Down wind faster than the wind

[ThinAirDesigns]

Humber:
>I think that is a valid test

Hmmm... perhaps humber *is* Mr. Platt.

I find it hard to believe that there are two distinct people in this world that would consider a dude with a fan chasing this device and a bunch of styrofoam chips to be a "valid test".

JB

 

[humber]

Humber:
>I think that is a valid test

Hmmm... perhaps humber *is* Mr. Platt.

I find it hard to believe that there are two distinct people in this world that would consider a dude with a fan chasing this device and a bunch of styrofoam chips to be a "valid test".

JB

So, I am no longer George?. However, you should be aware that I am The Dude.
I think the fan and circle idea is in your favour. Platt's version needs some refinement perhaps, but then I think it was intended to be a demonstration rather then definite proof.
It is by no means the only option.

ETA;
Micheal_C
I thought it was the science of the cart? I don't need to apologise for been presented bad evidence, and without adequate secondary support.
If that is your attitude, don't bother with the science, but pay someone $100 to confess on You Tube.

However, I would certainly accept the verdict, and post accordingly. If you would have me include "I was wrong" then I would do so. Beware of anybody who tells you he or she is never wrong.
Anyway, glad to have you aboard.

 

[ynot]

Spork & TAD - You both said you liked the turntable idea (shown below) and that it would work. Is there any chance that you will build such a device to test the principle?

http://www.internationalskeptics.com/forums/picture.php?albumid=116&pictureid=497

 

[John Freestone]

I concede that, in a very strict sense, successful demonstration of the cart moving forwards faster than windspeed in the treadmill, turntable or other analogous system is not precisely what was claimed

It is precisely what I claim. People often make the mistake that we are using the treadmill to "model" the real world. The fact is that the treadmill IS the real world. If there were any such thing as an absolute frame of reference, and we could show that the earth happens to be stationary in that frame, then I'd be wrong. But the reality is that all velocities are relative. The difference between the treadmill and the earth is that the earth is bigger.

I appreciate that in your position it is hard to keep up with what everyone else knows and thinks and disagrees with, etc., but if you are replying directly to me on this point, then you must not have read or understood the differences I have suggested are there. I was in fact saying the same thing about frames of reference, their arbitrariness in the real world, to Humber. However, I was making certain distinctions which IMO make the treadmill incidents not equal to the road conditions. I have also said that I believe these differences to be very very unlikely to make a scrap of difference. The differences I posted have been there for some time and not corrected before now, and one other at least has said they are 'irrelevant', suggesting by default that he did not disagree with them, and another may have expressed agreement.

Saying that both situations are the real world is to ignore that each is a different part of it, with different conditions. Let me demonstrate how, if we were to be a little less blase, the difference could be used as criticism against your claim. I have said it twice already, so I'll just call it the area of the carpark perhaps a few inches or feet away from the side of your land cart that would be, were we to translate one bit of real world onto the other, moving downwind at windspeed. Please just hesitate from dismissing this as outside the realms of the experiment, irrelevant, or whatever, for a moment, and recognise the fact. Now, next, remember that there is no actual windspeed - there is a gradient of windspeeds going upwards with height. Now consider that, in theory at least, if I were travelling along at windspeed on my cart directly downwind, on a piece of land that was in earth-stationary orbit as per most carparks, but to the side (and also behind and in front at some greater remove) the land was travelling with me directly downwind, and the air above that would suffer less drag from passing over the ground, since it isn't.

Right, now, you and I are happy that this is irrelevant (well, I'm reasonably happy, you may not even agree). However, it is a possible objection. It is a real physical difference. If there were two infinitely long and wide trucks stretching out to the horizon a few inches away from me, I'd be hard pressed to say I travelled faster than the wind, because there would be such an enormous drag from those. This is also, IIRC, a problem in windtunnel testing, where the model must be a sensible distance from the sides of the tunnel to avoid that slower air. Somewhere between those trucks and "all carpark" there is the actual drag involved in the correct translation. What its value is, I don't know. I don't pretend I understand the maths.

I am not personally trying to criticise your treadmill testing, and I understand fully the principle of boosts, I feel quite confident. I am also reasonably confident myself that such differences are negligible, but I am pointing them out nevertheless. This is exactly the kind of thing that was irritating me before, which you now demonstrate again: if I don't understand something relevant, I am ignorant; if I understand something (which I imagined all by my little old self) that seems (according at least to others on this thread) to be true, they are either denied, ignored or tagged irrelevant by some without comment on their actuality.

 

[humber]

<snip>

How are you going to make a wind tunnel that long at home?

There is no real need for the cart to move. As long as there is a tail wind, then a true "treadmill", that is, a moving road that neither takes nor supplies energy, can be employed.
It should not be difficult to make a regulated air flow over the cart.

The treadmill need only be long enough to allow for error. A simple control loop between the cart and treadmill should hold it in place as the wind velocity is increased. Failure would be indicated when the cart can no longer hold its position.

If done carefully enough, then control could be done by hand; simultaneously adjusting the belt and windspeed, so as to maintain the cart on the treadmill.
Starting from a tether would make life easier. I assume that the test is to be monitored, so that should not raise questions of cheating.
Do you have problems with Ynot's idea?

ETA:
John Freestone,
I don't have any problems of that sort with the treadmill, because the I think the model is wrong is principle. I have left a reply or two hanging on that topic, but I will get around to it.

The airflow of the above test can be verified in situ. Smoke tests, pitot tubes, whatever it takes to demonstrate that there are no significant boundary conditions. It would not be difficult to make consistent flow over a small vehicle.

 

[John Freestone]

There is no real need for the cart to move. As long as there is a tail wind, then a true "treadmill", that is, a moving road that neither takes nor supplies energy, can be employed.
It should not be difficult to make a regulated air flow over the cart.

The treadmill need only be long enough to allow for error. A simple control loop between the cart and treadmill should hold it in place as the wind velocity is increased. Failure would be indicated when the cart can no longer hold its position.

If done carefully enough, then control could be done by hand; simultaneously adjusting the belt and windspeed, so as to maintain the cart on the treadmill.
Starting from a tether would make life easier. I assume that the test is to be monitored, so that should not raise questions of cheating.
Do you have problems with Ynot's idea?

ETA:
John Freestone,
I don't have any problems of that sort with the treadmill, because the I think the model is wrong is principle. I have left a reply or two hanging on that topic, but I will get around to it.

The airflow of the above test can be verified in situ. Smoke tests, pitot tubes, whatever it takes to demonstrate that there are no significant boundary conditions. It would not be difficult to make consistent flow over a small vehicle.

Humber, sorry, I don't understand any of this. You would need to be clearer.

 

[Dan O.]

The prevailing question is: What is the speed of the wind?

Since the air velosity over a flat surface depends on elevation above that surface, I propose we define the speed of the wind as the maximum speed of the air flow relative to a point on the surface within the volume that the cart will occupy. This point should be at hight equal to the hihgest point on the cart since that is where drag on the moving air would be minimum.

 

[Furcifer]

- furthermore, to take a beginner's course in classical mechanics at the Open University or other accredited institute of higher education.

There's no such thing as a "Beginner's course in Classical Mechanics

It's a second year class at any respectable institution.

 

[Michael C]

If I may, I would like to add my pledge. I also claim that the wind powered cart can travel faster than the wind pushing it. If proven wrong, I promise:

- to put a video of myself on YouTube, where I will publicly admit that I was wrong and that I have a faulty understanding of basic physics.
- furthermore, to take a beginner's course in classical mechanics at the Open University or other accredited institute of higher education.

Of course this promise only holds good if Humber pledges to do the same should he be proven wrong.

Micheal_C
I thought it was the science of the cart? I don't need to apologise for been presented bad evidence, and without adequate secondary support.

