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