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

Background Frame Drivetrain Suspension Steering Brakes Electronics Safety, Testing & Manufacturing

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


Team Goals

Top 30 Finish in Competition

Leave a Legacy


Critical Improvements

Decrease the Weight of Car

Improve the Maneuverability

Optimize Suspension

Optimize Drivetrain


Budget

Total: $15,000 Remaining Budget: $3,000


$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


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


Goals For Frame

Lightweight: 100 lbs. 75lbs.

Compact in Length: 85 in. 80 in.

Driver Safety: Withstands applied forces


Frame Constraints


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


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


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


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


1.25 .062 29,732 95 6,221 1,217,074 .789


1 .062 29,732 95 3,575 541,987 .602

MATERIAL Outside Diameter (in)

Wall Thickness (in)



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


1 .120 29,732 95

6,215 972,581 1.13


1.25 .062 29,732 95 6,221 1,217,074 .789


1 .062 29,732 95 3,575 541,987 .602


Final Design

0

20

40

60

80

100

We

igh

t (l

bf)

Weight Comparison

2013-2014 2014-2015

100

61

BAJA BENGALS 2015


DRIVETRAIN

1 • Functional Requirements

2 • Goals

3 • Concept Generation

4 • Gearbox Analysis

5 • Final Design

BAJA BENGALS 2015



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


Goals For Drivetrain

• 40 MPH top speed

• Ascend a 35 deg incline

Performance

• Overall weight under 150lbs.

Lightweight


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


• 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


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


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


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

Background Frame Drivetrain Suspension Steering Brakes Electronics SafetyTesting

BAJA BENGALS 2015 BAJA BENGALS 2015

SUSPENSION


2 • Front Suspension Breakdown

3 • Rear Suspension Breakdown

4 • Goals

5 • Constraints

6 • Suspension Analysis

7 • Final Design

BAJA BENGALS 2015



• Couples key subsystems

Structural Integrity

• Reduce forces transferred to subsystems

Dampen Vibrations

• Power output

• Steering response

Maintain Tire Contact


Front Suspension Breakdown

B – Upper Control Arm

D – Tie Rod

F – Front Hub

E – Upright

C – Shock Absorber

A – Lower Control Arm


BAJA BENGALS 2015

Rear Suspension Breakdown

E – Rear Hub

A – Trailing Arm

D – Bearing Housing

C - Radial Arms

B – Shock Absorber

F – Output Shaft


BAJA BENGALS 2015

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


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


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



• 64” max width

• Wheel dimensions

Geometry

• CV angle limitations

• CV plunge

Drivetrain


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



Cornell Baja Team Louisville Baja Team


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)


Shock Absorbers

http://www.ridefox.com/technology.php?m=atv&t=psd&ref=lnav_tech


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



• Static Ride Height: +0.54 degrees

• Max compression: -3.05 degrees • Max Extension: -0.81

degrees


Final Front Suspension Design


BAJA BENGALS 2015


http://4.bp.blogspot.com/-JwCcTHh_h_A/U2WFE4K3vrI/AAAAAAAAAwc/cZT0jsKxJ48/s1600/IMG_20140422_245605009_HDR.jpg




BAJA BENGALS 2015

Final Rear Suspension Design


BAJA BENGALS 2015

STEERING


2 • Goals

3 • Steering Analysis

4 • Evaluation and Selection

5 • Material Selection

6 • Critical Specifications


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


Rotate Wheels

Tight Turn Radius

Maintain Direction

Safety


Enclosed Mechanisms

Unobstructed Egress

System Integration

Lightweight

Durable

Driver Comfort


Concept Generation

Research Previous LSU Teams & Competition

• Ackermann Steering Geometry

• Rack & Pinion Placement

Identify Critical Design Criteria


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”


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


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°


BAJA BENGALS 2015

BRAKES 1

• Functional Requirements

2 • Goals

3 • Constraints

4 • Concept Generation

5 • Engineering Analysis

6 • Final Design

BAJA BENGALS 2015



Cease Vehicle Motion

Effectively slow vehicle from speed

Competition Requirements

Brake light

Must lock all four wheels

on pavement


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



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



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



• 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:


Concept Generation: Pedal Type

• Floor-mounted Pedal vs. Hanging Pedal

Images from: http://www.wilwood.com/Pedals/PedalList.aspx


Concept Generation: Master

Cylinder Location

• Forward vs. Rear-Facing Master Cylinder

Images from www.speedwaymotors.com


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


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



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


Analysis: Braking Force

FB * rdisc = FF * rwheel FB = 2,450 lbs


Static:

Dynamic:

FB = ma(rwheel/rdisc) + (Iα/rdisc)

FB = 2,482 lbs BAJA BENGALS 2015

Analysis: Braking Force

FB = (2 * FOUT) * μ


Final Design

Total System Braking Force

FB = 3,780 lbs www.wilwood.com

BAJA BENGALS 2015

BAJA BENGALS 2015

BAJA BENGALS 2015


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


Brake Light Switch


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


Circuit Components

• 12 V, 2000 mAh

• Brake light runtime: 10 hrs.

Battery

• 22 AWG

• Voltage-drop: 3 mV/ft

Wire


Kill Switch Circuit


BAJA BENGALS 2015

Component Details

• One switch in reach of driver

• One switch near firewall

• Pushing either switch interrupts ignition

Kill Switches


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


Safety in Car Design


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


• Fuel splash guard

• Protective casing covering rotating components

• Two engine kill switches

Drivetrain

• 5-point safety harness

• Fire extinguisher

Other

Safety Moving Forward


• 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


Static Testing


• 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


Testing Timeline & Locations


Complete manufacturing one month before competition

LSU permits for testing on campus

Testing locations: Clint’s camp, Spillway

Manufacturing Plans


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


• 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


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

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)


29,732 29,732 29,732 29,732 29,732


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


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

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

Trailing Arm

F=1500 lbf

Pin Shear

Bump Steer

Steering

Functional Decomposition

Steering System


Rotate Wheels

User Input

Tight Turn Radius

Maintain Direction

System Integration

Compatible With Suspension

Lightweight

Durable

Driver Comfort

Safety


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

team 40 - · pdf filebaja sae team 40 lsu me capstone design: fall 2014 lsu baja bengals...

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