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aerohead 05-02-2015 04:40 PM

Low-drag automotive silhouettes
 
Here's a thread I can add to over time which shows a historical development of low-drag automobile test models or actual 'running' vehicles.
I'll try and keep them in chronological order.
NOTE: Low-Drag is defined as Cd 0.25 or lower for the sake of this thread.Sorry I didn't make this qualification at first.
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1850,derigible,Pierre Julien,1st longitudinally asymmetrical (teardrop) body.
http://i1271.photobucket.com/albums/...Untitled34.jpg
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1865,Air resisting train,Samuel Calthrop
http://i1271.photobucket.com/albums/...ntitled322.jpg
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1922 'pumpkin seed',Paul Jaray,Zeppelin Works,Germany,Cd 0.13.Based upon a streamlined half-body.First use of a 'diffuser.'
http://i1271.photobucket.com/albums/...ntitled1_7.jpg
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1922 streamline half-body,Wolfgang Klemperer, Cd 0.15
http://i1271.photobucket.com/albums/...d2/06-2412.jpg
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1924,patent illustration for streamlined car.Persu.
http://i1271.photobucket.com/albums/...ntitled2_7.jpg
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1933 wind tunnel model,Walter Lay,University of Michigan.Cd 0.12.
http://i1271.photobucket.com/albums/...titled13_7.jpg
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1933 R.H.Heald,U.S.Dept. of Commerce,Bureau of Standards,Cd 0.20
http://i1271.photobucket.com/albums/...ntitled6_8.jpg
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1934 Dymaxion Car,R. Buckminster Fuller, Cd 0.25 (estimated)
http://i1271.photobucket.com/albums/...titled12_7.jpg
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1934-1/2 Chrysler De Soto Airflow test mule,Carl Breer,Cd 0.244.
http://i1271.photobucket.com/albums/...tled2-10-1.jpg
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1935 (circa) 'Kamm' car,wind tunnel model,Baron Reinhard Koenig-Fachsenfeld
http://i1271.photobucket.com/albums/...ntitled7_7.jpg
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1935 DKW Meisterclasse, Jaray-bodied,by Sighard F.Hoerner,Cd 0.245.
http://i1271.photobucket.com/albums/...titled10_2.jpg
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1935-6 Elliott Gray Reid,Stanford University,Cd 0.15
http://i1271.photobucket.com/albums/...ntitled4_8.jpg
http://i1271.photobucket.com/albums/...ntitled3_8.jpg
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1937 AVA G'o'ttingen Sch'o'r wagen (pilbug car),Cd 0.186
http://i1271.photobucket.com/albums/...ntitled2_8.jpg
http://i1271.photobucket.com/albums/...ntitled3_7.jpg
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1938 Mobil Special,Reid Railton,Cd 0.18
http://i1271.photobucket.com/albums/...titled16_2.jpg
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1938 AVA G'o'ttingen 'Lange' car,Cd 0.14-0.16 (1/5-scale smooth model with zero features)(Cd 0.16 by Hucho et al @ Volkswagen tunnel)
http://i1271.photobucket.com/albums/...ntitled1_8.jpg
-------------------------------------------------------------------------
1957 MG EX181,land speed record car,Cd 0.12
http://i1271.photobucket.com/albums/...titled14_6.jpg
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1963 tractor trailer,Walter H. Korff,Lockheed, Cd 0.20
http://i1271.photobucket.com/albums/...ntitled331.jpg
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1969 Composite wind tunnel model 'recipe' car,R.G.S.White,MIRA,Cd 0.245.
http://i1271.photobucket.com/albums/...2/12-062-1.jpg
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1978 D-B M-B C-111 III,long tail, Cd 0.178
http://i1271.photobucket.com/albums/...Untitled45.jpg
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1978 D-B M-B C-111 III,short-tail, Cd 0.195
http://i1271.photobucket.com/albums/...titled1_10.jpg
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1978 D-B M-B C-111 III,no-tail, Cd 0.237
http://i1271.photobucket.com/albums/...titled2_10.jpg
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circa 1980 NASA van,long tail, Cd 0.238
http://i1271.photobucket.com/albums/...Untitled44.jpg
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circa 1980 NASA van,truncated tail, Cd 0.242
http://i1271.photobucket.com/albums/...Untitled43.jpg
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2000- HONDA 1st-gen Insight, Cd 0.25
http://i1271.photobucket.com/albums/...Untitled41.jpg
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Toyota Prius, Cd 0.25
http://i1271.photobucket.com/albums/...Untitled42.jpg
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2006 Daihatsu UFE-III, Cd 0.168
http://i1271.photobucket.com/albums/...Untitled46.jpg
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2012 Ford Probe-X ,Cd 0.152
http://i1271.photobucket.com/albums/...Untitled47.jpg

