Down wind faster than the wind

[H'ethetheth]

...I have earlier described the treadmills act, but perhaps this is clearer.

Replace the propeller with a tangential impeller, (like a waterwheel
with end-plates, such that it cannot generate lateral forces).
If you spin such a device in the hand, you will feel the opposing drag of the air.

Put this on the cart, and spin the wheel clockwise. The 'prop' will rotate
clockwise, and you will feel the opposing drag.
Turn the wheel CCW, and you will also feel opposing drag.
The cart is trapped in this force 'well'. I cannot so eadily move forward or backwards, so its natural tendency when on the belt, is to stay where it is.
The prop and the drive shaft oppose each other, resulting in an absolute torque that is the drag of the prop at that particular angular velocity, and a differential (driving) force of next to zero.
( Assuming there is adequate friction with the belt to transmit that absolute torque)

The real propeller is not symmetrical with respect to drag, though it is turned against its natural bias, so that drag will be dominant. The 'thrust' component will be smaller, as the propeller is not designed to spin in that direction,...

Stop right there!! This is not the case! The propeller is mounted exactly as it is designed to spin. The whole thing wouldn't function half as well if not. This is also exactly the unintuitive part (at least to me).

It is true that at low speeds (relative to the wind speed), the local angle of attack of the propeller blades is very high, but it is this drag that actually aids the acceleration to wind speed. As it accelerates the torque on the propeller from the wheels provides thrust, which is a positive feedback to the acceleration. This acceleration only disappears at some point above wind speed. It is essential that the prop spins in the direction it was designed to spin.

ETA:
To make things clear, H'ethethet, I do not say that vehicles cannot travel faster than the wind, but:
1. A direct propulsion device like this cart, no
2. I have not seem proof that it can, therefore I stick to 1.
3. The treadmill says nothing about the carts capacities, other than the wheels spin

Well, I hope that the two paragraphs above will give you some pause to think. You are working from an incorrect hypothesis of how all the parts interact, and working from an incorrect hypothesis will generally not yield correct results. If you have questions about this, do ask.

I had a lot more, but it's a bit pointless if we're not discussing the same machine.
Two things though:

I apologize for appealing to my authority. I admit that that is bad form. However, you have to realize that I approached this cart from a skeptical perspective as well as you do, mostly because of the "over-unity" tag. I subsequently figured out that I had made a false supposition about the working principles of the cart. When I realised this, it still took me about an hour to figure out how it actually does work. Now, I do not pretend to be infallible, but the operating principles aren't that complicated; they are just unintuitive.

Secondly, you are right that I am aware of the importance of validation and testing. However, I think that you are really showing spork c.s. too little respect for all of the experiments they have done to demonstrate just how the cart works. Their films are what made me realize I had made false suppositions about the cart.

 

[humber]

The wind is blowing at a speed of 10 kph. The cart is moving downwind along the road at a speed of 12 kph relative to the road. What is the "absolute magnitude" of the cart's velocity?

The velocity that is common to both the wind and the cart. The ground. Answer: 12kph ( assuming it can travel faster that the wind).
So how exactly does sitting in the cart and saying "my velocity is 2kmh"
help in a in any way? ( Except in support of a trivial hypothesis.)

X-----------------Y
|
|
|
A

There is a differential between X and Y, but a common-mode between A-X
and A-Y. Can a say anything about that common-mode by looking at X-Y only ?

This is the point, Micheal-C,
The wind is real, not a vector, but a dynamic force that cannot be equated to a simple static vector on a page. That's the major error:
concluding all things are related by velocity alone.

Do you remember the house and ball. Moving one towards the other is the same as the converse?

I am then to imagine the ball suspended in "space", as the earth spins under it and hits it. Please tell me how I might do that without giving the method away (remember equality must remain stable) and if not, how it would not look like it had been thrown?

 

[Dan O.]

Not at all. Skeptics I like. People that know for sure 100% that it can't be done, and call us fools, I could do without.

Some people may need a little help with the math and physics. By breaking it down into simple steps, we can help them solve the problem and show them how to find the truth in similar problems.

Anyone that finds the correct answer and still calls you a fool would be know as a liar and a troll.

Then there will always be the humbers in the world. They don't believe in physics, won't do the math and still call you a fool. They need to simply be ignored since they have nothing to contribute.

 

[humber]

Some people may need a little help with the math and physics. By breaking it down into simple steps, we can help them solve the problem and show them how to find the truth in similar problems.

Anyone that finds the correct answer and still calls you a fool would be know as a liar and a troll.

Then there will always be the humbers in the world. They don't believe in physics, won't do the math and still call you a fool. They need to simply be ignored since they have nothing to contribute.

Shoot down my analysis of the treadmill, then. Yes, there are Humbers, who will not simply take your word for it. Taunting me with maths- barefoot physicist!

