To Wheel Or Not To Wheel ?
 

I know a lot was talked in this forum about ALberto Morelli's ideal aerodynamic proposal:

http://img.photobucket.com/albums/v7...2at15322PM.png

https://encrypted-tbn0.gstatic.com/i...xlm8h96nC8rpc4

But this design, despite represent a 0,05 drag shape, do not consider any wheel. Aptera, based in Morelli's shape, reached 0,11 to 0,125 (varies according Aptera models) drag coefficient after add wheels, even if using streamlined covers to the wheels.

http://www.bloodyloud.com/wp-content...cd_576_352.jpg

For other side the Solar Aztec car from MIT, had 0,12 drag, despite have no streamedline covers to the wheels and even a open hole in the shell near wheels:

http://www.dempseymotorsports.com/images/Aztec.jpg

https://c1.staticflickr.com/3/2724/4...9066d235_b.jpg

Maybe because it was more rounded on top than Aptera, I don't know... Aptera's wheels was large, thick, and maybe it's the reason the drag raised a lot.

A third Morelli's shape car was the Solarworld No.1, but I could not find the drag coefficient for this vehicle, despite a lot of web research :

http://www.hochschule-bochum.de/file...World_No.1.jpg

https://media.gettyimages.com/photos...ure-id77423084

https://www.solarserver.de/uploads/pics/sw1_tour.jpg

I bet Solarworld No.1 have lower drag than Aptrera and MTISolar Aztec .

But the reason I created this thread is about Ecorunner VI, with 0,048 drag coefficient already with wheels.

https://duurzaam-actueel.nl/wp-conte...ecorunner5.jpg

The earlier model, Ecorunner V, already had a drag of 0,0512 with wheels. Other vehicles with similar size and "torpedo shape style" in Shell Eco Marathon had a drag of 0,08 with wheels.
Maybe there a key point, precise calculation for aerodynamic, simulation on computer, trying to find the best shape alread with wheels (streamed covered), instead of try a shape to just later try to add wheels to it.
I just wonder what is be Ecorunner VI drag coefficient without wheel...

The hope I have it's that maybe it's possible to find a much better way to add wheel to a Morelli's basic design, and still have a drag bellow 0. or even bellow 0,91

The most efficient design would be a torpedo shape, with 2 wheels inline, just barely poking through slits in the body. A collapsible kickstand could be deployed when the vehicle stops.

I understand the torpedo shape to have equal air resistance all around, but does not the ground affect the air pressure of the air deflected by the bottom line of the body? Should not there be a longitudinal crease in the bottom line of the torpedo to relieve some of that higher pressure felt on the bottom?

Like Ecomobile.

http://www.diseno-art.com/images/Ecomobile_Turbo.jpg

Not sure what is the drag or it.

But Monotracer (similar to Ecomobile) have a CdA of 0.18.
http://www.evo.co.uk/features/featur...onotracer.html

How convert to CD ?

And when you put wheels and full length skirts on, and lower the torpdos to where the tops are the same highth, it gets worse for the un-creased torpedo:

The Ecorrunner V and VI remambers a lot a torppedo, but the shape have some interesting variances from top to botton, probably to create a bettert aerodynamic than a simple torpedo shape.

This is probably the reason it have (already with wheel) much better drag (0,048 for version VI) than other torpedo like vehicles (with around 0,08) or their own quite earlier version.

https://media.gettyimages.com/photos...0296?s=612x612


https://www.cleantechdelta.nl/wp-con.../12/Eco_VI.jpg

Old version from years ago :
https://static.wixstatic.com/media/a...21a120~mv2.png


If their aerodynamic engeneer could try "his best shot" on Morelli concept, to try to add wheels and keep drag low...

Have Morelli ever said his model was the best possible, or said just it was the best for a reasonable space in the front area ?
After all, a flat plate in horizontal, following the wind orientation, have even lower drag, and some solar cars try to be a flat plate with a pilot and wheels, but just got around 0.078 or so.

http://news.panasonic.com/jp/press/d...120719-2-1.jpg

The higher number comes not from the flat plate, but from the wheel pods and cabin shape. Look at them alone, and you will not see a good aerodynamic

Yeah, Imagine that. But you can't kill the driver. ;)

Take Stella solar car (3 different models but similar in performance) :

https://en.wikipedia.org/wiki/Stella_(solar_vehicles)

One paragraphy sounded like crazy absurd or a error, perhaps the editor just forgot to say that the recharging by few minutes a day and low speed drive on sun would take a month to fully charge the battery, since it's a 15KWH battery and a 1,5KW solar cells array :

"According to the developers, "in real-world conditions, the Stella's large solar array would be able to charge the car's 15 kWh battery pack in 30 to 45 minutes of being parked, sitting in traffic, or tooling around town at low speed" "

Of course, once the battery is charged, maybe by 8 hours on sun in 2 or 3 days, if the car is not used for many hours, the car can really produce more energy in one day than what it would consume in a day.

