Team 40 - · PDF fileBAJA SAE Team 40 LSU ME Capstone Design: Fall 2014 LSU Baja Bengals...
Transcript of Team 40 - · PDF fileBAJA SAE Team 40 LSU ME Capstone Design: Fall 2014 LSU Baja Bengals...
BAJA SAE Team 40
LSU ME Capstone Design: Fall 2014
LSU Baja Bengals 2014-2015
Team Members Lance Angelle
James Burgard
Clinton Bourgeois
Colby Cheneval
Kevin Hall
Hannah Neitzke
Kevin Sextro
Carey Snell
Drake Strother
Faculty Advisor Dr. Waggenspack
Introduction
Alumnus Advisors Aaron McDonald
Devin Poirrier
The Team
Sponsors
Agenda
1 • What is Baja?
2 • Objectives
3 • Frame
4 • Drivetrain
5 • Suspension
6 • Steering
7 • Braking
8 • Electronic Components
9 • Safety and Testing
10 • Manufacturing Plans
11 • Component Integration
Photo Provided by 2013-14 Baja Team
Photo Provided by 2012-13 Baja Team
Static (300 points)
Dynamic (300 points)
Endurance (400 points)
• Design 200
Points • Acceleration
75 Points
• Cost 100
Points
• Tech Inspection
Pass/
Fail
• Suspension 75
Points
• Hill Climb 75
Points
• Maneuver-ability
75 Points
Baja Competition Structure
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LSU Baja History
2
32
22
23
50
6 11
18
35
72
0
10
20
30
40
50
60
70
80
1995 2000 2005 2010 2015
Pla
cem
en
t
Competition Year
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Team Goals
Top 30 Finish in Competition
Leave a Legacy
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Critical Improvements
Decrease the Weight of Car
Improve the Maneuverability
Optimize Suspension
Optimize Drivetrain
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Budget
Total: $15,000 Remaining Budget: $3,000
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$3,500
$3,000
$2,500
$2,500
$2,000
$500
$500
$500
$0 $1,000 $2,000 $3,000 $4,000
Drivetrain
Competition
Suspension
Miscellaneous
Frame
Body Paneling
Steering
Brakes
FRAME 1
• Functional Requirements
2 • Goals
3 • Constraints
5 • Material Selection
6 • Analysis
7 • Final Design
BAJA BENGALS 2015
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Functional Requirements
Safety
Includes All Required Members
Structural Integrity
Comfort
Adequate Driver Space
Mounting Point Location
Easy Driver Entrance and Exit
Dimensions
System Integration
Brakes
Suspension
Steering
Drivetrain
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Goals For Frame
Lightweight: 100 lbs. 75lbs.
Compact in Length: 85 in. 80 in.
Driver Safety: Withstands applied forces
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Frame Constraints
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
GEOMETRY
SIZE Must Fit Largest Driver Must Fit 95th Percentile
Male Must Fit 5th Percentile
Female
Constraints: Required Members
PRIMARY MEMBERS
ADDITIONAL MEMBERS
SECONDARY MEMBERS
• Steel Tubing • Minimum Wall Thickness= .035
inches • Minimum Outer Diameter= 1 inch
• Steel Tubing • Minimum Wall Thickness= .120
inches • Minimum Outer Diameter= 1 inch • OR • Custom Geometry with specified
Bending Stiffness and Strength
• No Constraints from SAE Rulebook
BAJA BENGALS 2015
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Concept Generation and Selection
Research
• Further Weight Reduction
• Reduce Stress Concentration
Optimize
• Based on Sub-Systems
Revise
• Based on Research & Constraints
Create Initial Model
• Rulebook
• LSU’s Frames
• Successful School’s Frames
Research
BAJA BENGALS 2015
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Analysis: Material Selection
Material Young’s
Modulus (GPa)
Tensile
Strength
(MPa)
Yield Strength
(MPa)
Density (g/cc)
AISI 1018 205 440 370 7.87
AISI 1020 200 395 295 7.87
AISI 4130 210 560 460 7.85
Material Young’s
Modulus (GPa)
Tensile
Strength
(MPa)
Yield Strength
(MPa)
Density (g/cc)
AISI 1018 205 440 370 7.87
AISI 1020 200 395 295 7.87
AISI 4130 210 560 460 7.85
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
Analysis: Cross Section Geometry MATERIAL Outside
Diameter (in)
Wall Thickness (in)
Modulus of Elasticity (kip)
Yield Strength (kip)
Bending Strength (lb*in)
Bending Stiffness (lb*in^2)
Unit Weight (lb/ft)
AISI 1018 (Reference)
1 .120 29,732 53 3,463 972,581 1.13
AISI 4130 (Option 1)
1 .120 29,732 95
6,215 972,581 1.13
AISI 4130 (Option 2)
1.25 .062 29,732 95 6,221 1,217,074 .789
AISI 4130 (Option 3)
