Morelli Shape

[RobertSmalls]

There are a number of members who would be happy to tell you they prefer the feel of a low vehicle. Besides the low center of mass and good handling inherent in a low vehicle, there's the fact that placing the driver's eye as close as possible to the front left tire gives him the best control over his vehicle. I hate a vehicle that leaves me wondering where its corners are.

[Rokeby]

What with the explicit and implicit references to Zeppelins in this thread,
here's something fun to watch:

Hinklestein

Helium, not hydrogen...

I think it needs some of these:

[NeilBlanchard]

Originally Posted by Jim Bullis

Yes, there will be separate aerodynamic entities near the ground, but these are very low profile so that the drag on these, including ground effect associated with these, is not large compared to the main aerodynamic entity which is the thin upper body.

So the two ways I know to achieve the two feet are attached with thin struts designed also to make the main body work as it would in free flow. These will not be as close to the ideal as the supports used in wind tunnel measurements, but the objective is to get as close as possible to this condition.

The wheels and the batteries and the motors all reside in the lower half. It is definitely not negligible. It has wheels that have to be faired or have strakes, and the bottom will have exactly the same issues as any other shape near the ground.

Separating the masses does nothing to avoid the problem you are fixated on. In fact, it probably introduces a bunch of additional problems.

And if you design it to be narrow, like the Tango, and want to try to have separate wheel sections, with articulated steering, that doubles again the challenges: hydraulics, control systems, structural stress from the "arch" of the passenger pod spanning between the wheel pods.

Ultra-efficiency demands simplicity. No added weight, no added complexity -- simply keeping the wheels precisely aligned is the absolutely most basic function of an efficient car. The simplest structure is a straight line between the wheels.

The Miastrada design is anything but simple.

Aerodynamically complex with interaction between the lower portion and the ground AND the upper portion with the lower portion.

Structurally, it is exceedingly complex.

Driving controls are very complex, with drive-by-wire demanded for steering at least.

Entry and exit is like an airplane at a terminal, and the seating design is tough.

Center of gravity issue won't be easy -- the Tango "solves" it by adding about 900 pounds of lead as low down as possible. This has to go into the lower portion, and guess what?

You are going to get aerodynamic interaction with the ground, unavoidably, with this design.

[miket]

Why does the miastrada have such a narrow wheelbase?

I think it would be interesting if you took a scale model of the miastrada and of a known car and did coastdown testing to compare the aerodynamics of the two.

[Jim Bullis]

Miket,

Things have evolved somewhat, and that has caused confusion. The original concept was intended to minimize width so as to solve congestion problems. It is a two axis articulated arrangement where the axes are offset from each other, unlike with a common tractor trailer arrangement. And also unlike the common tractor trailer arrangement, the front four wheels function like wheels on a forklift truck, and the steering is extended up to the driver station. On a functional model, this arrangement seems to be remarkably effective in making a narrow vehicle stable.

The original aerodynamic features were developed, on that wheel system. This narrow and tall car solves a lot of problems, but it does involve some complications, which will probably not be understood without more demonstration. The patent drawings do explain it though, if anyone wants to look.

But since money is not free, and complexity means money, I am looking at a much simpler version, which would still have the important aerodynamic advantages but would be about two feet wider to get adequate stability without the articulated wheel system features.

[Jim Bullis]

Neil,

Bottom issues exist of course, but they are not the same in magnitude for a thin horizontal tube as they are with a wide bodied car. I would say that makes the issues similar, but not the same.

My simplified elevated concept seems about as simple as anyone could want. It is different though, and maybe this makes it look complicated.

As I recall, the lead added by Tango was more like 350 lb. and it was only done in response to the Xprize test requirements. Maybe it should be kept in their production model.

There are some good reasons for the dogma that says weight has to be kept low, but I do not accept that as an absolute rule. With good regenerative braking, the weight problem is much reduced. Rolling resistance remains of course, but tire rolling resistance has been improving significantly, so even that fundamental cause of energy loss can be dealt with. If we can make rolling resistance negligible, then fundamentally, a car can move at constant high speed with no energy loss except aerodynamic loss. If we can cut that down by a factor of eight, then it will be time to go back and look at weight effects.

I get it that you do not believe what I say about aerodynamic improvement possibilities.

It would be great to have coast down testing as suggested by Miket, but it looks about as easy to build a full size model as a scale model, and that will address all the other issues as well.

[euromodder]

Originally Posted by Jim Bullis

And also unlike the common tractor trailer arrangement, the front four wheels function like wheels on a forklift truck,

Could you explain this a bit ?

I for one wouldn't want to drive anything at speed, when it steers even remotely like a forklift truck.

I am looking at a much simpler version, which would still have the important aerodynamic advantages but would be about two feet wider to get adequate stability without the articulated wheel system features.

While I can see the benefits in parts of the miastrada design, I can also see problem areas.
Such a radical concept always meets scepticism - it's up to the designer to prove the sceptics wrong

It'll take a proof-of-concept vehicle to show that the theory can be made into a practical, working vehicle that shows good mpg as well.

[miket]

You could rent an electric scissor lift, hot rod it and test the aerodynamics at different heights.

I saw a crane truck that had hydraulic outriggers that extended out wider and then extended down lifting the crane truck off the ground. With a bigger wheeled version of that the car could park right over other cars lessening parking lot congestion.

Why weren't the land speed record vehicles jacked up at all? They used jet engines, why not weld on some landing gear?

A very skinny light tandem vehicle lifted would probably be no more likely to tip over than an suv of the same wheel base. Less likely if it lowered itself on the turns, more less likely if it lowered and tilted itself on the turns. I want to see someone build or simulate this thing.

[NeilBlanchard]

I am a big fan of aerodynamics. The most aerodynamic car I have ever seen is Dave Cloud's Dolphin, I think. I'll bet it beats the Aptera and the Edison2.

What does the Miastrada have over the Dolphin? How does the Miastrada beat the Aptera?

I am not skeptical because I have not seen it before -- I am skeptical because I see that it causes more problems than other implementations of the Morelli shape (like the Aptera or the Li-ion Wave II) and I think it will have a higher drag than either of those. The Aptera 2e is reported to be a Cd of 0.15 and the Wave II is reported to have a Cd of 0.17.

The Edison2 Very Light Car (4 seater) has an "old" Cd of 0.145 and by the new SAE method it has a Cd of 0.161. I can dig out the frontal area number.

I think the Dolphin beats the Edison2, or equals it, because the open front wheels are it's weak point. But it's shape and pure, clean taper with the rear wheel strakes give it the distinct possibility to be lower drag than the Edison2.

[miket]

I think the dolphin has worse aerodynamics than the VLC becaue of its larger cross section.

Does the x-tracer have a lower CdA than the Aptera?