BAJA SAE Team 40 LSU ME Capstone Design: Fall 2014 LSU Baja Bengals 2014-2015
Introduction The Team Team Members Lance Angelle James Burgard Clinton Bourgeois Colby Cheneval Kevin Hall Hannah Neitzke Kevin Sextro Carey Snell Drake Strother Faculty Advisor Dr. Waggenspack Alumnus Advisors Aaron McDonald Devin Poirrier 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 Plans 11 Component Integration Photo Provided by 2013-14 Baja Team Photo Provided by 2012-13 Baja Team
Baja Competition Structure Static (300 points) Dynamic (300 points) Endurance (400 points) 200 Points Design 75 Points Acceleration 100 Points Cost 75 Points Maneuverability Pass/ Fail Tech Inspection 75 Points Hill Climb 75 Points Suspension
Placement LSU Baja History Competition Year 1995 2000 2005 2010 2015 0 10 20 30 40 2 6 11 22 18 23 35 32 50 60 50 70 72 80
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 Brakes Steering Body Paneling $500 $500 $500 Frame $2,000 Miscellaneous Suspension $2,500 $2,500 Competition $3,000 Drivetrain $3,500 $0 $1,000 $2,000 $3,000 $4,000 Total: $15,000 Remaining Budget: $3,000
FRAME 1 2 3 5 6 7 Functional Requirements Goals Constraints Material Selection Analysis Final Design BAJA BENGALS 2015
Functional Requirements System Integration Comfort Safety Brakes Suspension Steering Adequate Driver Space Mounting Point Location Easy Driver Entrance and Exit Includes All Required Members Structural Integrity Drivetrain Dimensions
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 95 th Percentile Male Must Fit 5 th Percentile Female
Constraints: Required Members PRIMARY MEMBERS Steel Tubing Minimum Wall Thickness=.120 inches Minimum Outer Diameter= 1 inch OR Custom Geometry with specified Bending Stiffness and Strength SECONDARY MEMBERS BAJA BENGALS 2015 Steel Tubing Minimum Wall Thickness=.035 inches Minimum Outer Diameter= 1 inch ADDITIONAL MEMBERS No Constraints from SAE Rulebook
Concept Generation and Selection BAJA BENGALS 2015 Research Research Create Initial Model Revise Optimize Rulebook LSU s Frames Successful School s Frames Based on Research & Constraints Based on Sub- Systems Further Weight Reduction Reduce Stress Concentration
Analysis: Material Selection Material Young s Tensile Yield Strength Density (g/cc) Modulus (GPa) Strength (MPa) (MPa) 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 Wall Modulus of Yield Bending Bending Unit Diameter Thicknes Elasticity Strength Strength Stiffness Weight (in) s (in) (kip) (kip) (lb*in) (lb*in^2) (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
Weight (lbf) Final Design Weight Comparison 100 100 80 61 60 40 20 0 2013-2014 2014-2015 BAJA BENGALS 2015
DRIVETRAIN 1 2 3 4 5 Functional Requirements Goals Concept Generation Gearbox Analysis Final Design BAJA BENGALS 2015
Functional Requirements Performance Structural Ease of Operation Safety Transmit power to wheels with minimal loses Lightweight Easily Maintained Guards around rotating components Rigid to withstand All Terrain Minimal Driver Skill for Operation
Goals For Drivetrain Performance 40 MPH top speed Ascend a 35 deg incline Lightweight Overall weight under 150lbs.
