Down wind faster than the wind

[ynot]

Regardless of how fast the propeller is spinning, it is travelling in the direction of the wind at the same speed as the vehicle. When the vehicle and propeller are travelling in the direction of the wind at the speed of the wind there is effectively no wind on the vehicle or propeller. For the wind to have an effect on the propeller the propeller has to be travelling in the direction of the wind slower than the wind.

 

[humber]

You could be right. I'm still operating under the impression that humber has trouble visualizing a change of reference frames and can't get over the idea that the reference frame of the ground is special. His misunderstandings seem fairly consistent for an intentional troll.

I don't think your assertion about the windtunnel is correct. I find it hard to imagine that a toy on a treadmill, driven around as I please, but always telling me that I am at windspeed, can be correct.

 

[ynot]

Your test demonstrates your fundamental lack of understanding of the device. You have asked for the device to be tested with it's power source (relative motion between wind and rolling surface) turned off.

Yes, you have replaced the 'wind' power source with a slope (gravity), but the device isn't designed to be gravity powered so what does it prove?. Try inverting the gasoline and diesel fuels in two perfectly functioning engines and see how they work.

Energy sources are not necessarily interchangable.

JB

I don’t see that it matters what energy source powers the vehicle and propeller. It’s okay to replace the wind with a treadmill but not with gravity. Why not?

How does using gravity turn off the “relative motion between wind and rolling surface” any more than using a treadmill?

 

[GreyICE]

There you go. The "see" became part of the link, but you know that.
http://en.wikipedia.org/wiki/Mathematical_maturity

Good. Now you just fail at understanding math and are covering it up with Wikipedia.

 

[ynot]

If the claim of this vehicle is correct, not only should it travel down an incline faster than would be normally expected, but it would also continue moving (forever) along a flat surface at the bottom of the incline.

Also if the incline was long enough the vehicle would exceed terminal velocity.

 

[humber]

Good. Now you just fail at understanding math and are covering it up with Wikipedia.

Considering the subject of the link, I have to take your remarks as being ironic.

 

[Rob Lister]

I don’t see that it matters what energy source powers the vehicle and propeller. It’s okay to replace the wind with a treadmill but not with gravity. Why not?

How does using gravity turn off the “relative motion between wind and rolling surface” any more than using a treadmill?

as asked before by another, why don't you read the thread before repeating questions already asked and answered at least a dozen times.

 

[sol invictus]

I think that considering the treadmill to be a windtunnel will do. That is falsifiable.

They are equivalent up to the fact that they both have a finite length. If you want to test something moving through the air, you need a wind tunnel because on a treadmill it would fall off the end after a short time. If you want to test something that moves at wind speed as in this case, a treadmill is better because in a wind tunnel you quickly hit the end.

Even a small child can understand that (I know, I checked).

A difference that makes no difference. Call it what you will.
The treadmill is not equivalent to a windtunnel.
Show me a text that supports that idea.

You've been shown four now to my knowledge in the last few pages of this, and you keep asking for more. That's amateur-grade trolling.

I have already stated many times, that Einstein has no place in this. Too bad that your colleagues appear not to agree.

They all agree with me - it's just that your understanding of the topic is so poor you evidently can't understand what we're saying.

There you go. The "see" became part of the link, but you know that.
http://en.wikipedia.org/wiki/Mathematical_maturity

Oh, the irony...

 

[sol invictus]

If the claim of this vehicle is correct, not only should it travel down an incline faster than would be normally expected, but it would also continue moving (forever) along a flat surface at the bottom of the incline.

Also if the incline was long enough the vehicle would exceed terminal velocity.

It would have a different terminal velocity than it would if it didn't have a propeller or the propeller wasn't connected to the wheels, yes. So what? If I stick my arms out while falling I have a different terminal velocity than if I don't.

 

[sol invictus]

I don’t see that it matters what energy source powers the vehicle and propeller. It’s okay to replace the wind with a treadmill but not with gravity. Why not?

Because the device is designed to make use of a relative velocity between air and ground, not gravity. Do you really need that explained to you?

Coca-cola contains energy, but if you pour it into your car's gas tank it's not going to work very well.

How does using gravity turn off the “relative motion between wind and rolling surface” any more than using a treadmill?

Read what you wrote again. Does your question make sense even to you?

