Down wind faster than the wind
- Thread starter my_wan
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sol invictus
Philosopher
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- Oct 21, 2007
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You mentioned this before.... it really surprises me that any professional physicist could have trouble understanding the equivalence of the treadmill to the wind. Perhaps they were worried about finite size effects or some such?
Obviously possible, but may not work? I see, 100% efficient machines are obviously possible, but not practically so?
It is also possible to build all sorts of faster than wind vehicles. My motorbike does it all the time. What is important, is the implementation.
Yes, a sailed vehicle. I converted my car to become an F1 vehicle.
It looked and performed exactly like one too. However, my insistence that is was still a standard car, fell on deaf ears.
What is not a bird, is also not a duck.
No, I meant to say that their knowledge means that they are no so easily fooled. It is a common observation, almost axiomatic, that those who deny orthodoxy, usually have nothing to add to it.
Sometimes professors humour people, because they are busy , and some are not so good as others.
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Professors of what, exactly? If you can, get a reason from them. I would love to hear them.
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No, just the almost infinite amount of BS.
Please expand upon that remark.
There is no ground power, The gears provide a pathway for the propellor's force to the ground. This may be advantageous when dispensing stored momentum, but there is no ground power.
A quaint idea, but pre-Newtonian If you ask the above questions, then of course you can call yourself a radical thinker, but a wrong one.
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Believe me, it really surprises me too. Definitely not a matter of semantics or details. As near as JB and I can figure out, it's based on judging the test setup based on the a-priori conclusion that DDWFTTW is not possible.
You'd never believe the debate we had with Wayne Whiteman of GA Tech. This guy has a PhD and is a professor of Mech Eng. Check his credentials here: http://www.me.gatech.edu/faculty/whiteman.shtml
He assures us that the treadmill bears no relation whatever to a road with a 10 mph tailwind. But it gets better. He also tells us that no test would ever satisfy him that our cart is faster than the wind. He said even if we had our cart race a neutrally buoyant balloon on a direct downwind 5 mile course, and our cart reached the finish line in half the time of the balloon, that would still prove nothing. He admitted that if an ice boat started and completed the course at the same time and place as our cart, it WOULD prove the ice boat is faster downwind than the balloon - but it would NOT prove our cart was. He assures us that 10 of his colleagues with vast experience in fluid dynamics have reviewed the problem and hold his same opinions.
There is an Aero professor in Illlinois that also refuses to believe this is possible. In fact all you have to do is check the physics blogs and forums to find that most physicists laugh at the idea that this can be done. And when we demonstrate it can be done on a treadmill, they laugh at the notion that the treadmill represents the "true" inertial frame in any way.
I still remember when education used to be about learning, and science used to be about explaining observed events. That was the good old days.
If you play with this reference nonsense, then you can get all sorts of answers, but none that may be realised.
No, it does not work with any vehicle, but is a harder sell for cars.
The idea is unsound, not my perception of it. The treadmill should tell you that there is a problem with this concept.
If this is a matter of pride to you, and crow-eating a prize, please don't tar me with the same brush.
I am curious to know whether any experimental result that could even be conceived could change humber's mind (as it were), or whether he is absolutely certain of his position despite any physical evidence that could ever possibly be brought to bear. Admittedly, this is a rhetorical question.
Marcus, your comments would be correct, and we would largely agree, if that is what the treadmill actually did, or the observer played any part. As I have said many times, the treadmill does nothing to deny or support windspeed claims. It is simply irrelevant. I say that the observer is seeing the correct and literal view, and not one relative to winspeed.
Please take a look at my drawings.
They are from the view of an observer on the ground. The first is a cart in real wind. The belt speed is zero, and so it is like a fixed road. The belt speed is then increased until the current treadmill situation is reached of zero local wind. Note that the co-ordinates of the graphs are translated according to the belt speed. When at windspeed, the wind relative to the cart is said to be zero (so justifying the still air argument). However, does that not suggest that even if successful, the final destination is (0,0) with respect to the observer? If the real one is correct, surely the last is too, or do I just add something else to it later, perhaps? You can observe your luggage from the airport carousel, but why? Is that worthwhile if you need to be on the belt to gain any benefit?
Okay. Let's accept that the "correct view" is is from the belt. When placed on the belt, the cart does not move back with the belt, but is already at windspeed. Is this because the cart is capable of immediate acceleration to windspeed? It displays none of the power that one would expect of a cart capable of driving itself against a powerful belt at any speed. No, it is put there by the operator, by external influence. What you are seeing is an illusion, supported by the misuse of equivalency, which is NOT required to explain this treadmill, nor real windtunnels. The latter do share a superficial similarity to the mathematical idea of equivalency, but a windtunnel is a model; a physically "equivalent" system. Windtunnel wind is not 'like' the wind it IS a wind.
