DDWFTTW - Tests.

[ynot]

Before leaving on my hoilday thought I would post a quick video of my patented turntable and magic marble test (I traded a cow for the marble ;-). The other DDWFTTW thread was getting very long and hard to keep up with so thought I would start a new one to debate this and other turntable tests I will be conducting and posting after my holiday. If anyone wants to post any other tests here as well that’s fine. Please keep the debate about the subject and not the person.

The large marble is made of glass so no magnetic cheating. The turntable is level and I “hovered” the marble at several positions around the turntable to demonstrate this.

Look Ma, no propeller!

http://www.youtube.com/watch?v=kc88SrMG5fA

Hold all bets? I haven’t time to offer my thoughts right now so will leave it to you guys to intelligently and courteously debate (yeah right). Will try to answer any questions but they will have to be quick answers and it may take some time to reply.

[spork]

Very nice first test. The marble does pretty much what I think we would expect. It will almost hover in place, but loses ground gradually due to rolling and aerodynamic frictions. We also see some more complex behavior as a result of gyroscopic precession of the marble, but you did a nice job of cancelling that out several times.

What we don't see - and won't see - is the marble advancing on the turntable. What I'm confident we will see is the prop-cart advancing on the turntable. I look forward to further videos.

It's good to have another hacker out there doing these tests and posting the results. Better still that you're a sceptic (or at least were - I'm not sure where you stand at the moment).

[ynot]

Very nice first test. The marble does pretty much what I think we would expect. It will almost hover in place, but loses ground gradually due to rolling and aerodynamic frictions.

Yep, same as I suspect happens with your cart.

Here's my current thinking . . .

If your cart is only held from travelling backwards on the treadmill (not forwards) it can only go the speed of the treadmill the same as the marble. When the thrust of the propeller matches the rolling resistance it will move ahead slightly and “hover”. Left for long enough it will lose ground gradually due to rolling and aerodynamic frictions.

To advance against the treadmill your cart has to be also held from advancing when it "wants" to so it can develop more thrust than it needs to merely hover. When the cart is then released the thrust is greater than the rolling resistance and the cart moves forward along the treadmill. Left for long enough, it will also lose ground gradually due to rolling and aerodynamic frictions.

The main purpose of this demonstration is not to show that the marble can hover but to show how gradual and slow the loss due to rolling and aerodynamic frictions is. It’s certainly a lot more gradual and slower than the loss observed when the cart is removed from the treadmill.


We also see some more complex behavior as a result of gyroscopic precession of the marble, but you did a nice job of cancelling that out several times.
If you mean the marble going around in circles then this is more due to the fact that the outside edge of the turntable moves faster than the inner than it has to do with precession.



What we don't see - and won't see - is the marble advancing on the turntable. What I'm confident we will see is the prop-cart advancing on the turntable. I look forward to further videos.
You see the marble travelling faster than the turntable when it moves from the outer edge to the inner. I have done tests with a heavier ball bearing and it performs better and is more stable than the marble. I may get time to do more filming with it tomorrow.

It's good to have another hacker out there doing these tests and posting the results. Better still that you're a sceptic (or at least were - I'm not sure where you stand at the moment).
Not definitive either way but leaning very heavily toward sceptic.

[spork]

Yep, same as I suspect happens with your cart.

Well, if you build one you'll find out differently.

The main purpose of this demonstration is not to show that the marble can hover but to show how gradual and slow the loss due to rolling and aerodynamic frictions is. It’s certainly a lot more gradual and slower than the loss observed when the cart is removed from the treadmill.

Give that marble a propeller and gear train. Reduce it's weight to surface area by about 90%, and then tell me how slowly it loses momentum on your wheel.

If you mean the marble going around in circles then this is more due to the fact that the outside edge of the turntable moves faster than the inner than it has to do with precession.

Shoot, this makes me wish I specialized in dynamics and control theory in my M.S. program... oh - wait, I did.

