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BAJA SAE 2010

BAJA SAE 2010. Conceptual Design Review. Statement of Work.

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BAJA SAE 2010

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  1. BAJA SAE 2010 Conceptual Design Review

  2. Statement of Work • Baja SAE is an international collegiate design competition sponsored by the Society of Automotive Engineers. The program simulates real-world engineering design projects and the related challenges with the goal of developing and building a small off-road vehicle. Teams from around the world compete in static and dynamic events to have their design accepted for manufacture by a fictitious firm.

  3. Team Responsibilities • Sam Moran – Chief Executive Officer; Frame Designer; Welder/Grinder • Michael Guilfoy – Steering Engineer; Chief Financial Officer; Welder/Machinist • Sam Weitkemper – Drivetrain Engineer; Executive Secretary • Ben McNealy – Braking Engineer; Analyst; Director of Internet Services • Matt Wantland – Analyst; Materials Acquisition Specialist; Fabricator • Dan Pickering – Suspension Engineer; Chief Mechanic • Ahmed Al-Gattan – Chief Safety Officer

  4. Customers • SAE Competition Fictitious Firm • Safe vehicle • Maneuverability, Traction, Suspension, Acceleration • Design/Manufacturability • Cost • Sponsors • Competitive vehicle • Promotion • Faculty Advisors • Competition success • Educational experience

  5. Benchmarking • Vehicle Engineering Specifications • Front Track Width • Rear Track Width • Wheelbase • Weight • Suspension • Drivetrain • Data from 2009 Baja SAE Alabama competition

  6. Benchmarking 2010 TU car 2009 TU car

  7. Benchmarking 2010 TU car 2009 TU car

  8. Benchmarking 2010 TU car 2009 TU car

  9. Benchmarking • Analysis of top 11 overall performing cars from 2009 Baja SAE Alabama competition

  10. Frame Concept 1 – The Nose Box • Advantages: • simple • few packaging constraints • Disadvantages: • inefficient use of space

  11. Frame Concept 2 – Integrated Cockpit • Advantages: • more legroom • efficient use of space • light • Disadvantages: • Complicated design

  12. Frame Concept 3 – “The Cage” • Advantages: • simple design • requires the least amount of planning • allows for last-stage drivetrain changes • Disadvantages: • heavy • difficult drivetrain maintenance

  13. Frame Concept 4 – Double Loop • Advantages: • lightweight • efficient • easy drivetrain maintenance • Disadvantages: • difficult to design • not conducive to double a-arm suspension • stuck with drivetrain choices

  14. Frame Concept & Design • Front • Length designed for the reach of the team’s smallest driver • Clearance designed for the 95th percentile male • Integrated cockpit design • Rear • Double loop design inspired by Queen’s University • Frame members do not interfere with removal of drivetrain components • Weight: 73 lbs • Length: 80.5” • Width: 31.0” • Height: 52.9”

  15. Final Frame Design

  16. Frame Material • Given in 1018 PCS • 2 different specifications -Strength/Stiffness • Critical Components – Roll Cage • Non-Critical Components – frontal/side impact

  17. Sizing Calculations

  18. Tubing Possibilities • Hi Performance – Expensive/Light • Economical – Cheap/Heavy • Compromise – In between

  19. Frame Specifications *http://www.airpartsinc.com/products/4130-steel-tubing.htm

  20. Drivetrain Benchmarking

  21. Drivetrain Concept #1 • CVT with chain drive • Pros: lightweight, simple, cheap • Cons: no reverse gear, requires tensioning system

  22. Drivetrain Concept #2 • Motorcycle gearbox with chain drive • Pros: easy to find, includes reverse gear • Cons: more difficult for the driver

  23. Drivetrain Concept Chosen • CVTech CVT with Dana H-12 transaxle • Pros: Simple, proven reliability, F/N/R, auto-locking differential • Cons: Heavy

  24. Drivetrain Layout

  25. 2010 Axle Design

  26. Drivetrain Specifications

  27. Front Suspension • Double A-arm configuration • The front suspension system for a majority of the cars at last year’s competition • Benefits • The length and orientation of the arms can be designed for the vehicle’s application. • Computers can be used to design the suspension geometry

