Down wind faster than the wind

[Michael C]

All due respect Michael C, this is about the cart. Introduced devices are not relevant. As you know, such devices as the cotton reel, can be made to move or roll according by exploiting the difference between rolling and static friction.

That "something" cannot travel faster than the wind is not a "myth" to which I subscribe. A prop-powered device, as promoted by its developers is one device that cannot achieve that aim.
There is no evidence, save for a trivial trick of the treadmill. It is nothing more than a force-balance toy, deceptively disguised.

OK, you still avoid the simplest question. Too bad.

Thanks for trolling this thread: in trying to get through to you, I've learnt a lot and had fun brushing up my school physics. I've also learnt a lot from all the others who have been pushed to make clearer and clearer explanations.

 

[humber]

Well, argument through absolute exhaustion. You keep saying this, no matter how wrong you've proven to be. Do you think hitting the "Post Reply" button 10 times instead of one makes bad logic better?

Could it be lack of response to particular criticisms?
We can test.

Please take a look at the outlines of operation that I have provided #854
is the nearest, I think.

Perhaps you can refute my claim that a cart in the wind is not modeled by a cart on a treadmill.
Simple inclined tests could be used to provide empirical support.

 

[humber]

OK, you still avoid the simplest question. Too bad.

Thanks for trolling this thread: in trying to get through to you, I've learnt a lot and had fun brushing up my school physics. I've also learnt a lot from all the others who have been pushed to make clearer and clearer explanations.

OK Michael_C, yes it can, as shown.

In response, perhaps you can tell me why my claims that the treadmill is a force-balance device, and the treadmill does not model the real cart , are false.

 

[Thabiguy]

<snip>

For a while now, this has reminded me of something. I knew that I had seen something like this before, but I've had trouble pinpointing it.

Now I remember.

Kleinman.

 

[humber]

If you have invented, as you claim, a "force balance" device that can hold its position on a moving treadmill indefinitely, without any attachment to anything other than the belt, and without a propeller or other significant coupling to air movement, then you have invented an over-unity device. I suggest that you patent it pronto.

The device cannot be receiving any power from the belt as it is not accelerating and therefore not subject to any net force in any direction from its contact with the belt (otherwise it would not hold its position). Power = force * distance / time. No force and no distance here, so zero power input from the belt.

If the device can hold its position on the belt, it can maintain constant velocity on a fixed surface. And since it clearly has friction to overcome (since one component is a "small wheel rubbing along the belt") that makes it an over-unity device, even if its only useful application turns out to be generating heat from that friction.

Respectfully,
Myriad

I have invented nothing here, Myriad.

No. The device is not completely static, so that argument fails.

There are movements and small accelerations, that do allow for its operation as described. The initial conditions are met by operator control, so that is not a problem either.

If the feedback mechanism does fail, then it will be dragged back by the belt. However, it is difficult to fail in the other direction, because that would require more than is immediately available from the belt.

But that immediate demand, can be provided by the momentum of the remaining components. That is enough to keep is moving slightly forward. or pick up enough energy to remain in place.

The actual operation is complex. If an object is placed upon a vibrating table, it can be moved about more easily, because amongst other reasons, the friction is lower, because the contact time is lower.

I think that this is present in this design (perhaps from the driving motor), because it moves about so easily.
Note that lateral movement, "scrubbing" the wheels is readily achieved. Friction is very low, so the energy taken from the belt is low, and that also explains why the craft has so little forward momentum.

However, that is a detail of operation, and does not deny the principle.

As you know rotating mechanical devices store momentum, the integral over time. Immediate satisfaction of the rules, is therefore not a limitation

 

[Michael C]

OK Michael_C, yes it can, as shown.

Good. Is there an essential difference between the principle of Dan O's toy and that of Spork's cart? If so, what is it?

In response, perhaps you can tell me why my claims that the treadmill is a force-balance device, and the treadmill does not model the real cart , are false.

