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

[NeilBlanchard]

Here's Dave Cloud's response (I think to these questions?):

motor efficiency @ 60 mph 80% to 90%. at 5 mph 10% to 60%. don't know . sorry

[The Toecutter]

Wow... 120 Wh/mile at 60 mph... for a 3,200 lb car... THAT is very impressive, especially considering that when you go over GVWR, rolling resistance on many conversions goes up dramatically due to the impacts on the suspension. I know similar figures are possible with converted Triumph Spitfires and GT6s(Reverend Gadget's GT6 needs 100 Wh/mile at 60 mph, has some aeromods like bellypan but nothing to impact looks, and a 14.9 sq ft area), but these conversions are more than 1,000 lbs lighter than this Geo, to make up for them not being nearly as aerodynamic as this particular Geo. They don't come close in range, since they typically only carry 450-700 lbs of batteries.

I bet this Geo would only need ~100 Wh/mile at 60 mph if its weight were cut to about 2,000 lbs... With a modest 20 kWh Thundersky pack, this could be done, although it would cost about $8,000. The car's 0-60 time would improve dramatically, range would stay about the same, top speed might see an extra 5 mph, and cornering would improve dramatically...

I love Dave's car. I hope he makes a kit.

[RobertSmalls]

Here's the drag coefficient calculation for y'all to play with:
http://www.wolframalpha.com/input/?i...2F17.3ft%C2%B2

Now here's the problem, as Orange4boy correctly points out. This very aero car expends about half its energy overcoming rolling resistance at 60mph. If the Crr is only known to within 20%, the Cd can not be known in any meaningful way.

For Crr=.006, Cd=.194
For Crr=.008, Cd=.151
For Crr=.010, Cd=.109

[The Toecutter]

Ask him what kind of tires he is using.

I highly doubt they aren't LRR tires at this time with a Crr of 0.010 or more. A 0.11 is about the theoretical Cd limit for a road-going 4-wheeled car, at least when you account for how the air interacts with moving parts. There are prototype cars that have scored less than that in a wind tunnel, but they were stationary. Put them in motion, and a 0.11 is about the limit.

Dave knows what he is doing. A 0.15 would not surprise me in the least, but a 0.11 is unlikely. The Ford Probe V has a 0.137 and Schlor car a 0.13, and they had extensive access to and modification resulting from wind tunnel results.

[NeilBlanchard]

Yes, the Schlörwagen is 0.18 for the actual working car. The 0.13 number was for a development model. A model of the Mercedes Bionic (Boxfish) was 0.095 -- it had wheels, but lacked seams, etc., and apparently scale models are always lower than the full size car.

The Aptera 2e is 0.15; and also the Edison2 Very Light Car is also 0.15. And of course the EV-1 was 0.19, so I'm guessing the Dolphin is ~0.15 now, and it may improve with a few more tweaks, like wheel strakes in front of all four tires.

Maybe, the Dolphin will have video mirrors?

[The Toecutter]

I stand corrected; I didn't know the 0.13 for the Schlor was from a scale model. A 0.18 is still quite impressive, especially for its time period.

[ShadeTreeMech]

Originally Posted by NeilBlanchard

I just about swooned when I saw this car! Someone on the EV Discussion List mentioned it, and posted a link to these pictures:

Picasa Web Albums - lektwik - Dave's Stream...



If you are not blown away by this, then you need to check your pulse...

This is as near to perfect an aerodynamic package as I have seen, period. Sure, it is a little bit long, and the front license plate needs a spot other than the windshield... but this car is a stunningly beautiful thing.

Apparently, Dave Cloud wanted to enter in the X-Prize, but was prevented from doing this because of the expense and difficulty of entering. And no surprise, he wins the contests he enters...

Here's what we know (so far):



[Edit: I found a page with more technical info: Dave Cloud's Rally Car. It is heavy, using sixty lead acid batteries that each weigh 33 pounds; totally 1,980 pounds for the batteries alone. The car weighs 3,200 pounds.]

I am going to find out more about this car, and it's builder. He has got more Bassjoos than Bassjoos!

Ya'll do realize these pics consist of ecomodder porn, right? Last time I saw this many curves on such a pleasant package.....well, it wasn't G-rated

[mcrews]

Shadetree,
Ya'll do realize these pics consist of ecomodder porn, right? Last time I saw this many curves on such a pleasant package.....well, it wasn't G-rated


Be careful........last time curves came up in conversation, Frank Lee, Christ, myself and a few others posted some REAL CURVES and they deleted the thread!!!!!!

imagine!!!!!!!

Was it our fault that all those scantly clad long legged high heeled ladies were leaning over some VERY cool.....huh.....hummmmm....what the hell WERE they leaning on....

oh I digress........


CARS!!!


that's it SCOTTY!!!!


gezzzzzz......

[JasonG]

Originally Posted by Bicycle Bob

I wonder if the lack of triangulation has or will cause problems. At least, with a more trike-like rear track, the need for torsional rigidity goes down.

My first response was "OH my god! Look at all those 90deg and parallell members"
The long wheelbase probably has some bounce, or he beefed it up to compensate. Looks like 2.5" angle. Heavy stuff there.
Bet you could knock off a few hundred #s with a FEA program.

[orange4boy]

Looks like 2" square. .065 wall impulse welded tube to me. Not heavy at all, actually. It does look heavy but I recognize it from the crisp corners and the dark impulse weld line.

I agree, that a bit of triangulation would be helpful in stiffening especially where the narrower rear section meets the larger battery box section.

Dave would be able to say how much flex there is.