Morelli Shape

[Jim Bullis]

Neil,

Maybe you missed the part of the boxfish story where they said that by simply lowering the model from its original test position that would be in free flow conditions, down to proximity to the ground, as is the rule for cars, the drag coefficient would go up some 40% to 45% or so. That had nothing to do with wheels; it was simply that the road disturbed the flow of air around the body that existed in free flow conditions, cutting off much of the flow underneath.

Then we find that earlier, Morelli showed a similar effect for a simple shape, which was a tear drop with some flattening on the bottom. Again, that is in that 1982 paper.

"Can't be physically done" is not a judgment that should be accepted without real trying.

[KamperBob]

Originally Posted by NeilBlanchard

I think it is pretty cool that nature and evolution has fine tuned things so well. Also, check out the structural "innovation" of the boxfish; with it's hex structure within the skin.

+1

Nature rocks!
KB

[euromodder]

Originally Posted by Jim Bullis

"Can't be physically done" is not a judgment that should be accepted without real trying.

Technological innovation sure needs people thinking out of the box.
If you don't even try, you have already failed
So I like your concept of lifting the main vehicle body out of ground effect from that point of view.

Yet I'm still left wondering why that would require more than 4 wheels, and an articulated drivetrain on top.
I'd expect that reducing the number of wheels and thus the size of the drivetrain that will need to be in ground effect, should have a positive effect on drag and ultimately on fuel consumption.

Looking at solar challenge vehicles, the Audi Avatar and the like, they tend to limit the bulk of the structure around the wheels to the bare minimum.

[NeilBlanchard]

Jim,

Which model was the lowering referring to? The original fish is 0.04 -- that beats Morelli by a few points. The free space measurement of the computerize version of the fish was 0.06, and the 1/4 scale blue clay model with wheels was 0.095.

What part am I missing?

[Jim Bullis]

Neil,

Sorry, but I am confused. The original Daimler Benz web page disappeared, but I remember it differently than you do.

As I recall, it seemed like that original page was a PR release written around the technical facts, and it was confusing even then.

Best regards, Jim

[Jim Bullis]

Hi euromodder,

Your observations and thoughts make sense.

Lifting the airship does not require more than four wheels. The six wheel articulated system is elaborate as shown because of the original goal of making a car that would also take up half a lane on a highway. That actually was the beginning of my involvement in futuristic vehicles.

I started when there was not a lot of talk about energy, but I always had in mind that anything narrow had to be a big fuel saver. But then when I began to fit an aerodynamic body on the articulated system, it was natural to go to an elevated arrangement, and the body of revolution was a logical and simple choice. Being a little CAD limited, it was easy to use their canned geometric solid shapes. And the combination of the cone, sphere, and cylinder was an easy way to draw the airship form, which was still lying there on the page in my old fluids book as the best ever shape.

Now that things have evolved some, and the requirements for solving energy problems are much clearer, I can see that the articulated system could perhaps wait for a later time. I also recall wise advise from the past that told me that it was a bad idea for a program to try to change too many big things at one time.

So I am with you now on priorities. The four wheel system works if the vehicle is made somewhat wider than the design at miastrada.com and the wheel trains are much simplified, but still include provisions for fairing in the wheels with batteries and motors in between.

If you can get the published patent application from 2007 that is on the miastrada.com site you can see on Fig. 18 and 19 how I carried that as an alternative, since even then the merits of simplicity were being considered. (That patent is now in the late prosecution stages.)

Thanks for your insightful comment.

[Jim Bullis]

KamperBob and Neil,

Yes the boxfish is amazing, but keep in mind it was designed by nature to scoop up food from near the bottom. Cars do not need to do that.

If my recollection of Cd of .065 for the ideal boxfish is right, and that seems credible since even nature has to give up something for functions like eating.

In the 1982 Morelli paper, Morelli shows the shark as a form that is also very effective in nature. And it is more of a cruiser than the boxfish. Still the shark has near bottom cruising requirements that are enhanced by the camber of its body for low level cruising, and this camber is adjustable by the shark himself (or herself). So Morelli is more interested in emulating that shape, which he does with his

But still, the rectangular form of the boxfish is advantageous, especially since it can be jammed into the preconceived notional box that is the hundred year old tradition of automobiles, which is driven by the absolute demand that an empty right front seat must be carried; I guess because we all hope to have some sort of friend riding along. Yup, that is the crime that needs to be fixed; maybe we all should go to psychiatrists to figure out that friends do not really want to ride with each other, to work and back every day.

I call it a crime because we were headed in a better direction in 1915 with the 'cycle cars' which commonly involved tandem seating. It is said that Henry Ford conspired to slime the cycle cars, putting out rumors suggesting they were dangerous. And of course as new machines, they had their problems. And the mass production accomplishments of Ford hit the magic quantity where fashion could be set by public recognition and big advertising campaigns. And of course, oil was subsidized with the investment tax credit and high speed was not important on roads then, so who cared about efficiency?

[RobertSmalls]

Originally Posted by NeilBlanchard

Hi Matt,

Mercedes may have accounted for the scale difference/Reynolds Number by increasing the velocity; we don't know? I tend to think that they know enough to have the right number. The final Bionic is a real car with a Cd of 0.19, and the progression up from the fish, fish model, car model, to the built car, all fit.

The Goldenrod has a Cd of 0.11-0.12. You could be right about the Dolphin, but the AeroCivic is ~0.17.

Neil,

What I mean is, while the blue clay model may have had a Cd of 0.095, I disbelieve that its basic body shape would make for lower drag than that of the other cars I mentioned. A direct translation from blue clay model to real, drivable car (which M-B didn't do) would add considerable drag and would give it an impressive but not unprecedented Cd, and a rather ordinary CdA.

Matt

[RobertSmalls]

Jim,

There are a few vehicles on our roads today with tandem seating - motorcycles. Yet very few people would accept tandems as their only vehicle. Such a car would have to be inexpensive and compelling enough to justify owning it as a second vehicle.

[Rokeby]

Originally Posted by RobertSmalls

There are a few vehicles on our roads today with tandem seating -
motorcycles. Yet very few people would accept tandems as their only vehicle.
Such a car would have to be inexpensive and compelling enough to justify
owning it as a second vehicle.

Something like the VW L1 concept vehicle perhaps:



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