Author Topic: Mess with your minds: A wind powered craft going faster than a tail wind speed.  (Read 147626 times)

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Offline IanB

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Unfortunately, if we show you the experiment where the cart in your diagram moves from left to right, you will dispute that too, and will claim that experiment also is being misinterpreted. So it's not worth our time showing you results that you will refuse to believe.

Here you go.

Sorry a piece of paper is not a treadmill but you can build a simple treadmill made of paper.

Prediction fulfilled.

We can be quite clear at this point that we are being trolled.
 

Offline ejeffrey

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Sorry a piece of paper is not a treadmill but you can build a simple treadmill made of paper. The paper will need to be glued in a loop and then use two cylinders with axis fixed to the table.

Oh for fucks sake.  It is exactly the same.  As we all predicted, I did your experiment and you don't care. 

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The reason the piece of paper is not a treadmill is because the paper moves relative to the ground/table where a treadmill will not do that. It is like powering OFF a treadmill and push it under the vehicle.

The vehicle doesn't care care what is going on with the rest of the treadmill except at the point of contact.  The paper is moving exactly the same way as the top surface of a treadmill would.  Whether the end returns to the beginning in a loop or whether the paper is supported by another object that doesn't move is completely irrelevant. 

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The paper will not push against the generator wheels it will just slide under

I am literally looking at it right now and the "generator" wheel has good traction and is not sliding against the paper. It is rolling exactly as it would on a "treadmill".  I can feel that the paper is pushing on the wheels.  If I push too fast, or if I change the gear ratio by using a different pulley it will slip and I can tell the difference.

Listen, despite your obstinance I have tried to take your arguments as in good faith if misguided and frustrating.  This is despite all evidence that you are interested in good faith discussion.  I did your experiment.  It performed exactly as I, and anyone else who can work out freshman physics problems knew would happen, and exactly in accordance with actual mechanics rather that your made up rules that don't exist in any textbook like vector kinetic energy.  Yet you continue to be a troll. Go do it yourself, read a book, take a class, or actually try to calculate something.
 

Offline bdunham7

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Your wheels argument does not reflect the real world environment governing the blackbird AT ALL.

Wait a second!  The wheeled models are demonstrating a principle, they don't have to cover all aspects of the real world operation of the original vehicle in question.  The fact that we can't agree on the basic principle of how forces can be made to operate given two mediums/objects/surfaces/whatever moving relative to one another makes it pointless to continue on further to discuss the full vehicle.  Sort of like if we can't agree on how levers work, there's no point in discussing gears.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline bdunham7

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The vehicle doesn't care care what is going on with the rest of the treadmill except at the point of contact.  The paper is moving exactly the same way as the top surface of a treadmill would.  Whether the end returns to the beginning in a loop or whether the paper is supported by another object that doesn't move is completely irrelevant. 

I proposed just using a block of wood (or paper) earlier as it seemed obvious that it would be providing the exact same moving surface as a treadmill.  However, his concept of energy transfer apparently means that they are different somehow and he did raise the same objection at the time. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline Brumby

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 :palm:  Do I really want to try......

Meh.  Here goes...................


I will follow on from this excellent suggestion...

Simplifying the the problem to take out some of the variables is usually good way to work past such errors.

To begin the conversation, let us take an 'ideal' situation (we can add in losses later for practical results).

Using the treadmill example as used in the Veritasium video, let us use a model with the propeller replaced with a stationary flat disc and there being no drive train from the wheels to the disc.  The air is still and the belt is moving.  We then place this model on the belt so that it rolls along the belt surface, but stays stationary with respect to the floor below (and, hence, stationary with respect to the air).

Proposition:  I maintain that, in an ideal situation where we ignore friction and other losses, the belt will continue to move under the model, but the model will remain in the same position relative to the rest of the environment.

Question: Do you agree?
 

Offline electrodacus

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But two 'sets' of wheels is not an appropriate analogue.

Excluding the propeller and it's interaction with the air is as relevant to this discussion as me saying I want to test a space suit by jumping into a pool with it.  Whatever else it might simulate, such an exercise does not reflect the real world environment.