1 .062 29,732 95 3,575 541,987 .602
MATERIAL Outside Diameter (in)
Wall Thickness (in)
Modulus of Elasticity (kip)
Yield Strength (kip)
Bending Strength (lb*in)
Bending Stiffness (lb*in^2)
Unit Weight (lb/ft)
AISI 1018 (Reference)
1 .120 29,732 53 3,463 972,581 1.13
AISI 4130 (Option 1)
1 .120 29,732 95
6,215 972,581 1.13
AISI 4130 (Option 2)
1.25 .062 29,732 95 6,221 1,217,074 .789
AISI 4130 (Option 3)
1 .062 29,732 95 3,575 541,987 .602
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Final Design
0
20
40
60
80
100
We
igh
t (l
bf)
Weight Comparison
2013-2014 2014-2015
100
61
BAJA BENGALS 2015
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DRIVETRAIN
1 • Functional Requirements
2 • Goals
3 • Concept Generation
4 • Gearbox Analysis
5 • Final Design
BAJA BENGALS 2015
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Functional Requirements
Performance
Transmit power to
wheels with minimal loses
Structural
Lightweight
Rigid to withstand All
Terrain
Ease of Operation
Easily Maintained
Minimal Driver Skill for
Operation
Safety
Guards around rotating
components
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Goals For Drivetrain
• 40 MPH top speed
• Ascend a 35 deg incline
Performance
• Overall weight under 150lbs.
Lightweight
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Engineering Constraints
• Lower center of gravity to prevent rollover
Overall Car
• SAE Rulebook requires the use of a Briggs and Stratton Intek Motor
• 10HP and 14.5 ft-lbs of torque at 3800 RPM
Motor
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• Minimize space needed within rear of frame (30” from back of firewall to rear of frame)
Frame
• CV axles need adequate plunge for suspension articulation (½” of plunge each in and out from zero position)
Suspension
Concept Generation and Selection
Research
• Last Year’s Car (LSU)
• Top competitors over the years
Transmission Selection
• Continuously Variable Transmission (CVT)
Final Drive Selection
• Single speed, dual reduction gearbox
• Offers compact design with choice of custom gear ratio
forums.bajasae.net
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Analysis: Gearbox
Minimum Gear Ratio to Climb Incline:
35°
Top Speed with Minimum Gear Ratio: 3800 RPM MAX ENGINE SPEED → 228,000 ROT/HOUR
0.9:1 FINAL CVT RATIO
TIRE RADIUS = 0.9 FT
TOP SPEED @ 3800 RPM = 40 MPH
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G1 G2
GRAVITY
TIRE RADIUS: 0.9 FT CVT LOW RATIO: 3.9:1 VEHICLE WEIGHT W/DRIVER: 600 LBS MAX INCLINE ANGLE: 35 DEGRESS
(VEHICLE WEIGHT)*(sin (INCLINE ANGLE))= REPELLING WEIGHT (600lbs) * (sin(35))= 344.14 lbs
REPELLING WEIGHT =(TIRE RADIUS)*(CVT RATIO)*(ENGINE TQ)*(X MIN) 344.14LBS= (0.9 FT) x (3.9) x (14.5 ft-lbs) x (X MIN) X MIN= 6.76
Final Design
Key Features of Improvement: • Dual Reduction Gearbox
with 6.8:1 ratio • Lightweight and compact
design • Final Drivetrain Weight:
90-100lbs
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SUSPENSION
1 • Functional Requirements
2 • Front Suspension Breakdown
3 • Rear Suspension Breakdown
4 • Goals
5 • Constraints
6 • Suspension Analysis
7 • Final Design
BAJA BENGALS 2015
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Functional Requirements
• Couples key subsystems
Structural Integrity
• Reduce forces transferred to subsystems
Dampen Vibrations
• Power output
• Steering response
Maintain Tire Contact
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Front Suspension Breakdown
B – Upper Control Arm
D – Tie Rod
F – Front Hub
E – Upright
C – Shock Absorber
A – Lower Control Arm
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BAJA BENGALS 2015
Rear Suspension Breakdown
E – Rear Hub
A – Trailing Arm
D – Bearing Housing
C - Radial Arms
B – Shock Absorber
F – Output Shaft
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Camber Angle
http://www.gomog.com/allmorgan/wheels3a.jpg
- Angle between centerline of tire relative to the vertical
http://www.formula1-dictionary.net/camber.html
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Roll Center The point in the transverse vertical plane through any pair of wheel centers at which lateral forces may be applied to the sprung mass without producing suspension roll
Suspension Analysis and Computational Geometry –John Dixon