  28. Front Suspension • The vehicle was designed around the suspension mounting points • To prevent conflicts between the suspension and other vehicle components • Mechanism synthesis was performed in SolidWorks with the help of Dr. Daily

  29. Front Suspension • Mounting points • Geometric constraint analysis was performed to determine the suspension mounting points for a given tie rod length and designed for no bump steer • Constraints: 5 degrees of camber and 10 inches of vertical travel for a 52-inch front track width • Top arm length: 16.375” • Bottom arm length: 16.50”

  30. Front Suspension • Roll center • The front roll center was determined using SolidWorks • For the desired mounting points, the roll center was found to be about 3.05 inches above the ground

  31. Rear Suspension • Solid Rear Axle/ Swing Arm • Top finishers such as Queen’s University and Michigan University used a swing arm with a solid rear axle. • Double A-arm • A majority of the cars at last year’s Mini Baja used a double wishbone configuration. • More appropriate for cars without a solid rear axle • Simple • After discussing options with the team, a double wishbone configuration was chosen

  32. Rear Suspension • Mounting points • Geometric constraint analysis was again performed to determine the suspension mounting points • Constraints: no camber change and 8 inches of vertical travel for a 50-inch rear track width • Top arm length: 16.50” • Bottom arm length: 16.50”

  33. Rear Suspension • Roll center • The rear roll center was determined using SolidWorks given parallel equal length arms • For the desired mounting points, the roll center was found to be at the ground

  34. Shocks and Springs • The shock mounting points were set by the frame design and restrained by the control arm movement. • The ideal shock travel for the given wheel travel was determined from mechanism synthesis.

  35. Steering Concepts • Power Steering • Additional components • Requires power • Complicated integrationinside steering box • Four-Wheel Steering • Challenging integration • Untested in competitionconditions

  36. Steering Concepts • Rack and Pinion Steering • Simplified system • Light • Ease of integration with suspension • Used by nearly every Baja SAE team

  37. Ackerman Geometry 51” 62.5”

  38. Modeling Steering Angles 27.73° 45.49° Outside Wheel Lock Position Inside Wheel Lock Position

  39. Turning Radius Results

  40. Steering Specifications • Chosen Concept: Rack and Pinion • 14 inch length; 4.5 inches of travel • 1.5 turns lock-to-lock • Turning radius of approximately 10.5 feet • Ackerman Geometry • Tie Rod Connection • Rack mounting to minimize lateral loads • Rack mounting considered in frame design • Front Suspension design clearance issues addressed

  41. Braking Concepts • Rules require two independent hydraulic systems • Disc brakes • Light • Compact • Used by nearly all Baja teams • Drum brakes • Heavy • Bulky

  42. Braking Concepts • Single cylinder, dammed reservoir • Pros: simple, packaging flexibility • Cons: longer than dual cylinders • Dual cylinders, overhead mount • Pros: shortest overall length • Cons: aesthetics • Dual cylinders, floor mount • Pros: elegant packaging • Cons: longer, may conflict with steering components

  43. Braking Concepts • Rigid lines • Pros: Rigid, look good • Cons: Difficult to install • Braided flex lines • Pros: Flexible, easier to install • Cons: Heavier

  44. Braking Concept Selected • Polaris discs and calipers • Dual US Brake master cylinders • Wilwood reverse mount pedal • Braided steel flex line

  45. Safety • Braking • Two independent hydraulic braking systems • Capable of locking the wheels • No plastic brake lines • Drivetrain • CVT cover – made of polymer • Gas catch – made of polymer • Kill Switches • Two kill switches required • One in cockpit, one in rear

  46. Safety • Frame pads • The minimum required thickness is ½”. • The cost is $17.95 per 3 feet. • Need 6 feet. • Safety helmet • Motor cross style, Snell M2005 specification

  47. Safety • Fire extinguisher • Two 5 B-C extinguishers. • One must be mounted next to the driver and the other in the pit area. • Head restraint

  48. Goals and Deadlines • January 25 – complete design • stress analysis • CAD models • February 28 – drivable vehicle • rolls under its own power • basic safety gear • March 28 – competition-ready vehicle • meets all rules • fully functional, painted, polished, done. • April 8-11 – 2010 Baja SAE Carolina competition

  49. Schedule

  50. Budget

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