Your wheels argument does not reflect the real world environment governing the blackbird AT ALL.

Continuing to do so simple underlines your ignorance, stubbornness and, dare I say (what is increasingly difficult to dismiss) your delusion.

In my diagram the generator wheel is exactly the same as the Blackbird back wheels while the motor wheel is the equivalent of the propeller.
This is about the same experiment as the small propeller cart running on a treadmill in Derek's video. The difference is that instead of propeller pushing against air there is a motor wheel pushing against the ground.  This is meant to show that since you have a wheel and a solid there is no way to store energy like it is the case with propeller and air (air is compressible so energy can be stored and that is the reason the vehicle can accelerate forward for some limited amount of time).
So my wheel experiment is exactly the same as blackbird just without the energy storage showing that without energy storage it will not work.
It will be more complex but blackbird type vehicle will also not work under water (driving at the bottom of a river) since water is not compressible. In case of water you will have a propeller but you can not exceed water speed even for a little bit since there is no energy storage to be able to do that.

When I ask how is the vehicle powered when above wind speed in the same exact direction as wind since no air molecule can push the vehicle the answer is it takes energy from the vehicle kinetic energy by breaking the wheel and that energy is then transferred to wind turbine that then accelerates vehicle.
The problem with that explanation is that propeller even if 100% efficient  can not put back the kinetic energy taken from the wheel and have some extra to increase that kinetic energy meaning increase speed.   

Offline Brumby

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Your wheels argument does not reflect the real world environment governing the blackbird AT ALL.

Wait a second!  The wheeled models are demonstrating a principle, they don't have to cover all aspects of the real world operation of the original vehicle in question.  The fact that we can't agree on the basic principle of how forces can be made to operate given two mediums/objects/surfaces/whatever moving relative to one another makes it pointless to continue on further to discuss the full vehicle.  Sort of like if we can't agree on how levers work, there's no point in discussing gears.

I look at the wheels discussion as stepping into over unity thinking.  This is what I see electrodacus trying to do, so that they can dismiss any arguments against their position as "defying the laws of physics".  IMO it as a complete distraction from the heart of the matter.

The only thing I see being gained from this path is to demonstrate they are, in fact, unable to comprehend some basics and even less able to be open minded.
 

Offline Brumby

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OK.

Since you claim to have all the answers with the physics knowledge and maths to support your conclusions, I put this challenge to you....

Take all reasonable references from the blackbird example and generate the maths to describe its operation.  Once you have done that, the run time limitation of such an experiment - which you claim will occur - should naturally fall out of those equations.  Please tell us what that time limitation will be, so that it can be validated experimentally.

The onus on doing this falls on YOU - not everybody else here - as
(1) You are the one claiming what was demonstrated in the Veritasium video is incomplete
and
(2) Those of us who understand the principle as it was presented agree that the demonstration proves the point.

You need to prove your point.
 

Offline Brumby

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Or, you can pull a number of of thin air - just make sure the error bar is included.

For example if you say "5 minutes" and the experiment runs for 10 minutes at higher than wind speed, then don't turn around and say - "Oh, it must be longer".


Pick a number and stick to it.
 

Offline IanB

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The interesting thing about the treadmill experiment is that they missed an opportunity to show something more. They let the model vehicle fly forwards and drive off the end of the treadmill. But if they had simply anchored it in place with some thread, they could have shown it pulling against the thread indefinitely while the treadmill was running.
 

Offline electrodacus

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OK.

Since you claim to have all the answers with the physics knowledge and maths to support your conclusions, I put this challenge to you....

Take all reasonable references from the blackbird example and generate the maths to describe its operation.  Once you have done that, the run time limitation of such an experiment - which you claim will occur - should naturally fall out of those equations.  Please tell us what that time limitation will be, so that it can be validated experimentally.

The onus on doing this falls on YOU - not everybody else here - as
(1) You are the one claiming what was demonstrated in the Veritasium video is incomplete
and
(2) Those of us who understand the principle as it was presented agree that the demonstration proves the point.