Sadly, I guess I may be forced into making a turntable afterall. I guess this is what it will take to show the cart will advance steadily and continuously.

Not definitive either way but leaning very heavily toward sceptic.

So can I assume you simply deny the GPS data, analyses, and personal accounts that show ice boats do this all the time?

[Michael C]

The marble loses energy very slowly, since there is very little friction and very little air drag. Can you make a cart that has comparably small energy losses due to friction and unwanted air drag? If you can manage that, I'm sure you'll see it whizzing around against the direction of the turntable.

In practice, your cart will have much more problems with friction and drag than the marble does. It will need to be well-built to overcome these forces. There's no impossibility here (as has already been demonstrated ;) ), but if the cart isn't efficient enough, it may not work. If your cart does not advance against the direction of the treadmill, it will not be a proof that DDWFTTW is impossible: it will simply demonstrate that your particular cart can't manage it. Should that happen, I hope you'll keep tweaking the design of the cart.

[casebro]

Hey Ynot, was that typo in your OP subject?

What else could have been on your mind, what with the double DD?

[H'ethetheth]

Hey Ynot, was that typo in your OP subject?

What else could have been on your mind, what with the double DD?I think the first D stands for 'directly'.

[HairBall]

I think I have a better explanation

I can't see anything powering your turntable. So I'm assuming that you spun it up by hand and it's coasting. If that it true, the ball bearing is simply losing momentum at the same rate as the turntable.

[spork]

If your cart does not advance against the direction of the treadmill, it will not be a proof that DDWFTTW is impossible: it will simply demonstrate that your particular cart can't manage it.

This is why I assume I'll be making a turntable in the end. It's hard enough to make a working cart when you know it can be done. It's extremely unlikely that you'd succeed when you don't believe or even want to see it work.

[Dan O.]

Unlike the earlier demonstrations with the cart, the rolling ball on a disk is apparently a useful model for real world effects. It is used in labs in several college physics courses.


ETA: Does the ball bearing make as much noise as the marble? It sound like either you have a heavy grain on your turntable or the ball isn't spherical which is causing it to bounce and rattle and loose more energy to sound and heat.

[spork]

Unlike the earlier demonstrations with the cart, the rolling ball on a disk is apparently a useful model for real world effects.


Interesting theory. But I'd point out that the treadmill IS real world. That being said, I don't deny that the turntable does allow us to perform certain tests that are not possible on a home treadmill.


I’ve been ciritcal of the treadmill demonstrations...Not to be beaten I have stolen time I don’t have and have quickly built a turntable and cart (and it works!!!). ...The construction is crude and there is still lots of fine tuning to do but early tests have been conclusive enough for me to say the answer to this question is 99.99999999% YES!


Then:

spork says: "The marble does pretty much what I think we would expect. It will almost hover in place, but loses ground gradually due to rolling and aerodynamic frictions."

and Ynot says: "Yep, same as I suspect happens with your cart."

So it seems Ynot has embraced that 0.00000001% doubt. But we're given no explanation as to what changed his mind. Further experiments that he hasn't told us about? Schizophrenia?

[technoextreme]

Unlike the earlier demonstrations with the cart, the rolling ball on a disk is apparently a useful model for real world effects. It is used in labs in several college physics courses.


The treadmill is a better model than the disk because the coupling gets really really really screwed up with that wheel unless you design the wheels of your cart really close together.

[ynot]

Well, if you build one you'll find out differently.
You guys have short or selective memories. I posted on the other thread that I have already built a cart that will hover and move against the turntable in the same manner as a cart does on a treadmill. That a cart can be made to do this is not in question. The question is (for me at least) can it continuously sustain these actions?

Give that marble a propeller and gear train. Reduce it's weight to surface area by about 90%, and then tell me how slowly it loses momentum on your wheel.
Isn’t the thrust of the propeller the very “advantage” of a cart? The marble only has inertia while a cart has inertia and propeller thrust. I wouldn’t be surprised if future tests show that the cart loses to rolling resistance slower than the marble.

