Author Topic: Mess with your minds: A wind powered craft going faster than a tail wind speed.  (Read 147620 times)

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Offline electrodacus

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Yes please test a treadmill to see the difference from moving piece of paper.  The difference is huge you just can not see that without doing the experiment.

What is your theory or explanation as to why they are different?

The simplest way I can explain is that paper rolls under the wheels while the treadmill will push the vehicle back. As the paper moves relative to ground while the treadmill is fixed to the ground.
I probably mentioned this before so if you can not see the difference between them you will just need to make a test. The treadmill can be just a simple paper loop rolling on two cylinders.
Is like having a powered treadmill vs one that is not powered but instead pushed towards the vehicle.

Offline Alex Eisenhut

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The treadmill belt moves relative to ground, what on Earth you smoking? BC bud?

The part of the treadmill that stays fixed to the ground is equivalent to the guy's feet in the paper sheet video.  :-//
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Offline electrodacus

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The treadmill belt moves relative to ground, what on Earth you smoking? BC bud?

The part of the treadmill that stays fixed to the ground is equivalent to the guy's feet in the paper sheet video.  :-//

I know it may look non intuitive to you but please think more about this or do a test.
You think that a powered treadmill is the same as a powered off treadmill that you push under vehicle ?
The vehicle needs to advance on the treadmill so if you push the treadmill under the vehicle that is not the same as a rotating treadmill.
I think this is a large point of misunderstanding so please anyone do a test as shown in my diagram and do not replace a treadmill with a flat piece of paper as they are not equivalent even if that seems the same thing to you.
I think for many of you this point needs to be clarified. So I will not answer other questions until this point is clear to everyone.
If someone understand the difference between a treadmill and that dragged piece of paper please help explain in a better way than I do. 

Offline bdunham7

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I probably mentioned this before so if you can not see the difference between them you will just need to make a test. The treadmill can be just a simple paper loop rolling on two cylinders.
Is like having a powered treadmill vs one that is not powered but instead pushed towards the vehicle.

OK, so let's say I'm inquisitive and I want to built the treadmill, but in stages to see where this transformation takes place.  I test the car at each stage as follows.

So I start with a raised platform with a frame around the edge so that all you or the car can see is a flat, moving surface surrounded by the frame.

First, I just put a piece of a paper in there and move it towards the car.

2nd, I put a roller on the front and wrap a long piece of paper around it so that I can move the paper by just pulling the bottom part backwards.

3rd I glue my paper in a loop, but just keep pulling the bottom part away from the car continuously to keep the top surface moving towards the car at a constant speed.

4th I add a back roller and loop the paper tightly around both rollers and again keep pulling the bottom part backward to keep the top surface moving.

5th I put a crank on the back roller and keep the paper moving at a constant speed .

So ejeffrey's video shows the first step--just the paper--and the car obviously moves from left to right, as we all expected.  According to your assertion, if we arrive at step 5 here, the car will NOT move from left to right.  So, if you can, tell us at what step the car will stop behaving as it did in the video and start behaving as you say it will in the end?  And since all 5 steps involve a surface that is moving in the same direction at the same rate, what allows you or the car to tell the difference?
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Offline bdunham7

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I know it may look non intuitive to you but please think more about this or do a test.

It's not about intuition, it's about logic and math.  In each case the two surfaces are moving at the same rate in the same direction.  What other characteristic could that surface have that would change how it interacts with the car?
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Offline electrodacus

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I know it may look non intuitive to you but please think more about this or do a test.

It's not about intuition, it's about logic and math.  In each case the two surfaces are moving at the same rate in the same direction.  What other characteristic could that surface have that would change how it interacts with the car?

The paper moves relative to the table while the treadmill is not moving relative to the table.
The vehicle rolls on to the paper while the vehicle will be pushed back by the treadmill.
Not sure how to better describe this but if something else come to mind I will make sure to let you know.
Question will be: If you will understand the large difference between the sliding paper and a treadmill will this do anything to convince you that  blackbird uses stored energy to exceed wind speed ?

Offline Alex Eisenhut

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I am but a humble amputated brain ape, but what on Earth do you mean by "The paper moves relative to the table while the treadmill is not moving relative to the table"?

