For those who want to think a bit ... amazing machine

[Surfeurseb]

Hello

Looping in: you practice an aviation activity?

Right, I'm glider pilot and glider and also Autoconstructeur a small wind turbine.

We may meet in the air one day, I'm a hang glider pilot
(in Brittany, or elsewhere)

[Olivier22]

Better not to cross too close, I am an airplane pilot, in Brittany too
(rest assured, as soon as I can I go gliding!)

[loop]

Hi Olivier

I was talking about instability in the case of the cart in the video with the treadmill. I thought I noticed that it was having trouble staying in line. The propeller thrust force is at the rear of the wheel which "picks up" the torque on the carpet. In this case the two opposing forces tend to be misaligned, and therefore to turn the carriage. But at the same time it is true that the thrust of the propeller is necessarily always in the axis!

For propulsion aircraft, I admit that I never asked myself the question. But come to think of it, I believe that an airplane with this type of design should slip off more easily (?) And undoubtedly require a good "foot" correction (symmetry rudder). The center of the drag forces is at the front of the propulsion, but it is true that the latter remains in the axis of the aircraft no matter what.

A+

[Remundo]

Oh oh strength of love ῷӁϠ 佼 厳 戒

Yeah, move forward facing the wind, with my little head I can imagine it,
but Remondo is going faster than him, downwind

And I dry

The original video shows a vehicle (not food low
-côtés ... because it is remote )
and that goes faster than the wind

Sorry ... but I'm a bit dropped Ouu

My study concludes that we cannot go faster than the absolute tailwind on the strength of the tailwind alone, and that even if we exceed the wind speed with an engine, it costs a lot more energy to put the wind turbine that it will not restore: this is explained by the drag it generates, the low wind power then available (small relative wind speed compared to the wind turbine), and the not very good yield of transmission of this power in advancing energy.

My study on wind turbine propulsion concludes that the advantageous situations compared to the sail are the headwind, the side wind, and to a lesser extent the relative tailwind (wind faster than the mobile in a common direction)


[Serious mode OFF] [Joke mode ON]
I only know one that goes faster than the wind
it was the child of fierce ages, Rahan, faster than the wind (rear) and without turbine, except his cutlass .

[Olivier22]

I did not have time to read your entire study, but if it shows that we cannot go faster than the absolute tailwind, it is because there is a flaw.
From an energy point of view, nothing stands in the way.

The propeller uses the relative wind that it creates in the same way as a sail, except that as its movement is perpendicular to the trajectory, it can generate a traction in the direction of the absolute wind.
The thing is no longer to demonstrate in the case of a sail, so I do not see why it would be different with a propeller

If I knew where to find a small angle gear I would start making a model like that of the treadmill! History to demonstrate that there is no special effects in these videos

[Remundo]

Hi Olivier,

If I follow your reasoning, there's something I don't understand ... A plane goes much faster than the wind (like Rahan, well I stop with him ), with a propeller ... But why do we put fuel in it then? The propeller should "self-feed" from its wind not and produce energy from ... nothing?

[Cuicui]

Y'en others who carried out the experiment in mini-boat, for example:
http://www.youtube.com/watch?v=NNbNNSDljGI
@+

Too bad we do not see him advancing against the wind.

[Olivier22]

We are not talking about an airplane but a wheeled cart ...

An airplane moves in a mass of air, it receives no power from the outside environment.

The carriage moves relative to the ground and receives energy from the wind.
Without wind, it would not work (it would be found in the case of the plane, where there is no speed gradient in the external environment)

On the other hand if we could make a wind tunnel with 2 horizontal air layers moving in opposite direction, that we placed an airplane with propeller back to the wind in the tablecloth of the top, the propeller being driven by a turbine blown by the tablecloth from below: then yes, the plane could go faster than the wind from the tablecloth above.

You understand that we can go facing the wind! We then go faster than the ground, in the opposite direction of the wind movement.
We can therefore go faster than the wind, in the opposite direction of the ground movement!
The only difference is the speed difference between the 2 phases of the external environment!

We can also make a purely mechanical system with a treadmill driving, via a wheel and a gear, a car placed on the ground next to the carpet, the car going faster than the treadmill! (with an epicyclic train it's childish)

[esgege]

If we replace the treadmill or the road with a fixed wheel (gray part) like this ...




the yellow wheels drive the elice and it turns forever

[Olivier22]

No, because the wind perceived by the propeller is only the relative wind. No external energy input.
It can work if in addition we rotate the big gray wheel (there is then a difference in power exchanged with the air and with the wheel, so a power supply)