Motor Overall Car Engineering Constraints SAE Rulebook requires the use of a Briggs and Stratton Intek Motor 10HP and 14.5 ft-lbs of torque at 3800 RPM Frame Minimize space needed within rear of frame (30 from back of firewall to rear of frame) Lower center of gravity to prevent rollover Suspension CV axles need adequate plunge for suspension articulation (½ of plunge each in and out from zero position)
Concept Generation and Selection Research Last Year s Car (LSU) Top competitors over the years Transmission Selection Continuously Variable Transmission (CVT) forums.bajasae.net Final Drive Selection Single speed, dual reduction gearbox Offers compact design with choice of custom gear ratio
Analysis: Gearbox Minimum Gear Ratio to Climb Incline: TIRE RADIUS: 0.9 FT CVT LOW RATIO: 3.9:1 VEHICLE WEIGHT W/DRIVER: 600 LBS MAX INCLINE ANGLE: 35 DEGRESS G1 G2 GRAVITY 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 (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 BAJA BENGALS 2015 BAJA BENGALS 2015 SafetyTesting
SUSPENSION Functional Requirements 1 Front Suspension Breakdown 2 Rear Suspension Breakdown 3 Goals 4 Constraints 5 6 Suspension Analysis BAJA BENGALS 2015 7 Final Design
Functional Requirements Structural Integrity Couples key subsystems Dampen Vibrations Reduce forces transferred to subsystems Maintain Tire Contact Power output Steering response
Front Suspension Breakdown A Lower Control Arm B Upper Control Arm C Shock Absorber D Tie Rod E Upright F Front Hub BAJA BENGALS 2015
Rear Suspension Breakdown A Trailing Arm B Shock Absorber C - Radial Arms D Bearing Housing E Rear Hub F Output Shaft BAJA BENGALS 2015
Camber Angle - Angle between centerline of tire relative to the vertical http://www.gomog.com/allmorgan/wheels3a.jpg 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 Front Suspension Rear Suspension BAJA BENGALS 2015 Online Source Unknown Suspension Analysis and Computational Geometry John Dixon
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
Engineering Constraints Geometry 64 max width Wheel dimensions Drivetrain CV angle limitations CV plunge
Concept Generation and Selection Weight Double A-Arm (equal) 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 Double A-Arm (unequal) Rigid Frame Louisville Cornell Baja Team
Concept Generation and Selection Rear Suspension Concept Selection Weight Double A-Arm (equal) 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 Double A-Arm (unequal) 3-Link Trailing Arm Modified Trailing Arm Solid Axle 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 z 2 = r 1 2 + r 2 2 2r 1 r 2 cosθ 2 = r 3 2 + r 4 2 2r 3 r 4 cosλ λ = cos 1 z2 r 3 2 r 4 2 2r 3 r 4 α = cos 1 z2 + r 4 2 r 3 2 2zr 4 β = cos 1 z2 + r 1 2 r 2 2 2zr 1
Engineering Analysis Max Max compression: Extension: -3.05-0.81 Static degrees degrees Ride Height: +0.54 degrees
Final Front Suspension Design BAJA BENGALS 2015
Final Front Suspension Design http://4.bp.blogspot.com/-jwccthh_h_a/u2wfe4k3vri/aaaaaaaaawc/czt0jskxj48/s1600/img_20140422_245605009_hdr.jpg
Final Front Suspension Design BAJA BENGALS 2015
Final Rear Suspension Design BAJA BENGALS 2015
STEERING 1 2 3 4 5 6 Functional Requirements Goals Steering Analysis Evaluation and Selection Material Selection Critical Specifications BAJA BENGALS 2015
Functional Decomposition System Control Vehicle Integration Direction Safety Lightweight Durable Driver Comfort Rotate Wheels Tight Turn Radius Maintain Direction Removable Steering Wheel Enclosed Mechanisms Unobstructed Egress
Concept Generation Research Previous LSU Teams & Competition Identify Critical Design Criteria Ackermann Steering Geometry Rack & Pinion Placement BAJA BENGALS 2015 http://www.hotrodders.com/forum/undestanding-ackerman-suspensiongeometry-227762.html BAJA BENGALS 2015
