German experimentation with low Cd automobiles in the 1930's

[Sven7]

Originally Posted by autogyro

Some of it's inspiration??!? LeFebrve was the inspiration. Here's a great link on the DS19,
Déesse Ex Machina: The Remarkable Citroën DS

and while you're there, check out the Traction-Avant piece. He did that too, and the 2CV to boot.

Quick. How many Grand Prix drivers can you name who were personally responsible for three ground breaking mass production automobiles?

I'll have to read that later.

Just found this video after unsuccessfully searching for anything about Jaray. It's funny how they talk about streamlining so much and their cars are still just a complete mess in terms of aerodynamics. What was cool was the little wind tunnel tuft testing with a ribbon on a stick, as it were.

http://www.youtube.com/watch?v=jZ4o9YVcFsc

[Cd]

Originally Posted by Sven7

I'll have to read that later.

Just found this video after unsuccessfully searching for anything about Jaray. It's funny how they talk about streamlining so much and their cars are still just a complete mess in terms of aerodynamics. What was cool was the little wind tunnel tuft testing with a ribbon on a stick, as it were.

I notice that the body of that car is backwards - the front end gets narrow and the back end flares out and is rounded .

[Bicycle Bob]

Originally Posted by autogyro

Surely we haven't forgotten about the Opel Rak 1 & 2 cars of the 20's?
File:Opel Rak 2 rocket car, at Avus (Montagu, Cars and Motor-Cycles, 1928).jpg - Wikipedia, the free encyclopedia

Ahh, it is indeed a previous wing on a car, but is cambered for lift, but adjusted for downforce, as if it had originally been intended to take some weight off the tires, until control issues surfaced. With rocket motors, it would not have needed traction for acceleration, etc.

[TFS]

Years ago a famous engineer recommended "Fluid Dynamic Drag," a book by Hoerner. You can find a paperback on Amazon. Hoerner was German and was writing about the time some of those cool designs were out.

[NeilBlanchard]

Here are some "new" much better images of the 1939 Maybach Stromlinienkarosserie:




Here's a drawing that shows an intent to cover the front wheels, which are not on the actual car:



These are great, especially the tuft test! Notice the lifting on the tufts behind the rear wheels -- if they had some plan taper, they would have been closer to perfect...

[Piwoslaw]

Originally Posted by NeilBlanchard

Here's a drawing that shows an intent to cover the front wheels, which are not on the actual car:

Maybe testing showed that the front wheel covers' increase in frontal area wasn't worth the reduced turbulence? On the other hand, the top view shows that the rear of the wheel well sticks out well beyond the front, scooping up lots of air, so that doesn't help either. On the tuft test you can see that the airflow isn't as clean behind the front wheel.

[Cd]

That rear slope angle looks a bit too steep for good attached flow, yet it is there.
Do you guys suppose this is a case of the side angles working together with the rear angle to keep flow attached - much the way the EV-1 had ?

It seems as though the air would spill over the sides with a side slope angle such as this and pull in any detached flow.

[Cd]

Looking at the last tuft on the roof - the darker painted section - there is no spillover !!!
The air just flows straight back.
( There is some spillover near the door that I didn't notice before . )
Air acts so unpredictably !

[NeilBlanchard]

Yes, I think that if the Maybach had some plan taper on the sides of the car, that the lifting tufts on the doors and the rear fenders would be largely corrected. The reflections on the side of the car (more so near the front) make it harder to see the tufts. I'm pretty sure that the trapezoidal louver on the front fender just ahead of the doors and the three longitudinal slots on the hood are cooling air exhausts, so they may be introducing some flow that is unexpected?

The difficulty I have with this car is the super long hood and the Jaray greenhouse and roofline conspire to make the passenger compartment pretty tiny for such a large and long car. Two seats is all they managed to get in.

The Cd (if I remember correctly from this EM thread) is 0.16 -- which is totally impressive for an actual car with the cooling, etc. They tested tires at high speeds -- it could go 150mph with just a 150HP engine, which is a testament to low drag chassis!

[NeilBlanchard]

Here's a picture of a quarter scale model of the Maybach, that is from 2006:



Here's a "new" picture of the Schlörwagen: