How Does DDWFTTW Work and What Are Its Key Principles?

[kmarinas86]

You're just all over the place. How about if we take a single one of your ideas and discuss it until we reach some understanding.

You talked about counter-rotating props. That alone will do you no good in the attempt to go DDWFTTW. Yes, putting one prop in one air-mass and the other in a separate air-mass that moves relative to the first could potentially be used to make a vehicle go DDWFTTW relative to one of those air-masses.

But in reality, you wouldn't use two props, but rather a prop and a turbine.

Of course you could answer this by bringing up railroad cars, balloons, and the slingshot effect. Or we could try and discuss this point until we reach some understanding.

What about a submarine with counter-rotating props? (i.e. DDSFTTS or Directly DownStream Faster Than The Stream)

 

[spork]

What about a submarine with counter-rotating props? (i.e. DDSFTTS or Directly DownStream Faster Than The Stream)

What about a helium powered baby buggy that's catapulted into space and uses the moon as a slingshot? Or a nuclear fusion reactor that harnesses wind power and rectifies that using crystals?

 

[jduffy77]

What about a submarine with counter-rotating props? (i.e. DDSFTTS or Directly DownStream Faster Than The Stream)

Are these props powered only by the stream?

 

[kmarinas86]

Are these props powered only by the stream?

If the stream is uniform, you would first have to drop the submarine in and then activate the propellers. This is nothing more than the submarine equivalent of Spork's treadmill. This acts as a break slowing the water behind it, so it is slower as it passes over (water flow, unlike the treadmill conveyor, is not uniform). You then already have a velocity difference. The crane which lowered the submarine can be divorced, and is no longer necessary.

So I can make one correction here. Some object is needed to hold it in place at first, but after that, it should not matter.
So either:
The amount of work required is similar to that required to apply brake discs - it's not very much at all - but that's only if the external actor holding the submarine is fixed (by superior inertia)... or
The external actor is not fixed (due to inferior inertia), in which case, significant work must be done to put the submarine there in the first place.

Otherwise, if you make the submarine lead the front of the water flow (i.e. if the water ahead is stagnant), then you shouldn't need either kind of actor.

So, yes, you would have to have some kind of velocity difference.
Perhaps in the case of an external conservative force such as gravity, we might have an exception to that though. I don't know yet. But if gravity itself is due to velocity differences (GR seems to imply this), then maybe that is not an exception either.

 

[jduffy77]

If the stream is uniform, you would first have to drop the submarine in and then activate the propellers. This is nothing more than the submarine equivalent of Spork's treadmill. This acts as a break slowing the water behind it, so it is slower as it passes over (water flow, unlike the treadmill conveyor, is not uniform). You then already have a velocity difference. The crane which lowered the submarine can be divorced, and is no longer necessary.

So I can make one correction here. Some object is needed to hold it in place at first, but after that, it should not matter.

Congratulations, you have designed a PM machine.

 

[A.T.]

What about a submarine with counter-rotating props?

What is this obsession with counter rotation about? You can use two rotors (prop & tubine) in two different media (that move relative to each other) to move relative to one of the media faster than the other medium. But the rotation direction of the rotors is irrelevant.

 

[spork]

We're not even going to talk about my nuclear powered baby buggy with crystal rectification that catapults around the moon?

 

[A.T.]

If the stream is uniform, you would first have to drop the submarine in and then activate the propellers. This is nothing more than the submarine equivalent of Spork's treadmill. This acts as a break slowing the water behind it, so it is slower as it passes over (water flow, unlike the treadmill conveyor, is not uniform). You then already have a velocity difference.

It cannot be powered by the velocity difference, that it creates itself. This would be perpetual motion.

The DDWFTTW cart is powered by the velocity difference that already exists (free stream air vs. surface) and not by the one it creates (free stream air vs. prop wash air).

 

[kmarinas86]

Congratulations, you have designed a PM machine.