As H'ethetheth suggests, reversing the propeller would change the level of torque, but not the drive, because that will always cancel while the cart is stable on the treadmill. As I have said, this is not a model of the real cart, no matter what its shortcomings, or how the cart actually works.

 

[spork]

Yes, there are Humbers....

HOLY CRAP! It's reproduced.

 

[H'ethetheth]

... or how the cart actually works.

Now, that's not entirely true: If the cart works such that it does what we think it does, it does matter how it works. In fact, you could say that that's what we are discussing here.

Silliness aside, you're assuming a conclusion here, where others with equal credibility have reached the opposite conlusion. In stead of simply stating that it cannot work you could do the math, refine the mathematical model to meet your standards of rigour, or do the test.

How would you go about disproving that this cart works?

 

[humber]

Now, that's not entirely true: If the cart works such that it does what we think it does, it does matter how it works. In fact, you could say that that's what we are discussing here.

Agreed. I wrote " As I have said, this is not a model of the real cart, no matter what its shortcomings, or how the cart actually works".
That is about the treadmill not the cart. Denial of one, is not necessarily denial of the other.
I have not commented too much on the cart itself, because it is so vaguebut since you ask, I will post something.
The treadmill is otherwise. I can simply look at it as a problem "How do you make a prop cart climb a treadmill". OK, I see how this one does it. I have several solutions. One uses no wheels. It's just a problem. I see no connection with windspeed travel.

Silliness aside, you're assuming a conclusion here, where others with equal credibility have reached the opposite conlusion. In stead of simply stating that it cannot work you could do the math, refine the mathematical model to meet your standards of rigour, or do the test.

Not adverse to silliness, but its intent, and the fact/silliness ratio matters.
Before maths can be applied, the idea must be logically sound.
Computers can aid the mathematically disinclined, but not with the analysis itself. That is perhaps the "original" bit.

Science is called a discipline for good reason. The treadmill provides no useful data, not only for me, but for you. That's the bit that you don't seem to appreciate. I look at it objectively and ask "What is it telling me?" A think that it equates to one binary bit.

Try it yourself. Can you make the device break its balance and stay on the treadmill?

I don't want to fool myself. I don't want a bogus and insecure result. That is worthless, like cheating at sport. You will not find an analysis I know to be false. Mistaken? Why not? You have to say why, in a reasoned way. Remember, you have the device.

Here it is what makes the difference;
Do you have reliably recorded data that shows the cart traveling faster than the wind? I mean controlled and measured data?

You are an engineer, you know the rules. Would it get by a peer-review? If those answers are yes, then please show me.

You know that there is not even the crudest data available, so analysis is not possible. But, wait. You say that you are certain that it works? Where is your data? How much torque is required? Power?
If you don't have answers to even those questions then how can you be sure?

ETA:
If we are talking about assuming the conclusion, doesn't testing the cart at windspeed rather do that? Getting there IS the problem.

 

[humber]

HOLY CRAP! It's reproduced.

Yes, I know that I am outnumbered. No problem.

I read your piece on Mr Bauer. Is this a prop cart?

 

[H'ethetheth]

Agreed. I wrote " As I have said, this is not a model of the real cart, no matter what its shortcomings, or how the cart actually works".
That is about the treadmill not the cart. Denial of one, is not necessarily denial of the other.
I have not commented too much on the cart itself, because it is so vaguebut since you ask, I will post something.
The treadmill is otherwise. I can simply look at it as a problem "How do you make a prop cart climb a treadmill". OK, I see how this one does it. I have several solutions. One uses no wheels. It's just a problem. I see no connection with windspeed travel.



Not adverse to silliness, but its intent, and the fact/silliness ratio matters.
Before maths can be applied, the idea must be logically sound.
Computers can aid the mathematically disinclined, but not with the analysis itself. That is perhaps the "original" bit.

Science is called a discipline for good reason. The treadmill provides no useful data, not only for me, but for you. That's the bit that you don't seem to appreciate. I look at it objectively and ask "What is it telling me?" A think that it equates to one binary bit.

Try it yourself. Can you make the device break its balance and stay on the treadmill?

I don't want to fool myself. I don't want a bogus and insecure result. That is worthless, like cheating at sport. You will not find an analysis I know to be false. Mistaken? Why not? You have to say why, in a reasoned way. Remember, you have the device.

Here it is what makes the difference;
Do you have reliably recorded data that shows the cart traveling faster than the wind? I mean controlled and measured data?

You are an engineer, you know the rules. Would it get by a peer-review? If those answers are yes, then please show me.

You know that there is not even the crudest data available, so analysis is not possible. But, wait. You say that you are certain that it works? Where is your data? How much torque is required? Power?
If you don't have answers to even those questions then how can you be sure?

ETA:
If we are talking about assuming the conclusion, doesn't testing the cart at windspeed rather do that? Getting there IS the problem.

