DDWFTTW Turntable Test: 5 Min Video - Is It Conclusive?

[vanesch]

I have already presented my detailed reason why this is NOT a valid inertial reference frame. Either you were missed it or simply chose to ignore it. Let me begin by an example: Place a sailboat in a frame in which the water is calm but the wind is blowing. The sail is up, and the skiff is sailing downwind. Now place the exact same sailboat in an equivalent reference frame, the air is calm, but the water has a current which is flowing in the opposite direction the wind was blowing in reference A. This causes a relative wind to blow which is indistinguishable in frame B from the wind in frame A. The sailboat sails downwind exactly as in frame A. The two frames are equivocal. I go through this exercise not to insult your intelligence, but just to be sure we are on the same page here.

We are.

OK. Now we take this cart, just a wheel with a propeller and hook it up as in the video and run it exactly as we have seen. The turntable spins CW, the cart gets dragged backwards for a short while due to inertia, static resistance but soon enough the apparent wind working against that wide yardarm, as well as the cart and propeller, slows the movement of the cart relative to the movement of the turntable. This slowing causes a relative difference in velocity as seen by the drive wheel, which spins up and via the cable also spins the propeller.

Yes.

The direction of spin and pitch of the propeller is such so that it acts as a true propeller, not a mill, and it propels the cart to move counter to the spin of the table. The cart can be seen advancing against the table. Now, your interpretation is that this is an equivalent reference frame to a stationary table and a true wind blowing on the back of the cart.

Yes.

You also interpret this as the cart going faster than the wind, since it is advancing against the table.

Yes.

Here is where you are wrong: This would ONLY be an equivalent reference frame if the cart were to move in exactly the same direction and at the same velocity, if it were driven NOT by the moving table, but instead by an actual wind blowing on the cart as it stands on a stationary table!

But where is the difference if you look upon this from the reference of the turning table ?

In what way can you say that the table is "really turning" and the air is "really stationary", and not that the table is actually standing still and the air is moving ? This is just a change of reference frame, no ?

(there IS a small difference, and that is the fact that the reference frame of the table also has a rotation which it shouldn't, as an inertial frame. But that can be made smaller with a larger turning table).

I have already shown, and Jeff agrees, that if a wind were to blow on the propeller, with the cart stationary on the table, the propeller will act as a turbine, turning the opposite way, turning the wheels the opposite way, and the cart will try to work AGAINST the wind, not go down wind!

Well, that's wrong. It will of course move with the wind in the beginning, because of the drag of the wind on the system (and the arm which acts as a sail). The propeller always acts as a propeller and not as a turbine. Because if that where the case, the cart on the turntable would speed FORWARD faster than the table and not run backwards. How would you explain that the cart is not running forward on the table, but would so when solicited with an external wind ? Again, it is a transformation of reference frames.

Do you still consider the two frames to be equivalent? Under the same relative environmental conditions, the cart will behave two different ways! That is NOT an equivalent reference frame by any means!

This is because you are wrong with your prediction of how it would behave of course.

As I have said, countless times, you cannot test a cart which is configured for upwind motion and claim that it proves down wind performance!

What is an "upwind configuration" ? If it runs downwinds, it will make the propeller *increase* that motion. If it runs upwind, it will make the propeller increase *that* motion. There could very well be TWO solutions to the equation of motion, depending on the initial conditions. Only, the upwind solution has not been demonstrated.

I have showed you how to set up the cart so that it is a true down wind cart; simply remove the drive cable from one side of the wheel and attach it on the other side that is all that is required.

No, if you do that, you have changed the "gear ratio" and hence you will change the motion.
That is not equivalent. It is as if you changed the gear ratio from p = 1/2 to p = -1/2 in my example. You don't get the same motions.

Now, when you run the test, it will be a TRUE equivocal reference frame with a cart in the wind. What you will find is that the cart on the turntable will run backwards with the table until the wind resistance turns the mill as a turbine, which turns the wheels, and it will indeed go down wind, but it will NEVER exceed the table velocity.

This is correct, but the two are not identical physical situations. Frame-independent quantities (such as the gear ratio) which are the same in every reference frame are now different. In order to have an equivalent frame, you should just apply a uniform velocity vector, and all the rest equal (for a galilean transformation). That's exactly what happens when you go from the turntable to the windtunnel (up to the small rotational motion).

This will PROVE the DDWFTTFW is impossible. Yodu can take that same cart, same configuration, and place a fan behind it and it will go downwind, something the original configuration could NOT do!

It will of course ALSO go downwind on the turntable, but not as much, because in order to act as a "turbine" in the downwind, it actually acts as a propeller making it move slightly with the turning table, and not against it, as was the case with the original cart (before changing the sign in the gearing ratio).

Can you now understand the importance of not mixing and matching reference frames? Test the DW cart on the turntable configured as it would be to go DW. Test the UP wind cart configured on the turn table in the same configuration it will be when going up wind. Please do not mix and match! Is there no one here who understands this?

I think it is you who do not seem to see that equivalent reference frames demand that you just apply a velocity transformation WITHOUT changing frame-independent quantities such as the sign of the gear ratio.

All that comes about because you make a wrong gedanken experiment of what the cart of the original poster WOULD do (according to you) when exposed in a wind tunnel.

You don't change the sails of your boat either when you do the equivalent frame transformation in the sea current versus wind case, do you ?

This is really very similar to the case of the winding of a wire on a wheel while you PULL on the wire. Only because of airodynamics, things are less evident.

 

[zoobyshoe]

But at wind speed, you have power available on the axle of the wheels ! You can use that in principle to make a prop turn and get you faster. The energy goes from the wheels to the prop. The slightest bit of power that you can extract from the axle and put into the air (which is now "standing still") will get you move faster than the wind.

"Friction never sleeps" means that I don't see how you will ever get up to wind speed as long as there is any friction in the cart's mechanical components. Going back to the 20mph wind; if the cart makes it to 19 mph, then the wind speed becomes 1 mph, which has 1/8000 the power of the original 20mph wind to add to the cart. I'm not sure a toy propeller will even freewheel in a 1 mph wind.

When you say there is power available on the axle, are you referring to stored flywheel power?

Let's say you make it to wind speed and have some little bit of energy. The prop is turning in the wrong direction to produce forward thrust into the head wind. Once it stops being driven by the wind its action will be to try to thrust the cart backward while continuing to turn the wheels forward. What's your solution to this?

 

[M Grandin]

The reality of this I thought was cleared up since long in this forum, both by video verifications and theoretical explanations.

This is not a new Einsteinian theory demanding abstract inertial frames
to explain - it is just a gearbox between two media, ground and air, with different velocities. By gearing this gearbox suitably, this difference in speed of medias could give this gearbox (at least theoretically) any speed in any direction. It is just an engineering task - where of course every specific solution has its practical limitations.

The power from differences of speeds of surrounding media can be extracted rather independently of gearbox`s (=vehicle`s) own speed. As maybe some pointed out
earlier. This is egineering, not abstract difficult comprehensible science.

 

[pallidin]

I agree. There is nothing particulary odd about this.
For example, it should not be surprising that a 10/lb constant force at 10/mph can be geared to have a resultant ground contact 5/lb force at 20/mph, minus losses of course.

 

[swerdna]

In relation to my original question can I assume the following . . .

Schroder and Zoobyshoe think DDWFTTW is impossible and not is not demonstrated by my turntable demonstrations and other demonstrations.

Jeff Reid, Vanesch and Phrak think DDWFTTW is possible and not is demonstrated by my turntable demonstrations and other demonstrations.

Is this correct?

 

[schroder]

But where is the difference if you look upon this from the reference of the turning table ?

In what way can you say that the table is "really turning" and the air is "really stationary", and not that the table is actually standing still and the air is moving ? This is just a change of reference frame, no ?

(there IS a small difference, and that is the fact that the reference frame of the table also has a rotation which it shouldn't, as an inertial frame. But that can be made smaller with a larger turning table).




Well, that's wrong. It will of course move with the wind in the beginning, because of the drag of the wind on the system (and the arm which acts as a sail). The propeller always acts as a propeller and not as a turbine. Because if that where the case, the cart on the turntable would speed FORWARD faster than the table and not run backwards. How would you explain that the cart is not running forward on the table, but would so when solicited with an external wind ? Again, it is a transformation of reference frames.



This is because you are wrong with your prediction of how it would behave of course.

What is an "upwind configuration" ? If it runs downwinds, it will make the propeller *increase* that motion. If it runs upwind, it will make the propeller increase *that* motion. There could very well be TWO solutions to the equation of motion, depending on the initial conditions. Only, the upwind solution has not been demonstrated.



No, if you do that, you have changed the "gear ratio" and hence you will change the motion.
That is not equivalent. It is as if you changed the gear ratio from p = 1/2 to p = -1/2 in my example. You don't get the same motions.




This is correct, but the two are not identical physical situations. Frame-independent quantities (such as the gear ratio) which are the same in every reference frame are now different. In order to have an equivalent frame, you should just apply a uniform velocity vector, and all the rest equal (for a galilean transformation). That's exactly what happens when you go from the turntable to the windtunnel (up to the small rotational motion).



It will of course ALSO go downwind on the turntable, but not as much, because in order to act as a "turbine" in the downwind, it actually acts as a propeller making it move slightly with the turning table, and not against it, as was the case with the original cart (before changing the sign in the gearing ratio).



I think it is you who do not seem to see that equivalent reference frames demand that you just apply a velocity transformation WITHOUT changing frame-independent quantities such as the sign of the gear ratio.

All that comes about because you make a wrong gedanken experiment of what the cart of the original poster WOULD do (according to you) when exposed in a wind tunnel.

You don't change the sails of your boat either when you do the equivalent frame transformation in the sea current versus wind case, do you ?

This is really very similar to the case of the winding of a wire on a wheel while you PULL on the wire. Only because of airodynamics, things are less evident.

It is very simple to test if my prediction is wrong or right...no need to argue endlessly about it. All swerdna has to do is reverse one cable and rerun the test. Then we will see. How difficult is that?

 

[schroder]

But where is the difference if you look upon this from the reference of the turning table ?

In what way can you say that the table is "really turning" and the air is "really stationary", and not that the table is actually standing still and the air is moving ? This is just a change of reference frame, no ?

(there IS a small difference, and that is the fact that the reference frame of the table also has a rotation which it shouldn't, as an inertial frame. But that can be made smaller with a larger turning table).