How would it get from moving back with the belt as the graph suggests, to being instantaneously at windspeed? There is an additional translation, an external unseen 'vector' to (0,0) and not (20,20) as is suggested. That's how.
The cart does look like is conforming to TAD's reasoning because it does stay on the belt, but that is simply the result of the cart balancing itself against friction with the belt. It is a secondary, spurious effect that completes the illusion. (When I say illusion, I do not mean a trick, just what is said to be happening)
Take a book and tie a thread to it. Place it on the belt. You will feel considerable force as you try to hold it against the belt. Now, cover the belt and book in teflon, and try again. Much easier. It can be moved up the belt with relative ease. (On an incline, the only work required would be against gravity). The cart behaves just like this. It is barely in contact with the belt, and may be pushed around with a plastic fork. The belt has no means by which it can 'grip' the cart so as to carry it back as it should. The only force that the cart needs to overcome, is that tiny amount of residual friction. If friction is increased, by using soft rubber wheels or some weight over the drive wheel, then the cart will go backwards (Unless is can indeed generate the required thrust)
Many attempts have been made to deny my balance argument, and they all seem to rely upon the fact that the cart will then go back with the belt. Yes, too much load and the balance fails, as I have said, but that is not a failure of my argument, but a failure of theirs. Too much friction exposes the illusion. Easy to test, I think. This is already understood I suspect, but the "it's already at windspeed" argument is used to deny it.
The treadmill contains many mistakes, but "equivalency" plays no part in its success or failure. All failures result in the same thing; back down the belt. The cart and treadmill are interdependent, it is a system that cannot be independently verified, and serves only to 'demonstrate' its initial premise, because the test system is also based upon that same premise. That is not science.
"Equivalency" as used in this thread, is a metaphysical idea. I will try to describe the error, but it does not influence the conclusion, because it has no influence on anything, but the subject always returns, silly as it is.
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A car hitting a person at 60kph, is the same as a person traveling at 60kph hitting a static car. No.
What equivalency says, if it can actually be applied here, is that the transfer of energy and the changes of velocities, will be the same from each point of view. Each 'observer' sees the same thing from their perspective, which is correct. (The observer: that's another canard). The car "feels" what the person "feels" and vice-verse. All vectors and forces are the same. A direct invocation not of "equivalence" but of Newton's laws of motion!
The equivalent of (A hits B), is NOT (B hits A), but perhaps (-B hits -A). (B hits A) is another event.
A car traveling at 60kph, hits a person. (A hits B). So what can (B hits A) mean for this event? It means nothing, they are the same. There are one and the same collision. There is another option. The car is labeled as being stationary, and the earth 'rotated' beneath the wheels, so that the person is driven into the car, but that would still have to be a the same as the original event, but can never be realised in a model.
Try to model a golfer. We are told the mass of the club, and the ball and its velocity of 30m/s. That is said to be the same as the ball traveling at 30m/S hitting the club. (A hits B) = (B hits A). So, the ball is projected at the club at that speed. It hits the club, bounces off, and goes out through the window. It seems we have forgotten about the golfer. Okay, we build a model golfer that absorbs the ball's energy so as to bring it to a stop at the tee. But how ? Don't we need to know in advance how to set up the golfer for each shot, or look into the future? To be accurate, would that not mean producing a time-reversed but carbon copy of the same event? There is no (B hits A) for the same event, save for that spurious time-reversed event. Time had an arrow, the collision is over.
A person traveling at 60kph, hitting a stationary car (B hits A) is another event. Totally different collision, and not a mirror of a 60kph car hitting a person. The kinetic transfer will be different. Timescales will be different. Impulse collisions are time defendant, and reversing the velocity vectors won't make them the same. The list is endless. A battery heating a resistor, is the same as heating a resistor connected to a battery? As I said, this makes no difference to the treadmill, either way. Good, that's done.
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A propeller in the wind is not always like a propeller in still air. They are not the same thing in this particular case, and that is simply a physical fact, and not of how the world is viewed, but "equivalency" is used to say that they are the same.
The force of the wind drives the propeller to drive the cart, where as on the treadmill, the belt drives the propeller but without driving the cart. There is no wind to drive the propeller in opposition to the force from the belt, so there is no force to drive the cart.
However, if the cart is dragged back by the belt, the propeller then meets moving wind, which will drive the propeller in opposition to the force from the wheels. Now, that is certainly a more accurate model, though the cart would be driven forward, but only if the force generated by the propeller is greater than from the belt, but that is obviously not possible, which is why it causes so much fuss. How can the forward thrust be greater than the force dragging it back?