Obviously the paper is the belt in the treadmill? Would you prefer there to be another sheet of paper between the table and the first sheet, moving in the opposite direction?
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Offline bdunham7

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The paper moves relative to the table while the treadmill is not moving relative to the table.

Does the top surface of the treadmill not move relative to the table?  If not, at what point in the 5 steps I outlined above does this change occur?
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Offline electrodacus

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I am but a humble amputated brain ape, but what on Earth do you mean by "The paper moves relative to the table while the treadmill is not moving relative to the table"?

Obviously the paper is the belt in the treadmill? Would you prefer there to be another sheet of paper between the table and the first sheet, moving in the opposite direction?

I'm sorry I do not have the ability to properly explain this but that dragged paper will not have the same effect on vehicle as a treadmill.
My analogy was if you power OFF the treadmill so the belt of the treadmill is not moving and then push the treadmill towards the vehicle then that will be analog to the dragged paper. But the fixed powered ON treadmill will not be the same with powered OFF treadmill that is pushed.

What actually happens is that in case of my diagram the treadmill represents the road moving underneath the generator wheels while vehicle is stationary the vehicle and road where switched and then the ground can represent the wind at same speed a vehicle speed so zero.
Now once you power off the treadmill so no rotation (basically no longer a treadmill)  and you drag that from right to left then this becomes the wind (input energy source) and the ground is the road so this will be a vehicle powered from the wind (moving paper or turned OFF treadmill) traveling in the opposite direction to the wind direction at lower speed.
So basically everything is completely changed when you decide to replace a treadmill with a piece of paper. 

Offline IanB

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Now, I accept that the terms being used are incorrect, in that 'suction' is perhaps confusing in a literal sense. However, from my point of view there is high pressure across the top of that pipe - if a sheet of something was placed there, at right angles to the flow, it would be pushed away from the hose outlet. Now, you might say that this is merely air flowing, but if it is flowing then it is being pushed against something. Either the sheet of whatever or just ambient air - there is a restriction against which the flowing air is being pushed, and that must surely be increasing the pressure. A fan is taking air from one side and pushing it to the other despite there already being air there, so the pressure must increase.
There is a directional component when you measure the pressure of a flowing air stream. If you measure the pressure head-on, you will see a higher pressure than if you measure the pressure at right angles. The flowing air has mass and momentum, so when you measure the pressure head-on it "pushes" against the measurement device and increases the effective pressure. The following Wikipedia article talks about this:

https://en.wikipedia.org/wiki/Pitot_tube

This is the reason that low pressure air can flow out of the vacuum cleaner against the higher pressure of the surrounding atmosphere. The static pressure may be lower than the surroundings, but the total pressure (including the effect of velocity and kinetic energy) is higher.

The key equation is this one:
$$p_t = p_s + \frac{\rho u^2}{2}$$
Along a stream tube, \$p_t\$ doesn't change, so whenever \$u\$ (velocity) goes up, \$p_s\$ goes down.

Of course, when the air passes through the compressor or blower, then energy is added to the system, so here \$p_t\$ is increased. But a typical blower changes the air velocity much more than the air pressure.

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The way I understood there being an area of low pressure, which the air in the pipe will flow to fill, is because the air moving across the end of the pipe drags molecules of air at the pipe entrance along with the flow.
This is a real effect, but it is relevant only in special kinds of vacuum pump. It is not applicable here.

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So I am suggesting that the chap is measuring an artifact caused by the act of measuring. Instead of the pipe, what if he put, say, a flap of paper in the airstream. Would that bend toward the blades? I doubt it. But if he placed the paper edge-on, would it be pulled into the stream? It likely would (if it could retain it's shape) but only because the surface of the paper is causing the low pressure that pulls it in.
The paper experiment is a good one to do. Get two sheets of paper and hold them in a V shape around the air jet from the vacuum nozzle (blow the air into the V shape between the parallel sheets of paper). You will see the two sheets of paper get squeezed tightly together. The harder you blow, the more tightly the paper will get squeezed. This is another way of demonstrating there is a vacuum in the space between the two sheets of paper. The dragging of air molecules cannot apply here, as the paper does not have any free molecules to get dragged.
 

Offline Alex Eisenhut

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I'm sorry I do not have the ability to properly explain this but that dragged paper will not have the same effect on vehicle as a treadmill.


How does the wheel know the difference in your diagram that clearly shows the arrow on the belt? How is it different if it's just the paper that moves and the person pulling the paper is the "mill"?