1. (The force-balance device). Myriad has addressed this, but I will elaborate:

If the cart was producing no forward thrust at all, it would soon run of the left end of the treadmill (orientation as viewed in Spork's video), due to forces of friction and drag. If it is to remain on the treadmill without running off the end, it must produce some thrust to counterbalance the loss of energy due to friction. Where is that thrust coming from?

In fact, as you can see in that video, it actually runs off the other end of the treadmill, against the direction of motion of the surface of the treadmill. To do that it much produce even more thrust. Where is this thrust coming from?

2. (Why the cart on the treadmill is equivalent to the cart on the road). Basic physics. People have been explaining this in many ways, throughout this thread. There have been all sorts of clear explanations. I cannot do better.

 

[humber]

For a while now, this has reminded me of something. I knew that I had seen something like this before, but I've had trouble pinpointing it.

Now I remember.

Kleinman.

Oh, I remember other people too, and the phrases they use. But you, not.

Perhaps you might change your view, if you study the treadmill operation. I doubt that you can deny my claims.

 

[Myriad]

I have invented nothing here, Myriad.

You repeatedly claimed that the DWFTTW carts under discussion were "mere force-balance" toys. You then demanded, over the course of several posts, that we discuss the "force-balance treadmill" you had previously described.

So, I looked at your force-balance treadmill and found that this "toy" you compare the DWFTTW carts to has miraculous powers unknown to science! You clearly claim that such a "toy" can stay in place indefinitely on a moving treadmill with no coupling with air and no contact with anything except the top of the belt, despite experiencing friction. That's over-unity.

Unfortunately, you now admit that you haven't actually invented this force-balance toy. I guess that explains how it can violate the laws of physics: because it doesn't and cannot actually exist.

So having addressed your request to discuss the force-balance treadmill, can we get back to discussing devices that could exist? Such as Dan O's device? How fast does the yo-yo move, relative to the wind?

Respectfully,
Myriad

 

[humber]

Good. Is there an essential difference between the principle of Dan O's toy and that of Spork's cart? If so, what is it?

That will only lead to the same question of energy. May I remind you that your argument "assumes windspeed travel as a fact" in support of itself.

I have no need to answer speculation when the treadmill alone denies it.
It seems that a "certain" winner is now looking in every closet for the scarcest supporting evidence. Perhaps today it is a yo-yo that explains its operation, if not then we can always try another, eh?

1. (The force-balance device). Myriad has addressed this, but I will elaborate:

If the cart was producing no forward thrust at all, it would soon run of the left end of the treadmill (orientation as viewed in Spork's video), due to forces of friction and drag. If it is to remain on the treadmill without running off the end, it must produce some thrust to counterbalance the loss of energy due to friction. Where is that thrust coming from?

In fact, as you can see in that video, it actually runs off the other end of the treadmill, against the direction of motion of the surface of the treadmill. To do that it much produce even more thrust. Where is this thrust coming from?

I think these points are covered in my reply to Myriad.

2. (Why the cart on the treadmill is equivalent to the cart on the road). Basic physics. People have been explaining this in many ways, throughout this thread. There have been all sorts of clear explanations. I cannot do better.[/QUOTE]

They have not argued that. They have taken as an assumption that the treadmill and real cart are the same, and from there.

You can do it at low speed. Newton's law of opposite and equal reaction means that a device that responds by opposing the force that is applied to it, with EQUAL force under all conditions, cannot be moved. That can't be right. Some others have expressed it in other ways "take off the prop and it will run without wind" and so forth.

An inclined slope test would clear your doubts, I think. Why are "skeptics" only interested in such matters? Don't you want to know?

 

[Dan O.]

3R2/R1 smoots pre microfortnight, in the direction of the wind.

You got the direction right but your math is wrong. Try looking at the edge conditions for R1=R2 and R1=0.

To get the correct answer, it might help if you solve for the movement of the parachute when the yo-yo rolls forward 1 unit then invert the answer to get the motion of the yo-yo for a 1 unit movement of the parachute.