You need to prove your point.

I started to do just that but the guy that designed Blackbird is to secretive about the spec. I used some approximations to get the amount of energy needed by blackbird to get to that speed record and was around 6Wh witch is almost nothing but since I used so many approximations all of them will add up to quite a margin of error.
Also wind speed in real world has huge fluctuations that will significantly impact the results like in that record they did I saw the wind speed data and wind fluctuated during the test between 8mph and 15mph while they decided the record was when vehicle got to 28mph and wind speed was lowest in that period thus the 2.8x record but I could say more realistically the record was maybe 2x they just took the best case as they completely ignored energy storage.

There is a much easier proof and that will be to push the blackbird or smaller model to a minimum design speed around 10 to 12mph in a day with no wind and see how vehicle will continue to accelerate way past the push speed.


(1) The explanation is not incomplete is completely incorrect.
(2) The explanation there made absolutely no sense and was wrong mathematically (modified formula to seem like it matches the results).

To disprove the current explanation all I need is a single phrase.
A vehicle power only by the wind driving in the same direction as the wind will be 100% efficient when it is at same speed as the wind (possible only in theory) and from this since no claim can be made that above 100% efficient device was ever proven higher than wind speed is impossible if powered only the the wind and no energy storage.

Seems super intuitive for me as no air particle can get to a vehicle that travels at or above wind speed in same direction so is clear wind can not power this.
The explanation to get around this was that vehicle can extract energy from the difference between the two mediums that is ground and air but that is disprove by my simple wheels only diagram as there treadmill has a different speed than ground and vehicle can not use that energy to move forward from left to right.
So my diagram is complete analog to the treadmill propeller cart since there wind speed is zero and treadmill represents the ground moving under a stationary vehicle.
The only reason propeller version works and wheel version is not working is the energy storage part.
I also made a diagram where I added energy storage to the wheel only version see diagram below where to motor wheel I added a spiral spring (similar to what you will find in a tape measure) and that connects the motor to the wheel.
So when you put the vehicle on the treadmill with generator wheel and the motor wheel on the fixed red box the spring will be compressed to a max level after that the motor wheel will just slip as it is the case for the propeller in air and so when you let go the vehicle will move forward as on top of the insufficient power provided by the generator wheel you have now spring stored energy to add the difference and some extra to move the vehicle from left to right.
So my explanation not only makes sense and breaks no rules but predicts exactly what the test results show


     


Or, you can pull a number of of thin air - just make sure the error bar is included.
For example if you say "5 minutes" and the experiment runs for 10 minutes at higher than wind speed, then don't turn around and say - "Oh, it must be longer".
Pick a number and stick to it.

Is not so much about time is about the distance same as in the above analogy with spiral spring. So if spiral spring is winded say 100x wheel rotation and wheel is say 2m circumference the vehicle can travel for 200m before it will start to slow down. 

So on the treadmill model if you stop the vehicle with hand from going forward the energy storage will be again fully charged up and as long as you keep your hand there you just have a treadmill powered fan.  You will observe the exact same thing with my spring based model and it will be easier to see.
« Last Edit: August 31, 2021, 06:03:46 am by electrodacus »
 

Offline cbutlera

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To disprove the current explanation all I need is a single phrase.
A vehicle power only by the wind driving in the same direction as the wind will be 100% efficient when it is at same speed as the wind (possible only in theory) and from this since no claim can be made that above 100% efficient device was ever proven higher than wind speed is impossible if powered only the the wind and no energy storage.

I think this is at the heart of the problem.  As I understand it, your claim is that if Blackbird is travelling faster than wind speed, then for every joule of its kinetic energy taken by the wheels, only about 70% of that energy is returned by the propeller, so the vehicle will slow down until it is travelling below wind speed, and therefore could not exceed wind speed unaided.