Seems like a simple question. I don't care if you don't have the ability to "properly" explain it, just try improperly explaining.
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Offline electrodacus

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How does the wheel know the difference in your diagram that clearly shows the arrow on the belt? How is it different if it's just the paper that moves and the person pulling the paper is the "mill"?

Seems like a simple question. I don't care if you don't have the ability to "properly" explain it, just try improperly explaining.

I just did improperly explained it.
The treadmill can push the vehicle back the paper moves under the vehicle so just rolls under.
For the treadmill version in order for vehicle to advance from left to right the G wheel will need to spin clockwise faster than the treadmill belt but that is impossible since the G wheel is not powered by anything other than the treadmill belt and in order to get power from the G wheel you will need to break the G wheel so vehicle will be moved backwards more than M wheel can push back.
So if the wheel slips on the treadmill so it still rotates clockwise but slower than treadmill the vehicle will be moved by the treadmill from right to left
On the paper version if the G wheel slips but still rotates a bit clockwise the vehicle advances forward when you look at the entire vehicle relative to the table but that will not happen for the vehicle on the treadmill as the treadmill pushes the entire vehicle back relative to table/ground.

I will want you to try and explain this to others once you will see the result of the experiment.

Another alternative explanation (not sure if is any better for you) is to imagine the treadmill as a wheel with axis fixed to the ground and under the vehicle G wheel so same as a treadmill but a circle instead of an ellipse.
Now imagine this wheel turns anticlockwise and maybe you can imagine that vehicle has no chance of moving forward powered only by this as vehicle will be pushed back since any power you try to take from that G front wheel even if all transferred to M wheel it will barely be able to stay in the same place.
Now imagine the same wheel but instead or rotating anticlockwise it is locked no rotation at all and no longer fixed to ground but is just pushed back (right to left).
Was this wheel instead of treadmill more helpful ?

Offline bdunham7

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Was this wheel instead of treadmill more helpful ?

Not really.  Please address my 5-step question.  You don't have explain why, just at what stage in those 5 steps it goes from working as we say it does to working the way you say.
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Offline electrodacus

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Was this wheel instead of treadmill more helpful ?

Not really.  Please address my 5-step question.  You don't have explain why, just at what stage in those 5 steps it goes from working as we say it does to working the way you say.

It will start working from step 2

Online Kleinstein

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For the treadmill version in order for vehicle to advance from left to right the G wheel will need to spin clockwise faster than the treadmill belt but that is impossible since the G wheel is not powered by anything other than the treadmill belt and in order to get power from the G wheel you will need to break the G wheel so vehicle will be moved backwards more than M wheel can push back.
The red parts are wrong, get the 2 points right, and you should be allright.
1) When the vehicle moves left to right, the wheel will spin faster  (unless it slips). One does not have to power the wheel, it is enough to move the vehicle.   After all this is the G wheel and not the motor. So the generator does not have to move the vehicle, it just follows where the motor says is should go.

2) the M wheel can move the vehicle to the right, if it can provide enough force to do so. The force needed is the breaking force of the motor. This force not power power that needs to be overcome. The lower the speed of the vehicle relative to the fixed frame, the more force the motor can provide from a given power.

The final point is, that for the case that the motor drives to the right and the generator brakes, the power available to the generator is higher than the power needed by the motor.  If you don't believe: take the simple example of the motor in stop (no power needed) and the generator is still driven by the treadmill speed. So there is plenty of power to spare and slowly move to the right.
Do the math and you see that it even works at higher speed if the efficiency is good (e.g. > 50%).
« Last Edit: August 31, 2021, 08:40:54 pm by Kleinstein »
 

Offline electrodacus

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The red parts are wrong, get the 2 points right, and you should be allright.
1) When the vehicle moves left to right, the wheel will spin faster  (unless it slips). One does not have to power the wheel, it is enough to move the vehicle.   After all this is the G wheel and not the motor. So the generator does not have to more the vehicle, it just follows where the motor says is should go.

2) the M wheel can more the vehicle to the right, if it can provide enough force to do so. The force needed is the breaking force of the motor. This force not power power that needs to be overcome. The lower the speed of the vehicle relative to the fixed frame, the more force the motor can provide from a given power.