Shoot, this makes me wish I specialized in dynamics and control theory in my M.S. program... oh - wait, I did.
Prove it’s precession by getting a ball to travel in circular paths on your treadmill and post a video of it doing it.

Sadly, I guess I may be forced into making a turntable afterall. I guess this is what it will take to show the cart will advance steadily and continuously.
I would be very pleased if you did.

So can I assume you simply deny the GPS data, analyses, and personal accounts that show ice boats do this all the time?
How is being “not definitive either way” denying anything.

[ynot]

I think the first D stands for 'directly'.
“Directly” is the most important word in the sentence.

[sol invictus]

You guys have short or selective memories. I posted on the other thread that I have already built a cart that will hover and move against the turntable in the same manner as a cart does on a treadmill. That a cart can be made to do this is not in question. The question is (for me at least) can it continuously sustain these actions?

Aren't you in a rather good position to answer that for yourself? Just let your cart run for a long while.

Isn’t the thrust of the propeller the very “advantage” of a cart? The marble only has inertia while a cart has inertia and propeller thrust. I wouldn’t be surprised if future tests show that the cart loses to rolling resistance slower than the marble.

You've gotten yourself confused again.

Look - if there were no losses due to friction, the marble could stay rotating in place on the treadmill/wheel indefinitely. But since there is some loss due to friction, it gets dragged a little in the direction the treadmill is moving. For the cart those losses are much higher, so if it didn't have a prop, or if the prop were oriented the wrong way, it would get pulled along with the treadmill belt even faster.

But the prop provides a force in the opposite direction which more than compensates for that force due to friction. That's why the cart can move steadily in the up the belt (or in the opposite direction as the rotation, in your case).

All of these things behave exactly as expected from basic physics.

[ynot]

Aren't you in a rather good position to answer that for yourself? Just let your cart run for a long while.



You've gotten yourself confused again.

Look - if there were no losses due to friction, the marble could stay rotating in place on the treadmill/wheel indefinitely. But since there is some loss due to friction, it gets dragged a little in the direction the treadmill is moving. For the cart those losses are much higher, so if it didn't have a prop, or if the prop were oriented the wrong way, it would get pulled along with the treadmill belt even faster.

But the prop provides a force in the opposite direction which more than compensates for that force due to friction. That's why the cart can move steadily in the up the belt (or in the opposite direction as the rotation, in your case).

All of these things behave exactly as expected from basic physics.
I don’t consider my current cart to be good enough to be used for testing.

I thought all that was exactly what I said. The cart is more disadvantaged than the marble by higher friction losses, but it is more advantaged overall than the marble against those friction losses by the thrust of the propeller. So much so in fact that if the claim is correct the thrust of the propeller overides all friction losses.

[mhaze]

The treadmill is a better model than the disk because the coupling gets really really really screwed up with that wheel unless you design the wheels of your cart really close together.

No, this is inaccurate. It just means you use a bicycle instead of a cart, and hook it via a simple forked rod to say, a fish scale. Then your mechanism stays upright and rigid at a single xy position on the disk, and you have a reading of force generated.

Better of course would be a circular treadmill, like the old ones used with hamsters. According to DDWFTTW, the cart beats the hamster! Maybe the hamster could be trained to get the thing going, then jump in the cart and get a free ride?

Wheee!!!!

[ynot]

No, this is inaccurate. It just means you use a bicycle instead of a cart, and hook it via a simple forked rod to say, a fish scale. Then your mechanism stays upright and rigid at a single xy position on the disk, and you have a reading of force generated.

Better of course would be a circular treadmill, like the old ones used with hamsters. According to DDWFTTW, the cart beats the hamster! Maybe the hamster could be trained to get the thing going, then jump in the cart and get a free ride?

Wheee!!!!
You can in fact use a unicycle (a single wheel).

[ThinAirDesigns]

Ynot:
You guys have short or selective memories.