Front Suspension
Rear Suspension Online Source Unknown
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BAJA BENGALS 2015
Goals
Withstand entire endurance competition
12” total suspension travel: 7” Compression, 5” Extension
Minimize Camber Variance to ±5° throughout travel
Achieve 10” ground clearance at static ride height
Limit wheel base to ˂80”
Minimize Weight
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Engineering Constraints
• 64” max width
• Wheel dimensions
Geometry
• CV angle limitations
• CV plunge
Drivetrain
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Wei
ght
Do
ub
le A
-Arm
(eq
ual
)
Do
ub
le A
-Arm
(u
neq
ual
)
Rig
id F
ram
e
Structural Integrity 10 + + -
Lightweight 9 + + +
Cost 7 + + +
Manufacturability 6 + + +
Camber Variance 5 - + -
Travel 4 + + -
Total + 5 6 3
Total - 1 0 3
Total Score 36 41 22
Concept Generation and Selection
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Cornell Baja Team Louisville Baja Team
Concept Generation and Selection
Wei
ght
Do
ub
le A
-Arm
(eq
ual
)
Do
ub
le A
-Arm
(u
neq
ual
)
3-L
ink
Trai
ling
Arm
Mo
dif
ied
Tra
ilin
g A
rm
Solid
Axl
e
Structural Integrity 10 + + + + +
Integration 10 + + + + -
Lightweight 9 + + + - -
Manufacturability 6 + + + + +
Cost 7 + + + + +
Camber Variance 5 - + + - -
Travel 4 + + + + +
Total + 6 7 7 5 4
Total - 1 0 0 2 3
Total Score 46 51 51 37 27
Rear Suspension Concept Selection
Source: Aaron McDonald (LSU Baja Alumni 2013)
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Shock Absorbers
http://www.ridefox.com/technology.php?m=atv&t=psd&ref=lnav_tech
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Engineering Analysis
• Camber Angle
𝑧2 = 𝑟12 + 𝑟2
2 − 2𝑟1𝑟2𝑐𝑜𝑠𝜃2 = 𝑟32 + 𝑟4
2 − 2𝑟3𝑟4𝑐𝑜𝑠𝜆
𝜆 = 𝑐𝑜𝑠−1𝑧2 − 𝑟3
2 − 𝑟42
−2𝑟3𝑟4
𝛼 = 𝑐𝑜𝑠−1𝑧2 + 𝑟4
2 − 𝑟32
2𝑧𝑟4
𝛽 = 𝑐𝑜𝑠−1𝑧2 + 𝑟1
2 − 𝑟22
2𝑧𝑟1
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Engineering Analysis
• Static Ride Height: +0.54 degrees
• Max compression: -3.05 degrees • Max Extension: -0.81
degrees
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Final Front Suspension Design
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BAJA BENGALS 2015
Final Front Suspension Design
http://4.bp.blogspot.com/-JwCcTHh_h_A/U2WFE4K3vrI/AAAAAAAAAwc/cZT0jsKxJ48/s1600/IMG_20140422_245605009_HDR.jpg
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Final Front Suspension Design
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Final Rear Suspension Design
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STEERING
1 • Functional Requirements
2 • Goals
3 • Steering Analysis
4 • Evaluation and Selection
5 • Material Selection
6 • Critical Specifications
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BAJA BENGALS 2015
Functional Decomposition
Control Vehicle Direction
Rotate Wheels
Tight Turn Radius
Maintain Direction
System Integration
Lightweight
Durable
Driver Comfort
Safety
Removable Steering Wheel
Enclosed Mechanisms
Unobstructed Egress
Control Vehicle Direction
Rotate Wheels
Tight Turn Radius
Maintain Direction
Safety
Removable Steering Wheel
Enclosed Mechanisms
Unobstructed Egress
System Integration
Lightweight
Durable
Driver Comfort
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Concept Generation
Research Previous LSU Teams & Competition
• Ackermann Steering Geometry
• Rack & Pinion Placement
Identify Critical Design Criteria
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BAJA BENGALS 2015
BAJA BENGALS 2015
http://www.hotrodders.com/forum/undestanding-ackerman-suspension-geometry-227762.html
Upright Design
• Average Tire Turn Angle – X = Mounting distance from axis of rotation
– 2.125” = Rack Travel
– 𝜃 = 50.5°
𝑋 =2.125
tan 𝜃=
2.125
𝑡𝑎𝑛 50.5= 1.75”
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BAJA BENGALS 2015
Engineering Analysis and Material
Selection
Tie Rod Material
Modulus of Elasticity (ksi)
Yield Strength (psi)
Outside Diameter (in)
Wall Thickness (in)
Unit Weight (lb/ft)
Price Per Foot ($/ft)*
AISI 4130
Steel
29,700
70,000
0.5
0.083
0.37
8.73
AISI 2024
Aluminum
10,600
42,000 0.5 0.083 0.13 12.44
AISI 2024
Aluminum 10,600 42,000 0.5 0.12 0.17 13.77
Component Tensile Force Buckling Force Bending Moment Torsion
Tie Rod N/A
Lower Steering
Shaft N/A N/A N/A