The final point is, that for the case that the motor drives to the right and the generator brakes, the power available to the generator is higher than the power needed by the motor.  If you don't believe: take the simple example of the motor in stop (no power needed) and the generator is still driven by the treadmill speed. So there is plenty of power to spare and slowly move to the right.
Do the math and you see that it even works at higher speed if the efficiency is good (e.g. > 50%).

No the points are not wrong.
1)What do you imagine will make the G wheel spin faster than the treadmill ?  The particular vehicle in my diagram will never move from left to right (I'm referring to that one without the spiral spring).
You are probably forgetting that motor wheel is powered only by the G wheel so power at the motor will be lower than power generated by G wheel.
Maybe you do not understand what generating a certain power at G wheel means (it means wheel will need to be breaking) and breaking G wheel means the treadmill will push the vehicle backwards and then M wheel can not push the vehicle back since it has only a bit less power than it was generated by G wheel. This is conservation of energy and was never broken.

2) It can not move the vehicle from left to right as it has less power than generated by G.  If you want to compare forces only then you need to consider a gear ratio of 1:1.  If you do not have the 1:1 gear ratio then you will need to consider the gear ratio and not only the force as force at the wheel acts against the chain / gear box and not directly against the vehicle.


That final point you try to make is valid for the dragged paper discuses by others here and not a treadmill. So that paper dragged from right to left is not the same with a treadmill.

So I think we first need to settle the fact that treadmill is not the same with a dragged surface. Understanding this may be the key to understanding the rest of the problem.
 

Online Kleinstein

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The vehicle will only see the upper side of the belt of the treadmill and it can not tell appart if the is a belt, or a piece of paper or rubber pulled by a human.
It is just stupid to insist on a difference between the paper and belt of the treadmill. For the sake of the discussion they are the same: a surface that is moved to the left.

------
for your response of the 2 simple points:
1) The vehicle moving to the right is the assumption you introduce in the sentence. So for the point 1) you assume it moves to the right - no matter what.
If the vehicle moves to the right, the wheel has to rotate faster - that is the geometriy and condition for the wheel no to slip. That is kind of the definition of a wheel. The treadmil and the motor combined drive the wheel - some of the power comes from the treadmill, that in the simple picture has plenty of power.  Using the conservation of energy is a tricky argument in this comtext, as the treadmill constantly provides power. The conservation of energy does not prohibit the movement to the right - that is kind of handled in the 2.nd point.

2) The motor does not need more power than the generator to move the vehicle. It only has to have the same (or more if there is friction)  force.
 The force is power divided by speed. So if you keep the speed low enough there is always enough force.
 (knowing the difference between power and force is really important here)
 Gear ratio is another way to express the speed of the motor. The gear ratio of 1:1 is the critical case that does not work -  so don't use it. But a gear ration so that the motor side is rotating slower (e.g. half the speed) does, and it provides enough force to do this against the generator pulling in the other direction.

If the final point works for the dragged paper, it also work for the treadmil, as the 2 cases are exactly the same. How should the vehicle tell the difference ?
« Last Edit: August 31, 2021, 09:23:47 pm by Kleinstein »
 

Offline electrodacus

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The vehicle will only see the upper side of the belt of the treadmill and it can not tell appart if the is a belt, or a piece of paper or rubber pulled by a human.
It is just stupid to insist on a difference between the paper and belt of the treadmill. For the sake of the discussion they are the same: a surface that is moved to the left.
That is your wrong intuition that they will be the same but they are not even close.



for your response of the 2 simple points:
1) The vehicle moving to the right is the assumption you introduce in the sentence. So for the point 1) you assume it moves to the right - no matter what.
If the vehicle moves to the right, the wheel has to rotate faster - that is the geometriy and condition for the wheel no to slip. That is kind of the definition of a wheel. The treadmil and the motor combined drive the wheel - some of the power comes from the treadmill, that in the simple picture has plenty of power.  Using the conservation of energy is a tricky argument in this comtext, as the treadmill constantly provides power. The conservation of energy does not prohibit the movement to the right - that is kind of handled in the 2.nd point.

2) The motor does not have the same power as the generator to more the vehicle. It only has to have the same (or more if there is friction)  force.
 The force is power divided by speed. So if you keep the speed low enough there is always enough force.
 (knowing the difference between power and force is really important here)
 Gear ratio is another way to express the speed of the motor. The gear ratio of 1:1 is the critical case that does not work -  so don't use it. But a gear ration so that the motor side is rotating slower (e.g. half the speed) does, and it provides enough force to do this against the generator pulling in the other direction.