Okay, I'm going out on a limb here, and say that if I make a thorough mathematical model of this cart, the treadmill experiment would pass peer review as an experimental verification of the model. Some reviewers may start complaining that boundary layer effects are not accounted for sufficiently, and may need to be persuaded by a test outside or in a large wind tunnel. However, this is of course assuming that this would count as an interesting scientific discovery. I think it might have been in the 18th or 19th century.

I'll try making a detailed model of this thing, but I am rather busy.

 

[Michael C]

The wind is blowing at a speed of 10 kph. The cart is moving downwind along the road at a speed of 12 kph relative to the road. What is the "absolute magnitude" of the cart's velocity?

The velocity that is common to both the wind and the cart. The ground. Answer: 12kph ( assuming it can travel faster that the wind).

It's clear that we can't go on discussing if we don't agree on a basic principle of physics. For the last time:

There is no such thing as absolute velocity.
This is one of the rules behind our present-day knowledge of physics. It is not just "theoretical", or a simplification. It describes the real world. If you wish to contest this, you'll be against Newton, Galileo, Einstein and all mainstream physics of the last three centuries. Of course this is an argument from authority, but that's one hell of a lot of authority that you're up against. So I suggest you consider the possibility that you might be wrong.

 

[Michael C]

I read your piece on Mr Bauer. Is this a prop cart?

It's a prop cart. Here is Andrew Bauer with the cart.

 

[spork]

I'll try making a detailed model of this thing, but I am rather busy.

Detailed models have been made and published. If you want to do it for the heck of it, that's great. But I can assure you the math will never sway humber. I can post writeups that have been done if you like.

 

[spork]

There is no such thing as absolute velocity.

And this is just one reason I wouldn't waste too much energy developing the mathematical analysis for humber. Why spend hours on something humber will dismiss without consideration or understanding?

If you wish to contest this, you'll be against Newton, Galileo, Einstein and all mainstream physics of the last three centuries. Of course this is an argument from authority...

It may be an argument from authority, but an interesting exercise is to try and devise any real-world experiment that can distinguish between inertial frames. When you fail at that long enough, you'd probably start to get the idea that maybe they're equivalent.

This is a bit like proving that perpetual motion is impossible by trying to invent a perpetual motion machine and failing enough times. It doesn't prove it, but it probably gets you thinking.

 

[Michael C]

Spork, do you have any details about the construction of Bauer's cart? From the photo I get the impression that the prop has variable pitch.

 

[humber]

It's clear that we can't go on discussing if we don't agree on a basic principle of physics. For the last time:

There is no such thing as absolute velocity.This is one of the rules behind our present-day knowledge of physics. It is not just "theoretical", or a simplification. It describes the real world. If you wish to contest this, you'll be against Newton, Galileo, Einstein and all mainstream physics of the last three centuries.
Of course this is an argument from authority, but that's one hell of a lot of authority that you're up against. So I suggest you consider the possibility that you might be wrong.

What makes you think that I am doing that? No, I am saying that the application is wrong. The treadmill is wrong, not science.

Are you aware, that it is common practice to make this sort of thing?
Isn't the treadmill, as used for its intended purposes, an application of the same principle? I can see the advertising "Now with added equivalency". Making more sense now?

I can only assume that you have taken some interpretation of what I wrote that is not intended, or have one of "equivalence" that we of not share. The actual definition is not so glibly stated, but in this simple context it is clear, but it is a difference that makes no difference.
It has nothing to do with the denial of absolute velocity. In fact, it makes no difference either way.

If all views are "equivalent" then this can be re-stated as;

"It makes no difference where you look from".

I agree, so why is it being done here? In support of a tiny windblown craft, no less?

A vector on a piece of paper is not a wind. The reason that the treadmill is a failure, is not because the cart has been set to zero, and the road moves underneath, but that it has not been properly implemented, so you have a "numerically equivalent" situation, but not a "physically equivalent" situation.
To raise equivalence as a factor, you would first have to deny its effect. Einstein's world is derigour The exception is to even mention it.

So, I agree. Forget it. It makes no difference.

This will give you more time to tell me how the treadmill is physically equivalent to being in the wind. I say that it is not even close, and why the treadmill says anything about how the cart will get there?
And you didn't answer the other questions. Thanks for the Bauer photo.

 

[humber]

Detailed models have been made and published. If you want to do it for the heck of it, that's great. But I can assure you the math will never sway humber. I can post writeups that have been done if you like.

Do you have reliably recorded data that shows the cart traveling faster than the wind? I mean controlled and measured data?

You are an engineer, you know the rules. Would it get by a peer-review?

Yes or no?

 

[humber]

And this is just one reason I wouldn't waste too much energy developing the mathematical analysis for humber. Why spend hours on something humber will dismiss without consideration or understanding?