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 Component Tensile Force Buckling Force Bending Moment Torsion Tie Rod N/A Lower Steering Shaft Upper Steering Shaft N/A N/A N/A N/A N/A N/A 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 * Price via McMaster-Carr.com
Steering Specifications Turning Diameter Rack Travel Steering Specifications 10 Feet 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 2 3 4 5 6 Functional Requirements Goals Constraints Concept Generation Engineering Analysis Final Design BAJA BENGALS 2015
Functional Requirements Cease Vehicle Motion Competition Requirements Effectively slow vehicle from speed 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
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
Engineering Constraints 10 wheel size for all four wheels Will need a brake for each front wheel Solid rear-end: - Only need one brake for rear wheels - 7 max disc diameter Open differential: - Will need a brake for all four wheels Limited space in foot box
Concept Generation and Selection Baja SAE Competition History Nearly all teams use hydraulic disc brakes Items to be addressed: Pedal type Master cylinder mounting and linkage Rear brake type
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 Open Differential 2 discs & calipers cutting brakes Solid Rear-End http://www.naxja.org/forum/showthread.php?t=1001264 Only one disc and caliper needed Central mounting location http://www.bmikarts.com/brake-hub-1-or-1-14-bore_p_545.html
Engineering Analysis Find braking force needed to decelerate the vehicle at 32.2 ft/s 2 Mass of car Inertial forces from rotating weight Find braking force needed to lock all four wheels on pavement
Analysis: Braking Force Static: F B * r disc = F F * r wheel F B = 2,450 lbs Dynamic: F B = ma(r wheel /r disc ) + (Iα/r disc ) BAJA BENGALS 2015 F B = 2,482 lbs
Analysis: Braking Force F B = (2 * F OUT ) * μ
Final Design BAJA BENGALS 2015 BAJA BENGALS 2015 BAJA BENGALS 2015 Total System Braking Force www.wilwood.com F B = 3,780 lbs
ELECTRONICS 1 Brake Light Switch 2 Circuit Components 3 Kill Switch Circuit 4 Component Details http://www.dhgate.com/product/universalmotorcycle-car-truck-red-ledreflectors/159772091.html
Brake Light Switch BAJA BENGALS 2015
Circuit Components Brake Switches Activated by brake fluid pressure One switch for each fluid circuit Brake Light Must meet certain SAE standards 12 V, 200 ma
Circuit Components Battery 12 V, 2000 mah Brake light runtime: 10 hrs. Wire 22 AWG Voltage-drop: 3 mv/ft
Kill Switch Circuit BAJA BENGALS 2015
Component Details Kill Switches One switch in reach of driver One switch near firewall Pushing either switch interrupts ignition
Component Dimensions Battery Length- 2.84 in, Width- 1.97 in, Height 1.14 in Weight: 10 oz Brake Light Width- 11.1 in, Height- 1.24 in, Depth-.76 in
Safety http://baja.rit.edu/wordpress/?tag=sponsorship
Safety in Car Design 2015 Baja SAE Rules and Regulations Frame: Protect the driver Mounting for safety harness & arm restraints Firewall, body panels, and belly pan Brakes: Two independent fluid circuits
Drivetrain Safety in Car Design Fuel splash guard Protective casing covering rotating components Two engine kill switches Other 5-point safety harness Fire extinguisher
Safety Moving Forward Driver Protection for Testing & Competition Motocross-style helmet Goggles with tear-offs or roll-offs Neck brace Gloves, pants, & a fire resistant long sleeve shirt
Testing Plans http://blogs.nd.edu/jlugo/category/sae-collegiate-design-series/ http://www.bajasaetennesseetech.com/venue.html
Static Testing Technical Inspection 5 second driver exit test All drivers must fit in vehicle 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
Plans BAJA BENGALS 2015
Plans Frame Frame bends and profiling done by Cartesian Tube Profiling Tabs and brackets machined in house Drivetrain Gears and gear shafts to be outsourced Casing machined in house CVT and CV axles purchased from supplier Suspension A-Arms, Trailing arm, Sway bars, mounting brackets machined in house Spherical bearings, rod ends, ball joints, bushings, shock absorbers purchased BAJA BENGALS 2015
