Willie via EV wrote:
On 5/18/19 12:38 PM, Haudy Kazemi via EV wrote:
drag and increased energy consumption (and reduced range). Simply
vehicle increases frontal area by virtue of the tires being more exposed.
I believe the under car air speed is also increased. Or, maybe
increased turbulence. Anyway, I think it is worse than just exposing
I think that is true. Keeping the car low is a way to reduce the amount
of air and turbulence underneath. Of course, a smooth bottom would help;
but that costs too much.
Big fat tires with lots of tread have lots of wind resistance. And, the
tops of the tires are moving forward at *double* the speed of the car!
Paul MacReady (of Aerovironment) talked a lot about auto aerodynamics
when he was designing the Impact (aka GM EV1). Things I recall:
- Aero testing is in wind tunnels, with car and tires not moving.
- The roughness of the bottom of the car is usually ignored.
- Spinning tires have much more drag than stationary ones.
- Most cars are more aerodynamic in reverse.
So, he designed the EV1 with a smooth bottom, with wheel wells optimized
as "ducts" to minimize turbulence, and a shape that actually *was*
aerodynamic (instead of what some stylist thinks will "look" aerodynamic).
If you need more ground clearance sometimes, maybe adjustable air bags
are an answer?
Fools ignore complexity. Pragmatists suffer it. The wise avoid it.
Geniuses remove it. -- Alan Perlis, "Epigrams on Programming"
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)