Fd= the force applied to the pedal pad by the driver

WhereL1 = the distance from the brake pedal arm pivot to the piston on TMC

WhereL2 = the distance from the brake pedal arm pivot to the brake pedal pad.

The Master Cylinder

It is the functional responsibility of the master cylinder to translate the force from the brake pedal

assembly into hydraulic fluid pressure.

Where Pmc = the hydraulic pressure generated by the master cylinder

WhereAmc = the effective area of the master cylinder hydraulic piston.

The Rotor

While the rotor serves as the primary heat sink in the braking system, it is the functional

responsibility of the rotor to generate a retarding torque as a function of the brake pad frictional

force. This torque is related to the brake pad frictional force as follows:

Where Tr= the torque generated by the rotor

WhereReff= the effective radius (effective moment arm) of the rotor (measured from the rotor

center of rotation to the center of pressure of the caliper pistons)

Stopping distance:

Where SDv = the stopping distance of the vehicle, Maximum safe deceleration (av )= 5.1met/sq.sec.


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Dynamic Impacts during Deceleration:

Whenever a vehicle experiences a deceleration, the effective normal force reacted at the four

corners of the vehicle will change. While the total vehicle normal force remains constant, the

front axle normal force during a deceleration event will increase while the rear axle normal force

will decrease by the same amount.

Where WT= the absolute weight transferred from the rear axle to the front axle

Where g = the acceleration due to gravity

Where hCG = the vertical distance from the CG to ground

Where Vt= the total vehicle vertical force (weight)

Effects of Weight Transfer on Tire Output

As a vehicle experiences dynamic weight transfer, the ability of each axle to provide brakingforce is altered. Under static conditions, the maximum braking force that an axle is capable of

producing is defined by the following relationships:

Where Ftires,f= the combined front tire braking forces

Where Ftires,r= the combined rear tire braking forces

Wherepeak,f= the maximum effective coefficient of friction between the front tires and the

road

Wherepeak,r= the maximum effective coefficient of friction between the rear tires and the

road


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Where Vf= the front axle vertical force (weight)

Where Vr= the rear axle vertical force (weight)

As a result of weight transfer during a deceleration event the maximum braking force that an axle

is capable of producing is

)


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We intend to control emissions by adopting two catalytic converters coupled in series to meet the

exhaust emission regulations for the vehicle.A catalytic converter is a device which is placed in

the vehicle exhaust system to reduce HC and CO by oxidizing catalyst and NO by reducing

catalyst.

The basic requirements of a catalytic converter are:

High surface area of the catalyst for better reactions.

Good chemical stability to prevent any deterioration in performance.

Low volume heat capacity to reach the operating temperatures.

Physical durability with attrition resistance.

Minimum pressure drop during the flow of exhaust gases through the catalyst bed; this will not

increase back pressure of the engine.


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Fig. shows a catalytic converter, which consists of two separate elements, one for NOx, and the

other for HC/CO emissions. The flow in the converter is axial.

Reactions involved:

Oxidation catalytic reactions: CO, HC and O2 from air are catalytically converted to CO2 and

H2O and number of catalysts are known to be effective noble metals like platinum and

plutonium, copper, vanadium, iron, cobalt, nickel, chromium etc.

Reduction catalytic reactions: The primary concept is to offer the NO molecule an activation

site, say nickel or copper grids in the presence of CO but not O2 which will cause oxidation, to

form N2 and CO2. The NO may react with a metal molecule to form an oxide which then in turn,

may react with CO to restore the metal molecule.

The following line diagram shows the arrangement of two catalytic converters in series.


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The design and control of an assembly line involves,

Leveling the load on each process within the line.

Keeping a constant speed in consuming each part of the line.

Since ATVs are the customer driven products a perfect pull based production system is best

suitable to produce it on a large scale. The RPW (Ranked Positional Weight) strategy is

appropriate in this case to design the assembly line.

