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Baja SAE
Baja SAE
Design Review #2
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Statement of Work
Baja SAE is an international engineering design competition. Student teams design, build, and test a single seat, four-wheel off-road vehicle. We will compete in the Baja SAE Carolina competition in April 2010.
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Team Responsibilities
Sam Moran Team Captain; Frame; Welder/Fabricator
Michael Guilfoy Treasurer; Steering; Machinist/Fabricator
Sam Weitkemper Powertrain; Secretary
Dan Pickering Suspension; Machinist/Fabricator
Matt Wantland Analyst; Materials Acquisition; Fabricator
Ben McNealy Brakes; Dynamic Analysis
Ahmed Al-Gattan Safety
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Project Background: Baja SAE
Baja SAE Carolina will be held April 8th-11th, 2010, in Greenville, South Carolina
106 teams registered
Dynamic Testing Events:
Acceleration
Suspension
Traction/Pulling
Maneuverability
4-hour Endurance Race
Static Events:
Design Presentation/Report
Prototype Cost
Project Background: Baja SAE
Why is this project important?
Real-world engineering design project
Concept Selection
Design decisions based on pre-determined competition specifications and safety concerns
Three-Dimensional Modeling
Limiting Factor 10 horsepower Briggs & Stratton Engine
Fabrication Experience
Welding
Machining
Vehicle Engineering Specifications
Overall Vehicle DimensionsSpecificationSpecified byDesignedGround Clearance10"Team10"Track Width55"Team55"Wheelbase60"Team60"Weight< 500 lbs.Advisors~500 lbs.FrameMaterialSteel, Sy = 52.9 ksiBaja SAESy = 52.9 ksiSize A1.25" 1018 steelBaja SAE32.0 feetSize B1.00" 1018 steelBaja SAE65.5 feetLength 80Team81.5Width 35Team30.25Height 52Team51.8Weight< 100 lbs.Team67.8 lbs.
Vehicle Engineering Specifications
PowertrainSpecification TargetDesignedMax Ratio35.6039.75Min Ratio6.985.7Top Speed35 MPH34 MPHMax Gradient70%52%Max Engine Power9.1 HP9.1 HPMax Engine Torque13.8 ft-lbs.13.8 ft-lbs.Idle1750 RPM1750 RPMMax RPM3800 RPM3800 RPMWeight< 150 lbs.120 lbs.Tire Diameter22 inches22 inches
Vehicle Engineering Specifications
SuspensionSpecificationSpecified byDesignedSuspension Travel10Team10Spring RatesFront: 105 lb/inRear: 145 lb/inSuspension SynthesisFront: 120 lb/inRear: 140 lb/inCamberFront: 5.0Rear: 0.0TeamFront: 5.0Rear: 0.0Bump Steer0.0Team0.0Weight< 65 lbs.Team~50 lbs.SteeringSpecificationSpecified byDesignedTurning Radius 10 feetTeam/Advisors10.02 feetRack & Pinion Travel4.25 inchesTeam4.75 inchesLock-to-Lock1.5 turns-----1.5 turnsAckerman Angle39.75Team39.55
Final Vehicle Concept
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Frame Bends
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Frame
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Drivetrain Design - Transmission
CVTech CVT mated to a Dana H-12 transaxle
Pros: Simple, proven reliability, F/N/R, auto-locking differential
Cons: Heavy
Drivetrain Design Axle
Drivetrain Stress Analysis
Conservative analysis:
Max axle torque = Max motor torque * max gear ratio = (14.5 ft-lbs) * (39.75) = 580 ft-lbs
Shear stress = T*C/J * Kt= (580 ft-lbs) * (0.362) ft / 0.0270 ft^4 * 1.78 = 138 ksi
Shear strength (4340 @ HRC 52) 0.577 * (260 ksi) = 150 ksi
Factor of Safety = 150 / 138 = 1.1
Fatigue life (calculated using FatigueCalculator tool) > 1500 cycles
Drivetrain Stress Analysis
Using same CV joints that worked well in the 2009 competition
Axle assemblies are rated by manufacturer to 700 ft-lbs (includes a factor of safety), and that vehicle uses an engine that produces twice as much power
Using hollow axles would at best save 0.5 lbs per axle and would increase part cost
In our case, conservative analysis did not add to cost
Drivetrain Design - Axle
4340 Q&T steel
Splined ends to fit CV joints
Suspension System
Suspension System
Suspension System
Front Suspension View
Suspension System
Rear Suspension View
Suspension Stress Analysis
A-Arm Material SpecificationsTubing Size1 Inch1.25 InchDiameter (in)11.25Wall (in)0.0750.075c (in)0.50.625I moment (in4)0.023460.04797Fmax Bending (lbs)156.5256.0A-Arm tube Length15.875 inTubing Yield Strength53 Ksi
Suspension Stress Analysis
Steering System
Major Goal turning radius less than 10 feet