On the contrary, we remember the contradictions of yours that you seem to conveniently forget.

From your referenced post:
What I wanted to test was whether the thrust of the fan could continuously exceed the the rolling resistance of the wheel (mine only has one drive wheel). The construction is crude and there is still lots of fine tuning to do but early tests have been conclusive enough for me to say the answer to this question is 99.99999999% YES!

When the cart is “hovering” and the turntable is sped up the cart travels against the motion of the turntable. I didn’t think it would.

You originally thought it was powered by kinetic energy.

You say above that you didn't think the "thrust of the fan could continuously exceed the the rolling resistance of the wheel" Now, "Continuous" would obviously rule out your kinetic theory.

You say your testing showed with 99.99999999% certainty that it will do it *continuously* -- contrary to what you thought.

Ok, there you have it -- your testing showed to the above certainty that we were right and your kinetic energy theory was wrong.

Now you come along and without announcing any subsequent tests or test results that you still believe your 'kinetic energy" theory is still correct.

Absolute contradition.

If you've done more testing and come up with different results causing you to change your 99.999999999% position, then OK --- share those tests. Otherwise your just confirming either a bias, or an inability to interpret test results.

I don’t consider my current cart to be good enough to be used for testing.

Your cart progressed against the rotation of the turntable. It did this to 99.9999999% certainty of continuous. WTF -- why the hell didn't you just leave it running another 2 seconds and answer that .000000001% question.

It's like "Oh, I better shut it off really quick before I have to admit that they are right and I was wrong." LOL

Here's a test for you Ynot ... when you have a turntable and the cart is advancing against the rotataion -- LEAVE IT THE F RUNNING AN EXTRA SECOND OR TWO!!

JB

PS: BTW, how do you like people telling you your tests are bogus? :-)

[ynot]

Ynot:


On the contrary, we remember the contradictions of yours that you seem to conveniently forget.

From your referenced post:


You originally thought it was powered by kinetic energy.

You say above that you didn't think the "thrust of the fan could continuously exceed the the rolling resistance of the wheel" Now, "Continuous" would obviously rule out your kinetic theory.

You say your testing showed with 99.99999999% certainty that it will do it *continuously* -- contrary to what you thought.

Ok, there you have it -- your testing showed to the above certainty that we were right and your kinetic energy theory was wrong.

Now you come along and without announcing any subsequent tests or test results that you still believe your 'kinetic energy" theory is still correct.

Absolute contradition.

If you've done more testing and come up with different results causing you to change your 99.999999999% position, then OK --- share those tests. Otherwise your just confirming either a bias, or an inability to interpret test results.



Your cart progressed against the rotation of the turntable. It did this to 99.9999999% certainty of continuous. WTF -- why the hell didn't you just leave it running another 2 seconds and answer that .000000001% question.

It's like "Oh, I better shut it off really quick before I have to admit that they are right and I was wrong." LOL

Here's a test for you Ynot ... when you have a turntable and the cart is advancing against the rotataion -- LEAVE IT THE F RUNNING AN EXTRA SECOND OR TWO!!

JB

PS: BTW, how do you like people telling you your tests are bogus? :-)
Fair cop, but I have been obviously suffering from premature articulation (thankfully not ejaculation). I’m not happy that I’ve flip-flopped so many times with this and I apologise for doing so. I’m not the only one to have changed their mind, I’ve just done it more times than anyone else. At least I’ve shown that my mind is capable of being changed. As I said in the other thread, my current position is that I simply don’t know but lean towards the negative. This will remain my position until I have credible evidence either way. My 99+% claim was a knee-jerk reaction to the very emotional and seductive effect of viewing the cart do the “impossible“ live for the first time. I’m sure you and others have experienced the same buzz.

If my yet to be proven thoughts are correct it will take much longer the a couple of seconds to get the “answer“.