There is a difference between 10-digit precision and laxity. You have not presented anything worthy of consideration.

It may be an argument from authority, but an interesting exercise is to try and devise any real-world experiment that can distinguish between inertial frames. When you fail at that long enough, you'd probably start to get the idea that maybe they're equivalent.

This is a bit like proving that perpetual motion is impossible by trying to invent a perpetual motion machine and failing enough times. It doesn't prove it, but it probably gets you thinking.

When you do travel fast enough, then we can make the appropriate adjustments. Otherwise, I will stick to the idea that I can deny or agree with the principle, and not have it make any difference to your cart's performance.

 

[Michael C]

What makes you think that I am doing that?

The answer you gave to my question:

The wind is blowing at a speed of 10 kph. The cart is moving downwind along the road at a speed of 12 kph relative to the road. What is the "absolute magnitude" of the cart's velocity?

The velocity that is common to both the wind and the cart. The ground. Answer: 12kph ( assuming it can travel faster that the wind).

Your answer makes no sense: there is no velocity "common to both the wind and the cart". The correct answer to my question is the "absolute magnitude" of the cart's velocity is a meaningless concept, since there is no such thing as absolute velocity. And yes, a ball hitting a spaceship is the same thing as a spaceship hitting a ball.

There is simply no point in continuing discussing the DDWFTTW cart if we can't even agree on this sort of basic principle.

 

[ynot]

Doesn’t that negate the claim that the cart (which includes the propellers) is going directly downwind?

Sorry guys I should have made it clear that the post above was meant purely as a humorous dig.

Is there anything incorrect with these statements?

To travel at the speed of the wind the thrust of the propeller against still air must equal the rolling resistance of the wheels.

To travel at greater than the speed of the wind the thrust of the propeller against a headwind must be greater than the rolling resistance of the wheels.

 

[humber]

Stop right there!! This is not the case! The propeller is mounted exactly as it is designed to spin. The whole thing wouldn't function half as well if not. This is also exactly the unintuitive part (at least to me).

It is true that at low speeds (relative to the wind speed), the local angle of attack of the propeller blades is very high, but it is this drag that actually aids the acceleration to wind speed. As it accelerates the torque on the propeller from the wheels provides thrust, which is a positive feedback to the acceleration. This acceleration only disappears at some point above wind speed. It is essential that the prop spins in the direction it was designed to spin.

Yes. At some point, it is said reverse its function without direction. Though not all seem to agree, and have the wheels going backwards. That is by no means demonstrated. A simple tethered windtest would do. A fan, and perhaps a plenum chamber to smooth things out.
I can tell you I would have done these tests, even if I saw faster than wind, because my explanation may not be the correct one.
I don't know. It seems quite normal to do this, though it seems exceptional in this case.

Well, I hope that the two paragraphs above will give you some pause to think. You are working from an incorrect hypothesis of how all the parts interact, and working from an incorrect hypothesis will generally not yield correct results. If you have questions about this, do ask.

The above makes no difference to the result of the treadmill, though. I described the balance as I see it operating in the video. I only mentioned the 'real' propeller to show that the balance does no rely on symmetry of the drag. It will always balance as long as the total torque produced can be supported by the level of friction between the belt and wheels.

I had a lot more, but it's a bit pointless if we're not discussing the same machine.
Two things though:

I apologize for appealing to my authority. I admit that that is bad form. However, you have to realize that I approached this cart from a skeptical perspective as well as you do, mostly because of the "over-unity" tag. I subsequently figured out that I had made a false supposition about the working principles of the cart. When I realised this, it still took me about an hour to figure out how it actually does work. Now, I do not pretend to be infallible, but the operating principles aren't that complicated; they are just unintuitive.

Secondly, you are right that I am aware of the importance of validation and testing. However, I think that you are really showing spork c.s. too little respect for all of the experiments they have done to demonstrate just how the cart works. Their films are what made me realize I had made false suppositions about the cart.

[/QUOTE]

Ist point, no problem.
I have read the explanations, but I find too many flaws. Too much speculation. This is why I don't comment on it much, except to ask for real evidence.

If I had this sort of criticism, you couldn't stop me from trying to prove it. I would find a way.

To which films are you referring? A preponderance of anecdote, is not evidence. The large machine posted by another builder is a momentum device. Entirely explicable.
The small cart in the street is not adequate. The claim is not trivial!
The treadmill is not related to performance.

( If I may, which film convinced you, and why? )

It is not up to the viewer to prove the point. It does not say that it can't work, but that it has not been shown to work. That is a difference.

The validation is not so demanding, it need not be precise, but workable. Plausible. That's all. If it works in the wind show it!

Effort is also the norm. Some go home at 17.00 some at 22:00. Science is a discipline, and the easy stuff has already been done.
These are the ground rules, if they are not acceptable, then don't go into science. You will be ignored, and rightly so.