But for drive on city, and reduced battery need, it's really a good idea. If we left the solar array in home we would need larger and much expansive batteries.

I saw threads in this forum from 3 years ago, about buy solar cells, and I saw people getting cells from ALiexpress. But ALibaba have better offer. I was surprised with Sunpower flexible solar cells that could be as little as 1,0 or1,5 dollars per cell, in a 150 cell pack.

Solar power is comming to stay.

Keep in mind that the goal is to minimize drag with these cars, not just Cd. Drag is a function of Cd x A (frontal area). Flat solar cars may sacrifice a little Cd in order to greatly reduce frontal area.

You are right. I must said drag coefficient instead of say just drag, when refering about Morelli 0,05 otherwise I would be reffering to another thing.

Drag coefficient it's the same for a vehicle or for a scale model of the same vehicle. For other side drag force it's different.

It's easier to a torpedo shell have reduced drag coefficient, as it have reduced drag force. The drag force fights less air with a reduced frontal area to push air.

For a solar car, the drag force it's important to calculate how much the motor will need to fight the atmosphere.
And there is also CDA, that is CD x Area (frontal). Os it can be calculated by removing the A in the equation od CD:

https://wikimedia.org/api/rest_v1/me...af22b2ec0d5c0e

Some designs makes me a bit confused, like how define the frontal area, if by looking at it, in some cases, we see not a very clear division. I supose it's the area in a transversal cut, like cutting a salami, right? Is the point of cut would be until the wider area before it stat to get narrow? Is the point where the "salami slice" is larger ?

Sorry if I'm going too fast, but I wonder how would be possible to find a way to easily relates CDA and top area for solar panels. I konw it would require many values, including solar cell efficience.

But for now I'm imaging a way to combine the low drag force and low CDA of a vehicle with small frontal area, with the principle of the horizontal plate cutting the air easilly.

Let take this vehicle for example :

http://www.diseno-art.com/images/Ecomobile_Turbo.jpg

Small frontal area, remambers a torpedo, two seats (wheels could be better but let's left it to another day talk). But the top it's narrow, poor for solar cells.
Instead of re-design a large frontal area and larger top area for the vehicle, to get better solar surface area, what about we just add a plates in horizontal, around the shell. The plate would have minimal drag force if it could preciselly follows the wind flow along the lateral sides of the shell, making probably some few wave curve in horizontal. The plate would also increase solar area to make solar cells available area more revelant.

The idea is to create a electric vehicle assisted by solar cells, able to cary two passangers, consuming less energy and having a better relation between energy consumed and energy produced (by solar cells) than Solarworld No.1

https://upload.wikimedia.org/wikiped...World_No.1.jpg

But keeping 2 wheels, manuever like this one bellowwould be a problem, malking the solar plates hit the ground.

http://ecomobile.megard.ch/images/eco5037a.jpg

That is a beautiful design.

I'll share a little advice that someone told me back in 1982-ish, do two wheels in front and one in back (handling reasons).

EDIT:
This 2008 thread has some nice images as well.
http://ecomodder.com/forum/showthrea...hape-3746.html

Aptera problem was the tick wheel tires, and the tall extructure in the back to fit the rear wheel. All large extructures that even with stream lined covers added much drag, and probably created turbulence to the center air flow bellow the shell.

The Solarworld No.1 (yellow car) probably opted one wheel in front and two behing to reduce such problems, but make the car more prone to accidents, including one that happed in a competition, breaking a piece of the shell in lateral portion near the front wheel.

Maybe 4 small narrow wheels, leaving the center free to the air flow, woulf be better.

13 posts in 24 hrs. Where to start?
I drew a design when I was in high school (may still have it) that was opposite. Enclosed wheels (and a split grille) in front and open wheels (and transaxle) in back.

Permalink #3:
R.B. Fuller's Omnidirectional Transport (the precursor to the Dymaxion Transport) had an air keel:
http://ecomodder.com/forum/member-fr...f5307910-o.jpg

Also ME-262. I knew I had this squirreled away, but I see now it is by Ross Lovegrove (a very interesting person):

http://ecomodder.com/forum/member-fr...03-7-03-44.png

Here's his design for a car on a stick that doubles as a street-light, plus offstreet parking.

https://static.dezeen.com/uploads/20...ssre-copy1.jpg
https://www.dezeen.com/2008/01/24/ca...oss-lovegrove/
My own contribution: A stern-wheeler hovercraft with a blown nose:
http://ecomodder.com/forum/member-fr...76-vwhover.jpg

Aptera suffered from interference drag between the nose and front wheels.