Upper Steering
Shaft N/A N/A N/A
* Price via McMaster-Carr.com
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Steering Specifications
Steering Specifications
Turning Diameter 10 Feet
Rack Travel 4.25 in “lock-to-lock”
Steering Ratio 12:1
Number of Steering Wheel turns “lock-to-lock”
1.5 turns
Average Tire Turning Angle 50.5°
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BAJA BENGALS 2015
BRAKES 1
• Functional Requirements
2 • Goals
3 • Constraints
4 • Concept Generation
5 • Engineering Analysis
6 • Final Design
BAJA BENGALS 2015
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Functional Requirements
Cease Vehicle Motion
Effectively slow vehicle from speed
Competition Requirements
Brake light
Must lock all four wheels
on pavement
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Goals for Braking System
Meet the requirements of competition
Keep weight of overall system to a minimum
Adjustable braking distribution
Allow for easy driver exit
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Engineering Constraints
2015 Baja SAE Rules and Regulations
• Hydraulic system
• At least two independent fluid circuits
• All brakes operated with a single foot pedal
• All brakes must illuminate brake light
• Rigid link between pedal and master cylinder(s)
• Braking on rear end must act through final drive
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Engineering Constraints
10” wheel size for all four wheels
Will need a brake for each front wheel
• - Only need one brake for rear wheels
• - 7” max disc diameter
Solid rear-end:
• - Will need a brake for all four wheels
Open differential:
Limited space in foot box
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Concept Generation and Selection
• Nearly all teams use hydraulic disc brakes
Baja SAE Competition History
• Pedal type
• Master cylinder mounting and linkage
• Rear brake type
Items to be addressed:
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Concept Generation: Pedal Type
• Floor-mounted Pedal vs. Hanging Pedal
Images from: http://www.wilwood.com/Pedals/PedalList.aspx
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Concept Generation: Master
Cylinder Location
• Forward vs. Rear-Facing Master Cylinder
Images from www.speedwaymotors.com
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Concept Generation: Balance
Bar and Bias Adjuster
• Linkage between pedal and master cylinders
• Adjustable braking distribution for each fluid circuit
Images from www.wilwood.com
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Concept Generation: Rear Brake
• 2 discs & calipers
• cutting brakes
Open Differential
http://www.naxja.org/forum/showthread.php?t=1001264
• Only one disc and caliper needed
• Central mounting location
Solid Rear-End
http://www.bmikarts.com/Brake-Hub-1-or-1-14-Bore_p_545.html
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Engineering Analysis
Find braking force needed to decelerate the vehicle at 32.2 ft/s2
• Mass of car
• Inertial forces from rotating weight
Find braking force needed to lock all four wheels on pavement
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Analysis: Braking Force
FB * rdisc = FF * rwheel FB = 2,450 lbs
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Static:
Dynamic:
FB = ma(rwheel/rdisc) + (Iα/rdisc)
FB = 2,482 lbs BAJA BENGALS 2015
Analysis: Braking Force
FB = (2 * FOUT) * μ
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Final Design
Total System Braking Force
FB = 3,780 lbs www.wilwood.com
BAJA BENGALS 2015
BAJA BENGALS 2015
BAJA BENGALS 2015
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ELECTRONICS
1 •Brake Light Switch
2 •Circuit Components
3 •Kill Switch Circuit
4 •Component Details
http://www.dhgate.com/product/universal-motorcycle-car-truck-red-led-reflectors/159772091.html
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Brake Light Switch
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BAJA BENGALS 2015
Circuit Components
• Activated by brake fluid pressure
• One switch for each fluid circuit
Brake Switches
• Must meet certain SAE standards
• 12 V, 200 mA
Brake Light
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Circuit Components
• 12 V, 2000 mAh
• Brake light runtime: 10 hrs.
