To Wheel Or Not To Wheel ?

[cRiPpLe_rOoStEr]

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.

[aerohead]

Originally Posted by All Darc

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





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.



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:





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 :







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.



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

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.

[Grant-53]

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.

[All Darc]

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).

[aerohead]

Originally Posted by All Darc

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).

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.

[freebeard]

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.

[Angel And The Wolf]

Originally Posted by freebeard

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.

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.

[freebeard]

What would Luigi Colani do?



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

exploder ii concept 02 by criarpo

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


http://bubblemania.fr/en/voitures-bulle-luigi-colani-creations/

[All Darc]

Is this also valid for Brazil ?

Originally Posted by cRiPpLe_rOoStEr

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.

[Angel And The Wolf]

Originally Posted by All Darc

Is this also valid for Brazil ?

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