high body or low? wanting to build a car from scratch

[sjr]

if you were going to build a car from scratch for high gas mileage would you go low to ground? high above road? or what? , Im thinkin 2 person car, use geo metro components , thinkin tandem seating , I can build fiberglass molds and parts so any shape is possible , under 1500 lbs, under 1000 lbs ideal

heres some examples

[Frank Lee]

Well... what do you want?

[sjr]

more

[sjr]

Originally Posted by Frank Lee

Well... what do you want?

like to know what works best and why

[Frank Lee]

Find the best econo cars on Earth and copy that.

[darcane]

Your only goal is efficiency?

Go low.

Cars are built high for practical reasons. Comfort, visibilty, safety.

Land speed racing has many ties to fuel efficiency. The better streamlined your car is, the less power you need to go a certain speed. In land speed racing, this translates to higher speeds with less power. For fuel efficiency, this means less fuel at the speed you drive.

One of the most innovative cars in racing is a series of cars called the Nebulous Theorem. They are built with nearly no ground clearance and extremely minimal frontal area. The NebII has set records at 360mph with a turbo 1.5L engine. (About 700hp). Power needed to overcome aero drag cubed is proportional to speed. So, if you assume 700hp to overcome drag at 360mph, only 3hp is needed at 60mph.

Pics can be found here:
Worlds Fastest 4 Cylinder Nebulous Theorem II

[Frank Lee]

Everything pictured so far is representative of above average efficiency. So perhaps it isn't true that if all cars were aero, they'd look alike.

[NeilBlanchard]

In the Hucho book, in the discussion about the Schlörwagen (page 35 in the 4th Ed.), they experimented with ride height. Too low and the air gets "congested" under the car, and too high and you expose more tire, etc. and increase frontal area.

I think the "ideal" height they settled on was 6-8" above the ground? Of course, this is based on a smooth bottomed car...

Have you seen Dave Cloud's Metro conversion, the Dolphin?

The *Ultimate* Aerodynamic Car? Dave Cloud's "Dolphin"

SketchUp Models of Concept Vehicles

I don't think a Metro would benefit from tandem seating?

[euromodder]

Originally Posted by sjr

if you were going to build a car from scratch for high gas mileage would you go low to ground? high above road? or what? , Im thinkin 2 person car, use geo metro components , thinkin tandem seating , I can build fiberglass molds and parts so any shape is possible , under 1500 lbs, under 1000 lbs ideal

Go low and reduce the amount of air going underneath the car.

You can go up and try to get out of the drag-inducing ground effect, but it brings along other problems :
- reduced stability ;
- outriggers for wheels adding weight, more wet area and drag, multiple aero bodies in rather close proximity cause complex interactions
- reduced useful volume
- structurally more complex
- less car-like

[euromodder]

Originally Posted by NeilBlanchard

I don't think a Metro would benefit from tandem seating?

Probably not that much as the overall width is probably determined by the Metro's front drive train anyway.
It'd be tough to start messing about with that.

But it could considerably reduce the width of the crew cabin, and total frontal area by about 1/4.

This one is offset, but you get the idea:
How to economise your car - Doug Heffron's super-efficient 1989 Geo Metro : Tech Digest



http://motoringjstyle.blogspot.com/2...geo-metro.html


Interesting link there :
http://minutia-microcarsminicars.blogspot.com/