Herr Schlör's "Göttinger Ei" had a Cd of 0.186.

[RobertSmalls]

http://www.göttingen.de/magazin/arti...p?artikel=3281
Aerodynamik des Automobils ... - Google Books

The oft-cited 0.125 figure seems to be a bit of an EcoModder myth. That figure only applies to a scale model of the Ei.

I believe the .186 figure is consistent with its appearance:

[NeilBlanchard]

Yes, the 0.13 number was a model or mock up earlier in testing. They also adjusted the ride height to get the optimum drag: too low increased it (due to increased pressure underneath?) and too tall also increased it (probably because more tire was exposed?). We have gone over this, and gotten a lot of pictures, including in the wind tunnel; here's my collection of Schlörwagen "Pillbug" pictures including the Mercedes 170H chassis it was built on:











The 0.18 number is for the actual working car, with cooling set up, etc.

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Dr. Charles Schlör died in 1997.

[The Toecutter]

Man, imagine if THAT was the VW Beetle that made cars affordable to Europe... what a different world it would be today.

[tasdrouille]

Beautiful set of pictures Neil, thanks!

[Otto]

Originally Posted by NeilBlanchard

Yes, the 0.13 number was a model or mock up earlier in testing. They also adjusted the ride height to get the optimum drag: too low increased it (due to increased pressure underneath?) and too tall also increased it (probably because more tire was exposed?). We have gone over this, and gotten a lot of pictures, including in the wind tunnel; here's my collection of Schlörwagen "Pillbug" pictures including the Mercedes 170H chassis it was built on:











The 0.18 number is for the actual working car, with cooling set up, etc.

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Got any pics of the underside of this vehicle?

It does not appear to have wheel fairings or spats, which would help.

And, gap between vehicle and ground relates to interference drag. There is an optimum height, as noted in Hoerner's Fluid Dynamic Drag book with cites of external stores of bombs, fuel tanks, etc. in aircraft. Too close means a bit of savings from less wetted area of pylon, but more than offset by too much interference of flows around wing and bomb. Too far apart means less interference drag, but increased pylon drag. So, there is a sweet spot in gap adjustment. I think Citroen with its adjustable height also dealt with this issue.

[NeilBlanchard]

No, there are no pictures of the underside -- all the pictures I know of are here:

Schlor Pillbug pictures by NeilBlanchard - Photobucket

Yes, wheel strakes would help a lot. From the wind tunnel tuft test picture you can see the main problem area: from just ahead of the rear wheels and behind them, the air is swirling up. The tail may need to be broadened and flattened, to improve things?

The other main issue with the Schlörwagen is the width: it is 2.1m (6'-11")which is very wide, indeed. They made it wide so that the front wheels could be fully enclosed, even when they are turned fully. I think that some system of articulated/moving enclosures would keep the advantage, while greatly improving the CdA.

[aerohead]

Originally Posted by RobertSmalls

http://www.göttingen.de/magazin/arti...p?artikel=3281
Aerodynamik des Automobils ... - Google Books

The oft-cited 0.125 figure seems to be a bit of an EcoModder myth. That figure only applies to a scale model of the Ei.

I believe the .186 figure is consistent with its appearance:

Yes,didn't Hucho say that while he was at VW,that they threw a full-scale version in the tunnel and come up with this value?

[NeilBlanchard]

I think VW tested a scale model, and they got 0.15, if I am not mistaken.

[JackMcCornack]

Originally Posted by NeilBlanchard

The other main issue with the Schlörwagen is the width: it is 2.1m (6'-11")which is very wide, indeed. They made it wide so that the front wheels could be fully enclosed, even when they are turned fully.

Plus so they could claim the lowest Cd of any passenger car of the era. Let us not forget, the easiest way to improve a vehicle's Cd is to make it bigger. "the .186 figure" for a 6'11" wide car would translate to a .257 figure for a 5' wide car with the same total drag. I suspect (cynic that I am) that modern car companies tout their low Cds (or is that "low Cs of d"?) because it looks better than quoting the CdA when promoting a big car. For example, the Cadillac Escalade boasts a "segment-best aerodynamic drag coefficient of 0.36 " which looks pretty cool compared with (for another example) a Mazda Miata at Cd 0.38

[RobertSmalls]

Agreed, but let's give credit where it's due. If the Göttinger Ei was 7' wide and 5' tall, it had a CdA of 5.53ft². That puts it on par with the CRX, which only seats two.

The VW Beetle had a CdA of 9.3-9.5ft².