It is onvious that the reference frame with the spinning table is NOT equivocal to the frame with the table stationary and wind blowing in the back of the cart. It is the spin up of the wheel which is driving the propeller and the cart advances against the table. Now, change the frame so the table is statiuonary and the wind is the force on the propeller. The propeller will be driven the OPPOSITE way, the wheels will go the OPPOsite way and the cart goes upwind, not down! How can you possibly call these frames equivocal! Everything must behave in a way which is indistinguishable to an outside observer! Thai is certainly not the case here.. I am repeating myself, but you are refusing to listen. You think I am wrong? Then ask swerdna to place a fan on the cart with the table stationary and see if it goes downwind. I am betting it will not! Better yet, ask him to swap that cable I mentioned and run the test again. We might find out I am right. But we will never know if everyone refuses to even test it!

 

[zoobyshoe]

In relation to my original question can I assume the following . . .

Schroder and Zoobyshoe think DDWFTTW is impossible and not is not demonstrated by my turntable demonstrations and other demonstrations.

Jeff Reid, Vanesch and Phrak think DDWFTTW is possible and not is demonstrated by my turntable demonstrations and other demonstrations.

Is this correct?

No, I do not assert it is impossible. I have serious problems with the idea which no one has adequately cleared up for me. I haven't seen a demonstration that has convinced me. I remain skeptical.

 

[schroder]

No, I do not assert it is impossible. I have serious problems with the idea which no one has adequately cleared up for me. I haven't seen a demonstration that has convinced me. I remain skeptical.

I would say I am Highly Sceptical but I would not mind very much being proven wrong. With this turntable, we have a device which can easily prove the case, one way or the other. But in order to do that some additional tests need to be done. I have already described these very simple tests in detail. It remains to be seen if anyone will do them.

 

[zoobyshoe]

The reality of this I thought was cleared up since long in this forum, both by video verifications and theoretical explanations.

This is not a new Einsteinian theory demanding abstract inertial frames
to explain - it is just a gearbox between two media, ground and air, with different velocities. By gearing this gearbox suitably, this difference in speed of medias could give this gearbox (at least theoretically) any speed in any direction. It is just an engineering task - where of course every specific solution has its practical limitations.

The power from differences of speeds of surrounding media can be extracted rather independently of gearbox`s (=vehicle`s) own speed. As maybe some pointed out
earlier. This is egineering, not abstract difficult comprehensible science.

I just apprehended this: "The power from differences of speeds of surrounding media can be extracted rather independently of gearbox`s (=vehicle`s) own speed." Stated this way, it suddenly made sense.

 

[vanesch]

It is very simple to test if my prediction is wrong or right...no need to argue endlessly about it. All swerdna has to do is reverse one cable and rerun the test. Then we will see. How difficult is that?

I don't see what it will prove. If you inverse the gear ratio sign, then you will now have something that will not go backward faster than the wind. So ? What will this learn us ?

The experiment you propose is NOT the "equivalent" of this test.

 

[vanesch]

The reality of this I thought was cleared up since long in this forum, both by video verifications and theoretical explanations.

This is not a new Einsteinian theory demanding abstract inertial frames
to explain - it is just a gearbox between two media, ground and air, with different velocities. By gearing this gearbox suitably, this difference in speed of medias could give this gearbox (at least theoretically) any speed in any direction. It is just an engineering task - where of course every specific solution has its practical limitations.

The power from differences of speeds of surrounding media can be extracted rather independently of gearbox`s (=vehicle`s) own speed. As maybe some pointed out
earlier. This is egineering, not abstract difficult comprehensible science.

Yes, that was what my example in post https://www.physicsforums.com/showpost.php?p=2031426&postcount=96 made more explicit in post
https://www.physicsforums.com/showpost.php?p=2031533&postcount=136

 

[schroder]

I just apprehended this: "The power from differences of speeds of surrounding media can be extracted rather independently of gearbox`s (=vehicle`s) own speed." Stated this way, it suddenly made sense.

Really? So if a shopping cart is extracting power from someone pushing it, and that someone slows dow or stops pushing or just walk away, the cart can still extract power from the person walking away? Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion? You might give it a mighty shove, but it will soon stop. Over any reasonable distance , it will never outrun you. And if you were not pushing the cart at all, you would cover the distance much faster. Same with the wind pushing that cart.

 

[schroder]

I don't see what it will prove. If you inverse the gear ratio sign, then you will now have something that will not go backward faster than the wind. So ? What will this learn us ?

The experiment you propose is NOT the "equivalent" of this test.

It will be something that can go downwind when pushed by the wind. And something which will go downwind on a turntable which simulates being pushed by the wind. Which is NOT what you have now! What you have now is a cart which will attempt to go upwind when pushed by the wind, and you are testing it in a downwind simulator! What does THAT learn us? Nothing!

What we will learn from doing it the correct way is that DDWFTTW does not work! But it seems no one wants to learn that, or do you?

 

[vanesch]

It is onvious that the reference frame with the spinning table is NOT equivocal to the frame with the table stationary and wind blowing in the back of the cart. It is the spin up of the wheel which is driving the propeller and the cart advances against the table. Now, change the frame so the table is statiuonary and the wind is the force on the propeller. The propeller will be driven the OPPOSITE way, the wheels will go the OPPOsite way and the cart goes upwind, not down!

But stop saying what you THINK that the propeller will do ! This is YOUR claim, and it is definitely wrong, given the behavior on the turntable. "Change the frame so that the table is stationary" means: change your *point of view* but everything happens of course the same way. It is not because you LOOK upon the same experiment differently that it behaves differently. And in this particular case, in the reference frame of the table, there IS a wind blowing in the direction of the cart and the cart IS moving faster back than the wind is blowing. You'd only need to put a webcam ON THE TURNING TABLE instead of fixed in the lab, and you have your change of reference frame.