Cd 05-02-2015 05:10 PM

Oh wow the 1938 Mobil Special,Reid Railton at Cd 0.18 ???

A full tear drop shape, fully covered wheels, a bubble canopy, and a smooth underbelly, yet point 18 ?

And then we have the Mercedes here at .22 without a boat-tail, no wheel covers, a gaping grille and rear glass that is too steep.

http://ww4.hdnux.com/photos/17/27/51.../3/628x471.jpg

Air flows in strange ways.

Vman455 05-02-2015 09:21 PM

This is the BlueEfficiency version of the CLA, the model for which Mercedes claims Cd .22:

http://blog.mercedes-benz-passion.co...-cla-180-B.jpg

http://blog.mercedes-benz-passion.co...180-32323B.jpg

Notice the mostly-closed wheel faces, paneling under the engine bay (and I presume the rest of the underbody as well), and completely redesigned rear bumper area.

freebeard 05-04-2015 09:03 PM

Like a flat stone on water, you're hitting all the high spots. How about Rumpler, or the Josep Ganz's Maikäfer [1931]? Here's what I have. It's a silhouette not a glamour shot.

http://i.imgur.com/lws33.jpg?1

http://ecomodder.com/forum/member-fr...ure6298-g1.jpg

ennored 05-05-2015 02:33 PM

Fair to mention the Vixen Motorhome here? Circa 1989. Cd .31 (actual number - not a scale test).

http://i.kinja-img.com/gawker-media/...eh6rosdjpg.jpg

To me, the lesson is (as has been stated before) round the front as much as needed (which isn't that much) and taper the rear as much as you can. Done.

The result? A brick that is more aerodynamic (relative to Cd) than most cars on the road.

freebeard 05-05-2015 04:17 PM

Nice for it's time. I saw one once.

Instead of those elephant ears behind the rear wheels, the lower rear should be like the upper rear of the VW GTTI-650 w12

http://ecomodder.com/forum/member-fr...w12-650-16.jpg

...with the radiators in the corners like Porsche does in the front now. A surface development that would be completely lost in silhoutte.

aerohead 05-05-2015 06:16 PM

Rumpler
 
Quote:

Originally Posted by freebeard (Post 478012)
Like a flat stone on water, you're hitting all the high spots. How about Rumpler, or the Josep Ganz's Maikäfer [1931]? Here's what I have. It's a silhouette not a glamour shot.

http://i.imgur.com/lws33.jpg?1

http://ecomodder.com/forum/member-fr...ure6298-g1.jpg

I'm not including anything over Cd 0.25.It has been used in the past as the cutoff mark for low drag.

aerohead 05-05-2015 06:21 PM

Cd 0.31
 
Quote:

Originally Posted by ennored (Post 478101)
Fair to mention the Vixen Motorhome here? Circa 1989. Cd .31 (actual number - not a scale test).

http://i.kinja-img.com/gawker-media/...eh6rosdjpg.jpg

To me, the lesson is (as has been stated before) round the front as much as needed (which isn't that much) and taper the rear as much as you can. Done.

The result? A brick that is more aerodynamic (relative to Cd) than most cars on the road.

I went back to the top of the thread and added a NOTE which I should have posted initially,that the cutoff for low drag would begin at Cd 0.25.Sorry!

aerohead 05-09-2015 03:46 PM

5-new images
 
I've added 5-new images:
*1933 Heald car
*1935-6 Reid cars (2)
*Front and rear elevation views of the 1938 pilbug car
*1938 Lange car (influenced Porsche 911)

aerohead 05-30-2015 04:41 PM

7-new images today
 
I've added 7-new scans to the bottom of the table.


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