I really don’t mind people telling me my tests are bogus if they provide credible evidence that they in fact are. I also don’t mind the personal criticism regarding my stupid flip-flopping as it is valid. I do mind however the level of “if you’re not with us you’re against us” type of petty personal attacks that aren’t helpful or called for. But I can easily live with them.

I will produce an efficiently working cart and turntable that are worthy of using for testing and I will conduct many tests and publish the results. Won’t be for a few weeks though due to holidaying in Oz.

[ThinAirDesigns]

Ynot, for the record, I had no issue with your flip flopping *before* you did your test. It's after you go to all the trouble and run it to within 99.99999999995 of continuous that I'm mistified.

Fair enough.

BWT. How is your turntable powered?

Thanks

JB

[spork]

Fair cop, but I have been obviously suffering from premature articulation (thankfully not ejaculation). I’m not happy that I’ve flip-flopped so many times...

And yet when I pointed out that you contradicted yourself, your response was: "You guys have short or selective memories..."

This is about par for the level of consistency we seem to get from you. I guess all that's left is for me to start demanding that you do any number of bizarre, meaningless, and ill-defined tests with your turntable - and then cry like Nancy Kerrigan when you don't do them.

At least I’ve shown that my mind is capable of being changed.

For you amnesia seems to be a train of thought.

If my yet to be proven thoughts are correct it will take much longer the a couple of seconds to get the “answer“.

Yes, we understand that you have to actually witness it for eternity to believe it is steady state. Please don't report back until your findings are conclusive.

I will produce an efficiently working cart and turntable that are worthy of using for testing and I will conduct many tests and publish the results.

You can't even tell us whether your turntable is powered, or is steadily decelerating, and presumably can't even understand the relevance of that.

[John Freestone]

Ynot, I'm sorry you're coming in for some flak. I was surprised, and think you deserve some slack for actually getting on and doing this. I was surprised, however, after you said your initial test suggested a positive outcome. Anyway, I don't give a monkey's uncle how much you flip flop. I'm more irritated that you've started another thread (not really that much). The other one was so full of bull often (yes, I know, mine), it would have been good to drop it in there. It's also very wide in scope and could have accommodated the turntable tests too. Anyway, no matter. I'll send you my therapy bill later.

I guessed that you had the turntable powered somehow, but maybe not. If you want to be really clear about leaving a cart running a long time to establish steady state, it will be essential to make sure the turntable is going at a steady rate too. I'm sure you know that, I'm just saying. Probably a mains motor is good enough. A single index mark on the edge could be useful for verifying on video.

I'm very interested to read about your experiments. Have a good holiday.

[CyCrow]

A turntable is useful for determining maximum performance of the cart, as it is endless unlike a treadmill. Some care should be taken though, as the radius needs to be much larger than the propeller radius to avoid the speed being significantly different for the inside and outside blades. It will also be running into it's own propwash. Other issues are of course keeping it level and smooth etc. A unicycle design will help.

That said, the marble is subjected to a lot of unintuitive forces on the turntable. A rotating frame of reference is not inertial. Rotational inertia and centrifugal forces create a semi-stable balance. Moving inward it wants to go faster than the surface, which tends to move it outward again. The video shows this oscillating motion. Interesting, but not really relevant to DDFTTW devices.

// CyCrow

[mender]

Ynot, I'm sure that further testing will convince you that the cart really does work.

The marble test on the turntable was quite interesting, not at all what I thought! The circular motion as it tried to move to the slower moving centre was particularly fascinating; has it ever been flung off the edge when the circles get big enough?

Anyway, it definitely does lose momentum as it runs, continually moving either inwards or with the direction of the turntable travel, or a combination of the two. Having a cart hover indicates clearly that the cart is actively countering the drag, and that with a bit more turntable speed will start to progress forward around the table.

Try that with the marble; speed up the turntable while the marble is on it and see what happens!

I'll be building a turntable as well for my experiments. I have a neat little device that allows me to adjust the speed very easily from a dead stop all the way to about 20 mph. I can even test it in reverse! Spork knows what I'm talking about.