How can you possibly call these frames equivocal! Everything must behave in a way which is indistinguishable to an outside observer! Thai is certainly not the case here..

It is not the case because you PRETEND that it will behave differently. That is as saying: look, a glass in a train with some wine in it is not the same as a glass on a table next to the railway. Because of course the wine in the train will bend over in one direction, and hence, it cannot be a frame transformation, because otherwise it would mean that the wine would be horizontal and clearly it isn't.

 

[vanesch]

Really? So if a shopping cart is extracting power from someone pushing it, and that someone slows dow or stops pushing or just walk away, the cart can still extract power from the person walking away? Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion?

Of course. One way is calling it a bicycle. Another example is the wheel with the rope. If you pull slowly on the rope, the wheel will come faster towards you than you try to walk away from it (see my post 96, first attachment).

 

[pallidin]

Really? So if a shopping cart is extracting power from someone pushing it, and that someone slows dow or stops pushing or just walk away, the cart can still extract power from the person walking away? Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion? You might give it a mighty shove, but it will soon stop. Over any reasonable distance , it will never outrun you. And if you were not pushing the cart at all, you would cover the distance much faster. Same with the wind pushing that cart.

A shopping cart is not geared. But if it were, say, with a 2:1 ratio, than as you pushed it it would move at twice your pushing speed but half the force, thus quickly leaving your hands, then eventually stopping as no further input force is applied.

 

[schroder]

But stop saying what you THINK that the propeller will do ! This is YOUR claim, and it is definitely wrong, given the behavior on the turntable. "Change the frame so that the table is stationary" means: change your *point of view* but everything happens of course the same way. It is not because you LOOK upon the same experiment differently that it behaves differently. And in this particular case, in the reference frame of the table, there IS a wind blowing in the direction of the cart and the cart IS moving faster back than the wind is blowing. You'd only need to put a webcam ON THE TURNING TABLE instead of fixed in the lab, and you have your change of reference frame.



It is not the case because you PRETEND that it will behave differently. That is as saying: look, a glass in a train with some wine in it is not the same as a glass on a table next to the railway. Because of course the wine in the train will bend over in one direction, and hence, it cannot be a frame transformation, because otherwise it would mean that the wine would be horizontal and clearly it isn't.

I am not pretending anything! Do you understand the pitch of a propeller at All? A propeller turning and cutting into the air aheasd has a Leading pitch, and it shoves the air in front backwards. If you now blow wind on that propeller from the back, that same pitch will exert a normal force on the pitched blades which WILL turn the blades in the opposite direction. This is so incredibly easy to prove that I am surprised you question it! Do you own two electric fans? That is all you need to demonstrate this. If swerdna will simply let a fan blow on the propeller from the same direction the relative wind is coming from, it will definitely turn in the opposite direction it turns in the video. I do not THINK so, I KNOW so. It cannot do anything else!

 

[zoobyshoe]

Really? So if a shopping cart is extracting power from someone pushing it, and that someone slows dow or stops pushing or just walk away, the cart can still extract power from the person walking away? Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion? You might give it a mighty shove, but it will soon stop. Over any reasonable distance , it will never outrun you. And if you were not pushing the cart at all, you would cover the distance much faster. Same with the wind pushing that cart.

Quiet, I'm cogitating. And the zoobie brain is a slow, rust-encrusted, squealing, steam- emitting, gear-grinding, contraption with lots of loose hoses and shorted wires, and no one remembers the last oil change.

 

[schroder]

Of course. One way is calling it a bicycle. Another example is the wheel with the rope. If you pull slowly on the rope, the wheel will come faster towards you than you try to walk away from it (see my post 96, first attachment).

The point was: Pushing it.

 

[swerdna]

I went to the trouble and expense of building this equipment because I want to find out if DDWFTTW is possible or not. On the face of it the claim doesn’t make sense to me and I expected that my tests would be more likely to disprove the claim than prove it. It has turned out however that they seem to have done the opposite and I want to know if my interpretation of the tests are correct or not.

I had some reservations about the treadmill demonstrations that were being offered and these reservation were as follows . . .

Holding the wheels of a cart against a moving surface until they reach the speed of the surface is like pushing a cart up to wind speed in an outside test and doesn‘t represent the cart getting the energy to do this from the wind or prove that it could do so. A treadmill simply isn‘t long enough to allow the cart to get the speed from the apparent wind on it‘s own accord.

Holding the wheels of a cart against a moving surface beyond the point where the thrust of the prop would otherwise have moved the cart forward against the surface is “boosting” that forward motion. In other words a cart that would never be able move against a moving surface on it’s “own accord” can be forced to do so by artificially holding it against the surface and then releasing it. I may provide a video demonstration of what I mean.

Because I believe a cart can be artificially forced to move forward against the motion of a moving surface I was never happy that a treadmill demonstration could adequately demonstrate that the forward movement wasn’t some temporary effect of stored energy that was being lost to friction very gradually.

Because a treadmill is of limited length the cart can’t move backward or forward much and doesn’t gain the same amount of inertia that it would moving along the ground outside. Not sure if this is important but it is something that is not equivalent to and outside test.

A turntable is essentially a treadmill of indefinite length and I believe overcomes all these treadmill “problems”.

