[Halc]

Concerning these Gaunaa lines quoted from wiki:

As seen from the vantage point of the earth (e.g. by a spectator), the rotor (acting like a wind turbine) decelerates the air and drives the wheels against the earth, which it accelerates imperceptibly.

Gaunaa is wrong here, and the wiki doesn't have a secion pointing out the flaws in his argument. In the frame of Earth, the rotor accelerates the air since it is pushing from behind. Since both air and car accelerate, that violates energy conservation.

As seen from the vantage point of the air stream (e.g. by a balloonist), the wheels impede the vehicle—decelerating the earth imperceptibly—and drive the rotor (acting like a propeller), which accelerates the air and propels the vehicle.

Again wrong. Relative to air, the earth and car are moving in opposite directions, so the thrust on the Earth again serves to accelerate both Earth and car, same violation.
Apparently there is no peer review section in the wiki article, which just reports Gaunaa's faulty physics.

IMO, people who are sceptic about it think that it would enable perpetual motion and overunity energy generators. But that's not the case.

That's my argument, yes. Show me where It's not the case. I'm referring to the case of going with the wind.

I'm pretty sure that the Blackbird also produces less power than they consume

Exactly. That means it must be consuming stored energy, which is what a normal car does when going faster than the wind. It's cheating. There's a battery in it somewhere.

Is it really supposedly a mechanical linkage between prop and wheels? I'd have gone for electric connection like they use with railroad engines. I've been in one diesel train in my life with an actual mechanical linkage and it was hilariously awkward.

[charles1948]

Can't sailing-ships go in an opposite direction to the wind.  They can sail westwards against an easterly wind.

That might seem a physical impossibility.  A sailing-ship is blown along by the wind in its sails, so how can the ship go in the opposite direction from the wind?

[Bored chemist]

Is it really supposedly a mechanical linkage between prop and wheels? I'd have gone for electric connection like they use with railroad engines. I've been in one diesel train in my life with an actual mechanical linkage and it was hilariously awkward.

I was rather hoping they would train a small army of squirrels to carry small clockwork motors around the system, winding them up using the power of the  prop, and then taking them down and connecting them to the wheels as drive.

Can't sailing-ships go in an opposite direction to the wind.  They can sail westwards against an easterly wind.

That might seem a physical impossibility.  A sailing-ship is blown along by the wind in its sails, so how can the ship go in the opposite direction from the wind?

You would know this if you had bothered to read the stuff cited but...
https://en.wikipedia.org/wiki/Tacking_(sailing)

[hamdani yusuf (OP)]

Gaunaa is wrong here, and the wiki doesn't have a secion pointing out the flaws in his argument. In the frame of Earth, the rotor accelerates the air since it is pushing from behind. Since both air and car accelerate, that violates energy conservation.

No. The energy harvesting will make the velocity of the air closer to the velocity of earth surface. That's still true even when the vehicle runs faster than the wind.

[hamdani yusuf (OP)]

Again wrong. Relative to air, the earth and car are moving in opposite directions, so the thrust on the Earth again serves to accelerate both Earth and car, same violation.

They accelerate to the opposite direction. Your reasoning implies that the air doesn't accelerate due to the interaction. That's not the case in the experiment.

[hamdani yusuf (OP)]

That's my argument, yes. Show me where It's not the case. I'm referring to the case of going with the wind.

The vehicle collects energy by reducing relative velocity between earth surface and the air. It would be easier if the analysis is done in a reference frame where the total momentum of interacting system is 0. Conservation of momentum guarantees that observers staying in this frame doesn't change their velocity due to the interaction.

The fact that the vehicle only interacts with a small part of the wind adds the complexity of the problem. So, to simplify the system, we can replace the salt lake bed with a conveyor on the floor moving to the left. The wind is replaced by a conveyor hung on the ceiling, moving to the right. The vehicle starts at the same velocity as bottom conveyor.

[hamdani yusuf (OP)]

Exactly. That means it must be consuming stored energy, which is what a normal car does when going faster than the wind. It's cheating. There's a battery in it somewhere.

The energy was stored in the wind that was moving relative to the earth surface.

