Oregon State University Solar Vehicle Team

1. Oregon State University Solar Vehicle Team

2. Solar Car Mechanical Design “How do you start the design of a new solar car?”

3. Mechanical Design Maximize Power Input Maximize efficiency (tractive force) Minimize drag Slide 7 of 62

4. A variety of vehicle designs Michigan Bochum Honda MIT Principia Minnesota Taiwan OSU, First Car Queens OSU, Odyssey

5. Design Tools • Solidworks 2012 • Computer Aided Drafting • Solidworks Simulation 2012 • Finite Element Analysis • Solidworks Flow Simulation 2012 • Computational Fluid Dynamics

6. Initial Design • Maximum power with minimum drag: • Lowest drag with maximum solar cell surface area • Design process: • Start with 6ft driver with helmet • Fit driver with body with max. surface area for cells (6 m2) • Good rule of thumb is to go to maximum width and length allowed • Wrap wheels, frame and suspension around driver inside body • Optimize body

7. Initial Design Process • Insert driver model • Design solar car body, draw in “dummy wheels” • Fit body to driver model, dummy wheels. Maximum low curvature array area • Run wind tunnel testing (Computational Fluid Dynamics, Flow Simulation 2012) • Evaluate drag force, power • Evaluate cross sectional area vs. coefficient of drag • Alter body shape • Can be “arbitrary” change • Repeat steps 3 and 4 www.xkcd.com/844

8. Design to Rule (Initial Design) • 6.5.B Forward Vision: • From the normal driving position, the driver must be able to see at all times, without artificial assistance, points at the following locations: • (1) A point on the ground 8 m in front of the solar car • (2) A minimum of 17° above the horizon on level ground • (3) A full 100° to either side of center • (4) The driver will be required to identify 40 mm high letters at a distance of 3 m through any of the required viewing angles. • 6.1 Solar Car Dimensions • The solar car (including solar array) may not exceed the following maximum dimensions when moving under its own power: • (1) Length = 5.0 m • (2) Height = 1.8 m • (3) Width = 1.8 m • 6.4.B Seating Position: • The driver must be seated at less than or at a 27° angle, as measured in Appendix B. The driver’s head must be above and behind the driver’s feet. The seat must be appropriately constructed with a solid base and back rest.

9. Chassis/Body Reconciliation • Best “body” initially designed with only driver, dummy wheels • Must “reconcile” body with chassis, due to chassis, suspension members taking up space • Remember: • Aerodynamics most important • Handling performance secondary • Mass considerations secondary

10. Chassis Design • Build smallest chassis necessary to hold driver, wheels and withstand structural requirements • 5G frontal, side, rear impact • 4G roll over impact • Verify chassis, suspension design with Finite Element Analysis (Solidworks Simulation 2012)

11. Body Re-work • Chassis/suspension will “poke out” of body • Remake the body for least drag that will fit chassis tightly

12. Things to Remember • Tips for a “smoother” design process: • All designs valid unless proven otherwise • Burden of good design proof is upon designer • Must meet all rules, or design is invalid • Absolutely avoid qualitative assertions: quantitative discussions much more useful • Offer constructive help, avoid criticism in general. • “You could perhaps enhance your design by X,Y,Z” and not “Your design is failing in X, Y, Z!” • Avoid stating absolutes, unless you can absolutely prove it! • Go offline to compute numbers. Don’t argue with qualitative arguments: doing so will often result in circular discussions. • Don’t be married to your own design if someone else’s design is better – we’re all in it together to make the best car possible! • No place in solar car team for ego contests. • Remember – you’re working with friends. Be friendly!!!