Or we simply have energy transferring from the water to the submarine.
Sails work above water. There's no reason why an adapted sail couldn't do the same thing for a submarine. Sails can even work in space. Nothing about air is special or magical.

 

[kmarinas86]

It cannot be powered by the velocity difference, that it creates itself. This would be perpetual motion.

The DDWFTTW cart is powered by the velocity difference that already exists (free stream air vs. surface) and not by the one it creates (free stream air vs. prop wash air).

The velocity difference is already there. Propellers can be used to trade one difference (crane and treadmill) for another difference (air in front and air in back) at an entropy loss. During that transition, yes, you would need at least 3 (or at least 4 in the treadmill case) mediums and not two. I guess you can call that "leverage" in a sense. Increases of entropy occur due to frictional losses. These frictional losses are not recovered by the DDWFTTW. Other machines can only recover some of it, but they never get all of it.

 

[jduffy77]

Or we simply have energy transferring from the water to the submarine.
Sails work above water. There's no reason why an adapted sail couldn't do the same thing for a submarine. Sails can even work in space. Nothing about air is special or magical.

Agreed and one consistent feature of all sails is they can not drive something faster than the media which is pushing them without leverage.

 

[spork]

Or we simply have energy transferring from the water to the submarine.

Which means the submarine could approach, or even reach, the speed of the water - but nothing more.

Sails work above water.

With sails you have two choices.
- You can stick a sail up in the air and let the air push you. In this way you can approach the speed of the air.
- You can stick a sail up in the air, and stick another wing down in the water. Now you're in business. You can exploit the energy available at that interface. That's because the water has energy relative to the air - and vice versa.

In your submarine example, you're just sitting still under water. The water has no energy relative to itself.

 

[A.T.]

Or we simply have energy transferring from the water to the submarine. Sails work above water.

Sail craft use two foils (sail & keel) in two media (air & water).

There's no reason why an adapted sail couldn't do the same thing for a submarine.

A submarine has only contact to one medium.

 

[rcgldr]

Or we simply have energy transferring from the water to the submarine. Sails work above water. There's no reason why an adapted sail couldn't do the same thing for a submarine.

An example of a DSFFTTS (down stream faster than the stream) water vehicle is a Brennan Torpedo. The wires could be attached to non-moving posts instead of take up reels, and the torpedo released downstream so it travels DDSFTTS. In this case, comparing to DDWFTTW cart, the wires are the "ground" and the water is the "air".

http://en.wikipedia.org/wiki/Brennan_torpedo

 

[kmarinas86]

If all that is so, I still wonder how you get the "slingshot effect" to work with only two bodies.

I mean, if you had an ensemble of such slingshot effects at the particle level, you are basically allowed to increase the velocity difference.

This happens with a probe and a planet.

You slow down the orbit of the planet and speed up the probe. That results in a transfer of energy.

But there is no third medium to interact with in this case (assuming no ether).

This can happen multiple times, still without a third medium, and still using the same two objects.

The orbital "center" could be the center of mass of those two bodies (I would guess that this arrangement would not be stable and would disintegrate or collapse). In any case, there is potential energy involved... so.

At microscopic level, you still have this going on between attracting particles.

I guess you only invoke the third object when you try to explain the velocity difference in the first place. Or maybe in place of the third object, you can consider already present rotations (which only brings the problem back even further).

 

[jduffy77]

An example of a DSFFTTS (down stream faster than the stream) water vehicle is a Brennan Torpedo. The wires could be attached to non-moving posts instead of take up reels, and the torpedo released downstream so it travels DSFTTS. In this case, comparing to DDWFTTW cart, the wires are the "ground" and the water is the "air".

http://en.wikipedia.org/wiki/Brennan_torpedo

Yes, with the most important point, (for kmarinas) being that the wires are necessary.

 

[rcgldr]

"slingshot effect" ... You slow down the orbit of the planet and speed up the probe. That results in a transfer of energy. This can happen multiple times, still without a third medium, and still using the same two objects.