Then try this next problem that is closer to the wind and cart situation.



Assume that the leverage (A,B,C) is such that the paddle is moving backwards relative to the cart at 1/2 the forward motion of the cart.

Describe all the forces at the instant when the paddle strikes the ball.

 

[humber]

You repeatedly claimed that the DWFTTW carts under discussion were "mere force-balance" toys. You then demanded, over the course of several posts, that we discuss the "force-balance treadmill" you had previously described.

So, I looked at your force-balance treadmill and found that this "toy" you compare the DWFTTW carts to has miraculous powers unknown to science! You clearly claim that such a "toy" can stay in place indefinitely on a moving treadmill with no coupling with air and no contact with anything except the top of the belt, despite experiencing friction. That's over-unity.

Unfortunately, you now admit that you haven't actually invented this force-balance toy. I guess that explains how it can violate the laws of physics: because it doesn't and cannot actually exist.

So having addressed your request to discuss the force-balance treadmill, can we get back to discussing devices that could exist? Such as Dan O's device? How fast does the yo-yo move, relative to the wind?

Respectfully,
Myriad

Which part requires over-unity?
The energy dissipated in the air (prop), wheels and belt friction, comes from the belt. There is more than enough. The cart does not produce energy, but redistributes it.
The forces balance. They must. Otherwise it would move more rapidly.

There is no magic here. If you use a thread , then all it takes is some friction between the belt and that thread to show that is is possible to send a device up the belt.

Now you just need control to maintain that friction so that the cart will remain in place. Because the prop is connected to the wheels, then the total from the belt, must be the sum of the drive and prop forces, so it automatically balances, because that is the most stable condition. It has no choice.

 

[Myriad]

Dan O's Yoyodyne plans were just an early prototype. The limited range due to the yo-yo eventually winding up all the rope was a serious flaw.

I managed to get hold of the smuggled plans for the next prototype. (This is a synthesis of many of the different designs in this thread. Combined with Dan O's work and perhaps my downchain crawler, it's pretty much self-explanatory.)

Happy para-yoyo-ing all!

Respectfully,
Myriad

 

[Myriad]

I've just received a complaint from John Small Quibbles down at Yoyodyne, who points out that once the para-yoyo gets up to full speed (faster than the wind, of course), the parachutes are experiencing an up-chute wind on both sides of the circuit, not just the bottom inbound side. So as drawn, the chutes would unfurl in both directions. Fortunately there is a simple remedy: run the upper outbound side of the loop through a tube (a chute-chute) that keeps the chutes furled.

Respectfully,
Myriad

 

[Thabiguy]

Dan O's Yoyodyne plans were just an early prototype. The limited range due to the yo-yo eventually winding up all the rope was a serious flaw.

I managed to get hold of the smuggled plans for the next prototype. (This is a synthesis of many of the different designs in this thread. Combined with Dan O's work and perhaps my downchain crawler, it's pretty much self-explanatory.)

After testing that device for some time, they found out that the parachutes got caught and entangled in the wheels all too often. The next prototype they considered therefore looked like this:

(coincidentally leaked by Spork in page #4 of this thread )

 

[spork]

I love the para-yo-yo. We've got to build one for the treadmill.

 

[Thabiguy]

You got the direction right but your math is wrong. Try looking at the edge conditions for R1=R2 and R1=0.

The correct answer is v_wind/(1-R1/R2).

There are two ratios here: the ratio of backward speed of the propelling surface and the backward speed of the ground, wrt vehicle. This is the "advance ratio", or f₁.

And the ratio of forward speed of the propelling surface and the forward speed of the vehicle, wrt ground. This is the "leverage factor", or f.

f = 1 - f₁. They happen to coincide for 1/2, which may lead to confusion and interchanging of the two. But the theoretical speed of the vehicle in relation to the windspeed is determined by f.

This was mentioned a couple times before, but the thread is long, so it's worth repeating.

