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 All Darc 02-18-2018 07:30 AM

Hello from a curious guy searching for information.

Hi there. How are you doing ?

I'm registring to this forum to learn more about new technologies, aerodynamics, ecologic approaches, electric vehicles .
English it's not my native language, but I will try my best.

I don't know from where to star...
If a good soul could help to guide me, I will be thankfull.

For example the drag coefficient. It give a value about the percentage of force that is necessary just to the vehicle push the air, based in the frontal area. Right ?
But since it's a coefficient based on frontal area, it do not tell us direct how many newtons of fore the air is pulling the car. Correcy?

So the drag coefficient, unless I'm wrong (I need to be humble) of a vehicle, it's not perfect to judge if a car it's effective in economy, since vehicles can transport the same number of people (let's take 2 persons for two different vehicles) but one can have a small frontal area, like a encapsulated motorbike (Ecotracer/Monotracer), and other can have a larger frontal area, like Aptera car.

So let's just supose Aptera and Ecotracer had same Drag coefficient. This would not be enough to say both vehicles are under the same force of air pulling them back, since Aptera have a larger front area than Ecotracerk. Am I right ?

So how to better judge things in these terms to find out how many newtons, find & measure the force that makes the motor works more just to fight the air resistance ?
Is not it only a matter of use Fd (drag force), is it ? This force it's not the final resultant force in the vehicle's shape pushin back, but just the force of the wind flow.... ...At Least I presume so...

Sorry if my text somehows can sound arrogant (a bit contestant), but I'm just trying to better understand the details about aerodynamics.

 Angel And The Wolf 02-18-2018 04:31 PM

CD is a number based on the ease of a shape to move the air aside as it passes through it compared to a billboard of the same frontal area. A better term is CDa, which takes into account how large the shape is seen from the front.Given two vehicles that have identical CD numbers, the larger vehicle (higher frontal profile) will have to move more air aside, and will have a larger CDa, thus lower miles per gallon. Other factors influence, such as rolling resistance of tires, friction of powertrains, and efficiency of engines.

 All Darc 02-18-2018 06:40 PM

Thank you both, Angel And The Wolf & Old Tele Man. I will search about CDa.

I was wondering if was possible to create a better, "crazy", coefficient, for aerodynamic electric car assisted by solar energy.
Think with me. A car to be economic and ecologic can be electric, low weight, good in aerodynamic and have a fine surface to solar panells.
A car have very low CD, like that SHell Eco-marathon's Ecorunner V and VI model with 0,05 drag already with wheels. But Ecorunner V&VI it's almost "a torpedo with wheels", for just 1 person in lying position. Even if we increase scale to 3x , it would be small to sit and would end up too long even for a typical car. Besides, the upper surface area it's small, allowing just very few watts of solar energy.

Type ecorruner on Google image search, since I'm not allowed to post images yet.

Now take SolarWorld NO1. It have probably a drag of 0,1 or 0,11 or less (need to check with their team), similar to Aptera Type 1 and MIT's Solar Aztec (drag 0,12 with nude wheels without streameline covers). Despite have probably the double drag and larger frontal area, it have a fine upper area for solar panels.

Search SolarWorld NO1 and Solar Aztec Car, on Google image search, since I'm not allowed to post images yet.

With few interior modifications Solarworld No1 it could probably fit 2 persons.

So how could we creat a coefficient or something to help determine effectivines of a vehicle shape, considering also the top surface area ?
I imagine it for 21% efficient solar cells (SunPower), since cheapers are not flexible and are just 16,5% efficient, and the 26% (gallium arsenid) are too expansive, and the 39% (mult junction) just for satellite or milionaires.

Such "coefficient" would require to take in account available area for solar cells, drag, perhaps solar power output, body weight, but probably not electric motor power consumption. It would take in account a average speed, enough to use almost exclusivelly solar power or just 50% of battery to assist.

The idea it to judge not only drag&drag for area, but also judge the solar capability (surface area). With more power, and still acceptable low drag (despite not the best ever) we would need less powerfull motors, less battery power, reducing cost and getting more green.

I know it sounds crazy, too complex for a coefficient, a challenge to a scientist, but I believe something like this could be of help. Maybe I'm just being nonsense... I don't know. Fell free to critic my idea.

 Angel And The Wolf 02-18-2018 07:14 PM

 All Darc 02-18-2018 07:37 PM

Thank you, I will. The proper place for the comments.

 All Darc 02-18-2018 07:42 PM

One more question, If you allow me.

Where is the better place about composite material, new materials, low weight materials. ?
I want to talk about some possibilities for future lower cost carbon fiber.

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