Herbie (The Love Bug) got amputated... :D

The buble car it's elegant, but how can a such small solar panel move it with 4 people?
Only the verey developed countries. In countries in development it would be easy target of vandalism and thiefs.

What you do is called top-posting. Comment first and cite second. If you cite first it flows better. No offense?

The Lovegrove design shows two on the road and one on the pole. Supposed the street were lined with them. The poles would be empty during the day while people go around their busyness. At night the street would be lined with street-lights. As long as utilization as a car was maybe 20%, they could trade charge locally for load balancing.

The back-to-back seating might be a deal killer. Who knows.

edit:
Possibly the bubble window is a see-through solar cell? No more fanciful than the rest.

Very transparent solar cells, or see-through solar cell as you said, are only 5% efficient in present time. They will try to reach 15% in few years or so.

http://psipunk.com/wp-content/upload...-green-car.jpg
Future Transportation - X-Frame All-Electric Vehicle Folds Up Vertically For Storage

I posted this in another thread. I would classify it as a squircular Morelli body. It consists of four curved edges that meet at an X at the stagnation point.

Where it fit the batteries??
In the huge orange wheel??

¯\_(ツ)_/¯

The provided link (ecofriend.org) 404s. I searched on 'Nagoya Institute of Technology X-frame' and found a Spanish language site, but all it had was the same picture. I'd like to see that graphic that's on the wall behind it. There is an exploded diagram.

No matter what you ultimately set to do, make it a 3-wheeler in order to get its registry as similar to a motorcycle, then overcoming much trouble due to the exemption from some safety requirements.

Ecorunner
 

My opinion is,that there's a bit of intellectual dishonesty with respect to the Ecorunner Cds claimed.
The caveat,is that these vehicles operate at around an average of 15-miles per hour,and due to there limited size (length),technically,they never achieved super-critical Reynolds number,and can be considered 'laminar' cars.
In 'traffic' racing with other cars in proximity,or if any crosswind existed on the track,the transverse contamination shear would force the flow to immediately transition over to a full turbulent boundary layer.If so,it would be impossible to have a Cd any lower than 0.08 according to Hucho.

The contest vehicles are limited to the conditions of a closed track. One does not need solar power to go 15 mph in a stream liner. Morelli designed for road vehicles and understood the limits of ride height and ground clearance. Since angle of incidence has an affect on solar collectors, one might consider tracking mounts for cells under a clear skin.

Reynolds number ??
I confess I don't know what is it.

Drag it's much more relevant in high speed :

http://www.ecomobile.gouv.qc.ca/en/b...amic_force.php

Some solar cells, like monocrystaline, works better tha others (like pollycrystaline) for now ideals of lower angles. The top can have solar cells, ans some of the laterals too, for when the sun reach a low angle and rit such area. The solar array in general would not be ideal for all cells at same time even in the best sun'angle possible, but it would help to get more power.

My idea (maybe crazy) is about to use the principle of torpedo low drag, maybe carring two persons, like ecotracer/Monotracer, since it would have a low CD and a low CDA, due small area and aerodynamic, and at same iome combine with the principle of flat plate in horizontal, following the wind. The plate would create a large area for solar cells and add very little drag. But the plate would not be completely flat, but with a curvature , specially near the torpedo shell, to follow the wind curve relted to the shell.
Imagine a torpedo with bat wings or something like it.
This would create a vehicle for two, with lower drag than APtera or Solarworld No.1, and with similar solar cells area to Solarworld No.1
It would miss the skill to performe low angle inclined 45 degree curves like Monotracer, but would be very economic. Not sure if it could be 2 wheel or would require at leat 3 wheels (more probable).

Reynolds number
 

Motor vehicle aero drag is basically a function of pressure drag.
Pressure drag is a function of flow separation,or lack thereof.
Flow separation is closely associated with the health of the boundary layer.
The best attached flow for 'real' vehicles is with a fully turbulent boundary layer.
This will occur when the Reynolds number goes super-critical,which for 'real' cars, occurs at about 20-mph.
If you keep a car below 20-mph,you can keep it in a laminar boundary layer,which really reduces turbulence-induced surface friction.
Surface friction isn't a problem with 'real' cars and a laminar boundary layer would actually increase pressure drag (overall drag) in a 'real' car.
The Ecorunner,by being 'short' ,and driving 'slow' can claim a very low 'laminar' Cd,but this would never possible with a 'full-size car,moving at real highway velocity.
The Reynolds number is associated with length,kinematic viscosity,and velocity.Once you get to around Rn = 500,000,the boundary layer will transition,from laminar,to turbulent (TBL).Golf balls are artificially roughened to trigger the immediate transition to TBL,allowing flow to remain attached longer before separating,thereby reducing the low pressure wake (pressure drag),and extending the distance of the drive.
The Rn of cars is measured in millions.

http://news.panasonic.com/jp/press/d...120719-2-1.jpg

At first glance that may look like a flat plate, but the edges are rolled, there is an overall crown and a reflex curved aft. It's like a Morelli shape that swallowed a solar panel.