[spork]

Ynot, I'm sorry you're coming in for some flak.

Attack begets attack.

I was surprised, and think you deserve some slack for actually getting on and doing this.

If he takes half the crap we have for doing it all wrong and not jumping when people (like him) tell us to, he should be very happy.

Anyway, I don't give a monkey's uncle how much you flip flop.

Nor do I. But I don't intend to stand for his claims that I have a short and selective memory when I ask about his seemingly random change in conclusion.

[John Freestone]

The marble test on the turntable was quite interesting, not at all what I thought! The circular motion as it tried to move to the slower moving centre was particularly fascinating; has it ever been flung off the edge when the circles get big enough?I didn't want to say that the marble didn't do what I expected, but now someone else has, I feel able to. Maybe your idea wasn't as bad as mine, mender, but I really expected the marble to hardly stay on there at all. I thought it would slip off the edge in very little time. Of course, it is not being sent in a circular motion just because its on a surface that is going in a circle, so it doesn't experience centrifugal force (oh god, someone's going to tell me there's no such thing now), and yet I could swear when I put marbles on record players (long time ago) they got spun off very quickly.

That would be, I presume, because the surface had enough friction to accelerate my marbles, drag them with the turntable movement, whereupon they would experience that virtual thing we call centrifugal force (actually, travelling in a straight line, since the turntable could not exert a centripetal force on them, I guess). But that is also a surprise to me, that your marble is not accelerated more by the turntable.

As Dan O points out, it seems to be a very lumpy contact, but I would have thought that would increase the tendency to be taken for a ride with the turntable, then roll off. As it would tend to roll towards the edge, which is moving faster, I would expect that accelerating force to increase, making its departure even more sure. Instead, for whatever reason, it goes in that elliptical motion. It seems to go CW (with the turntable rotation?*) towards the edge, move inwards, and then move CCW (against it), as the relative speeds of its rotation and the turntable's movement under it would predict. It seems slightly dragged down-turntable overall, as spork said, but it seems as likely to fall into the bike spokes as fall off the edge at times. There seem to be more counterintuitive things in this project the more we delve into it. Your hovering marble is a little brainteaser itself.

*It might be good to make the direction of rotation as clear as possible, with wide-spaced marks on the edge or a big arrow drawn on the surface, and accompanying notes. Wheels have a habit of appearing to go backwards on video, and I'm still not sure which way it's going, but from how you resist the marble's motion originally, it seems to be clockwise (viewed from above)...ETA: oh yes, and from the fact that the marble is gradually going that way. If you get a rolling marble to go against the turntable, you really do need to contact Randi.

[John Freestone]

Attack begets attack.



If he takes half the crap we have for doing it all wrong and not jumping when people (like him) tell us to, he should be very happy.



Nor do I. But I don't intend to stand for his claims that I have a short and selective memory when I ask about his seemingly random change in conclusion.Ok, I maybe missed something. I'll leave you to it.

[technoextreme]

No, this is inaccurate. It just means you use a bicycle instead of a cart, and hook it via a simple forked rod to say, a fish scale.
You just restated the same thing I said. I don't think a bicycle would necessairly been that essential and a much better design would be to use a diferent cart where only one wheel drives the propellor and the other one is free spinning.

[ThinAirDesigns]

Ynot, I'm sorry you're coming in for some flak. I was surprised,

John, to understand our position you have to know the history of this thread and that of other forums where Ynot participated with us.

He had been very critical of our tests and has repeatedly requested that we execute poorly thought out and useless test of his definition.

He deserves some guff when he blames our memory for his own inconsistency and won't even answer the simple question "how is your treadmill powered (or is it powered at all)?"

I am very glad Ynot has built his own turntable and kudos to him for it. It's his turn to see what it's like to try to test for a bunch of internet yahoos. :-)

JB

[Zeuzzz]

Anyone tested the FTPUTDG or FHHYD recently?