The flaw with this argument is that it is not taking account of frames of reference.  The wheels are extracting kinetic energy from the vehicle in the frame of reference of the ground, so the number of joules extracted by the wheels will match the number of joules of kinetic energy (with respect to the ground) that are lost.  The propeller is imparting kinetic energy to the vehicle in the frame of reference of the air, so the number of joules provided by the propeller (less transmission losses) will match the number of joules of kinetic energy (with respect to the air) that are gained.  The gain in kinetic energy with respect to the ground will be greater than this, and can easily be greater than the amount originally lost, even with the transmission losses.

A thought experiment may help to clarify this.

Imagine that I am a passenger who weighs 70 kg, seated in an aircraft cruising at 200 m/s (about 450 mph).  Suppose now that I stand up and walk forwards along the aisle at 1 m/s (about 2.2 mph) with respect to the aircraft.  In the frame of reference of the aircraft, I have increased my kinetic energy from 0 to 35 joules (mv2/2), and that energy has been provided by my muscles.  However, when the same event is viewed from the frame of reference of the ground, I have increased my speed from 200 m/s to 201 m/s, so I have increased my kinetic energy from 1,400,000 joules to 1,414,035 joules, a difference of 14,035 joules.  No laws of physics are being broken, because the aircraft engines had to work a little harder to maintain the aircraft speed while I was accelerating, so they provided the additional 14,000 joules, to add to the 35 supplied by my muscles.

What you are doing in your explanation of Blackbird, is the equivalent of the ground observer in my thought experiment, thinking that my kinetic energy in his frame of reference can only have increased by 35 joules, because that is how much energy my muscles have generated. So he concludes that if I started with 1,400,000 joules of kinetic energy, I can now only have reached 1,400,035 joules.  Therefore my speed can only have increased to 200.0025 m/s, or 0.0025 m/s with respect to the aircraft.  The ground observer can see that this is obviously wrong, and so there must be a flaw in his reasoning.

Now imagine if Blackbird plus driver weighs 200 kg, and is travelling at 11 m/s, with a 10 m/s tailwind, both with respect to the ground, so Blackbird's speed in the frame of reference of the air is 1 m/s.  With respect to the ground, Blackbird has a kinetic energy of 12,100 joules (mv2/2).  Suppose that the wheels now extract 1,000 joules of this energy, reducing the kinetic energy (with respect to the ground) to 11,100 joules and therefore the ground speed  to 10.54 m/s.  With respect to the air, Blackbird now has a speed of 0.54 m/s and a therefore a kinetic energy of 29 joules. Suppose that the propeller, after losses, manages to add 700 joules to this kinetic energy, increasing it to 729 joules.  The speed with respect to the air will now be 2.7 m/s, so the speed with respect to the ground will be 12.7 m/s.  This is greater than the starting figure of 11 m/s.  So Blackbird can indeed accelerate beyond wind speed without breaking any laws of physics or requiring energy storage.
 

Online Kleinstein

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To disprove the current explanation all I need is a single phrase.
A vehicle power only by the wind driving in the same direction as the wind will be 100% efficient when it is at same speed as the wind (possible only in theory) and from this since no claim can be made that above 100% efficient device was ever proven higher than wind speed is impossible if powered only the the wind and no energy storage.
This is not true, as going at 100% the wind speed with a sail is not 100% efficient, as least not as energy efficency. You actually use no wind-engy at all. So at best you could call it a zero divide by zero to get 100%, but math does not approve this.

If one finds a clever way to harness the wind power even when moving faster than the wind, there is problem using this power to go fater than the wind.
The point is that there is such a clever way.

So your arguing is that it should not be possible to go faster because you assume that it is possible to get power from wind when going as fast as the wind or fast.  One can not assume something from your intuition to prove it. This is not how logic works.


Seems super intuitive for me as no air particle can get to a vehicle that travels at or above wind speed in same direction so is clear wind can not power this.

The explanation to get around this was that vehicle can extract energy from the difference between the two mediums that is ground and air but that is disprove by my simple wheels only diagram as there treadmill has a different speed than ground and vehicle can not use that energy to move forward from left to right.
The effect is a bit complicated, so one should be care ful with the intuition  - this is why the thread title is "Mess with your minds: ..", as this is an effect that may conflict with simple intuition.