I have been told that I must "understand" that the cart is already at windspeed, so no force is required. We have a cart moving at windspeed, yet has no applied force, and no kinetic energy that indicates a history of acceleration? That would be unknown to science. Gearboxes cannot provide power gain, so arguments to that effect are not valid.
So how does it stay where it is? The friction is too low as I have said, but there is another consideration. Because the propeller and wheels are connected by gears, there is an analogy with the rear differential drive of a car. If one of the drive wheels is off the ground, the car cannot be moved by turning that wheel, no matter how much force or speed is applied to it. If put on a jacks such that both wheels are off the ground, and a wheel turned, the other contra-rotates. That is the situation with the wheel and propeller shafts of the cart. They spin in contra-rotation only to react against each other, because the friction is so low and the propeller so lightly coupled to its air mass. Without moving wind, there is insufficient effective air mass to do any work.
The cart is as if it were on floating jacks, like a disembodied differential gearbox. This is likely to be the result of laminar airflow lifting the wheels. The only downward force is gravity, and the cart is light. The motion up the belt is an artifact, that is the consequence of those facts.
My remarks about an object's history, are so, but not really relevant. I used them as a foil against the prevailing frames idea, that seems to consider only disembodied and isolated interactions. All objects on this planet are influenced by the earth's motion around the sun. It can be argued that the influence does not affect all objects equally, but the effects are trivial, and the local differences between objects even more so - were it even possible to take advantage of them. That is called 'locality'. Sometimes, in some experiments, it is necessary to acknowledge these effects, but they do not apply to this cart. The differences in local gravity will be of more significance, as would the local gravitational influence of nearby buildings. Differences in air temperature alone would swamp any effects. What about the difference is treadmill belts? Are they "equivalent" As you say, frames are frames. It makes no difference, other than a change in perspective. All else remains the same, so how can it help?
Do scientists agree? You can see in this thread, that a 'good' professor is one who agrees with the claimant. There is no value in this vernacular information. Radar engineers are masters of vectored velocities, but the aircraft don't seem to care. I have tried not to use outside references, because I think that it is not necessary in this case, as the errors are so fundamental, and can be otherwise explained.
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I will organise my spewage, so that it is less random.
Nice link to the professor, but how about what he said?
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Can carts travel faster? That is another debate, and requires evidence. The treadmill is otherwise, and can be tested.
So to answer your question, yes, if some tests are done.
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Christian Klippel
Master Poster
Dude, it is obvious that you have no clue about physics, and now it is obvious that you lack any kind of reading skills of the english language.
If you can show me exactly where in that post, that you refer to, i have talked about professors, you get 100 points. If you fail to do so, i really urge you to get the heck out of here. You are nothing more than a royal pain in the back.
I'm wondering what kind of satisfaction this kind of stupid trolling gives you?
Again, show me exactly where in that post i referred to professors. If you can't do that, simply don't speak to me any more. Also, if you can't do it, go back, reread and rethink what you wrote in responses to what. Analyze it. You may find that indeed you inly spew garblegook, twist words, and so on.
Ah, so the subject of the quote was professors but your reply was about the reaction of some dudes you met?
Well, OK. Sorry if I insulted you by thinking that your response might be relevant to the topic at hand.
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Christian Klippel
Master Poster
So, as i have thought. You can not tell me where in my post, that you quoted from, i have talked about professors. Of course you can not, because i simply have not. This just shows again your selective reading combined with your deliberate ignorance of what was written. Together with your mixing-up of separate postings and treatment of them as they were one meaning the same clearly shows where your problem is. Not to mention your 0-2=0 stunt.
H'ethetheth
fishy rocket scientist
These are some truly bizarre statements. You seem to think that wind tunnels can only be used to model wind, whereas in the real world they're almost always used to model still air, which is what makes them tricky to make, not to mention huge.
One last try:
If we test a car in a wind tunnel on a treadmill, and the wind speed in the wind tunnel is equal to the speed of the belt, this is equivalent to driving in still air. If you think this is a ludicrous idea, I advise you to take it up guys like these
If we turn off the wind tunnel, and keep everything else running the same, what is it equivalent to?
If your answer is not "driving on a road with a tail wind that matches the speed of the car", you have the wrong answer. And the kind of car does not matter in this respect, so this is valid for sailboats, chickens, corn flour, aprons, squirrels, beef, and the cart.
If you don't see this, I'm pretty sure I can't help you see it.
Michael C
Graduate Poster
Well said.
Michael C
Graduate Poster
I've put a new demonstration on YouTube. Inspired in particular by Modified and Brian M, I've made a simple mechanical cart that moves under the ruler faster than the ruler:
The large wheel, turning against the direction of movement of the ruler, is very similar to the propeller of the wind-powered cart, turning against the wind.
The large wheel, turning against the direction of movement of the ruler, is very similar to the propeller of the wind-powered cart, turning against the wind.