As far as I can tell the tests I have done have demonstrated that the thrust of the propeller can be greater than the rolling resistance. Also that there is no form of stored energy involved as I have run the cart opposing the surface direction for over 10 minutes with no apparent loss of speed. I have also physically slowed the cart while it is running and it quickly returned to it’s “cruise” speed.

Sorry if the layman’s wording I’ve used is confusing.

 

[pallidin]

The point was: Pushing it.

Doesn't one "push" on bicycle pedals?

 

[swerdna]

I would say I am Highly Sceptical but I would not mind very much being proven wrong. With this turntable, we have a device which can easily prove the case, one way or the other. But in order to do that some additional tests need to be done. I have already described these very simple tests in detail. It remains to be seen if anyone will do them.

I would be very happy to perform any test that you suggest as long as it makes some sense and is possible. This thread is moving very fast and I’m behind a heap of previous posts without even keeping up with the new ones. Rather than me looking through heaps of posts to find out what test you want could you please explain (again) exactly what test you want me to conduct and what the purpose of the test is and what will it is designed to prove.

 

[schroder]

I went to the trouble and expense of building this equipment because I want to find out if DDWFTTW is possible or not. On the face of it the claim doesn’t make sense to me and I expected that my tests would be more likely to disprove the claim than prove it. It has turned out however that they seem to have done the opposite and I want to know if my interpretation of the tests are correct or not.

I had some reservations about the treadmill demonstrations that were being offered and these reservation were as follows . . .

Holding the wheels of a cart against a moving surface until they reach the speed of the surface is like pushing a cart up to wind speed in an outside test and doesn‘t represent the cart getting the energy to do this from the wind or prove that it could do so. A treadmill simply isn‘t long enough to allow the cart to get the speed from the apparent wind on it‘s own accord.

Holding the wheels of a cart against a moving surface beyond the point where the thrust of the prop would otherwise have moved the cart forward against the surface is “boosting” that forward motion. In other words a cart that would never be able move against a moving surface on it’s “own accord” can be forced to do so by artificially holding it against the surface and then releasing it. I may provide a video demonstration of what I mean.

Because I believe a cart can be artificially forced to move forward against the motion of a moving surface I was never happy that a treadmill demonstration could adequately demonstrate that the forward movement wasn’t some temporary effect of stored energy that was being lost to friction very gradually.

Because a treadmill is of limited length the cart can’t move backward or forward much and doesn’t gain the same amount of inertia that it would moving along the ground outside. Not sure if this is important but it is something that is not equivalent to and outside test.

A turntable is essentially a treadmill of indefinite length and I believe overcomes all these treadmill “problems”.

As far as I can tell the tests I have done have demonstrated that the thrust of the propeller can be greater than the rolling resistance. Also that there is no form of stored energy involved as I have run the cart opposing the surface direction for over 10 minutes with no apparent loss of speed. I have also physically slowed the cart while it is running and it quickly returned to it’s “cruise” speed.

Sorry if the layman’s wording I’ve used is confusing.

You have done a nice job and have contributed greatly to this discussion. But what you have still does not "prove" DDWFTTW. Are you willing to do a few more tests with your set up?

 

[swerdna]

You have done a nice job and have contributed greatly to this discussion. But what you have still does not "prove" DDWFTTW. Are you willing to do a few more tests with your set up?

Yes please - This is what I want!

 

[A.T.]

Really? (...) Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion?

Yes, if the person is pushing the cart via a gearing mechanism. This has been demonstrated by Carlos and his friends, and already referenced in this thread:
http://de.youtube.com/watch?v=9Yt4zxYuPzI&feature=channel
You just need a very long ruler, to keep contact with the cart.

 

[schroder]

I would be very happy to perform any test that you suggest as long as it makes some sense and is possible. This thread is moving very fast and I’m behind a heap of previous posts without even keeping up with the new ones. Rather than me looking through heaps of posts to find out what test you want could you please explain (again) exactly what test you want me to conduct and what the purpose of the test is and what will it is designed to prove.

Thanks! We were posting at the same time and went right past each other.

OK. In order to prove that this does not truly simulate a cart in a down wind situation: I would like you to place an electric fan so it blows only on the propeller, not on the crossbeam, wheel or anything else. Try to place the fan so it effects only the propeller, Please note which way the propeller turns from the wind on it. The fan must be blowing from the direction of the relative wind in your running experiment. The table is not running. Does the propeller turn in the same way as in your running test or the opposite way? Do the wheels turn, and if so which way, same as before or opposite? That is test number one. I have another for you but this one is of immediate importance. Thanks again.

 

[swerdna]

Thanks! We were posting at the same time and went right past each other.

OK. In order to prove that this does not truly simulate a cart in a down wind situation: I would like you to place an electric fan so it blows only on the propeller, not on the crossbeam, wheel or anything else. Try to place the fan so it effects only the propeller, Please note which way the propeller turns from the wind on it. The fan must be blowing from the direction of the relative wind in your running experiment. The table is not running. Does the propeller turn in the same way as in your running test or the opposite way? Do the wheels turn, and if so which way, same as before or opposite? That is test number one. I have another for you but this one is of immediate importance. Thanks again.

I think the answers to your questions are fairly obvious without doing any testing but I’m happy to do the test as you ask and will do so right away. While I’m doing it could you please explain the purpose of this test. What is being demonstrated/proven?

 

[zoobyshoe]

Really? So if a shopping cart is extracting power from someone pushing it, and that someone slows dow or stops pushing or just walk away, the cart can still extract power from the person walking away? Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion? You might give it a mighty shove, but it will soon stop. Over any reasonable distance , it will never outrun you. And if you were not pushing the cart at all, you would cover the distance much faster. Same with the wind pushing that cart.