The "science of the cart" is nothing but classical mechanics. You've been presented with a lot of explanations of the underlying principles. You contend that these explanations are incorrect. Either I am totally wrong in my understanding of basic Newtonian physics, or you are. Whichever one of us is wrong should be prepared not only to admit it, but also to put some effort into learning about why he is wrong.

However, I would certainly accept the verdict, and post accordingly. If you would have me include "I was wrong" then I would do so. Beware of anybody who tells you he or she is never wrong.
Anyway, glad to have you aboard.

Let's be clear: I am "aboard" only if you accept the conditions I originally stated.

 

[Michael C]

Humber:
>I think that is a valid test

Hmmm... perhaps humber *is* Mr. Platt.

I find it hard to believe that there are two distinct people in this world that would consider a dude with a fan chasing this device and a bunch of styrofoam chips to be a "valid test".

JB

But it would be so much fun! Of course, as I already said, it's only worth doing if the dude chasing the cart with a fan is Charles Platt. Or Humber.

 

[Marcus]

No, the treadmill is always long enough: just keep it going and it rolls out more surface. Look at this video where the cart runs for more than 1 minute 40 seconds on the treadmill. If the treadmill is running at around 15 km/h (I think most treadmills can manage that), 1 minute 40 seconds would correspond to more than 400 meters of road.

How are you going to make a wind tunnel that long at home?

Interesting video, but it only shows the cart keeping up with the wind, not going faster as shown in the other video. As Humber points out, putting the treadmill in a wind (homemade wind tunnel) would enable the cart to go faster than the wind without running off the treadmill.

 

[Marcus]

If you gave the cart say, a 5 mph headwind while it is rolling on the treadmill, you are creating the same situation as the cart exceeding it's tailwind by 5 mph on the road. If it could continue for an appreciable length of time, it would prove the cart could go faster than it's tailwind.

 

[humber]

The "science of the cart" is nothing but classical mechanics. You've been presented with a lot of explanations of the underlying principles. You contend that these explanations are incorrect. Either I am totally wrong in my understanding of basic Newtonian physics, or you are. Whichever one of us is wrong should be prepared not only to admit it, but also to put some effort into learning about why he is wrong.



Let's be clear: I am "aboard" only if you accept the conditions I originally stated.

No, then.
You are doing exactly what I and other critics contend. Being seen to be right is more important than being right. You see making mistakes as shameful.
That is easy if never do much, or simply bark at each naysayer and then describe them as stupid, or whatever schoolyard retort comes to mind.
You are not so much that way as the others Michael_C, but the first remark sticks.
You didn't acknowledged that you were quite wrong about the function of a real treadmill, did you?

ETA:
It seems that only money or pride is sufficient motive to obtain evidence. If a test is established, I will donate $100 (via Paypal) to offset costs. As the current bet is with Dan O, an email exchange can confirm him as the recipient.

 

[humber]

Humber, sorry, I don't understand any of this. You would need to be clearer.

John, sorry, but I can address only the proposed test at the moment.

The treadmill I describe is simply a rolling belt, in a wind of known velocity. It is in fact, an "equivalent" of the current treadmill.
The power source is the wind, and the belt the dissipator, rather than the belt motor being the source, and the air (via the propeller ) the dissipator.

Now, it would be disingenuous of me to hold my opponents to a model that I describe as meaningless. I have said that the treadmill does not model the cart in use. In this case, the method is valid, because it is what the treadmill should be and therefore the correct model.

If the cart were to be restrained against the wind when upon the belt, then the cart wheels would spin the belt backwards.
If the belt is loaded so that it dissipates energy, then the cart has a load. When unrestrained and motionless, you would expect the dissipation to equal the amount of work done by the cart to maintain its position in the airstream, which is the amount of work that the cart acquires from the wind as motive power.( The remainder being lost to the wind)
If the wind speed is increased, then the cart should not advance up the belt, because the energy will be lost to the load as the wind and belt speeds increase. (Recall that the propeller speed is directly related to the speed of the wheels)
Eventually, the cart should fail to maintain its position, or reach "windspeed", where the wind and belt speeds are the same.