If the final point works for the dragged paper, it also work for the treadmil, as the 2 cases are exactly the same. How should the vehicle tell the difference ?

This depends so much on you understanding that treadmill is something different that it will not make sense for me to try and answer them until you can understand that treadmill can not be replaced by a dragged piece of paper.

Offline Alex Eisenhut

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Are you telling me a person standing on a stopped treadmill is going to have to run in another direction when the treadmill starts, than someone who has the rug under them pulled in the same direction?

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Offline electrodacus

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Are you telling me a person standing on a stopped treadmill is going to have to run in another direction when the treadmill starts, than someone who has the rug under them pulled in the same direction?

A person on a treadmill is not between two separate mediums at the same time unless it has a foot on treadmill and one on the ground.
Not sure if this sort of analogy is good for anything.
A person on a treadmill that is turned on is not powered by the treadmill it will need to use his own calories just to stay on the treadmill.
But if you turn OFF the treadmill and instead someone pushes the treadmill then person on treadmill has no need to use any of his calories.
This at least shows that a running treadmill is not the same with a powered OFF treadmill that is pushed backwards.

Offline Alex Eisenhut

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A person on a treadmill is not between two separate mediums at the same time unless it has a foot on treadmill and one on the ground.

That's not what I asked. Which way will you fall or run if a treadmill starts, or a carpet is pulled under you? Then we can add your separate mediums and being between dimensions or whatever.

You're in Time Cube territory now. You're not even making sense in your own problem space.
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Offline electrodacus

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A person on a treadmill is not between two separate mediums at the same time unless it has a foot on treadmill and one on the ground.

That's not what I asked. Which way will you fall or run if a treadmill starts, or a carpet is pulled under you? Then we can add your separate mediums and being between dimensions or whatever.

You're in Time Cube territory now. You're not even making sense in your own problem space.

Make a test. That is my best advice if you think there is no difference between a treadmill and a turned OFF and dragged treadmill.
It is not even a small difference it is a huge difference.
The vehicle in my diagram can not move left to right on a running treadmill but it can easily do so on a turned OFF treadmill that is pushed towards the vehicle with what the piece of paper in that video and others represents and is also the same with a flipped vehicle where motor wheel is in front on the generator wheel. 



Let me ask you this.  If you turn a bicycle upside-down so seat touches the ground and you rotate one of the wheels. Is the wheel moving relative to the ground ? Hope you will say no.  Then if you have a non rotating wheel on the bicycle but instead you push the bicycle (still upside-down). Is now the wheel moving relative to the ground ?
Can you consider this two cases exactly the same ?
« Last Edit: August 31, 2021, 10:17:24 pm by electrodacus »
 

Offline Alex Eisenhut

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Which way will you run when a treadmill starts? Which way will you run if someone pulls a rug from under you in the same direction?

Stop avoiding the question, stop making up weird scenarios, stop prevaricating.

Stick to the question as presented.
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Offline electrodacus

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Which way will you run when a treadmill starts? Which way will you run if someone pulls a rug from under you in the same direction?

Stop avoiding the question, stop making up weird scenarios, stop prevaricating.

Stick to the question as presented.

The rug is pulled at constant speed and I'm siting on it and I can just relax. On a treadmill at constant speed I still need to burn plenty of calories.

There are no weird scenarios is just you (most of you) not able to understand there is a big difference between a treadmill and that rug.
You just need to do your own experiment and even if you do not understand why it happens you will see the big difference.
So just build the experiment as it is in my diagram using a treadmill and and do not make modifications and/or replacements.
My diagram is perfect analogy to the treadmill propeller cart experiment and shows that without energy storage the vehicle can not move from left to right.

Offline IanB

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The rug is pulled at constant speed and I'm siting on it and I can just relax. On a treadmill at constant speed I still need to burn plenty of calories.
Here is someone standing on a treadmill, feeling very relaxed, and not burning any calories:

https://youtu.be/GvfF4TeXz7U

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There are no weird scenarios is just you (most of you) (all of us) not able to understand there is a big difference between a treadmill and that rug.
There, fixed that for you.
 


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