The necessary wheel penetrations on the bottom aren't any problem, but a tandem two-seater cockpit canopy would be. People want their view of the countryside, can't sling them underneath.

Needs better solar panels, like ones that absorb infrared that is re-radiated from the road or even after dark:

https://inhabitat.com/solar-panels-work-at-night/

edit: [links on that page 404. :( ]
Try https://duckduckgo.com/?q=inl%20sola...nna&t=palemoon

Here's another one, capturing the blue part of the spectrum through re-radiation in a hydrogel:

This New 'Green' Antenna Could Double Solar Panel Efficiency

So — blue absorbing panels on the top, and infrared absorbing panels on the bottom. :thumbup:

Above, below, same difference, except that below, combined with the rear center wheel fairing would eliminate that protrusion above.

Cameras and view screens would get rid of the claustrophobia.

in fact, lieing flat with the screens above, or google glasses, could keep the driver within the upper and lower skins of the plate.

What would Luigi Colani do?

http://ecomodder.com/forum/member-fr...wu5wo1-500.jpg

That was based on the water strider [insect]. He ran it at Bonneville. Here's another concept with simple-curved surfaces:

http://ecomodder.com/forum/member-fr...po-d5b2ct2.jpg

edit: I went looking for another example of the Colani car:

http://bubblemania.fr/wp-content/upl...b78gzs02z3.jpg
http://bubblemania.fr/en/voitures-bulle-luigi-colani-creations/

Is this also valid for Brazil ?

Don't know. It's not valid for some states of the USA.

https://www.worldsolarchallenge.org/...hoto_solar.jpg

https://news.engin.umich.edu/2017/07...lar-challenge/

https://www.msn.com/en-us/autos/auto...cid=spartanntp

This 4-wheel solar car can go highway speeds and has .1Cd. It is raced on public roads in a region complete with foul weather and high winds but I don't know how much interaction the racers have with other traffic.

You need not worry about whether your one-off is a trike or not for safety regulations; it won't be crash tested and if it has the lights, horn, etc. your State requires and it passes inspection, it's golden.

1fr/2rear trikes can be more than adequately stable. There are more of them than tadpoles.

That orange tired thing has a loooong way to go to be classified as a Morelli shape! I mean, there's a kinda-sorta overall similarity but the Morelli is all about aero and that orange tired thing has the aero of a barn.

the CD of this car it's lower than Aptera, but the LDA it'a even better, am I right ? Due much reduced frontal area than Aptera.

My idea it'sa bit different. I have to draw...

Bye bye plan to contact their team to the creation creation a ideal wheel streamlined covers for Morelli's design...

Speed it's a factor for supersonic planes. In supersonic the aedynamics it's a bit different. I remamber this reading this forum somewhere. I didn't knew very low speed was also factor.

Interesting, but it probably have low solar panel output.

How we determine exactly where frontal area ends, if by looking to the a given shape we get confuse ?

Maybe the hope for a affordable electric solar vehicle for families comes from a poor country.
No offennse to USA and Europe people, but their industry want to make $$$, and not give clean car to save the planet.

Engineering Students build India's 1st Solar-Powered Vehicle - Team-BHP
SERVe: An amazing solar car designed by Indian students - Rediff.com Business

For a solar lightweight car, why we need 15kWh battery ? Why not just 7KWH ?

It needs Wheel spats shaped like a little double-sided plow.

It lacks the reflex curve on top of the nose. Morelli specifies a circular cross-section, this has (or could have) a superelliptic cross-section. Surface development is an issue, like ...putting doors on it.

The hope, maybe; but the R&D will come from capitalists and the production will come from China.

A electric vehicle to fit in you pick-up ?
NASA made it in 1971, the Lunar Rover :

https://youtu.be/5aDSYTMqyQw?t=2057

https://www.youtube.com/watch?v=7OL3OmM-CYQ


I wonder if such foldable vehicle could be redesigned to get flexible solar cells, like a tent to easily assemble over it.

I remamber about the news of solar panels that worked by night. Indeed interesting, harvesting the heat and turning it electricity. Collect energy from the very hot asphalt sounds great.
But it could interfear with electromagnetic waves, like from cell phones.

As long as it's fitted with a motorcycle-type handlebar, it works.

In Texas, the regs were changed from "Stradle type seat, handle bars, and open topped, to include closed cabinned, steering wheeled, car type seat. In Texas, three wheels or less means "Motorcycle"

Your State may vary.