Plans Steering Rack and pinion purchased from supplier Tie rods, extensions, steering shaft, and all mounts and connections manufactured in house Braking All braking components to be purchased Mounting components to be manufactured in house Electrical Wire and soldering to be purchased BAJA BENGALS 2015
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 Protection Components relative to driver Adequate space for driver Structural Support Around Driver Foot Pedals Foot Space Seatbelt Support Provided Steering Head Space Elbow Space Body Room
FUNCTIONAL DECOMPOSITION: FRAME (DRIVER INTERFACE) Component Interface Mounting Barrier between components & surroundings Suspension Support Drivetrain support Steering Support Brakes Pivot Points Rigid Support for Engine Allow Pivot for Steering Column Provide support for Brakes Shocks Gearbox Mounting Support Steering Mechanism
FRAME MATERIAL SELECTION MATERIAL AISI 1018 SAE 4130 (1) SAE 4130 (2) SAE 4130 (3) SAE 4130 (4) Modulus of Elasticity (kip) Yield Strength (kip) Outside Diameter (in) Wall Thickness (in) 29,732 29,732 29,732 29,732 29,732 53 95 95 95 95 1 1 1.25.969 1.165 0.120 0.120 0.062 0.062 0.062 Bending Strength (lb in) Bending Stiffness (lb in 2 ) 3,463 6,215 6,221 3,575 5,338 972,581 972,581 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/in 3 (matweb.com). Equations Used: Bending Strength = S yi c Bending Stiffness = EI I = π 4 r o 4 r i 4
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 A r, A l, B r, B l 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: GRAVITY G1 G2 GRAVITY 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 TIRE ROLLOUT: (2π)*(0.9 FT) = 5.6548 FT DISTANCE PER ROT ENG = ( 5.6548 FT) / (0.9*6.76) = 0.92946 FT/ROT ENG (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 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
Analysis: Gears BAJA BENGALS 2015 BAJA BENGALS 2015 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 SafetyTesting
Suspension
Fox Float 3 EVOL R Source: Joey Avilla (Fox Racing)
Force (lb) Approximated Spring Coefficient 1600 Spring Coefficient of Fox Float 3 EVOL R 1400 1200 y = 46.712e 0.8601x R² = 0.9552 1000 800 600 400 200 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Shock Stroke (in)
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 System Integration Safety Rotate Wheels Compatible With Suspension Removable Steering Wheel User Input Lightweight Unobstructed Egress Tight Turn Radius Durable Enclosed Mechanisms Maintain Direction Driver Comfort Safety/Testing
Brakes
Braking Force Calculations r wheel = 10.5 inches = 0.875 ft r disc = 3 inches = 0.25 ft (effective braking radius) I = 0.216 slug*ft 2 (For all 4 wheels) a = 32.2 ft/s 2 (linear deceleration) α = 36.8 rad/s 2 (angular deceleration) m = 21.74 slugs (vehicle plus driver and fluids)
Braking Force Calculations F B *r disc = I*α Eq. 1 Slowing rotating mass F B *r disc = m*a*r wheel Eq. 2 Slowing moving mass Combining Eq. 1 and Eq.2 for total braking force F B = ma(r wheel /r disc ) + Iα/r disc
Electronics
Battery charger circuit
Battery charger simulation
Organization
Timeline Order Frame 12/8/14 Begin and Assemble Frame 12/19 Drivetrain Assembled 1/25/14 Suspension Assembled 1/25/14 Steering Assembled 2/3/14 Brakes Assembled 2/18/14 Begin Testing 3/1/15 5 Weeks Prior to Competition
Key Takeaways Complete SolidWorks Assembly Discovered Importance of Engineering Design Process & Documentation Jump started Baja as a Student Organization Understanding of how to apply theory learned in classes to a practical application LSU Baja Bengals Team: 2014-2015 Developed Team Chemistry in Order to have a Successful Spring Semester