There would need to be a another planet (or sun) for the probe to change it's path to result in the probe re-intercepting the original planet at a later time. Otherwise it's just a 2 body system, and depending on the intial state, it either ends up with both objects in elliptical orbits, or if escape velocity is achieved or exceeded, with both objects moving away from each other.

 

[spork]

If all that is so, I still wonder how you get the "slingshot effect" to work with only two bodies.
...
You slow down the orbit of the planet and speed up the probe. That results in a transfer of energy.

Correct.

But there is no third medium to interact with in this case (assuming no ether).

But there is something else - there is the coordinate system in which you're measuring all velocities. You talk about the planet slowing down and the satellite speeding up. So you're clearly not using either of them as the basis of your coordinate system. You're presumably using the Earth or Sun as the basis of the coordinate system in which the satellite increases it's velocity.

Both energy and velocity are entirely frame dependent. Depending on the frame chosen, we could say the satellite sped up and got energy from the planet, or that it slowed down and gave energy to the planet.

This can happen multiple times, still without a third medium, and still using the same two objects.

I'm not so sure about that. Perhaps it could do so if that planet was orbiting another body at exactly the right period so that satellite intercepts its orbit at the right time and place on subsequent passes, but that does involve a third body.

 

[periboob]

May a noob post a simple thought experiment that may convince a few doubters?

Think: spokes of a tall wheel, half way down each spoke is a sail that folds up on the reverse. Sail moves at Vw, hub goes 2*Vw

Fits in a tweet. I humbly suggest that this may convince a greater percentage of the public than equations of torque, propellers and fluid dynamics.

 

[A.T.]

Think: spokes of a tall wheel, half way down each spoke is a sail that folds up on the reverse. Sail moves at Vw, hub goes 2*Vw

https://www.youtube.com/watch?v=Ufk6HVWdSzE

 

[spork]

Think: spokes of a tall wheel, half way down each spoke is a sail that folds up on the reverse. Sail moves at Vw, hub goes 2*Vw

Agreed. I've used that and similar examples many times. I encourage people to grab a spoke on their bike below the hub and push it forward - or pull a yo-yo along a table with the string exiting below the hub.

I humbly suggest that this may convince a greater percentage of the public than equations of torque, propellers and fluid dynamics.

I fear that you drastically underestimate the challenge of convincing those that prefer not to be convinced.

 

[periboob]

...
I fear that you drastically underestimate the challenge of convincing those that prefer not to be convinced.

I am rarely anymore surprised by the stubbornness and stupidity of my fellow beings. In younger days I was equally guilty, though I think I have out grown most of it. It just seems that the solution to this cute little problem, which has little practical value, and no money on the table, is particular difficult to see.

But I am told, if you only communicate with people who agree with you, you learn nothing.

 

[spork]

It just seems that the solution to this cute little problem, which has little practical value, and no money on the table, is particular difficult to see.

I certainly didn't think it up (and it turns out I was not the first to think it up in any case) for any practical value. But it turns out that it could potentially have a good deal of practical value. You can harvest a great deal more wind energy with a moving propeller or turbine than you can with a stationary setup.

 

[GiTS]

Ddwfttw

Direct Down Wind Faster Than The Wind.

First, I am not refuting that it is true. I've seen the videos and believe.
Second, this is about the treadmill test with no apparent wind.
Third, I am looking for an explanation of how this works from someone who understands DDWFTTW.

Link to video


As I understand it, the propeller gets energy from the wheels and departs this energy to the air to produce thrust. What I don't understand is, doesn't the energy have to come from the wheels in the form of drag? So If the propeller was geared up more and more to generate more and more energy, then the effect should be higher and higher drag on the wheels.

So if I wanted to calculate the drag on the wheels at any given moment it would be equal to the thrust of the propeller right?