You idea with getting energy from the difference in velocity is perfectly correct and the wheeled model on the threadmill is also perfectly fine. However the interpretation of the wheeled vehicle on the treadmill is different.  One can look at it in 2 ways and both ways are perfectly valid.
In any case if you don't find a case covered in the experiment (e.g. circular motion or enery storage) the experiment tell absolutely nothting about it. So it can not prove that this is not possible. It can not even prove that it is impossible to go backwards in time - though we all know we can't.

The first way to look at it as to take the band as the wind. In this picture the vehicle is morving in the direction against the wind. This is also working with real wind, as a windmill driving a vehicle with the windmill aginst the wind.  I don't think there is a controversy about this.

However the same experiment can also be interpretet in a differnt way. One can consider the band of the treadmill as the earth and the outer frame of the treadmill as the moving system. This is a Galilean transformation ( https://en.wikipedia.org/wiki/Galilean_transformation) and a well know method in thought experiments.
In this picture the "wind" goes from left to right and the vehicle going from left to right is this moving faster than the "wind" / moving frame. Just immagine a camera moving with the belt.

So the experiment with the belt diven vehicle proves that it is possible to move faster in the direction of the driving system (e.g. wind).
So the idea of using the speed difference works. The simple wheels only mode proves that it is possible. The ideal wheels only case can also be calculated
and shows that is work.  Going from the wheeled case to the prop drive need the extra technical hurdly to get the prop efficient enough. So this one "needs" the experiment and as shown on the treadmill it works.

The same identification is also used in the treadmill experiment with the prop driven vehincle. The wind inside is the still standing air. Which is the same speed as the frame of the treadmill. The belt represents the ground the vehicle is drivind on.
 

Offline Brumby

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Seems super intuitive for me
In other words, you've already made up your mind.

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as no air particle can get to a vehicle that travels at or above wind speed in same direction so is clear wind can not power this.
It's not just wind.  It's wind plus something else.

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The explanation to get around this was that vehicle can extract energy from the difference between the two mediums that is ground and air
Careful ... you're almost getting it!

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but that is disprove by my simple wheels only diagram
Utter rubbish.  Your "wheels only diagram" is not relevant - never has been - but as you continue to insist it is, you are condemned to never understand correctly.
 

Offline Brumby

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The interesting thing about the treadmill experiment is that they missed an opportunity to show something more. They let the model vehicle fly forwards and drive off the end of the treadmill. But if they had simply anchored it in place with some thread, they could have shown it pulling against the thread indefinitely while the treadmill was running.
Now THAT is a brilliant idea.  Put a tension measurement device on that thread and you could generate data of tension vs speed with alternative gearing and propeller parameters.

You could chart the results and get a very good visual understanding of the behaviour.
 

Offline PlainName

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Quote
Quote

    As you can see, blowing air across the pipe sucks air out of the bag, giving the exact same effect as the chap in your video.

    How does he, and you, know that he is not recreating this situation?

Yes, I can see what you see, and here is the explanation.

Firstly, there is no such thing as "suction". Therefore, the pipe cannot suck air out of the bag. When we talk about suction this is just loose and imprecise terminology.

Gases (like air) consist of particles that are all pushing each other apart and trying to spread out. In the absence of overriding gravitational or accelerating fields, gases will spread out to evenly fill any container. The gas pushing against the walls of the container manifests as pressure, which can be measured. There is no such thing as "suction" because gases are pushing apart and trying to spread out, not pulling together. To have "suction" requires a "pull", which gases do not have.

I cut the quote short to save space - I did read it :)

First, to be absolutely clear, that vacuum cleaner pipe is blowing air. I first used an airline and swarf clearing nozzle, but it was very directional and I didn't want to have the effect of the nozzle (the venturi) intruding so switched to the relatively large and slow output.

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.

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. Kind of like water eroding the sides of a stream. So technically there is low pressure there, but it is caused by the existence of the pipe - if the pipe weren't there then there wouldn't be a created low pressure.

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.
 