Battery
• 22 AWG
• Voltage-drop: 3 mV/ft
Wire
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Kill Switch Circuit
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BAJA BENGALS 2015
Component Details
• One switch in reach of driver
• One switch near firewall
• Pushing either switch interrupts ignition
Kill Switches
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Component Dimensions
• Length- 2.84 in, Width- 1.97 in, Height 1.14 in
• Weight: 10 oz
Battery
• Width- 11.1 in, Height- 1.24 in, Depth- .76 in
Brake Light
Safety
http://baja.rit.edu/wordpress/?tag=sponsorship
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Safety in Car Design
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2015 Baja SAE Rules and Regulations
• Protect the driver
• Mounting for safety harness & arm restraints
• Firewall, body panels, and belly pan
Frame:
• Two independent fluid circuits
Brakes:
Safety in Car Design
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
• Fuel splash guard
• Protective casing covering rotating components
• Two engine kill switches
Drivetrain
• 5-point safety harness
• Fire extinguisher
Other
Safety Moving Forward
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• Motocross-style helmet
• Goggles with tear-offs or roll-offs
• Neck brace
• Gloves, pants, & a fire resistant long sleeve shirt
Driver Protection for Testing & Competition
Manufacturing
Testing Plans
http://blogs.nd.edu/jlugo/category/sae-collegiate-design-series/
http://www.bajasaetennesseetech.com/venue.html
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Static Testing
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
• 5 second driver exit test
• All drivers must fit in vehicle
Technical Inspection
Brake Lights
Kill Switches
Dynamic Testing
Acceleration, Top Speed, & Dynamic
Braking
Hill Climb Suspension
Steering & Maneuverability
Endurance
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Testing Timeline & Locations
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
Complete manufacturing one month before competition
LSU permits for testing on campus
Testing locations: Clint’s camp, Spillway
Manufacturing Plans
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BAJA BENGALS 2015
Manufacturing Plans
BAJA BENGALS 2015
• Frame bends and profiling done by Cartesian Tube Profiling
• Tabs and brackets machined in house
Frame
• Gears and gear shafts to be outsourced
• Casing machined in house
• CVT and CV axles purchased from supplier
Drivetrain
• A-Arms, Trailing arm, Sway bars, mounting brackets machined in house
• Spherical bearings, rod ends, ball joints, bushings, shock absorbers purchased
Suspension
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
• Rack and pinion purchased from supplier
• Tie rods, extensions, steering shaft, and all mounts and connections manufactured in house
Steering
• All braking components to be purchased
• Mounting components to be manufactured in house
Braking
• Wire and soldering to be purchased
Electrical
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BAJA BENGALS 2015
Manufacturing Plans
Final Design
• Estimated Weight= 375 lbs.
• Top Speed= 40 mph • Max Incline= 35 degrees
• Turning Diameter= 10 feet
• Ground Clearance= 10
inches
BAJA BENGALS 2015
Appendix
FRAME
FUNCTIONAL DECOMPOSITION: FRAME (DRIVER INTERFACE)
Driver Interface
Comfort
Components relative to driver
Foot Pedals
Steering
Adequate space for driver
Foot Space
Head Space
Elbow Space
Body Room
Protection
Structural Support Around
Driver
Seatbelt Support Provided
FUNCTIONAL DECOMPOSITION: FRAME (DRIVER INTERFACE)
Component Interface
Mounting
Suspension Support
Pivot Points
Shocks
Drivetrain support
Rigid Support for Engine
Gearbox Mounting
Steering Support
Allow Pivot for Steering Column
Support Steering Mechanism
Brakes
Provide support for Brakes
Barrier between components & surroundings
MATERIAL AISI 1018 SAE 4130 (1) SAE 4130 (2) SAE 4130 (3) SAE 4130 (4)
Modulus of Elasticity (kip)
29,732 29,732 29,732 29,732 29,732
Yield Strength (kip)
53 95 95 95 95
Outside Diameter (in)
1 1 1.25 .969 1.165
Wall Thickness (in)
0.120 0.120 0.062 0.062 0.062
Bending Strength (lb∙in)
3,463 6,215 6,221 3,575 5,338
Bending Stiffness (lb∙in2)