I have seen lots of diagrams depicting velocities but nothing depicting energy. I just want to understand this and I figured by now people have a good grasp on what's happening.

Thank you,
GiTS

 

[willem2]

The energy you can get from the wheels can't be highter than the energy you can put into the propellor, because of conservation of energy, but this isn't true of the forces on the wheels and on the propellor, because Power is force * speed.

Power gained from the wheels is F_wheel * v_road, and power put into the propellor F_prop * v_air.

because v_road = v_air + v_wind > v_air (with a tail wind). It's possible to have F_wheel * v_road <= F_prop * v_air, together with F_wheel > F_prop.

 

[A.T.]

So if I wanted to calculate the drag on the wheels at any given moment it would be equal to the thrust of the propeller right?

No. Thrust and drag are forces. There is no such thing as "Conservation of Force" in physics. Every lever can output more force, than you put in. But at a lower speed than the input force.

Here, the thrust is greater than the wheel drag, because it is applied at a lower speed. The air moves slower relative to the cart, than the ground.

I have seen lots of diagrams depicting velocities but nothing depicting energy. I just want to understand this and I figured by now people have a good grasp on what's happening.

Energy balance here is best done in terms of power, which is energy / time (instantaneous energy transmission rate). You will find the power analysis in this papers:

http://www.aapt.org/physicsteam/2013/upload/E3-1-7-solutions.pdf (page 11)

http://orbit.dtu.dk/fedora/objects/orbit:55484/datastreams/file_3748519/content (section 2.3)

http://www.boatdesign.net/forums/attachments/propulsion/28167d1231128492-ddwfttw-directly-downwind-faster-than-wind-ddw2.pdf

http://projects.m-qp-m.us/donkeypus...aster-Than-The-Wind-The-Ancient-Interface.pdf

 

[GiTS]

I came across this youtube video.


It explains what you both are explaining. The key to the contraption working seems to be the angle of attack of the prop blades creates for force in the forward direction than the downward direction. If the angle of attack was steeper, the vehicle would go backwards into the wind.

 

[rcgldr]

Second, this is about the treadmill test with no apparent wind.

All "wind powered" devices rely on a difference in speed between the air and the ground. In the case of an observer on the ground watching the treadmill and the ddwfttw mini-cart, the treadmill surface is moving at some speed, while the ambient air is not moving. In this case the ultimate source of energy is the motor driving the treadmill belt, which in turn drives the wheels, which in turn drive the propelller at a greater force but at a lower (air) speed. The induced wash aft of the propeller will be less than the speed of the treadmill, so as mentioned in post #2, the output force is greater, but the output power is less than the input power due to the reduced output speed.

If the observer were moving at the same speed as the upper surface of the treadmill (perhaps a very long treadmill), or if this was done outdoors with an actual tailwind, then to this observer, the treadmill or Earth's surface would not be moving (relative to the observer), but there would be a tailwind (relative to the observer). In this case, the source of the power is the slowing down of the relative wind (relative to the observer).

 

[rcgldr]

I came across this youtube video.


It explains what you both are explaining. The key to the contraption working seems to be the angle of attack of the prop blades creates for force in the forward direction than the downward direction. If the angle of attack was steeper, the vehicle would go backwards into the wind.

If the effective prop speed (effective pitch x angular velocity) is less than the ground speed, it's a downwind cart. If the effective prop speed is greater than the ground speed, it's an upwind cart. The closer the speed ratio is to 1.0, the faster the cart, if the cart is efficient enough.

If the effective prop speed is negative, it's a directly downwind slower than the wind cart, where the prop is acting as a turbine driving the wheels as opposed to a directly downwind faster than the wind cart, where the wheels drive the propeller.

If the effective prop speed is greater than twice the wind speed, it's a directly upwind slower than the wind cart. For an upwind cart, the propeller always acts as a turbine and drives the wheels.