I think that a person doesn't constitute a surrounding medium. We're pretty much limited to air over land or air over water. The geared vehicle has to be able to take advantage of the difference in speed of the surrounding media over a large range for it to matter.

Fear not: I was not necessarily announcing a conversion, just that I finally understood the principle that Jeff Reid kept alluding to without formally stating it. It explained why he kept referring to friction as if it were a power source.

 

[schroder]

I think the answers to your questions are fairly obvious without doing any testing but I’m happy to do the test as you ask and will do so right away. While I’m doing it could you please explain the purpose of this test. What is being demonstrated/proven?

They are obvious to you and to me, but not to some others here so we would like to do this layer by layer, if you do not mind. If the prop turns the opposite way, and the wheels turn the opposite way, it shows that the cart is actually configured to go upwind, not down but it is being tested in a down wind jig. It will invalidate any conclusions being drawn on the basis of similar reference frames. But I am getting ahead of the story. Can we please peel this onion one layer at a time?

 

[swerdna]

No problem in conducting the test as requested.

Test 1 - When the motion of the turntable was held and the fan held close to the “wind side” of the prop virtually nothing happened (no movement of prop or wheel). For the prop to turn the way it “wanted” to the wheel would have turned and moved the prop and cart closer to the fan. The opposing forces of the fan and wheel through the prop and cable were pretty much equal and opposite. If the force of the fan had been greater than the force of the wheel the prop would have moved closer toward the fan.

Is this what you expected and what are your conclusions?

 

[schroder]

No problem in conducting the test as requested.

Test 1 - When the motion of the turntable was held and the fan held close to the “wind side” of the prop virtually nothing happened (no movement of prop or wheel). For the prop to turn the way it “wanted” to the wheel would have turned and moved the propand cart closer to the fan. The opposing forces of the fan and wheel through the prop and cable were pretty much equal and opposite. If the force of the fan had been greater than the force of the wheel the prop would have moved closer toward the fan.

Is this what you expected and what are your conclusions?

OK. Thank you. That is exactly what I expected. I think it would be safe to say that if we could place this cart out in the wind, with the wind blowing from the back, same direction as the fan and same direction as the apparent wind in your running test, that the cart would go nowhere. It would not go downwind, and it would certainly not go downwind faster than the wind. What we have shown here is how totally erroneous conclusions can be drawn by incorrectly matching reference frames. Do you agree?

If so we can proceed to the next test.

 

[swerdna]

OK. Thank you. That is exactly what I expected. I think it would be safe to say that if we could place this cart out in the wind, with the wind blowing from the back, same direction as the fan and same direction as the apparent wind in your running test, that the cart would go nowhere. It would not go downwind, and it would certainly not go downwind faster than the wind. What we have shown here is how totally erroneous conclusions can be drawn by incorrectly matching reference frames. Do you agree?

If so we can proceed to the next test.

I will think about it before commenting and I have some other things that I need to be doing right now. I will get back as soon as possible.

 

[schroder]

I will think about it before commenting and I have some other things that I need to be doing right now. I will get back as soon as possible.

OK Thanks for your help. You have already proven more than five or six threads of arguing. You may not achiueve fame for making a DDWFTTFW machine, but you will be the one who finally debunks this thing. That is something!

 

[zoobyshoe]

I will think about it before commenting and I have some other things that I need to be doing right now. I will get back as soon as possible.

I can't believe he wimped out after only 20 hours of posting.

 

[pallidin]

Yes, if the person is pushing the cart via a gearing mechanism. This has been demonstrated by Carlos and his friends, and already referenced in this thread:
http://de.youtube.com/watch?v=9Yt4zxYuPzI&feature=channel
You just need a very long ruler, to keep contact with the cart.

Exactly. I've seen that vid before.
Now, the question is how to sustain this reaction without an infinite linear ruler.

 

[pallidin]

I can't believe he wimped out after only 20 hours of posting.

Yeah, this whole subject can fry a couple brain cells.

 

[A.T.]

Can a shopping cart go faster on level ground, than the person who is pushing it, in a continuous fashion?

Yes, if the person is pushing the cart via a gearing mechanism. This has been demonstrated by Carlos and his friends, and already referenced in this thread:
http://de.youtube.com/watch?v=9Yt4zxYuPzI&feature=channel
You just need a very long ruler, to keep contact with the cart.

Exactly. I've seen that vid before.
Now, the question is how to sustain this reaction without an infinite linear ruler.

The air is the infinite linear ruler in DDWFTTW machines.

 

[swerdna]

OK. Thank you. That is exactly what I expected. I think it would be safe to say that if we could place this cart out in the wind, with the wind blowing from the back, same direction as the fan and same direction as the apparent wind in your running test, that the cart would go nowhere. It would not go downwind, and it would certainly not go downwind faster than the wind. What we have shown here is how totally erroneous conclusions can be drawn by incorrectly matching reference frames. Do you agree?

If so we can proceed to the next test.

Sorry but I can’t agree with your conclusion or test. It’s not a valid test to have the wind only blowing on the prop. In “real life” the wind blows on the cart fame as well as the prop. This is important because in the first instance the cart and prop have to act as a sail to start the cart moving with the wind (the prop doest act as a prop in the very first instance). When I add a flat cardboard sail to the tether arm close to the prop the cart moves away from the fan, the wheel turns and the prop spins to thrust against the fan wind. After the cart begins to move over the surface the wheel spins the prop the wind doesn’t directly spin the prop. Surely you have seen video evidence (mine for example) of the cart moving downwind only powered by wind?