972,581 972,581 1,217,074 541,987 972,600
Unit Weight (lb/ft)1 1.13 1.13 .789 .602 .732
1. Based on a density of .284 lb/in3 (matweb.com).
Equations Used:
𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ = 𝑆𝑦𝐼
𝑐
𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑖𝑓𝑓𝑛𝑒𝑠𝑠 = 𝐸𝐼
𝐼 = 𝜋
4𝑟𝑜
4 − 𝑟𝑖4
FRAME MATERIAL SELECTION
The purpose of this document is to aid in the design of the roll cage and serve as a checklist to pass technical inspection. Component List Primary
RRH - Rear Roll Hoop RHO - Roll Hoop Overhead Members FBM - Front Bracing Members LC - Lateral Cross Member FLC - Front Lateral Cross Member
Secondary LDB - Lateral Diagonal Bracing LFS - Lower Frame Side SIM - Side Impact Member FAB - Fore/Aft Bracing USM - Under Seat Member All Other Required Cross Members Any tube that is used to mount the safety belts
Material Requirements Primary Members: Circular steel tubing with an OD of 25mm (1.0in) and a wall thickness of 3mm (0.120in) and carbon content of at least 0.18%. Secondary Members: Circular steel tubing with a minimum OD of 25.4mm (1.0in) and having a minimum wall thickness of 0.89 mm (0.035in). Driver Spacing Head
Minimum of 152mm (6in) of clearance from any space from the roll cage. Body
Minimum of 76mm (3in) of clearance from any space from the roll cage. Note: Clearances are relative to any driver selected at technical inspection, seated in a normal driving position, and wearing all required equipment. No part of the driver’s body may extend beyond the envelop of the roll cage. General Requirements Members which are not straight must not extend longer than 711mm (28in) between supports. Small bend radii (<152mm, 6in) at a supported end of a member are expected, and are not considered to make a member not straight The minor angle between the two ends of a not-straight tube must not exceed 30°. No sharp edges. Notes Rules concerning the roll cage that are not necessary in the geometric design such as the welding process check, destructive testing samples, and roll cage specification sheet are not covered. Tube joints and bolted roll cages are not covered and are to be avoided in the geometric design of the roll cage. Rules in the regards to the constraints to the former statements should be referred to in the competition manual.
Lateral Cross Member (LC) Requirements - Primary Cannot be less than 203.5mm (8in) long. Cannot have a bend
Can be a part of a larger bent tube system, between bends. Members that connect the left and right points of AF, SF, and C must be made of primary materials. Rear Roll Hoop (RRH) Requirements - Primary May be inclined by up to 20° from the vertical. Minimum width is 736mm (29in).
Measured at a point 686mm (27in) above the inside seat bottom. Vertical members may be straight or bent.
Defined at beginning and ending where they intersect the top and bottom horizontal planes. Points Ar, Al, Br, Bl in Figure 1.
Vertical members must be continuous tubes. Vertical members must be joined by LC members at the top and bottom LC members must be continuous tubes. Must be diagonally braced.
Must extend from one vertical member to the other Lateral Diagonal Bracing (LDB) Requirements - Secondary Top and bottom intersections between the diagonal bracing and rear roll hoop vertical members must be no more than 127mm (5in) from the top and bottom horizontal planes. The angle between the diagonal bracing and rear roll hoop vertical members must be greater than or equal to 20°.
Lateral bracing may consist of more than one member. Roll Hoop Overhead Member (RHO) Requirements - Primary Point C in Figure 3 must be at least 305mm (12in) forward from a point in the vehicle’s elevation view.
Point C is defined as the forward end of the roll hoop overhead member. Defined by the intersection of the roll hoop overhead members and a vertical line rising from the after end of the seat bottom.