Not mentioned in the video is that given the same overall efficiency, the upwind cart moves 1x wind speed (relative to ground) slower than the downwind cart. If the downwind cart can move at 3x wind speed, the upwind cart can move at 2x wind speed. This ignores efficiency issues such as the reduced energy related to rolling resistance times a slower ground speed for the upwind cart.

 

[A.T.]

The key to the contraption working seems to be the angle of attack of the prop blades creates for force in the forward direction than the downward direction. If the angle of attack was steeper, the vehicle would go backwards into the wind.

Yes, it becomes an upwind turbine. And if you make the pitch negative it becomes a downwind turbine. But to go downwind faster than the wind, you must set it in between, as a downwind propeller. All the cases are shown here:

http://oi54.tinypic.com/2gv0kew.jpg

You can see the cart as a gearbox, working between two large objects in relative motion. Here some analogies:

https://www.youtube.com/watch?v=E7vcQcIaWSQ

https://www.youtube.com/watch?v=k-trDF8Yldc

https://www.youtube.com/watch?v=pw_B2MnMqZs

And here how the gear ratio A affects the velocity ratio V/W. To go DDWFTTW you must set 0 < A < 1

For the wind-cart at the bottom the pitch of the rotor P is part of the gear ratio. Unlike the rigid models the wind-cart will never achieve exactly the speed dictated by the gear ratio, because the rotor has slippage. But as efficiency is increased it can get arbitrarily close to that limit.

 

[GiTS]

Assuming there are no losses to friction, what's the maximum velocity ratio (wind-cart : wind)?

 

[rcgldr]

Assuming there are no losses to friction, what's the maximum velocity ratio (wind-cart : wind)?

The maximum velocity ratio depends on the efficiency of the cart. If there are no losses, then the maximum velocity is infinite.

ws = wind speed
gs = ground speed
ps = prop speed (the speed of the air flow through the prop)

gs = 1 / (1 - (ps/gs))

ps/gs  gs

   -1  1/2 ws
 -1/2  2/3 ws
    0    1 ws
  1/2    2 ws
  2/3    3 ws
  3/4    4 ws
  7/8    8 ws
    1    ∞
  9/8   -8 ws
  5/4   -4 ws
  4/3   -3 ws
  3/2   -2 ws
  2/1   -1 ws
  5/2 -2/3 ws
  3/1 -1/2 ws

 

[CWatters]

I came across this youtube video.


It explains what you both are explaining. The key to the contraption working seems to be the angle of attack of the prop blades ...

Indeed. Prop pitch (eg on an aircraft) is analogous to gear ratio. Fine pitch prop = fast acceleration/low top speed. Coarse pitch prop = low acceleration/high tops speed.

The magic is all in getting the right effective pitch for the air prop vs the water prop or wheel gearing.

 

[A.T.]

Assuming there are no losses to friction, what's the maximum velocity ratio (wind-cart : wind)?

What is the maximum gear ratio a loss less gearbox can have? There is no hard limit on the ratio. The only hard limit is the speed of light on the actual speed. But long before that becomes an issue in the real world, efficiency and material strength will limit it.

 

[rcgldr]

Indeed. Prop pitch (eg on an aircraft) is analogous to gear ratio. Fine pitch prop = fast acceleration/low top speed. Coarse pitch prop = low acceleration/high tops speed. The magic is all in getting the right effective pitch for the air prop vs the water prop or wheel gearing.

Prop pitch has reduced effect at relative low speeds (the prop become inefficient due to excessive relative angle of attack which is affected by aircraft speed relative to the air). Simple thrust calculators for static thrust (the thrust produced when an aircraft is not moving relative to the air) don't even bother inputing pitch as a parameter.

 

[A.T.]

I'm assuming it uses the momentum of the rotors to get across the dead zone of no wind speed.

No stored momentum is used. The rotor is turned by the wheels with fixed transmission ratio. It cannot slow down if the wheels are accelerating.

The acceleration is due to the wheels. It doesn't matter which direction the wind is blowing, it's(the wind) just used to move the object.