I like your step by step approach and we shouldn’t move to the next step until the current step is resolved. So no next test yet please. If you don’t agree with anything I’ve said please explain why.

 

[swerdna]

I can't believe he wimped out after only 20 hours of posting.

Am I right to take that as humour?

 

[schroder]

Sorry but I can’t agree with your conclusion or test. It’s not a valid test to have the wind only blowing on the prop. In “real life” the wind blows on the cart fame as well as the prop. This is important because in the first instance the cart and prop have to act as a sail to start the cart moving with the wind (the prop doest act as a prop in the very first instance). When I add a flat cardboard sail to the tether arm close to the prop the cart moves away from the fan, the wheel turns and the prop spins to thrust against the fan wind. After the cart begins to move over the surface the wheel spins the prop the wind doesn’t directly spin the prop. Surely you have seen video evidence (mine for example) of the cart moving downwind only powered by wind?

I like your step by step approach and we shouldn’t move to the next step until the current step is resolved. So no next test yet please. If you don’t agree with anything I’ve said please explain why.

I don’t agree because the carts do not have “sails” to catch the wind and force the cart to move downwind, turning the wheel, which then turns the propeller to act as a propeller instead of a turbine. Not only that, but they do not have a big crossarm on which you can mount such a sail. The carts are just skeletal frames, which offer very little blunt body wind resistance. The prop by far offers the most wind resistance and it will turn the opposite way, as we have just verified. If you were to put up such a sail do you still think you can achieve DDWFTTW? Would it not offer substantial wind resistance at wind velocity? Tell you what, this was not my second test, but we can try this instead: Put up your sail, it will need to be fairly rigid, and run your test again just as before. As long as the sail does not blow off, I would bet the cart never exceeds the table velocity because of the new drag. We either need to stick to the original configuration or keep testing in different configs over and over again. If the carts have no sails, it is a violation of the original reference frame to introduce one now. Up to you what you want to do next. Your call.

 

[schroder]

Am I right to take that as humour?

He wimped out also, so yes that was definitely humor! In fact, I can't stay with this much longer but would like to see one more test if possible. I do appreciate what you are doing. I never could have gotten this sort of cooperation from the thinair group!

 

[swerdna]

I don’t agree because the carts do not have “sails” to catch the wind and force the cart to move downwind, turning the wheel, which then turns the propeller to act as a propeller instead of a turbine. Not only that, but they do not have a big crossarm on which you can mount such a sail. The carts are just skeletal frames, which offer very little blunt body wind resistance. The prop by far offers the most wind resistance and it will turn the opposite way, as we have just verified. If you were to put up such a sail do you still think you can achieve DDWFTTW? Would it not offer substantial wind resistance at wind velocity? Tell you what, this was not my second test, but we can try this instead: Put up your sail, it will need to be fairly rigid, and run your test again just as before. As long as the sail does not blow off, I would bet the cart never exceeds the table velocity because of the new drag. We either need to stick to the original configuration or keep testing in different configs over and over again. If the carts have no sails, it is a violation of the original reference frame to introduce one now. Up to you what you want to do next. Your call.

We really should stick to one point at time but . . . (this is the last time I will do this ;-) - I have designed a sail concept where the sail stands vertical while the cart is in the wind then it falls down to the horizontal at wind speed and beyond. It could fall away from the cart altogether.

Back to the current point please (there’s actually two)

Point 1 - Do you agree that a valid test should have the wind blowing on the full cart surface?

Point 2 - Do you agree that however skeletal a frame is it is an increase in wind resistance (however slight) compared to it not being there?

Question - How do you explain the many videos where carts can be clearly seen moving forward in a wind from a stationary position? I can provide links if you haven‘t seen them.

 

[swerdna]

He wimped out also, so yes that was definitely humor! In fact, I can't stay with this much longer but would like to see one more test if possible. I do appreciate what you are doing. I never could have gotten this sort of cooperation from the thinair group!

I don't care how long it takes (it's not a DDWFTTW race ;-) and think it's really important to stick to one point at a time.

 

[schroder]

Surely you have seen video evidence (mine for example) of the cart moving downwind only powered by wind?

I have seen some downwind tests but they are very inconclusive. At first, the prop seems to swing one way, then swings the other way. I am sure in at least one video that it is rotating as a turbine, and yet the wheels are driving in the correct direction to go down wind (but not faster than the wind) I have yet to have anyone explain how the gear reversal was arranged to allow that to happen. There HAD to be a gear reversal because the prop was turning the opposite way as on the treadmill but the wheels were turning the same. A bit of foul play at work, had to be! I don't believe I have seen your outdoor test.

 

[atyy]

No, of course not. The windmill could almost be massless (made out of neutrinonium ?) and the car could go as fast as it goes (call it "lightbullet").

You could consider having two extremely light windmills, planting one down (connected with a rope to your car) that will generate electricity for a few seconds, then fold it up and take it in (with the rope, almost no effort as it is essentially massless), and plant at the same time the second windmill, having it produce electricity for a few seconds, fold it up and take it in while planting the first one again, etc...

A kind of "walking on windmills". Very clumsy, but as a proof of principle, I don't see what stops it.