The point on the seat is defined by the seat bottom intersection with a 101mm (4in) radius circle which touches the seat bottom and the seat back. The top edge of the template is exactly horizontal with respect to gravity.
Point C in Figure 3 must not be lower than the top edge of the top edge of the template. 1041.4mm (41in) above the seat.
Lower Frame Side Member (LFS) Requirements - Secondary Define the lower right and left edges of the roll cage.
Joined to the bottom of the rear roll hoop and extend forward to at least as far as the driver’s heels when seated in a normal driving position.
Forward ends are joined by the front lateral cross member. Point AF.
Side Impact Member (SIM) Requirements - Secondary Define a horizontal mid-plane within the roll cage
Joined to the rear roll hoop and extend forward to at least as far as a point forward of the driver’s toes, when seated in a normal driving position.
Forward ends are joined by a lateral cross. Define the point SF.
Must be between 203mm (8in) and 356mm (14in) above the inside seat bottom. Figure 3. Under Seat Member (USM) Requirements - Secondary Must join the lower frame side members. Must pass directly below the driver.
Where the template in Figure 3 intersects the seat bottom. Must be positioned in such a way to prevent the driver from passing through the plane of the lower frame side members in the event of seat failure. Front Bracing Member (FBM) Requirements - Primary Must join the roll hoop overhead, side impact, and lower frame side members.
Figure 5. Upper front bracing member must join point C on the roll hoop overhead to the side impact member at or behind point SF. Lower front bracing member must join point AF to SF. Must be continuous tube. Angle between the upper front bracing member and the vertical must be less than or equal to 45°. If the roll hoop overhead and front bracing member on at least one side of the vehicle are no comprised jointly of one tube, bent near point C, then a gusset is required at point C.
To support the joint between the roll hoop overhead and front bracing members. The total weld length of the gusset must be 2 times the tubing circumference (of the primary material). If a tube is used to brace the front bracing and roll hoop overhead members, it must be a primary tube.
Fore/Aft Bracing (FAB) Requirements - Secondary Note: Better design will result if both front and rear are incorporated. Rear Bracing Directly restrain point B from longitudinal displacement in the event of failure of the joints at point C. Must create a structural triangle.
Must be same on both sides. Each triangle must be aft of the rear roll hoop. Must include the rear roll hoop vertical as a member. Must have one vertex near point B and one vertex near either point S or point A. The third vertex of each rear bracing triangle must additionally be structurally connected to whichever point, S or A, is not part of the structural triangle.
This additional connection is considered part of the fore/aft bracing system. Subject to B8.3.1. May be formed using multiple joined members.
Assembly of tubes, from endpoint to endpoint, may encompass a bend of greater than 30 degrees. Attachment of the rear fore/aft bracing system must be within 127mm (5in) of point B. Must be within 51mm (2in) of point S and A. The rear bracing structural triangles must not be angled more than 20 degrees from the vehicle centerline. The after vertices of the fore/aft bracing structural triangles must be joined by a lateral cross. Or Front Bracing Restrain point C from longitudinal and vertical displacement.
Supporting point B through the roll hoop overhead member. Must connect the upper front bracing member to the side impact member.
Must be same on both sides. The intersection with the upper front bracing member must be within 127mm (5in) of point C. The intersection with the side impact member must be vertically supported by further members connecting the side impact member to the lower frame side member.