The wheels are braking, while the rotor provides the forward thrust. Turning the rotor with the relative headwind to turn the wheels would accelerate the true wind. instead of slowing it down to extract energy

 

[Suraj M]

No, the wheels are braking, while the rotor provides the forward thrust. Turning the rotor with the relative headwind to turn the wheels would accelerate the true wind. instead of slowing it down to extract energy

I'm sorry but i don't have the patience to read 235 posts to understand it, could you please tell me how the object moves in the video in the other thread! And i don't understand what's going on here, any link or video that would explain the total working? , thank you.

 

[A.T.]

any link or video that would explain the total working?

It's like this spool, just with the airmass instead of the paper strip:



It terms of sailing, it's like circular tacking:

 

[Suraj M]

I understood the 1st video, but the 2nd doesn't say why it goes faster than the wind.

 

[A.T.]

I understood the 1st video,

That's the key, because it is a more general explanation of the concept.

but the 2nd doesn't say why it goes faster than the wind.

The 2nd one is for sailors, who already understand how a sailboat works. The situation shown there is explained here:

 

[Suraj M]

Okay, i think i got a rough idea, thank you!

 

[Tom_K]

This is amazing! But all I have seen is analogies and somewhat fuzzy explanations. This is a math and physics forum. Is there no mathematics and sound physics theory behind this thing?

 

[A.T.]

Is there no mathematics and sound physics theory behind this thing?

See links here:
https://www.physicsforums.com/threads/questions-about-ddwfttw.562993/page-12#post-4547512

 

[Tom_K]

Thank you for the links. I am having a look now and will have more to say later. For now I can say that I find it all surprisingly unconvincing.
What I mean is, the one paper cited appears to be an internal house organ and as such doesn’t carry much weight. Another seems to be an unpublished calculation (posted on a boating forum). I will need some time to review it.
The only one that seems to have any credibility is the test question on a physics exam and I would have answered it differently than the answer given.
I may be tilting at windmills here, but for now I am skeptical.
These two statements (from the test question) look contradictory to me:
1) All of the power used to move the car comes from the wind.
2) Power should always be produced by the force corresponding to the larger relative velocity.
Then it goes on to say the wheels are producing the power, not the wind?
The wheels are developing or transforming the wind power, but the source of all power must be the wind. By that reasoning, it is the force corresponding to the lower relative velocity, not the greater that is producing the power. No?
Then there is the very unconvincing statement that with "sufficiently low energy loss, any speed is possible"!

That statement can be used to claim perpetual motion! All that is needed for ant PM scheme to work is "sufficiently low losses".
Forgive my skepticism, is there better evidence that this is for real? Has there been a peer review or any independent laboratory confirmation (wind tunnel test)?

 

[A.T.]

I am having a look now and will have more to say later.

Good. Please note that your informal / semantical questions have most likely already been addressed somewhere in this thread, one of the threads linked below under "Similar discussions" or in hundreds similar threads on the WWW.

 

[A.T.]

These two statements (from the test question) look contradictory to me:
1) All of the power used to move the car comes from the wind.
2) Power should always be produced by the force corresponding to the larger relative velocity.

In case you haven't already figured it out on your own:

1) Is a general statement about the energy source: velocity difference between air and ground (true wind).

2) Is explained best by Figure 1 in Gaunaa's paper (right side labels):

Since P = F * v you can generate lots of power with a small braking force at the fast moving surface with the wheels. And because the air moves slower relative to the cart than the surface, you need less power to generate equal or greater thrust, than the braking force at the wheels.

 

[rcgldr]

These two statements (from the test question) look contradictory to me:
1) All of the power used to move the car comes from the wind.
2) Power should always be produced by the force corresponding to the larger relative velocity.

The difference is the frame of reference.

1) - From a ground based frame of reference, all of the power comes from reducing the speed (kinetic energy) of a portion of the wind.

