Optimal Car Shape

[GasSavers_maximilian]

That's much closer than the car I saw! Thanks! Looks pretty wide, but I failed to find actual dimensions anywhere. Engine counterbalancing the driver, which is what you'd expect. Neat stuff. Taruffi's Italian, so it'd be interesting to know what prompted his decision to sit on the right, since they drive on the right in Italy. Lanes and other traffic on his test run aren't probably an issue, I guess. That cutaway is actually of a different vehicle, FYI.

I found a short article about it. Also, here's a thread about other similar vehicles. It should've occurred to me that in the pure speed arena where general practicality is less of a concern this would've been tried.

[Sludgy]

I'm sure that NASA has data on the lowes drag shapes........

[GasSavers_maximilian]

Since car design is a compromise between utility and aerodynamics it comes down to more than just the simulations. It's more the process of trying to make a weird shape work that I find interesting.

[theholycow]

Originally Posted by Sludgy

I'm sure that NASA has data on the lowes drag shapes........

There's some NASA data on aerodynamics in my Sig Meta Thread...

Originally Posted by theholycow

The effect of boattails and other aerodynamic modifications on tractor trailers:
http://www.nasa.gov/centers/dryden/p...ain_H-2283.pdf
http://permanent.access.gpo.gov/webs...00-01-2209.pdf
http://www.greencarcongress.com/2005...at_tail_d.html
There's diagrams in those links that show the airflow around trucks, which may help car drivers better understand drafting.

[GasSavers_maximilian]

Sorry, Sludgy, I mistook your point. I'll take a look.

[oneinchsidehop]

Originally Posted by dkjones96

I'd like to see where someone did an aerodynamics study to show that the teardrop shape is the most efficient. The teardrop shape would create a high pressure area in front of it as opposed to cutting through like a cylinder with tapered ends.

Gustave Eiffel, 1903 http://www.allbusiness.com/professio.../290566-1.html

the shape isn't what he expected either, just what empirical observation pointed to. I'll see if I can find the ball studies, it explains it well. teardrops may be ugly, but they work.

[GasSavers_maximilian]

Here's the part in that relating to aerodynamics:

* Aerodynamics. In 1903, at the age of 71, Eiffel set up a small laboratory on the second platform of the Tower. Eiffel decided that if aviation was to have a future, the first question to investigate was air itself. His objective was to calculate the resistance of air and to move forms through the air with the least amount of effort.

Eiffel ran wires connected to recording devices from the second platform to a point 377 feet directly below and calculated the rate of fall of round, square, rectangular, and triangular plane surfaces. He concluded that previous tests conducted by others based on objects whirled on turntables were off by as much as 56 percent. His coefficient was corroborated by aviation pioneer and director of the Smithsonian Institution, Samuel Pierpont Langley.

Not satisfied with his first contribution to aerodynamics, Eiffel devised a wind tunnel to conduct more complex experiments, which he constructed at the foot of the Tower. A 70-horsepower electric motor was powered by the Tower's generators; it drove a fan system providing a steady, controlled, and turbulence-free flow of air at speeds up to 40 miles per hour. Airplane models were measured for overall aerodynamic balance, lift over wing surfaces, and propeller efficiency.

Eiffel's Law of Similitude provided an equation for designing propellers of any size. He also provided new insights into variable pitch and counterrotating propellers. His study of airfoils proved conclusively that more lift was produced by the air flowing over a cambered wing than by the air striking the wing's underside.

A larger and more powerful wind tunnel in the Paris suburb of Auteuil replaced the Tower facility. It provided an airflow of 71 miles per hour in a 6 1/2-foot-wide tunnel, permitting Eiffel's continued experiments on lift characteristics. At the age of 80, Eiffel was commended for "giving engineers the data for designing and constructing flying machines upon sound, scientific principles."

Eiffel really put emphasis on transcending mathematics and understanding things on an intuitive level. As an engineer I try to do the same and think our schools should teach math and science with a direct application method to reinforce it. I jokingly call it the "go-kart teaching system", because I know as a school kid I'd have loved to be part of a team to design and build one. You learn trigonometry when you need trigonometry, etc. Obviously you'd need a bunch of different projects for students to gravitate to, carefully chosen to include a useful assortment of skills and theory.

[samandw]

Here's an interesting example of a very low drag car that looks nothing like a teardrop . . .

Mercedes Bionic Car

[GasSavers_maximilian]

Cool! Has a Cd of .19. I did a quick search and a teardrop based vehicle should be somewhere in the .13-.15 range (please correct me if I found bad sources). Of course, the Bionic has a much less limiting shape.

[GasSavers_RoadWarrior]

I keep looking at the bionic and wondering if I can get Marvin close(r) to that shape.