PRIMARY SECONDARY
1. Rear Roll Hoop 1. Lateral Diagonal Bracing
2. Roll Hoop Overhead Members
2. Side Impact Member
3. Front Bracing Members 3. Fore Bracing
4. Lateral Cross Members 4. Under Seat Members
5. Front Lateral Cross Member
6. Lower Frame Side Member
Drivetrain
Analysis: Gearbox
Minimum Gear Ratio to Climb Incline:
35° GRAVITY
TIRE RADIUS: 0.9 FT CVT LOW RATIO: 3.9:1 VEHICLE WEIGHT W/DRIVER: 600 LBS MAX INCLINE ANGLE: 35 DEGRESS (VEHICLE WEIGHT)*(sin (INCLINE ANGLE))= REPELLING WEIGHT (600lbs) * (sin(35))= 344.14 lbs REPELLING WEIGHT =(TIRE RADIUS)*(CVT RATIO)*(ENGINE TQ)*(X MIN) 344.14LBS= (0.9 FT) x (3.9) x (14.5 ft-lbs) x (X MIN) X MIN= 6.76 Top Speed with Minimum Gear Ratio:
3800 RPM MAX ENGINE SPEED → 228,000 ROT/HOUR
0.9:1 FINAL CVT RATIO
TIRE RADIUS = 0.9 FT
TIRE ROLLOUT: (2π)*(0.9 FT) = 5.6548 FT
DISTANCE PER ROTENG = ( 5.6548 FT) / (0.9*6.76) =
0.92946 FT/ROTENG
(228,000 ROT/HR)*(0.92846 FT/ROT) = 211,688.88
FT/HR
(211,688.88 FT/HR)*[(1 MILE) / (5280 FT)] = 40.092 MPH
TOP SPEED @ 3800 RPM = 40 MPH
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing
G1 G2
GRAVITY
Analysis: Gears
• Displacement of gear tooth with 385 ft-lb force
• Stress on gear tooth using 4340 Steel
• Bending and Contact stresses calculated with AGMA equations
• Factor of safety was also calculated from these equations
Background Frame Drivetrain Suspension Steering Brakes Electronics SafetyTesting
BAJA BENGALS 2015 BAJA BENGALS 2015
Suspension
Fox Float 3 EVOL R
Source: Joey Avilla (Fox Racing)
Approximated Spring Coefficient
y = 46.712e0.8601x R² = 0.9552
0
200
400
600
800
1000
1200
1400
1600
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Forc
e (l
b)
Shock Stroke (in)
Spring Coefficient of Fox Float 3 EVOL R
Fox Float 3 EVOL R
Source: Joey Avilla (Fox Racing)
Fox Float 3 EVOL R
Source: Joey Avilla (Fox Racing)
Fox Float 3 EVOL R
Motion Ratio
𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑊ℎ𝑒𝑒𝑙 𝑇𝑟𝑎𝑣𝑒𝑙
𝑆ℎ𝑜𝑐𝑘 𝑆𝑡𝑟𝑜𝑘𝑒=
𝑅𝑎𝑑𝑖𝑎𝑙 𝑊ℎ𝑒𝑒𝑙 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒
𝑆ℎ𝑜𝑐𝑘 𝑃𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡
• Front: 𝑆ℎ𝑜𝑐𝑘 𝑃𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 = 18" (5.3"
12") = 7.95”
• Rear: 𝑆ℎ𝑜𝑐𝑘 𝑃𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 = 26" (5.3"
12") = 11.5”
Damping
Impact Force
Impact Force cont.
Lower A-Arm
Lower A-Arm
Trailing Arm
F=1500 lbf
Pin Shear
Bump Steer
Steering
Functional Decomposition
Steering System
Control Vehicle Direction
Rotate Wheels
User Input
Tight Turn Radius
Maintain Direction
System Integration
Compatible With Suspension
Lightweight
Durable
Driver Comfort
Safety
Removable Steering Wheel
Unobstructed Egress
Enclosed Mechanisms
Background Frame Drivetrain Suspension Steering Brakes Electronics Safety/Testing
Brakes
Braking Force Calculations
rwheel = 10.5 inches = 0.875 ft
rdisc = 3 inches = 0.25 ft (effective braking radius)
I = 0.216 slug*ft2 (For all 4 wheels)
a = 32.2 ft/s2 (linear deceleration)
α = 36.8 rad/s2 (angular deceleration)
m = 21.74 slugs (vehicle plus driver and fluids)
Braking Force Calculations
FB*rdisc = I*α Eq. 1
Slowing rotating mass
FB*rdisc = m*a*rwheel Eq. 2
Slowing moving mass
Combining Eq. 1 and Eq.2 for total braking force
FB = ma(rwheel/rdisc) + Iα/rdisc
Electronics
Battery charger circuit
Battery charger simulation
Organization
Steering Assembled
2/3/14
Drivetrain Assembled
1/25/14
Suspension Assembled
1/25/14
Brakes Assembled
2/18/14
Order
Frame 12/8/14
Begin
Manufacturing
and Assemble
Frame
12/19
Begin
Testing 3/1/15
5 Weeks Prior to
Competition
Manufacturing Timeline
Key Takeaways
• Complete SolidWorks Assembly
• Jump started Baja as a Student Organization
• Discovered Importance of Engineering Design Process & Documentation
• Developed Team Chemistry in Order to have a Successful Spring Semester
• Understanding of how to apply theory learned in classes to a practical application
LSU Baja Bengals Team: 2014-2015