 

[Myriad]

(coincidentally leaked by Spork in page #4 of this thread )

Ha! Just like Yoyodyne, to put the wind-catching paddles in the least advantageous position relative to the vehicle, on the undercarriage!

Actually, I did remember that design and was looking for it when you posted. I know we've ended up pretty near where we started but when you're looking not for the best practical design but for the clearest explanation of the principle behind that design, things can go that way. I would choose parachutes over paddles for the same reason Spork chose gravity-deployed underside paddles instead of wind-deployed topside paddles with a reversing gear and a return chute: prioritizing understandability over practicality.

Thanks to humber's assistance (and despite some digressions that didn't pan out productively) we've come up with some good answers to that problem, some of which might assist in similar discussions on other forums.

Respectfully,
Myriad

 

[Seymour Butz]

The treadmill experiment in no way demonstrates proof.

The treadmill eliminates 1 variable found in a real world, wind driven situation:

The cart experiences the same relative windspeed - 0 mph. Since the cart, as it goes faster on the street, "sees" less tailwind, power input will also be less.

I think the way to correct this would be to put the cart on a 10 mph treadmill, and then put a 10 mph fan behind it. I'm assuming that the prop is reversed on the treadmill vs the street, correct?

If you do this, then the wind differential that the prop "sees" would be zero, the same as when a cart going 10 mph in a 10 mph breeze "sees".

On the side of the believers, I understand how the cart works. From a standstill, as the breeze passes over the angled blades, simple deflection of the wind will result in the cart "starting up". Torque input will also be high. As the cart picks up speed, and therefore the prop picks up speed, the prop will provide "lift" - in the horizontal direction.

This lift being maintained depends on the rotation of the prop being maintained. This requires *some* torque being input to the prop. this is provided by the wind passing through the blades. At below wind speed, wind flow through the blades will provide enough torque to maintain this lift. But once AT windspeed, what provides this torque?

From what I can see, the cart at the beginning of the Mythbusters video uses kinetic energy stored in the spinning prop to maintain a speed that can be briefly higher than than the windspeed AT THAT MONENT ONLY, when the wind briefly slackens. The fact that at times, the cart is slower than wind speed is proved that at times, the wind sock blows towards the front. Just before the windsock is being blown forward is when kinetic energy is being expended. When the windsock is being blown forward is when torque is once again being put into the system.

Kinetic energy can be very high in a spinning element, just ask a chopper pilot that loses power while in flight - *some* lift can be maintained for a short while as the spinning rotor blades release their kinetic energy.

I would be willing to admit that there are many aspects of an airfoil that I don't understand, and therefore there may be some aspects of it that I can't fathom, but the only way to achieve this through aerodynamic means would be if the lift provided by the prop exceeds the drag it experiences. LOL, I think.....

 

[sol invictus]

On the side of the believers, I understand how the cart works.

No you don't - you've missed the whole point.

From a standstill, as the breeze passes over the angled blades, simple deflection of the wind will result in the cart "starting up". Torque input will also be high. As the cart picks up speed, and therefore the prop picks up speed, the prop will provide "lift" - in the horizontal direction.

This lift being maintained depends on the rotation of the prop being maintained. This requires *some* torque being input to the prop. this is provided by the wind passing through the blades. At below wind speed, wind flow through the blades will provide enough torque to maintain this lift. But once AT windspeed, what provides this torque?

The spinning of the wheels, which torque the prop. The spin is maintained by friction between the wheels and the ground.

Look at the chain crawler myriad posted a page or so back - it's very clear, and it's precisely the same principle.

 

[ThinAirDesigns]

From what I can see, the cart at the beginning of the Mythbusters video uses kinetic energy stored in the spinning prop to maintain a speed that can be briefly higher than than the windspeed AT THAT MONENT ONLY, when the wind briefly slackens.

What you see in our MythBusters video has been edited to fit our dialog needs. Watch this video in it's entirety -- particularly the last 2 minutes after the cart gets up to speed.

http://www.youtube.com/watch?v=aJpdWHFqHm0

JB