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Old 08-10-2012, 08:02 PM   #441 (permalink)
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It is interesting on the Benz tropfenwagen that that they did not take the rather obvious step of streamlining the wheels. Maybe I'm wrong and they were right;-)

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Old 08-11-2012, 01:42 PM   #442 (permalink)
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VW's Cd 0.16 'Orbit',1988

Quote:
Originally Posted by California98Civic View Post
In another thread, aerohead referred to this car, and I did not find it in a ecomodder search. I found it on the web, and here is a pic (below). And this site claims it had Cd 0.26.
In one of my dream car books they depict a Cd 0.16 Volkswagen Orbit wind tunnel model from 1988.It's a 1:1 scale car and looks 'production-ready',although you can't see through the glass so it might just be a Dynox over 'clay.'
It was developed in the 'new' Aerothermic Center of the day.
It has :
* grille-blocked nose
* low nose
* high tail
* slim mirrors downstream of A-pillars
* 1st-gen HONDA Insight front fender trailing radii
* Flush wheel covers
* Flush glass
* Hidden wipers
* Plan taper of greenhouse
The photograph is orthogonal,so no measurements can be had.
As higher CAFE standards come in force we'll see if the 'form' emerges from the shadows.
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Old 08-11-2012, 01:55 PM   #443 (permalink)
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wheels

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Originally Posted by jimepting View Post
It is interesting on the Benz tropfenwagen that that they did not take the rather obvious step of streamlining the wheels. Maybe I'm wrong and they were right;-)
Later,Daimler-Benz would publish a paper from wind tunnel research they conducted on their Gran Prix race cars.
The crux of what they learned,was that by enclosing the 'monoposto',exposed-wheel car,even with a greater frontal area,the overall drag was reduced.
In 1987,GM's Oldsmobile Division would use the same trick with AEROTECH,by enclosing a March Indycar chassis in a shrink-wrapped aero body,cutting drag by more than one-half and beating Mercedes' C-111 closed-course speed record at speeds up to 278-mph.(They considered higher speeds but A.J.Foyt was experiencing involuntary lane changes as gusts pushed him around on the Ft.Stockton,Tx Bridgestone/Firestone test facility track,same track where Car and Driver's test driver of my CRX was killed while at speed in a Renn Speed M-B.)
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Old 08-16-2012, 07:36 PM   #444 (permalink)
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Regarding Vertical Tail Fins

Was reading through randomly after 30+ pgs on this thread today...

The Bullet Project - Wikipedia, the free encyclopedia
According to the Aerodynamics section, they refer an advantage utilizing Compression Lift

And Here:
Compression lift - Wikipedia, the free encyclopedia

I think that with whats being stated, with the XB-70's(1960's) fins "decreased the induced drag about 30%". And the fins having a greater effect at supersonic speeds as of the LSR car, is happening with these fin'd race cars. While at moderate speeds, they must assist in some degree.

The first car 1964 LM64, not matching the template and its shorter length, its steep slope may be creating a larger "wake", and has long fins needed to catch the wake with its high "attack" angle, could be Forcing this phenomenon to happen at a greater rate with its slower specified speeds to further assist in Stabilization(this is a race car after all) and producing just enough downforce, at the same time reducing drag. (All this Aero evolution around the same 1950-60's era)

Then moving to the more template based 1967 Peugeot 66C with its more Upright fins, then to the newer Matra640 requiring further less "force" to enduce this "compression lift/stabilization" with even shorter fins, with again less "attack" angle.

(Like Pitch control of an F-117 Nighthawk)



...Reminds me of the EVO Lancer, with their ultra sciency vortex generators and spoiler to produce attached flow, massive amounts of downforce and lowering the Cd at the same time...
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Old 08-17-2012, 05:47 PM   #445 (permalink)
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compression

Quote:
Originally Posted by RiderofBikes View Post
Was reading through randomly after 30+ pgs on this thread today...

The Bullet Project - Wikipedia, the free encyclopedia
According to the Aerodynamics section, they refer an advantage utilizing Compression Lift

And Here:
Compression lift - Wikipedia, the free encyclopedia

I think that with whats being stated, with the XB-70's(1960's) fins "decreased the induced drag about 30%". And the fins having a greater effect at supersonic speeds as of the LSR car, is happening with these fin'd race cars. While at moderate speeds, they must assist in some degree.

The first car 1964 LM64, not matching the template and its shorter length, its steep slope may be creating a larger "wake", and has long fins needed to catch the wake with its high "attack" angle, could be Forcing this phenomenon to happen at a greater rate with its slower specified speeds to further assist in Stabilization(this is a race car after all) and producing just enough downforce, at the same time reducing drag. (All this Aero evolution around the same 1950-60's era)

Then moving to the more template based 1967 Peugeot 66C with its more Upright fins, then to the newer Matra640 requiring further less "force" to enduce this "compression lift/stabilization" with even shorter fins, with again less "attack" angle.

(Like Pitch control of an F-117 Nighthawk)



...Reminds me of the EVO Lancer, with their ultra sciency vortex generators and spoiler to produce attached flow, massive amounts of downforce and lowering the Cd at the same time...
With respect to road vehicles,compressibility effects of air do not occur until transonic flow,which for automobiles begins at around 250 mph (409 km/h).
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Old 09-04-2012, 06:40 AM   #446 (permalink)
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An Illustrated History of Automotive Aerodynamics

Paul Niedermeyer has been working on a top notch article on an historical overlook of automotive aerodynamics:

Automotive History: An Illustrated History Of Automotive Aerodynamics – Part 1 (1899 – 1939)

An Illustrated History Of Automotive Aerodynamics: Part 2 (1940 – 1959)

An Illustrated History Of Automotive Aerodynamics: Part 3 (1960 – Present)

Read it and enjoy!
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Old 09-04-2012, 10:42 AM   #447 (permalink)
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Awesome.
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Old 10-08-2012, 11:00 PM   #448 (permalink)
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Old 10-11-2012, 01:28 PM   #449 (permalink)
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^^That's sweet.

Here's an example of flow detachment on the roof. Despite many ignorant threads asking again and again how to "fix" their roof forms, you can see here that it takes quite a lot to trip the airflow.

The blue one on top is stock (0.44Cd) and the orange camper is the (main) detached one (0.51Cd). Without even considering frontal area the camper shows much higher drag due to detached roof flow.

Look at that windshield to roof angle! And yet the stock one maintains attached airflow.



And a reason to remove that roof rack fairing.

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Old 10-11-2012, 06:41 PM   #450 (permalink)
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Quote:
Originally Posted by Sven7 View Post
^^That's sweet.

Here's an example of flow detachment on the roof. Despite many ignorant threads asking again and again how to "fix" their roof forms, you can see here that it takes quite a lot to trip the airflow.

The blue one on top is stock (0.44Cd) and the orange camper is the (main) detached one (0.51Cd). Without even considering frontal area the camper shows much higher drag due to detached roof flow.

Look at that windshield to roof angle! And yet the stock one maintains attached airflow.



And a reason to remove that roof rack fairing.

Now that's interesting ! Despite adding frontal area, the rounded camper on the black and white van dropped from a stock - attached flow - Cd of .44 , to .40.
Overall drag in this case rose due to the massive hit in frontal area, but on our previous discussions on adding a tear drop roof to a boxy SUV, a much slimmer roof extention was imagined.
With so many SUVs having roof racks, it would be very easy to test - just take a thin sheet of wood and attach it to the roof rack, tapering it back .

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