Online iMo

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The propeller's blades act as airplane's wings as they have got a so called "airfoil" cross-section.
The blades with a proper angle of attack create a forward lift force because the air pressure above the upper surface of the blade ("suction surface") is lower than the pressure below the lower surface ("pressure surface") of the blade.
The pressure difference is "local" to the blade's surfaces actually (all happens close to the blade's surfaces).

The fact you may see a huge air stream flowing into the intake part of the propeller is because the Earth's atmosphere is "pushing" the surrounding air masses into the place with the local lower pressure (at the blade's suction surface). On the outtake side the local high pressure (at the blade's pressure surface) "pushes" the Earth's air masses to the places with lower pressure.

The propeller's lift force is proportional to the square of blade's velocity (ie. its leading edge rotational speed) and the blade's area (plus other params). The propeller also stores energy as it works as a flywheel.

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

« Last Edit: August 31, 2021, 01:13:35 pm by imo »
Readers discretion is advised..
 

Offline PlainName

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The fact you may see a huge air stream flowing into the intake part of the propeller

Ah-ha! I think I've spotted the problem...

The prop on the bench is blowing towards the camera. That is, the opposite of if the bench were an airplane. Perhaps I am wrong (I checked the angle of the blades and rotational direction, but may have got confused), if half of us assume that and the rest assume the reverse then we'll never find an acceptable explanation :)
 

Offline electrodacus

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The interesting thing about the treadmill experiment is that they missed an opportunity to show something more. They let the model vehicle fly forwards and drive off the end of the treadmill. But if they had simply anchored it in place with some thread, they could have shown it pulling against the thread indefinitely while the treadmill was running.
Now THAT is a brilliant idea.  Put a tension measurement device on that thread and you could generate data of tension vs speed with alternative gearing and propeller parameters.

You could chart the results and get a very good visual understanding of the behaviour.

Look at my model that has the spiral spring to understand why this is not a proof of anything.  The anchored vehicle will be nothing more than a treadmill powered fan.  As soon as you keep the vehicle in place you are fully charging the energy storage so if you keep the vehicle in place you can do that indefinitely since the stored energy is not being used (is better to see that in my model).
 

Offline electrodacus

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Now imagine if Blackbird plus driver weighs 200 kg, and is travelling at 11 m/s, with a 10 m/s tailwind, both with respect to the ground, so Blackbird's speed in the frame of reference of the air is 1 m/s.  With respect to the ground, Blackbird has a kinetic energy of 12,100 joules (mv2/2).  Suppose that the wheels now extract 1,000 joules of this energy, reducing the kinetic energy (with respect to the ground) to 11,100 joules and therefore the ground speed  to 10.54 m/s.  With respect to the air, Blackbird now has a speed of 0.54 m/s and a therefore a kinetic energy of 29 joules. Suppose that the propeller, after losses, manages to add 700 joules to this kinetic energy, increasing it to 729 joules.  The speed with respect to the air will now be 2.7 m/s, so the speed with respect to the ground will be 12.7 m/s.  This is greater than the starting figure of 11 m/s.  So Blackbird can indeed accelerate beyond wind speed without breaking any laws of physics or requiring energy storage.

Maybe it is a good idea to solve a problem.
So 200kg vehicle traveling at 11m/s with 10m/s tailwind.
Kinetic energy of the vehicle is indeed 12100Ws and that is referenced to ground.
So you say we extract 1000 joules (1000Ws) from vehicle wheel reducing vehicle kinetic energy and obviously speed.
Now say total efficiency from wheel to propeller is 70% that will mean you put back just 700 joules (700Ws) in to vehicle meaning the vehicle now has lower kinetic energy and speed than we started with.

