Designing an FE Car from the ground up.

[Sludgy]

No discussion of an extreme FE car built from the ground up would be complete without mentioning Buckminster Fuller's Dymaxion.

http://en.wikipedia.org/wiki/Dymaxion_car

This amazing car was built in 1933 using a low compression Ford V8. It got 30 mpg and went 120 MPH. The Wiki article doesn't mention the engine's power, but early flathead Ford V8's were rated at 65-75 HP.

Can you imagine the FE a car like this would get when equipped with a modern Toyota or Honda 4 cylinder engine and a five speed transmission?

Suddenly, the 2007 models look incredibly stupid.

[The Toecutter]

The Dymaxion had a .25 drag coefficient.

I'd prefer a Tatra T77a myself. That had a .21. Put a modern pushrod V8 in it, and it would still have no problem getting over 35 mpg combined, mostly from a large boost in highway FE. Performance? *cackle*

[Gary Palmer]

Toecutter: Do you have a link to a picture of one, that you could post?

[The Toecutter]

Here's a few pics of the Tatra T77a, a full size luxury car:








Pretty nice, isn't it?

I've always dreamed of building an eco-friendly hotrod from a body style like this. Imagine swapping in the same 322 horsepower 4.2L V8 turbodiesel used in the Audi A8. A car with such good aerodynamics would easily get 50+ mpg combined with even that monster engine. And it could be run on B100.

Think of how that would look with a charcoal black paintjob, and ghost purple flames painted on the sides.

The acceleration would be a bit on the enticing side, probably around 5-6 second 0-60.

Even with a gasoline V8, a car with aerodynamics like this could still likely approach the FE of a Honda Civic.

[Mighty Mira]

I was thinking that EV cries out for a rear engine design... especially considering that the weight comes from the batteries and can be distributed near the front. That way you can have the front downforce provided by lead and the rear by directing the air (slightly) upwards.

[The Toecutter]

The Tatra screams to be converted to electric. Just look at it!

Imagine copying that design, slightly raising the ride height so you can have a huge lead acid battery pack sunk into the floor. With a few aerodynamic improvements, perhaps a .18 Cd or so can be achieved.

This would get an electric that could do 200 miles per charge on lead acid batteries at highway speeds, if you have a car weighing 4,500 pounds with 2,000-2,500 of that in batteries. With a Zilla 2k controller, twin netgain 9" motors coupled to a Ford 9-inch differential and configured to allow a series/parallel shift, you could have a car that needed no transmission, and did 0-60 mph in around 5 seconds. Not one drop of gas needed. The conversion really wouldn't be that expensive either. Even if all the components like the Zilla controller and PFC charger remained hand-built, the electric components wouldn't cost any more than ~$17k, including the huge *** amount of AGM batteries. With mass production of car and parts, we'd have the possibility of a $20-25k luxury car that was pure electric, accelerated like a Ferrari, could seat 6 overweight adults, go 200 miles per charge, and have operating costs lower than even today's hybrids.

Or you could use a V8 diesel platform, and have a 50 mpg luxury/muscle car of sorts, also sold for around $18-20k.

A small inline 4 cylinder turbodiesel of about 150 horsepower would provide more sedate acceleration like a normal car, but easily allow 100+ mpg highway. Would be pretty damned good for a full size car! Could probably be done for around $12k.


Mind you, if such cars were ever built, they could fetch more money than that given what the demand for them would be, but the entire point would be to keep them affordable to begin with.

[Gary Palmer]

You know, as far as aerodynamic shape, it occurred to me today that possibly a source for insight on shape would be to look at the shape a drop of water makes, as it's falling. This would seem like it would change it's shape, to minimize the pressures around the drop and create a optimum shape. Anybody got a picture of a raindrop falling?

[ZugyNA]

They are not teardrop shaped.

http://www.shorstmeyer.com/msj/geo165/shape.jpg

[Gary Palmer]

Cool! So, it doesn't seem like a mushroom shape would be very efficient, does it? One thing I've always wondered about is that in sailing, their is a hull speed which is largely related to the length of the boar. If I am sailing a 22 foot boat, about the best speed I can make is 4 to 4 1/2 knot's. If I am sailing a 35' boat, I can make more like 6 - 6 1/2 knot's. It seems like their might be a similar phenomenon with the wind, but the barrier is not generally so noticible as it is with a boat. Anyway, something of curiosity.

[Mighty Mira]

Originally Posted by Gary Palmer

Cool! So, it doesn't seem like a mushroom shape would be very efficient, does it? One thing I've always wondered about is that in sailing, their is a hull speed which is largely related to the length of the boar. If I am sailing a 22 foot boat, about the best speed I can make is 4 to 4 1/2 knot's. If I am sailing a 35' boat, I can make more like 6 - 6 1/2 knot's. It seems like their might be a similar phenomenon with the wind, but the barrier is not generally so noticible as it is with a boat. Anyway, something of curiosity.

Hmmm.

For the same weight, the same volume of water is displaced, right? Which would mean that all else being equal, double the length of hull and you halve the cross sectional area.

e.g. V = l * w * h = l * (cross sectional area)

Now, there must be some diminishing returns to this (friction with the water), but they probably aren't felt at the range that boat lengths are practical.