British science fiction writer Arthur C. Clarke formulated three adages that are known as Clarke's three laws, of which the third law is the best known and most widely cited. They are part of his ideas in his extensive writings about the future.[1] These so-called laws are:

When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
Any sufficiently advanced technology is indistinguishable from magic.

https://en.m.wikipedia.org/wiki/Clarke%27s_three_laws

Before accusing someone of cheating, you should be pretty sure that it really is physically impossible.
Extraordinary claims requires extraordinary evidence. In the bet, Derek's claim is that a wind powered vehicle can go faster than the wind without additional power sources. The evidence is that he has driven the vehicle himself. He accepted the explanation using sail boat analogy for the turbine.
On the other hand, Alex' claim is that it cannot be done sustainably. It occurs due to wind gusts. The evidence is mostly theoretical. It would be better if he replicates the experiment and show that it doesn't work as claimed.

Your claim that there's a hidden battery is even more extraordinary than theirs. Before putting his money on the bet, Derek must have checked the possibility of cheating, which he didn't find any. Otherwise the bet won't happen. Your only evidence is your application of established theory of physics, which is not more extraordinary than theirs.

[hamdani yusuf (OP)]

You would know this if you had bothered to read the stuff cited but...
https://en.wikipedia.org/wiki/Tacking_(sailing)

I realized that not everyone is willing to follow a link, so I guess I'll just quote it here.

Tacking is a sailing maneuver by which a sailing vessel, whose desired course is into the wind, turns its bow toward and through the wind so that the direction from which the wind blows changes from one side of the boat to the other, allowing progress in the desired direction.[1] The opposite maneuver to tacking is called jibing, or wearing on square-rigged ships, that is, turning the stern through the wind. No sailing vessel can move directly upwind, though that may be the desired direction, making this an essential maneuver of a sailing ship. A series of tacking moves, in a zig-zag fashion, is called beating, and allows sailing in the desired direction.

[hamdani yusuf (OP)]

The vehicle collects energy by reducing relative velocity between earth surface and the air. It would be easier if the analysis is done in a reference frame where the total momentum of interacting system is 0. Conservation of momentum guarantees that observers staying in this frame doesn't change their velocity due to the interaction.

The fact that the vehicle only interacts with a small part of the wind adds the complexity of the problem. So, to simplify the system, we can replace the salt lake bed with a conveyor on the floor moving to the left. The wind is replaced by a conveyor hung on the ceiling, moving to the right.

Let's start the analysis using this simplified version of the experiment. First, using Rand's razor, any relevant assumptions should be made explicit.
- The mass of the vehicle (m) is much smaller than bottom or top conveyor (M, they are identical).
- At the start of the experiment, the vehicle's velocity is the same as bottom conveyor's which is -v, while the top conveyor's is +v.
- Loss of mechanical energy due to internal friction in the vehicle is negligible.

The question is, is it possible to make the vehicle move at velocity more than +v?

At the beginning of the experiment, the kinetic energy of the vehicle is ½ m v².
At the end of the experiment, the kinetic energy of the vehicle is > ½ m v².
This additional energy must come from the reduction of kinetic energy of the conveyors. But since M is much bigger than m, their change of velocities would be insignificant.

[Bored chemist]

So, we can build a machine that ...

As far as I can tell, that's a non sequitur.
Just because we can use one form of energy supply to do one job, does not mean we can use a different form to do some other job.

[Bored chemist]

I think I might have changed my mind about this.

Where does this go wrong.
Imagine I'm in the basket of a helium  balloon and there's a steady wind blowing.
From the point of view of someone on the ground I'm already travelling at the same speed as the wind. Let's say I'm heading North (from their point of view)
I see the ground rushing past me to the South.
I put a generator on the end of a stick and fit a wheel and tyre to the shaft of the generator.

I can lean out of the basket and put the wheel in contact with the ground so it spins the generator and creates electricity.
I can use that electricity to run a motor and have that drive a propeller and I can use that to move my balloon through the air in any direction I choose.

If I choose, I can point the propeller to blow air Southward and thus move myself North WRT the air.