 

[Myriad]

To go with Modified's demo, here is a simple version of a chain-driven device that goes downchain faster than the chain.

This is to address the incredulity of those asking, "but if the wind pushing on the propeller is what provides power to the cart, how can the propeller also push against the wind at the same time?"

Here, we have the chain pulling the vehicle forward via the lower edge of the inner sprocket, but the vehicle is also pulling itself forward along the chain (that is, pushing backward against the chain).

It's very easy to verify that this works using various easily obtained or constructed real physical models (including a bicycle).

It's also easy to visualize that it works, and how it works, by imagining it in a different reference frame in which the chain is fixed and the track is moving right to left.

So, to be explicit about the analogy:

What provides the energy to move the vehicle forward and rotate the wheels, overcoming friction and drag? The force of the moving chain, acting on the vehicle over a distance.

How does the vehicle move forward faster than the chain? It pushes backward against the chain.

Isn't that a contradiction? Obviously not.

Same answers for the DWFTTW carts:

What provides the energy to move the vehicle forward and rotate the wheels and propeller, overcoming friction and drag? The force of the moving wind, acting on the vehicle over a distance.

How does the vehicle move forward faster than the wind? It pushes air backward against the wind.

Isn't that a contradiction? Obviously not.

Respectfully,
Myriad

 

[sol invictus]

To go with Modified's demo, here is a simple version of a chain-driven device that goes downchain faster than the chain.

Nice!

 

[Modified]

The belt has very low mass. The car is in the usual stationary position, and the belt is 10m long. I am unaware of the car's mass, or the the other car on the road. The energy is stored, so I can make comparisons at my leisure.

The generator is a big load. It brings the car to a stop within 5 meters.

One has charge, and the other not.

"The belt has very low mass" is irrelevant. For the situations to be the same, the treadmill motor must maintain exactly constant belt speed no matter what happens. If that is the case, both cars will stop with respect to their surfaces in the same distance, both generators will behave identically, and the same amount of energy will be stored in both cases.

 

[Modified]

It's very easy to verify that this works using various easily obtained or constructed real physical models (including a bicycle).

I have the sudden image of some of the posters to this thread with bloody hands caught between bicycle chains and sprockets.

 

[ThinAirDesigns]

I don’t see that it matters what energy source powers the vehicle and propeller.

See "gasoline and diesel" example from previous post and then tell me that again.

It’s okay to replace the wind with a treadmill but not with gravity. Why not?

That one's easy:

This device is designed to extract energy from the relative motion between air and solid surface. As long as we can provide the needed motion, it can extract the need energy.

Here is a list of some of the ways we could provide said motion:

A: Put it outside and let the sun create the relative motion

B: Put it in a wind tunnel and let an AC motor provide it.

E: Put it on a treadmill and let an AC provide it.


Now, I know you wish to see a test using gravity, and that could be done as follows:

Rig up a "gravity motor" consisting of a large weight hanging from a cable wrapped around a spool. The output of the spool can power either the fan in "B" above, or the treadmill in "C".

Now you have replaced the "AC power" of the device and replaced it with your desired "gravity power", but we can still perform valid tests on the device.


What you can't do is ignore the *form* of the energy. A soapbox derby car is a great "gravity powered" device, but put it in a wind tunnel and it's not going to have much success racing to the far end of the room against a cardboard box. Even if you power the wind tunnel through "gravity", (see above) you will not improve the performance of the derby car and the box will still win.

As you can see, energy is energy but form matters. Different forms for different devices.

In summary, as long as we provide relative motion between air and surface, the device won't care *how* we power said motion -- petrol, electricity, solar, stored potential energy (gravity), kinetic (flywheel), hydro etc. -- but we must provide it in a form the machine has been designed for.

How does using gravity turn off the “relative motion between wind and rolling surface” any more than using a treadmill?

In your example of taking the device out to the hill, it isn't "gravity" that turns off the relative motion between wind and rolling surface -- it is YOU who have turned it off. You have removed the device from an environment that *has* said motion and placed it in and environment that does not. You can roll that cart down that hill at any speed you wish and you will never create the needed motion between air and rolling surface and thus no energy source.

JB

 

[Modified]

... here is a simple version of a chain-driven device that goes downchain faster than the chain ...

If you replace the center wheel with something like ynot's avatar, it might work as a DWFTTW vehicle. I wonder if such a thing would be practical.