This thread makes me think of back to the future - War edition.

[John Freestone]

John, to understand our position you have to know the history of this thread and that of other forums where Ynot participated with us.

He had been very critical of our tests and has repeatedly requested that we execute poorly thought out and useless test of his definition.

He deserves some guff when he blames our memory for his own inconsistency and won't even answer the simple question "how is your treadmill powered (or is it powered at all)?"

I am very glad Ynot has built his own turntable and kudos to him for it. It's his turn to see what it's like to try to test for a bunch of internet yahoos. :-)

JBI wasn't intending any judgement of your criticism, or any judgement of his deserving of it, only to share my surprise and encouragement.

I imagined that he didn't answer about the power question because he's either on holiday or busy, since he said he was going away soon, you asked at #21 and he hasn't posted in the thread since, but maybe you asked before and he has refused to answer or evaded the question.

Anyone tested the FTPUTDG or FHHYD recently?What are they?

[spork]

I imagined that he didn't answer about the power question because he's either on holiday or busy, since he said he was going away soon, you asked at #21 and he hasn't posted in the thread since, but maybe you asked before and he has refused to answer or evaded the question.

But this is posted in #8

I can't see anything powering your turntable. So I'm assuming that you spun it up by hand and it's coasting. If that it true, the ball bearing is simply losing momentum at the same rate as the turntable.

No answer by ynot. I assume it's because the answer does not support his theory of the moment. My theory of the moment is the same as it has been for 3 years - the cart works. It goes faster than the wind steady-state, and it does this for relatively straightforward reasons that are well understood by a number of people here.

If ynot does come around to the same theory, it will mean little to me - because I will have no way of knowing what tests were done, how he reached this conclusion, or whether it will be the same when I wake up tomorrow.

[John Freestone]

But this is posted in #8

<etc>

No answer by ynot. I assume it's because the answer does not support his theory of the moment. My theory of the moment is the same as it has been for 3 years - the cart works. It goes faster than the wind steady-state, and it does this for relatively straightforward reasons that are well understood by a number of people here.

If ynot does come around to the same theory, it will mean little to me - because I will have no way of knowing what tests were done, how he reached this conclusion, or whether it will be the same when I wake up tomorrow.I see. I missed that at #8.

Anyway, looks like this might be a quiet thread until ynot does some more.

[fredriks]

I don't get how people believe the treadmill result happens due to stored energy in some way. Not only for a short time.

The problem is that stored energy can't make the cart go faster than the speed that was used when you stored the energy unless you change the gearing.

You can't get an accelerating cart from stored energy, low friction or a sail. You can only get a cart that very slowly loses the initial speed.

The cart on the treadmill shows that the forward force (trust from the propeller) is larger than the braking force when the cart moves at wind speed. This is always going to be the case if the cart moves at that speed unless there are problems with slipping.

So moving forward a couple of seconds shows that it is going to go forward for an infinitely long time.

[ynot]

Gidday from Oz - Thought I would take a little time out from my holiday on the Gold Coast and answer a few points I missed earlier.

HairBall - Yes, the turntable was spun up by hand and was gradually slowing in the video. I was always fully aware of the consequences of this but I didn't mention it as I wanted to see if anyone would "spot the flaw" which you did very quickly. Even when I kept the turntable spinning at a constant speed (or even sped it up) however the marble behaved in much the same way and didn't seem to slow down relative to the turntable any quicker (even though it would have been).

Mender - "I'll be building a turntable as well for my experiments. I have a neat little device that allows me to adjust the speed very easily from a dead stop all the way to about 20 mph. I can even test it in reverse! Spork knows what I'm talking about." Cool. Will you be posting videos of your experiments?

The video and "test" was put together very quickly and probably shouldn't have been called a test. What I was wanting to show was that a thing can be made to move in the opposite direction of a moving surface using stored kinetic energy alone, and that it can retain this energy for much longer than most may think.