Procured rack and pinion drive had greater travel than specified by vendor
4.75 inches rather than 4.25 inches of travel
1.5 turns lock-to-lock
Allows for a greater steering angles
Allows for shorter turning radius
Outside Wheel Steering Angle37.5degreesInside Wheel Steering Angle41.6degreesAckerman Steering Angle39.55degreesTurning Radius10.02feet
Braking system
Components:
Dual US Brake master cylinders, 7/8 bore
Wilwood reverse mount pedal
Polaris Outlaw front rotors and calipers
Polaris Ranger rear rotors and calipers
AN-3 flex steel brake lines
Polaris 10mm pressure switch
Polaris brake light
Weight Distribution Analysis
Design Specifications:
55% rear weight bias
Center of Mass as low as possible to ground level
Design Results:
54.3% rear weight bias
Center of Mass = 25.3 in above ground level
Rollover Potential Analysis
Dynamic analysis based on COM height, roll center, and spring rate
Vehicle will be rollover-resistant when cornering at reasonable speeds
Dynamic Rollover Threshold
New car10152025303540455012.63977148749057715.48049530486576117.87533626290591119.98523350226232221.8927264123941423.64684717665192425.27954297498114426.81300439435893428.263388266092615
Turning Radius (ft)
Maximum Safe Velocity (mph)
Torque Analysis
Based on front/rear weight distribution and torque at wheels
Result: Front wheels will stay on the ground under foreseeable circumstances
Torque vs. Incline
01.74524064372835123.48994967025009695.2335956242943886.97564737441253788.715574274765822710.45284632676536612.1869343405147513.91731009600654415.64344650402309817.36481776669305119.08089953765448120.79116908177591222.49510543438649924.19218955996675625.88190451025209227.56373558169989129.23717047227367530.90169943749472732.55681544571563534.20201433256692514951481.29600031711521467.1407835228971452.53866143350611437.49408199678511422.01162793736781406.09601536074841389.75209231668921372.98483732248021355.79935784642021338.20088875203691320.19479070349581301.78654853269431282.98176956852011263.786181928811244.20563277551491224.24608653358341203.91362307415671183.21443586256781162.15483007175981140.7412206616671034.202014332566925450450
Percent Grade
Resistive Torque (lb-ft)
Vehicle Safety Considerations
Engine Spill Shield made of HDPE
CVT Cover eliminate hand access, made of HDPE
Kill Switches 2 required, cockpit and external
Transponder MYLaps rechargeable power
Safety Harness 5 strap system, 3 lap belt, quick release connecters
Fire Extinguisher 5 BC rating, dial pressure gauge
Tube Padding standard 1.5 foam padding
Vehicle Safety Considerations
Welding Helmet new auto-darkening mask
Safety Glasses always required during fabrication
Ear Plugs required for cutting/grinding metal
Helmet motor-cross style, 1-piece composite
Neck Collar SFI 3.3, full 360 coverage
Arm Restraints SFI 3.3, attach to driver harness
Head Restraint SFI 42.2, foam pad
Budget
Original Budgeted Retail Cost Retail Cost Customer CostCompetition Expenses $ 3,000.00 $ 3,100.00 $ 2,100.00 Vehicle System CostsFrame $ 1,100.00 $ 1,100.00 $ 50.00 Powertrain $ 3,785.00 $ 6,290.34 $ 3,033.69 Suspension $ 2,178.29 $ 3,600.00 $ 1,648.00 Steering $ 345.00 $ 269.95 $ 269.95 Braking $ 1,124.09 $ 1,124.09 $ 653.00 Tires and Maintenance $ 396.00 $ 500.00 $ 200.00 Miscellaneous $ 500.00 $ 1,750.00 $ 1,000.00 TOTAL VEHICLE EXPENSES $ 9,428.38 $ 14,634.38 $ 6,854.64 Team Operation Expenses $ 1,450.00 $ 900.00 $ 900.00 Team Labor Expenses $ 151,350.00 $ 154,950.00 $ - Total Anticipated Costs $ 165,228.38 $ 173,584.38 $ 9,854.64
Budget
Hourly RateExtended CostItemDescriptionRetail RateCustomer RateQuantityRetail CostCustomer CostEngineeringDesign & Analysis$75.00 $0.00 1300$97,500.00 $0.00 FabricationMachining Time$50.00 $0.00 30$1,500.00 $0.00 Welding Fixtures$45.00 $0.00 20$900.00 $0.00 Tube Bending$45.00 $0.00 6$270.00 $0.00 Welding$45.00 $0.00 144$6,480.00 $0.00 Assembly$45.00 $0.00 840$37,800.00 $0.00 TestingTesting & Analysis$75.00 $0.00 140$10,500.00 $0.00 Total Labor Costs2480$154,950.00 $0.00
Donations Received
Polaris Industries:
$5,647.23 in parts for $2,533.00
Suspension, brake, safety, and driveshaft components
CVTech-IBC:
$232.00 CVT for $130.00
Tubing:
Tenaris Coiled Tubes 150 feet of tubing
QwikService Steel 200+ feet of various tubing and steel
Ariens:
$2