Now consider what my ground based  observer sees.
He saw me heading North at the same speed as the wind. (and not moving WRT the air- because I'm a drifting balloon)
Then he saw me turn on a propeller and start to move North WRT the air and thus he sees me moving North faster than the wind.

This is true whether or not he knows that I am getting my motive power from a battery or from the generator on a stick.

So he sees my "craft" going faster than the wind.
It isn't powered by anything apart from the wind.

If I dangle a chassis with low friction castor wheels from my balloon so it just touches the ground, I can call the balloon a "car".
And if I use a paddle wheel on a stick (and floats rather than wheels) I can use the same principle to travel across water. If I do that I can call my balloon a boat.
So, as far as I can see, that's a way to travel faster than the wind powered by the wind, and call it "sailing"

[Halc]

I read the line in the article: "the rotor (acting like a wind turbine)" to mean that the air drove the propeller, the energy of which was sent to the wheels, which violates energy conservation per my post above. But reading closer, the opposite is what is going on. The rotor acts as a propeller, not a turbine. The wheels apply a braking action and the propeller applies thrust. Thus energy is taken from the air movement and no violation of energy conservation takes place.

The wheels generate the energy.  Work is force*distance and so say F=1, then work is proportional to distance. The road is moving past the vehicle faster than is the air when the vehicle is moving with the wind, so more energy is taken from the road than is given to the air.  I.E. less work is done by the propeller because distance is lower. Hence the thing works. Wet noodle to me for reading it wrong, and to the website for incorrectly label the prop as a turbine.

[Origin]

I think this contraption can go faster than the wind for a few moments but that would be it.  When the wind causes the vehicle to begin moving the wheels will cause the fan blade to to spin and it can certainly get it to move a bit faster than the wind, but it will immediately begin to decelerate as it exceeds the wind speed due to friction (both from the ground and air).  So while the vehicle could exceed the speed of the wind for short periods it will on average move slower than the wind.  If there was a perfectly steady wind over a level course that is say a kilometer in length the vehicle will certainly average a speed less than the wind, even though there could be times in the run where the speed of the vehicle is faster than the wind.
If the average speed was faster than the wind that would violate conservation laws, clearly if there is no force from the wind (because you are moving faster than the wind) why would you continue to maintain speed?  It is nonsensical.

[hamdani yusuf (OP)]

So, we can build a machine that ...

As far as I can tell, that's a non sequitur.
Just because we can use one form of energy supply to do one job, does not mean we can use a different form to do some other job.

I used the analogies merely to break the mental barrier that keeps our minds inside the box, which says that energy users can't get to higher energy density than the sources.

[hamdani yusuf (OP)]

I think this contraption can go faster than the wind for a few moments but that would be it.  When the wind causes the vehicle to begin moving the wheels will cause the fan blade to to spin and it can certainly get it to move a bit faster than the wind, but it will immediately begin to decelerate as it exceeds the wind speed due to friction (both from the ground and air).  So while the vehicle could exceed the speed of the wind for short periods it will on average move slower than the wind. 

How long is short period?

How do you think it can go against the wind?

[hamdani yusuf (OP)]

If the average speed was faster than the wind that would violate conservation laws, clearly if there is no force from the wind (because you are moving faster than the wind) why would you continue to maintain speed?  It is nonsensical.

Did you watch the videos?
Did you read the Wikipedia article?
Did you even read previous posts by me and other members?

Your comment indicates that the answers are no for all of the questions above.

[Origin]

How long is short period?

87 seconds or less.

[Origin]

Did you watch the videos?
Did you read the Wikipedia article?
Did you read previous posts by me and other members?
Your comment indicates that the answers are no for all of the questions above

Then why ask?

[hamdani yusuf (OP)]

How long is short period?

87 seconds or less.

Where does that number come from?

[hamdani yusuf (OP)]

Did you watch the videos?
Did you read the Wikipedia article?
Did you read previous posts by me and other members?
Your comment indicates that the answers are no for all of the questions above

Then why ask?

To give you a chance to defend yourself from accusations. The discussion is meant to exchange ideas to find the best explanation to the problem. If your mind has already been made up before even considering competing ideas, why bother joining a discussion?