 

[humber]

They are equivalent up to the fact that they both have a finite length. If you want to test something moving through the air, you need a wind tunnel because on a treadmill it would fall off the end after a short time. If you want to test something that moves at wind speed as in this case, a treadmill is better because in a wind tunnel you quickly hit the end.

I notice that as I inquire, the claim seems to weaken.
That is only part of the problem, I have been explicitly told that they are indistinguishable, including the kinetic energy. No satisfactory answer has been supplied.

Even a small child can understand that (I know, I checked).

I am sure he didn't have to correct you too much

You've been shown four now to my knowledge in the last few pages of this, and you keep asking for more. That's amateur-grade trolling.

They all agree with me - it's just that your understanding of the topic is so poor you evidently can't understand what we're saying.

Oh, the irony...

Too late.

You keep telling me that everything is relative, that the car on the belt is equivalent. That is not a small claim, because it contradicts experience and empirical measurement. The concept contained in the physics-bite you quoted is simple enough, but I fail to see why only the parameters of convenience are transferred to the new frame. It is so selective in these parameters, such that it seems fit only for one peculiar situation; always moving at windspeed.

Given that the treadmill itself is a friction controlled force balance, I wonder how any of this can be related to the verification of the proposed design.
The claim of windspeed seems not to be falsifiable. It is at windspeed, or not on the belt.
In practice, there will certainly be turbulence. The actual effect upon the craft not withstanding, there is no evidence that the craft has sufficient torque or momentum to make the position stable, let alone advance.
The vehicle produces only vestigial torque, as a result of opposing torques applied to the same gearbox. It is more than short on length.

 

[Michael C]

The wheels are turning against the ground only because the wind is moving the vehicle relative to the ground. If it wasn’t for the wind the vehicle wouldn’t move relative to the ground at all. When the vehicle reaches the speed of the wind there is no wind speed left to move it relative to the ground any faster. Yet you say that it can accelerate from this speed to go faster than the wind. Where does the energy to do this come from? It can’t come from the wind or the kinetic energy of the vehicle.

As has been said before, the energy comes from the difference in speed between the air and the ground. The vehicle is in contact with the air through the propeller and in contact with the ground through its wheels. The correct gearing between propeller and wheels allows the vehicle to move faster in relation to the ground than the air is doing. The principle is equivalent to what Myriad explains here. The same principle is exemplified by Martin Gardner's spool that rolls backwards: the spool moves faster than the thread that is pulling it. You can make one yourself and try it out.

 

[humber]

"The belt has very low mass" is irrelevant. For the situations to be the same, the treadmill motor must maintain exactly constant belt speed no matter what happens. If that is the case, both cars will stop with respect to their surfaces in the same distance, both generators will behave identically, and the same amount of energy will be stored in both cases.

It would not be possible to transfer the force from the belt to the generator.
without motion. The increased load will increase the contact resistance, so the car will move back with the belt, and therefore accelerated. The car is said to be equivalent when stationary.
Also, the amount of energy absorbed by the vehicle, if it were possible to connect the generator, cannot be said to be dependent upon the mass of the vehicle.

 

[sol invictus]

I notice that as I inquire, the claim seems to weaken.
That is only part of the problem, I have been explicitly told that they are indistinguishable, including the kinetic energy.

Don't lie - it makes it even worse.

You keep telling me that everything is relative, that the car on the belt is equivalent. That is not a small claim, because it contradicts experience and empirical measurement.

Keep repeating falsehoods, they remain false. It is supported by every piece of empirical data ever collected. It's your ignorant and uninformed opinion against every physics book, published and on the web, every physicist, every layperson with even a passing familiarity with physics. Are you really that arrogant?

The concept contained in the physics-bite you quoted is simple enough, but I fail to see why only the parameters of convenience are transferred to the new frame. It is so selective in these parameters, such that it seems fit only for one peculiar situation; always moving at windspeed.

Again you illustrate your utter lack of comprehension. Something on a treadmill is not "always moving at windspeed". It's moving at wind speed if it's at rest with respect to the air. For a treadmill in a closed environment that means at rest with respect to the room/van/planet/whatever the treadmill is sitting on. If it's moving with the treadmill belt, for example, it's equivalent to something at rest on the ground in a steady wind.