You can think about the air as a parallel lane that is like a treadmill surface and that travels at 10m/s so vehicle can decide to use the 1000Ws extracted from the wheel on the ground and either push against the ground with another wheel at 90% efficiency is 900Ws or use another less efficient wheel 70% efficient 700Ws and push against the parallel lane than itself travels at 10m/s relative to the ground.
So since vehicle has now 10.54m/s that parallel lane look from vehicle perspective as traveling backwards (opposite to vehicle direction of travel) at 0.54m/s
If you decide to go with the 90% efficient wheel on the same road / ground the vehicle travels you recover 90% of the lost kinetic energy so now vehicle is at 12000Ws a bit less than we started.
If you decide to use the 70% efficient wheel t push against the parallel lane witch is like a treadmill moving at 10m/s so relative to vehicle that will look like opposite to travel direction at 0.54m/s
Keep in mind that not the entire vehicle will move on that lane just one of the traction wheels will be touching that lane and vehicle will need to be pushed against that lane but on the ground road.

So your mistake is that you decided the entire vehicle moved in to air same as the entire vehicle will have moved on to that other lane. I think with that treadmill lane you can see the consequences of such action (vehicle changing lanes instead of just using one wheel to push against that lane).

Offline electrodacus

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Quote
as no air particle can get to a vehicle that travels at or above wind speed in same direction so is clear wind can not power this.
It's not just wind.  It's wind plus something else.

There is no wind energy that vehicle can use when vehicle is above wind speed in same exact direction. And what else is there ? The vehicle is supposed to be powered only by wind.  There is of course energy storage but you can not admit to that.


Quote
but that is disprove by my simple wheels only diagram
Utter rubbish.  Your "wheels only diagram" is not relevant - never has been - but as you continue to insist it is, you are condemned to never understand correctly.

Please point out where my wheel only diagram deviates from the propeller cart shown on treadmill.
The propeller pushes against air at zero speed while the vehicle in my diagram pushes against a zero speed solid (red box).
There is absolutely no difference and they are perfectly equivalent but you do not like to think they are equivalent as you will have a harder time explaining how the vehicle in my diagram is incapable to move from left to right without the energy storage (spiral spring).
I can take out the spring to show vehicle can not work without it but I can not take the compress-ability of the air unless I replace air with water (much harder to setup such an experiment).

Offline bdunham7

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So your mistake is that you decided the entire vehicle moved in to air same as the entire vehicle will have moved on to that other lane.

And your mistake, among many many others, is that you don't see that this distinction doesn't matter.  The vehicle is simultaneously rolling on the road and 'in the air'.  You made a similar error when you claim that the surface of a treadmill is somehow different than the surface of a moving piece of paper.  It's ridiculous and I don't think there's much point in discussing it further when your intuition misguides you so badly and you refuse to actually use math in a meaningful way.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline electrodacus

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    • electrodacus

This is not true, as going at 100% the wind speed with a sail is not 100% efficient, as least not as energy efficency. You actually use no wind-engy at all. So at best you could call it a zero divide by zero to get 100%, but math does not approve this.

Say you have a vehicle with a sail raveling on ground and the wheels have zero friction. Will eventually the vehicle travel at same speed as the wind ? If not why ?
Is there any way to get more energy from the wind when vehicle and air molecules travels at the exact same speed ? If yes then how.

Yes at wind speed the sail vehicle will not accelerate at all since it is already traveling at constant speed and has the same speed relative to ground as the air molecules (wind) thus 100% of the available wind energy is used and thus 100% efficient wind power vehicle.
A real vehicle will never get to same speed as the wind so it will be less than 100% efficient.
This also includes a propeller based vehicle that is also way below 100% efficient. The only propriety of the propeller air combination that allows vehicle to exceed wind speed for a limited amount of time is energy storage.

Offline electrodacus

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    • electrodacus
And your mistake, among many many others, is that you don't see that this distinction doesn't matter.  The vehicle is simultaneously rolling on the road and 'in the air'.  You made a similar error when you claim that the surface of a treadmill is somehow different than the surface of a moving piece of paper.  It's ridiculous and I don't think there's much point in discussing it further when your intuition misguides you so badly and you refuse to actually use math in a meaningful way.

The vehicle is rolling on the ground that is a fact and at no point the blackbird or the treadmill prototype even left the ground.  Please read my entire reply where I give the example with the parallel lane. Think what is till mean for vehicle to move to that other lane (that will be equivalent with vehicle moving in air only no longer rolling on the ground).

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.

Offline bdunham7

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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?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 


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