The 2-Part Aero-Body Concept

[Sven7]

Of course the 1 part is the best of all. As you note, it's got the most bang for the buck.







LeMans cars like you posted are not meant to reduce drag, and mimicking them will not be a lot of help. They are made to prevent this:

[kach22i]

Originally Posted by Sven7

Of course the 1 part is the best of all. As you note, it's got the most bang for the buck.

Tyler, do you think the Honda Insight can be called a 2-part body?

I might try to draw up that middle scheme I did on graph paper to a scale, it has some potential, just meant it as a cartoon.

I'm not trying to copy the Mooncraft racing car, it just happens to work. It does a lot of things well, and I'm playing the student by trying to learn from it. Really wish I knew it's Cd number.

[Sven7]

The Insight is a 1 part. The bodywork only pushes out to clear the rear track and integrate the bumper. The rest of it is, as many say, a "blob".

When building a 2 part body, make sure you radius everything generously. Look at the (~10cm?) radii on the Tatra, and note how the entire Saab body side is curved. You don't want sharp edges except to detach flow at the rear of the vehicle (see DS, EV1, Volt).

[serialk11r]

Originally Posted by Sven7

LeMans cars like you posted are not meant to reduce drag, and mimicking them will not be a lot of help. They are made to prevent this:

Well to be fair, LeMans cars are required to have a completely flat underbody which makes them prone to being unstable when their "angle of attack" changes. If they allowed underbody venturis then things would be different.

[NeilBlanchard]

George,

I understand your question now -- it is my understanding that the template is completely scalable in size; and it "works" up to ~250MPH.

Look at the template. It is one part, and one part is better than multiple parts, all else being equal. Two parts of more mean there is some additional interaction. On the classic Jaray two part body, the lower main part is what initiates the movement of the air, and the second part is then working within a "pre-pressurized" zone, and the air that has already been moved is then forced to move outward more. The air "wants" to return to it's original pressure, so it will flow towards where ever there is lower pressure.

The profile of your two part design is pretty much cab-forward, so in that direction it would act like a one part body. But because the second part is narrower in plan, some of the air that would have gone up over the roof moves instead to the sides of the second part; because the pressure is lower there than it is at the top of the roof.

This may or may not be better than if the roof extended to the sides of the car body, in terms of Cd; though it would add area. It would add interior room, and if the Cd was lower, then this might (more than?) offset the greater area.

Or think of it the other way around -- narrow the sides of the car in towards the passenger compartment. This simplifies the air flow *and* greatly reduces the frontal area.

If you think about the function of a car -- carrying people -- then a two part design like the Maybach Stromlinienkarosserie or the Porsche with their relatively tiny interiors don't make as much sense. Compare the Maybach to the Schlörwagen -- 2 seats vs 7 and you get my point. Neither is a small car, and the Schlörwagen is very wide and probably has the greater frontal area, but it also is better at a car's primary function. If 7 is too many, then scale it down. Most of the Maybach's frontal area is just for the car itself.

[kach22i]

Originally Posted by NeilBlanchard

George,

I understand your question now -- it is my understanding that the template is completely scalable in size; and it "works" up to ~250MPH..............

........ Maybach Stromlinienkarosserie

Thank you for the explanation Neil, very useful in recalibrating my mindset.

http://ecomodder.com/forum/showthrea...-11732-27.html


Now that's art.

[aerohead]

Originally Posted by kach22i

Another liberal use of the aero-template.

Industrial Design - Transportation pictures by kach22i - Photobucket

If your school had a copy of the 1951 book, 'Aerodynamic Drag,' by Sighard Hoerner,I think it would really help you.
Hoerner was a German aerodynamicist brought over to the US under the 'Operation Paper Clip' and went to work at Wright Aeronautical Laboratory at Dayton,Ohio.
He was involved in aircraft and automobile wind tunnel research.His book is a gold mine of information.With it,you'd have a sense for :
*canopies
*blisters
*fairings
*wings
*struts
*super-velocity
*interference
*induced drag
*transverse flow
*vorticity
There's a complete section on boundary layer theory.
It's all in there!
The school should also have a copy of Baron Reinhard von Koenig-Fachsenfeld's 'Aerodynamiks des Kraftfahrtzeugs',also published in 1951.It's as important as Hoerner's book.
Between the two you'd have some really hard science to borrow from when doing these complex designs.I think you'd love 'em both.

[kach22i]

Originally Posted by aerohead

If your school had a copy of the 1951 book, 'Aerodynamic Drag,' by Sighard Hoerner,I think it would really help you...

The school should also have a copy of Baron Reinhard von Koenig-Fachsenfeld's 'Aerodynamiks des Kraftfahrtzeugs',also published in 1951.It's as important as Hoerner's book.

Thank you for the book list, I appreciate it.

I'm not a student, you might be thinking of someone else. I have spent most of my adult life working my way though school, and then later teaching (been running my own architecture firm for 12 years). This book list will allow me to self-teach - I hope.

I'll try Ann Arbor's main branch first, then U of M's north campus library. I won't be able to check anything out there, but I have my camera.

Like I've said, I'm trying to adjust my basic mindset, not solve a specific problem. The answer I get may be the answer to a question no one has asked, but it will be what it wants to be, and perhaps the way it should be.

[skyking]

sorry, I had an off topic ramble there.

[aerohead]

Originally Posted by kach22i

Thank you for the book list, I appreciate it.

I'm not a student, you might be thinking of someone else. I have spent most of my adult life working my way though school, and then later teaching (been running my own architecture firm for 12 years). This book list will allow me to self-teach - I hope.

I'll try Ann Arbor's main branch first, then U of M's north campus library. I won't be able to check anything out there, but I have my camera.

Like I've said, I'm trying to adjust my basic mindset, not solve a specific problem. The answer I get may be the answer to a question no one has asked, but it will be what it wants to be, and perhaps the way it should be.

Apology for confusion.In a way,if we're at EcoModder,then we're all students.
These books have been an integral part of my learn-at-home education.I had to travel to other cities and copy the books on the library copy machine,as they were not allowed to leave the reference section.
The University library should have both books I should think.Hope so.They helped me lose my attachment to urban myths and legends and glimpse some of the hard science.