Perhaps you are thinking I have pulled a fast one. Even at "windspeed" the air velocity between the cart and the wind will not be zero.
No, it won't, but it does first have to get there, and I have repeatedly said that the cart will not reach windspeed, so that condition is moot in that respect.
However, there is nothing preventing the belt from reaching wind speed equivalence, which I understand is thought to be the same thing.

It might be difficult to maintain this load based upon velocity of the belt alone, but if both are adjusted incrementally, then that will better maintain the balance. It could be argued that the load remain constant. The cart is said to reach windspeed at any non-trivial velocity, so the wind could be kept constant and the load increased until the cart cannot maintain its position. If the beltspeed is less than the wind speed, then that would be a failure.

Guidance can perhaps be maintained by cambering the belt. It could be automated, by the use of a generator driven by the belt, and control of the load that it presents....

 

[Dan O.]

ETA:
It seems that only money or pride is sufficient motive to obtain evidence. If a test is established, I will donate $100 (via Paypal) to offset costs. As the current bet is with Dan O, an email exchange can confirm him as the recipient.

From that post, I'm not sure that you understand the concept of a donation.

The structure of this wager is that neither of us will receive anything from the other. The only payment will be the donation directly to JREF. Since the wagers are equal, JREF will receive $100 regardless of the outcome so they remain a neutral party.

 

[John Freestone]

Whoops, I missed this. Sol, thanks for saying

What you said is just fine. You're right that there are some differences due to the fact that the treadmill is of finite size, that the ground outside is made of something different than treadmill belt material, etc. You're equally right that these differences are irrelevant.

As for kinetic energy, it remains kinetic energy under a change of reference frame

Gosh!

(which is called a "boost" in physics lingo)

Thanks, I didn't know that.

, but of course its value changes. Energy is not conserved by boosts, but the equations of motion and the laws of physics are.

I don't understand that part. Isn't energy part of the equations of motion? No that can't be. You mean something else? "Energy is not conserved by boosts" is the bit. Oh wait, crash walls into cars, the wall has the k.e. and vice versa? Wind has the energy, transfered to cart, on the road; the treadmill has the energy, which is being transfered to the cart? But aren't these dependent on the speed and the mass, and thus relative, too? I mean, don't all these bodies have great kinetic energy measured from the POV of the sun?

 

[humber]

From that post, I'm not sure that you understand the concept of a donation.

The structure of this wager is that neither of us will receive anything from the other. The only payment will be the donation directly to JREF. Since the wagers are equal, JREF will receive $100 regardless of the outcome so they remain a neutral party.

Of course. I meant in addition to. JREF does not pay expenses.

 

[Dan O.]

We are not going to be holding the cart fixed while letting the wheels drive a treadmill.

If we cannot agree on the use of a conventional treadmill then we will be forced to perform an outdoor test with all the associated uncertainties. We could however agree to let the arbiter choose a test or series of tests to confirm or disprove the claim to our specifications.

 

[humber]

We are not going to be holding the cart fixed while letting the wheels drive a treadmill.

If we cannot agree on the use of a conventional treadmill then we will be forced to perform an outdoor test with all the associated uncertainties. We could however agree to let the arbiter choose a test or series of tests to confirm or disprove the claim to our specifications.

If you mean a powered treadmill and wind, then there would be two independent power sources. That would not be acceptable.

 

[humber]

Spork & TAD - You both said you liked the turntable idea (shown below) and that it would work. Is there any chance that you will build such a device to test the principle?

http://www.internationalskeptics.com/forums/picture.php?albumid=116&pictureid=497

[qimg]http://www.internationalskeptics.com/forums/picture.php?albumid=116&pictureid=497[/qimg]

Ynot,
If I understand correctly, then the arm (tether) will provide a reaction path for the force of the wheels, other than the propeller. I would expect the cart would match the turntable, without a propellor.