Of course, there is conservation of momentum, and hence what must remain at the same velocity is the center of gravity of the air (consider a big, but limited amount) and the car, which should move at a velocity slightly smaller than the wind speed (as the car is initially at rest). So we have to "slow down" enough wind to compensate for the increase in speed of the car ; but as there is no limit as to the amount of wind we slow down (or even reverse direction), this doesn't put a hard limit on the speed of the car. This will come out of the energy balance of the whole thing I guess.

I guess I buy your original scenario in the case where the car experiences no drag, isolating all resistance to the windmill ie. I buy it even without walking windmills, since the car can be accelerated to any finite speed greater than wind speed, and after a sufficiently long time the average speed of the centre of mass of car and windmill will exceed the wind speed.

In the case where there is drag on the car also, it seems the scenario can also hold by making the windmill bigger to get more power from the wind.

 

[swerdna]

I have seen some downwind tests but they are very inconclusive. At first, the prop seems to swing one way, then swings the other way. I am sure in at least one video that it is rotating as a turbine, and yet the wheels are driving in the correct direction to go down wind (but not faster than the wind) I have yet to have anyone explain how the gear reversal was arranged to allow that to happen. There HAD to be a gear reversal because the prop was turning the opposite way as on the treadmill but the wheels were turning the same. A bit of foul play at work, had to be! I don't believe I have seen your outdoor test.

Yes, in the very first instance it’s a battle between what the wind wants the prop to do and what the wheel wants the prop to do, For the cart to move forward with the wind the wheel has to win and it does it by the prop and cart frame acting as a sail against the wind.

I haven’t done an outside test yet. Are you saying that you will only accept outside tests as being valid? If so why are we bothering to use my turntable to do your tests?

If you have time now or later could you please answer two “point” questions. A simple yes or no in each case would be fine - thanks.

 

[rcgldr]

if a wind were to blow on the propeller, with the cart stationary on the table, the propeller will act as a turbine, turning the opposite way, turning the wheels the opposite way, and the cart will try to work against the wind, not go down wind.

I've come up with a better explanation for why the cart will respond to a tailwind by moving downwind if the advance ratio is sufficiently < 1.

Assume zero loss factor in movement of air by the prop. For each revolution of prop and wheel, the prop moves the air 6" upwind, while the cart moves 10.5" downwind because the advance ratio (prop pitch / wheel circumference) is 6 /10.5. That means for each forward revolution of the prop and wheel, the air moves 4.5" downwind. The net air flow is in the direction of travel of the cart. The path of least resistance is to allow the air to flow downwind and this only occurs if the cart moves downwind in response to a tailwind.

The air does exert a countering torque on the propeller and wheels, which causes the wheels to exert a forward force on the ground at the contact patches of the wheels, and the ground will respond with an equal and opposite backwards force on the wheels, the Newton 3rd law pair of forces here. The air also exerts a forward force on the propeller, and this force will be greater than the opposing backwards force from the ground related to the windmill torque effect, if the advance ratio is sufficiently < 1. Since the forward force from the air is greater than the backwards force from the ground (related to windmill torque), the net force is forwards and the cart accelerates downwind.

Yes, in the very first instance it’s a battle between what the wind wants the prop to do and what the wheel wants the prop to do. To move forward the wheel has to win and it does it by the prop and cart frame acting as a sail against the wind.

For the reasons explained above, what the wind wants the prop to do and what the wheels want the prop to do results in equal and opposite torques, because the ground will only react to the torque related forward force from the contact patch of the wheel with an equal and opposing force, in compliance with Newtons 3rd law. The real battle is beteen the forward force of the air on prop and cart, versus the backward force from the ground. Even if the cart were drag free, the forward force of the air on the prop will be greater than the backwards force from the ground opposing the windmile torque on the prop.

In reality, any rolling resitance factors also create a countering torqe on the wheels, so the total backwards force from the ground also includes these loss related factors. Still, if the advance ratio is sufficiently < 1, then the forward force of the air will be greater than the backwards force from the ground and the cart accelerates forwards.

 

[schroder]

We really should stick to one point at time but . . . (this is the last time I will do this ;-) - I have designed a sail concept where the sail stands vertical while the cart is in the wind then it falls down to the horizontal at wind speed and beyond. It could fall away from the cart altogether.

Back to the current point please (there’s actually two)

Point 1 - Do you agree that a valid test should have the wind blowing on the full cart surface?

Point 2 - Do you agree that however skeletal a frame is it is an increase in wind resistance (however slight) compared to it not being there?

Question - How do you explain the many videos where carts can be clearly seen moving forward in a wind from a stationary position? I can provide links if you haven‘t seen them.

I have just answered your question three with another post (while you were posting)

1)OK, if you can manage to point the fan so that it covers teh prop and the cart body, that would be fine. I am concerned about that crossarm acting as a sail. I don't know how you can ensure that the crossarm will not act as a sail and move the cart. It should be only the body of the cart and the prop. I still believe the prop will spin the opposite way. And remember you should not allow the cart to get away from the fan it should follow right along with the cart, same as the natural wind would do. I cannot believe you will achiene any significant downwind speed under those conditions.

2) Yes there has to be some increase, but I have seen many of these carts and the body amounts to almost nothing. They are almost all propeller!

 

[schroder]

I haven’t done an outside test yet. Are you saying that you will only accept outside tests as being valid? If so why are we bothering to use my turntable to do your tests?

I definitely did not say that! I think what we are doing here is quite valid and it would be great if we could continue.