2) - From the vehicles frame of reference, the source of power comes from the faster moving medium (surface or air), which is then effectively geared down to produce more force at a lower speed upon the slower moving medium (air or surface), and at a lower rate of power output (due to losses) than power input.

Both 1) and 2) have to be true in order for these vehicles to work. For example, in the case of the DDWFTTW vehicle, the thrust from the propeller has to slow down a portion of the wind wrt (with respect to) ground. Say the wind speed is 10 mph wrt ground, and the DDWFTTW vehicle is traveling at 30 mph wrt ground, then the thrust speed wrt vehicle has to be greater than 20 mph in order to slow down a portion of the wind wrt ground.

 

[Tom_K]

That doesn’t sound right. Generally speaking, a propeller operating in a tailwind is less efficient than when operating in still air or into a relative headwind. At cruise speeds an airplane propeller produces very little thrust so is very inefficient and it has the benefit of an internal combustion engine.
You seem to be saying the propeller on the car is producing thrust above wind speed yet all of the power to produce thrust is coming from the wind. Or are you saying the surface moving under the wheels is somehow transferring energy to the car, like a belt drive turning the wheels?
I don’t see the logic here at all!
By my reasoning, once the car is traveling at the same speed as the wind there is no longer any wind force acting on the car since there is no longer any Δ Velocity. Force = mass x acceleration which is mass x Δ Velocity. No Δ Velocity, no Force.
I can see you saying there is Δ Velocity at the propeller because it is spinning but that is a circular argument. The car is moving so the propeller is spinning and the propeller is spinning so the car is moving! Every perpetual motion aficionado will believe you, but I don’t!

 

[A.T.]

Generally speaking, a propeller operating in a tailwind is less efficient than when operating in still air or into a relative headwind.

In DDWFTTW the propeller is operating in a relative headwind. But the relative headwind is less than it would be without the true tailwind. This improves the achievable propeller performance. You need less power to generate the same force on something that moves slower relative to you. This follows directly from:

P = F * v

You seem to be saying the propeller on the car is producing thrust above wind speed

Yes

yet all of the power to produce thrust is coming from the wind.

Yes (wind = velocity difference between surface and air, which is being reduced by the car)

Or are you saying the surface moving under the wheels is somehow transferring energy to the car, like a belt drive turning the wheels?

Yes, but note that some energy statements are frame dependent.

By my reasoning, once the car is traveling at the same speed as the wind there is no longer any wind force acting on the car since there is no longer any Δ Velocity.

Propellers can produce thrust in this condition, so your reasoning fails right here.

I can see you saying there is Δ Velocity at the propeller because it is spinning but that is a circular argument. The car is moving so the propeller is spinning and the propeller is spinning so the car is moving!

Feedback loops are circular, but they do work and can amplify certain quantities (here velocity). This is where your logic fails again: You cannot analyze feedback loops using a linear cause-effect chain.

Every perpetual motion aficionado will believe you, but I don’t!

PM ideas often involve isolated feedback loops, that work without any energy input. This one is not isolated at all, as it continuously removes kinetic energy from the surface-air system, by reducing the velocity difference between the two.

 

[Tom_K]

Or are you saying the surface moving under the wheels is somehow transferring energy to the car, like a belt drive turning the wheels?

Yes, but note that some energy statements are frame dependent..

You really are saying that energy is transferred from the ground to the wheels? Fascinating! In what frame of reference is that happening? What is the source of this amazing energy from the ground? Energy is frame dependent, but forces are not. Please describe the forces involved in this supposed energy transfer from the ground to the wheels. Can I roll a wheel on the ground and extract this energy?

Propellers can produce thrust in this condition, so your reasoning fails right here.


Feedback loops are circular, but they do work and can amplify certain quantities (here velocity). This is where your logic fails again: You cannot analyze feedback loops using a linear cause-effect chain.

No, nothing has failed here except your strawman arguments against something I did not say.