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TEAM DIRT-CRUSADERS Team ID 98375

VIRTUAL MINI BAJA REPORT

WHEELBASE = 1600mm

FRONT TRACKWIDTH = 1380 mm

REAR TRACKWIDTH = 1380 mm

GROUND CLEARANCE = 240 mm

TOTAL HEIGHT = 1540 mm

MAX. CHASSIS WIDTH = 1000mm

MAX. CHASSIS LENGTH = 2150 mm

KERB WEIGHT = 340 kg

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CHASSIS

The main objective of developing the chassis is to

make a firm wireframe that can accommodate all

components of the vehicle efficiently and provide

maximum safety to the drivers.

CAD MODEL OF THE CHASSIS:

The First designed chassis model is given below:

Shortcomings:

A arm mounting problem

Rear end too big

No provision to mount suspension

Complicated to fabricate This is the evolved model in response to the above shortcomings

MATERIAL SPECIFICATION:

Plain carbon steel SAE 1020/ ASTM A513

alloys 1020

Yield strength 450 MPa

Ultimate strength 600-620 MPa

Rockwell hardness B89

Composition(%)

Fe C Mn P S

99.08 0.18~0.23 0.3~0.6 0.04max 0.05max

Calculation of CG and Mass Distribution

Unsprug weight = 260 Kg CGX =1287.3 CGY = -8.85 CGZ = 612.3

TABS

Tabs to mount (5KN)

(Syt = 350 MPa)

Tabs provide FOS = 3

Pin Provides FOS = 2.5

Pin is made weaker.

Tab Thickness = 8 mm

Analysis Using ANSYS I. Pre-processing

C/S of Main pipe: OD 26.67mm T= 3.917 mm

C/S of auxiliary pipe: OD 26.67mm T= 2.84 mm

Common properties Density 7860 kg/m3 Poisson’s ratio 0.3 Young’s modulus

205GPa (Dim are in mm)

Meshed View

ITEM WEIGHT X Y Z

Chassis 60 1120 0 700

Engine 50 1700 900 490

Gear Box 20 1700 110 350

Seat 10 1300 0 640

Driver 110 1200 0 690

Front Assemblies

10 350 0 340

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Analysis of Four cases 1. Static Bending – all Forces Distributed

according to Weight distribution(g acc)

2. Toppled condition- All Forces applied in the

Upward direction according to Wt Dist.(2.5g)

Crash analysis: 3. Front Impact

a. Vehicle to Rigid body impact

b. Assuming Crash pulse = 0.185 sec

c. Equivalent Acceleration = 90 m/s2

d. Force multiplier = 9.174g

4. Side Impact

a. Vehicle to vehicle impact

b. Force Multiplier = 5 g

Improvements tested

1. RRH cross member(LDB)

2. SIM Cross members

3. Floor Bracing

a. At 45o From Max Strain point – Showed

very poor results

b. Two parallel Floor bracing members-

Subjected to Buckling c. Two members from max strain point to SIM

cross member Common point And one member joining them-

Showed very good results in both front and side impact

Prevent Buckling of SIM and LFS

Topp

le Static

Front impact

Side impact

Simple X(518MPa) X(350Mpa)

With bends

X(518MPa) X(518MPa)

With Cross Member

Improved (417 MPa)

Improved (200MPa)

Floor bracing

Max stress point relocated (Increased safety)

(130MPa)

Expected Improvements using Crash Tube • Assuming 10 cm

of Crash length of crash tube.

• The given length can absorb as much as 70% of damage provided that its perfect frontal collision.

Human ergonomics Provides Given Head clearance and side clearance Easy exit

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Final Body

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TRANSMISSION SYSTEM

Engine Power :- 10 Hp at 3000 rpm

Engine torque :- 19.68 Nm

Ideal engine rpm :-1750 rpm

Maximum speed :- 3800 rpm

Torque is considered constant :-19.65 Nm

Overall efficiency :-80%

Rear Wheel size :- 23 Inch

Since it is a full floating axle therefore we need to design only on basis of torsion.

Selecting material for axle as C45 and FOS as 3.

Diameter comes out to be 22mm.

Approximate Torque required for gradient of 25 is 6.329 Nm.