RPW:

The problem requires packing n objects of different sizes into as few ordered bins as possible in

which each bin has the same capacity and the packing order is partially constrained. The

finiteness of the task sizes makes this a difficult problem to solve. The motivation for the

problem is the assignment of tasks to operators along an assembly line. Task size corresponds to

its operation time( ti) and the bin size represents the cycle time for the line(c). The partially

constrained ordering results from technological constraints that require certain assembly tasks to

be performed before others.

Positional weight defines a useful attribute of a task. The positional weight of task i , PW i is

defined as the sum of task is processing time plus that of all its necessary successor tasks.

Notationally, we can write this as PWi = where si is the set of tasks that must come

after task i in the assembly sequence to satisfy precedence constraints. You can think of

positional weight as a lower bound on the amount of work remaining once task i is started. Inthis sense, positional weight is one measure of the degree to which task i is a bottleneck, and we

should do tasks with high PW i values as soon as possible. The ranked positional weight

technique simply orders tasks from high to low PWi and then sequence assigns tasks to the first

workstation in which they will fit. Fit requires enough free time and the satisfaction of all

precedence constraints.

Once we get the finalized BOM after fabrication of the prototype, we can decide about optimum

number of workstations to produce 4000 units with a perfectly balanced line using this strategy.

Sequencing of Multi Model Assembly Line (Goal Chasing Method) :

Not allowing the customers to think about other brands is another way to market the product. We

can do this by increasing the number of product varieties by modifying the basic one. But this

creates a new problem of sequencing in the production house. This section of report is intended

to solve this problem. Under the pull system, the variation in production quantities or

conveyance times at preceding processes must be minimized. Also, their respective work-in-

process inventories must be minimized. To do so, the quantity used per hour (i.e., consumption


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speed) for each part in the mixed-model line must be kept as constant as possible. To understand

this sequencing method, it is important to define several notions and values:

Q = Total production quantity of all products Ai (i=1,. )

= , (Qi = production quantity of each product Ai)

Nj = Total necessary quantity of the part aj consumed for producing all products Ai(i=1,. ;

j=1,.., )

Xjk= Total necessary quantity of the part aj to be utilized for producing the products of

determined sequence from first to Kth.

With these notations in mind the following two values can be developed:

Nj/Q = Average necessary quantity of the part aj per unit of a product.

K.Nj/Q = Average necessary quantity of the part aj for producing K units of products.

In order to keep the consumption speed of a part aj constant, the amount of Xjk must be as

close as possible to the value of K.Nj/Q. This is the basic concept underlying Toyotas

sequencing algorithm and is depicted in the following figure.

It can now further defined that:

Nj

Xjk

K0

(Q, Nj)

Q

K.Nj/Q


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A point Gk= (K.N1/Q, K.N2/Q,. K.N /Q),

A point Pk= (X1k, X2k,.. X k).

In order for a sequence schedule to assure the constant speed of consuming each part, the

point Pk must be as close as possible to the point Gk. Therefore, if the degree is measured for

the point Pk approaching the point Gk by using the distance Dk:

Dk= || GkPk|| = K.Nj/Q- Xjk)2

Then, the distance Dk must be minimized.

After the fabrication of prototype we will be having the required data in our hands to go for the

design of virtual factory based on the principles of Lean and Just-in-Time production and also to

design a systematic approach to identify and eliminate waste through continuous improvement,

flow the product at the pull of the customer in pursuit of perfection. In short its all about Doing

the right things and doing the things right

1. SAE BAJA RULE BOOK 2011.

2. A text of Automobile engineering by R.K.RAJPUT.

3. www.susprog.com

4. THE TOYOTA WAY, by Jeffrey k liker

5. Fundamentals of motor vehicle technology by V.A.W.HILLIER.6. www.stoptech.com

:Team MAIDEN MOB

C/o Mr. P.S.S.Murthy,

Lecturer and faculty advisor,

Dept. of mechanical engineering.

Kakatiya institute of technology and science,

WARANGAL-506015, Andhra Pradesh, India.

Ph no: +91 9347551710
http://www.susprog.com/http://www.stoptech.com/http://www.stoptech.com/http://www.susprog.com/

Sae Baja India 2011(Fdr)

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