• Logs

Book Notes

10.1 - Constraints and Specifications

• Constraints are external boundaries within which a designer must work
  • These include the rules of the competition and the parts/ tools available
• Performance - Lay out performance goals
  • Ex. Acceleration/ top speed capabilities, cooling capabilities
  • These can be calculated by hand or carried over from previous year’s designs’
• Handling - The car should be designed in a way that allows the driver to reach these performance goals
  • Consider: the steering system, suspension system, chassis stiffness, aero, etc.
• Structure - torsional and bending strength needed to deal with the maximal forces on the car from all directions (use FEA)
• Driver Accommodations and Safety - Adequate cockpit size, comfortable and ergonomic seating, comfortable cockpit temperature, all other safety requirements
• Tires - performance is limited by tire choice
• Adjustable Features - Design should be capable of adjustment for different conditions
  • Weight distribution - (adjustable CG and wheelbase)
  • Aerodynamics - different wings
  • Suspension - different ride height, damping, geometry, etc.

10.2 - A Design Process

• Many compromises will have to be made in design, parallel design concepts at each stage

• Consider fabrication techniques (what would be most cost effective)

• Start by brainstorming in a group to make sure everything is covered

• Unbalanced designs - emphasize one feature above the rest (figure out right balance/ emphasis for competition)

• Preliminary Design - Fix general arrangement of components in the car

  1. Gathering data on all the parts to be used in the car
     1. Use weight and dimensions of parts to construct sketch of car and estimate CG
     2. Want CG to be as low as possible, optimal location (front to back) is based on choice of tires and aero
  2. Develop a top and front view of the car, considering:
     1. Wheelbase, track - affect basic handling
        1. Larger track gives larger maximum lateral acceleration
        2. Shorter wheelbase gives more maneuverability, less directional damping
     2. Ride height/ ground clearance
     3. Overall body shape
     4. Cooling
     5. Battery location
     6. Accessibility
     7. Types of suspensions
     8. Overall structure shape
     9. Area for driver
  3. Make new CG estimate from more detailed design

• Detailed Design and Analysis - design and analysis proceed in parallel

  • Start off with the below from Preliminary Design
    • Overall dimensions and component locations
    • Body shape
    • Weight/ approximate CG location
    • Power curves (from battery and motors)
    • Tire data
  1. Start with aerodynamic considerations of airflow around the vehicle
  2. Chassis geometry, suspension geometry, steering geometry, cockpit layout, battery and drivetrain mounting, other systems (these can all be modified going forward)
  3. Stress analysis - may require edits
  4. Ensure that vehicle design is good for all the competition settings