SAE Mini Baja Car Drive Train Design

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SAE Mini Baja Car Drive Train Design

• Senior Project by
• Jason Elbot
• Project Advisor Professor William Keat

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Presentation Outline

• Background
• Gear ratio analysis
• Drive train analysis
• Alternative design strategies
• Continuously Variable Transmission (CVT)
• MER-197 progress MER-198 objectives

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2004 East Competition

• Where Montreal Quebec
• When May 2004

• Safety Inspection
• Static Events Design Report, Design Evaluation,
  Cost Report.
• Dynamic Events Speed, Acceleration, Power,
  Maneuverability/Suspension, Water
  Maneuverability, and Endurance Race

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Design Objective

• To design a drive train for superior performance
  in all of the SAE competition events,
  specifically optimizing speed, acceleration,
  power, and endurance.

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Drive Train Analysis

• Torque vs. Rpm
• Gear ratio study
• Optimal operating point

Briggs Stratton Motor Curve
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Optimum Drive Train
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Why Use a CVT

• Continuously changes reduction ratio
• Smooth transmission of power to the driving
  wheels
• Robust belt load reduction extends lifetime of
  components

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Continuously Variable Transmission

• Belt and pulley mechanism is clutch and the gear
  system.
• Two pulleys which have the ability to open and
  close axially (sideways).

• Typical Clutch System
• (Shown in High "Gear")
•  

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Continuously Variable Transmission

• Spring pressure
• Low RPM
• Pulley halves apart
• De-clutching
• High RPM
• centrifugal forces close pulley
• Engage belt

• Upper Pulley Section

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Continuously Variable Transmission

• Torque spring twists
• Power is transmitted through these torque
  sensitive cams

Lower Pulley Section
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Polaris CVT Specs.

• Responds to both engine RPM and vehicle torque
  load
• 3.5111 gear ratio variation
• 10 axle-axle distance
• 20 lbs overall weight
• 460.00

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Implementation Challenges

• Pulley and frame interferences
• Pulley/crankshaft interface
• Pulley/gearbox interface
• 10 axle to axle requirement

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References Acknowledgements

• www.sae.org
• www.polarisindustries.com
• www.gates.com
• www.briggsandstratton.com
• Professor William Keat
• Internal Education Fund (IEF)
• Griffen Motor Sports
• Ryan Grant - Baja Club President
• Don Schaeffer - Former Baja car designer

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Questions?
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Drive Train Analysis

• This table shows that designing to run the car at
  maximum the rpm is more important than designing
  to the torque.