As the gear is mounted on the left side of the engine(as seen from rear) due to space constrains ,

using helical gear pair for direction changing as coupling member for engine and gear box

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Helical gear specification

Precision Grade JIS Grade N6 ,JIS Grade 2

Gear teeth Standard full depth

Pressure angle 20 deg

Helix angle 17deg

Material SCM440 (Alloy Steel)

Gear No 1 2 3 4 Reverse

Gear ratio 31.48 18.70 11.40 7.35 55.08

Traction

(N)

1694.165 1006.38 631.52 395.56 2964.25

Range of vehicle speed

(kmph)

10-14 18-22 30-36 46-57 6-8

Torque at Differential

(Nm)

619.52 367.45 224.01 144.43 1082.32

Actual torque available at both the

wheel(Nm)

495.62 293.96 179.208 115.54 865.8

Bell crank angle(for gear shifting) 56.25 42.83 30.12 -11.55 51.5

SUSPENSION SPECIFICATIONS

Double Wishbone Unequal Arms

Front suspension

Spring Stiffness Front = 25 N/mm (Passion)

Free Length with Damper Front = 34.29mm

Max. Compression allowed = 110mm

Rear Suspension

Spring Stiffness Rear = 44N/mm (Yamaha Rx-100)

Free Length with Damper Front = 35mm

Max. Compression allowed = 120mm

Wheelbase = 1600 mm

Front and Rear Trackwidth = 1380 mm

Front Kingpin angle = 10.61 deg

Front Camber angle = -2 deg

Toe in = -1 deg

Front Castor Angle = 3 deg

Scrub Radius = 22.11mm

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Sprung Mass = 260 kg

C.G. Along X-axis = 1287.3 mm

Designed for Bump of 100mm And Droop of 100 mm

Calculated Results

Motion Ratio = 0.3(Front)

= 0.337 (Rear)

Front Ride Frequency = 1.078 Hz

Rear Ride Frequency = 1.258 Hz

Bounce Frequency = 1.19 Hz centre at 5099.33 mm Front

Pitch Frequency = 1.15 Hz centre at 148 mm Rear

Graphs

CHANGE IN CAMBER ANGLE CHANGE IN ROLL CAMBER

CHANGE IN TOE ANGLE UPRIGHT ANLYSIS

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STEERING SYSTEM

NAME COST WEIGHT SENSITIVITY AND RESPONSE

EFFICIENCY

Rack and pinion Low Light Good Good

Recirculating ball type

High Medium Poor Very good

Worm and roller Medium Heavy Poor Medium

Worm and sector

Medium Heavy Very poor Good

Hence we selected rack and pinion steering system from above given table Steering ratio of the system as 17:1 Turning radius R= 2.886m ACKERMAN ANGLE (for 540 degree of rotation of steering wheel) Inner wheel turning angle = 41.746 degree Outer wheel turning angle = 25.636 degree OVERSTEERING CONDITION Same tyres are used for both Front and Rear C.G is more towards rear axle k= - 0.034 deg.sec2/m

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TIE ROD LENGTH

The length of the tie rod is found to be 385 mm.

3-D MODEL IN CATIA

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BRAKES

Assumptions and Given Data:

Mass of vehicle = 350 kg

o Vertical height of C.G above ground = 0.6m

o Co-eff. Of friction between tyre and road = 0.7

o Track width = 1.38m

o Wheel base = 1.6m

o Wheel dia = 23” and rim dia = 11”

o Test speed = 52kmph = 14.44m/s

o Static load distribution: Front axle = 40%, Rear axle = 60%

o Co-eff. Of friction of brake lining = 0.4

o Pedal Ratio = 8

o Tandem master cylinder bore dia = 19mm

o Caliper piston dia = 48mm

o Disc diameter 7 inches with effective radius of 6cm

Calculated Data:

o Stopping Distance = 15.18m

o Deceleration = 6.87m/s2 (0.7g)

o Dynamic Load Distribution: Front Axle = 118.085kg, Rear Axle = 231.915kg

o Braking Force = 2404.5 N

o Braking Torque = 702.35 N-m

o Clamp Load on all 4 wheels = 14632.29 N, on single wheel = 3658.07 N

o Calliper piston pressure=2.02 MPa

o Force on Tandem Master Cylinder Piston = 573.16 N

o Pedal Force = 71.645 N

o Energy Losses:

o K.E=36490 J

o P.E=2427.85 J fr 450 slope

o Total Energy=38917.85 J, Average Power=18.53 kW

Time on Brake=2.1 seconds

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DESIGN VALIDATION PLAN

1. Ansys analysis of Chassis

a. Static

b. Impact

2. Static testing of suspension

3. Sample Testing of welded joints on chassis

4. Sample Testing of bends on chassis

PROJECT PLAN

Work Profile Date

PVC Pipe Model 21-26 Aug

Trials of Different Weld joints as per Roll cage

Design and its Destructive Testing

27 Aug – 2 Sept

Chassis Manufacturing (Cutting tubes to

parameters)

6 – 12 Sept

Chassis manufacturing (Welding) 13 – 25 Sept

Assembling A-Arms with Chassis and upright 25 Sept – 2 October

Brakes and Wheel Hub Assembly 3-10 Oct

Positioning of Master Cylinder, Seat 11-17 Oct

Positioning of Steering Rack,

Pedal and Gear Changer

18-24 Oct

Finalizing the Chassis(without Engine and Gear Box

mounting)

1st Nov

Engine Order placement According to BAJA specified Dates

Engine Mounting and Gear Box Mounting After Receiving Engine (around Jan 2013)

Vehicle Ready for Road test in Campus Around 10-15 Jan 2013

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Components Order Placement

Chassis(Tubes, Metal Plates for tabs) 3-6 Sept

Joints(Hiem, Ball) 7-23 Sept

Bolts and Nuts 7-23 Sept

Front And Rear Upright 7-23 Sept

Brake Parts 20 Sept – 5 Oct

Seat and Seat Belt 30 Sept – 7 Oct

Steering Assembly 30Sept – 14 Oct

Electricals 7 Oct – 20 Oct

Gear Box and Axles 30 Sept – 10Nov

Tyres and Rims 10 Sept – 30 Sept

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College Facilities Outside Facilities

All types of welding -Milling

Cutting -Gear Cutting

Drilling -Destructive test of Welds

Bending -Jig Boring

Tapping and Threading

COST REPORT

SYSTEM COST (Rs.)

Chassis 20000/-

Transmission 20000/-

Suspension 28000/-

Rims & Tires 35000/-

Steering 5000/-

Braking 38000/-

Engine 17000/-

Electrical System 20000/-

Seat 10000/-

Paint 5000/-

Total: 198000/-

DFMEA ( Transmission System) :

Item Function Failure Mode Severity Cause Occurrence

Detection Rating

Risk Priority Number

Remedies

1. Transaxle Gearbox

Power transmission, Gear reduction, Differential.

a. misalignment

8 Shocks and vibrations

2 1 16 Use of rubber mountings, Proper alignment, Reduction of shocks and vibrations through use of suspension system.

b. wear of multiplate clutch

8 Lubricating fluid leakage / low viscosity index

1 2 16 Check for leakages, Replace lubricating fluid if necessary.

c. 6 Lubricat 1 2 12 Check for leakages, Replace

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overheating ing fluid leakage, Improper air cooling

lubricating fluid if necessary. Correct placement to facilitate airflow over the unit surface.

2. Full Floating Axle

Torque transmission.

a. Torsion Failure

8 Overloading

1 1 8 Axle size is calculated using the failure criteria and safe values are obtained.

b. misalignment

8 Shocks and vibrations

2 1 32 Proper alignment, Reduction of shocks and vibrations through use of suspension system.

c. Wear of rubber coupling

8 Hardened rubber due to chemical contamination

1 3 24 Replace with spare.

DFMEA (Crash Tube (chassis component)):

Item Function Failure Mode Severity Cause Occurrence

Detection Rating

Risk Priority Number

Remedies

Crash Tube

Destructive absorption of impact energy

a. damage to chassis without crash tube

9 Frontal Impact

4 1 36 Use of crash tube absorbs most of impact damage thus protecting the chassis

b. damage to chassis with crash tube

9 Frontal Impact, Short crash tube

4 1 36 Size of crash tube is optimized so that there is minimum or no damage to chassis.

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ELECTRICAL CIRCUIT