Another thing that's shown is that the marble can appear to be moving faster than the turntable when it's moved from a faster (outside) area to a slower (inside) area. This is similar to an outside cart getting faster than the wind speed from wind gusts and this should be taken in to account when conduction outside tests.

When I get back to NZ I plan to build new device for a turntable that has two single wheel carts directly opposite each other that share the same tether for balance. The main thing I want to test is whether the carts are hovering or travelling relative to whatever surface they get their energy from with stored or sustainable energy.

[ynot]

I don't get how people believe the treadmill result happens due to stored energy in some way. Not only for a short time.

The problem is that stored energy can't make the cart go faster than the speed that was used when you stored the energy unless you change the gearing.

You can't get an accelerating cart from stored energy, low friction or a sail. You can only get a cart that very slowly loses the initial speed.

The cart on the treadmill shows that the forward force (trust from the propeller) is larger than the braking force when the cart moves at wind speed. This is always going to be the case if the cart moves at that speed unless there are problems with slipping.

So moving forward a couple of seconds shows that it is going to go forward for an infinitely long time.
I believe you are totally wrong. When the cart is prevented from travelling backwards only on the moving surface the propeller will develop enough thrust to allow the cart to "hover". When the cart is prevented from travelling forwards as well as backwards on the moving surface however the propeller will develop more than enough enough thrust to "hover" and it will travel forwards against the surface. In other words the cart will be able to travel faster than the moving surface that gives it it's energy. As I said above, the question I'm interested in is this "extra" energy stored or constant?

[fredriks]

I believe you are totally wrong. When the cart is prevented from travelling backwards only on the moving surface the propeller will develop enough thrust to allow the cart to "hover". When the cart is prevented from travelling forwards as well as backwards on the moving surface however the propeller will develop more than enough enough thrust to "hover" and it will travel forwards against the surface. In other words the cart will be able to travel faster than the moving surface that gives it it's energy. As I said above, the question I'm interested in is this "extra" energy stored or constant?


I don't really understand what you are saying and in what way you disagree with me but to your last point.

"As I said above, the question I'm interested in is this "extra" energy stored or constant? "

Put a cart on a treadmill. Hold it fixed at the same place letting the wheel rotate. You now have wheel speed, omega1, prop speed omega 2, prop trust F2 and force on the wheel F1.

There are 3 possibilities.
F2>F1 -> the cart accelerate forward (relative the room/wind)
F2<F1 -> the cart accelerate backwards (relative the room/wind)
F2=F1 -> the cart is at the same place (relative the room/wind)

The amplitude for the acceleration depends on the inertia (hope it is the right word here) of the parts of the cart.

A cart with a huge flywheel is going to have F2=0 but it has a large inertia so it is only going to accelerate slowly. It can't gain speed though.

The important thing now is that the relevant forces depends on the carts relative motion to the belt. They are exactly the same if you hold the cart or if the cart is sitting there by it self or if the cart moves through that position.

F2>F1 at wind speed is always going to be the case if it was true when you let of the cart.

The important property for the cart is that everything for the cart can be determined from the wheels speed (or prop speed). We don't have any extra flywheel or gear box or something that can be changed to let the cart go faster for a short time.

There are some assumptions in the above explanation.

The wheel don't slip or at least don't slip more when you don't hold the cart.

There might be but I doubt it stability issues (in a control theoretical sense) but these are above the discussions for the cart.

edit:

What I was wanting to show was that a thing can be made to move in the opposite direction of a moving surface using stored kinetic energy alone, and that it can retain this energy for much longer than most may think.


Your experiment didn't show this. What you see is the effect of different speed of the turntable. You experiment wouldn't work on a treadmill.

What you claim above is that a thing could get more energy (higher speed) when you let it of.

One possibility to make something like this work is to store energy in some other "direction" compared the movement and then change the direction of the thing. For example also spin the ball around a vertical axis.

[John Freestone]

When I get back to NZ I plan to build new device for a turntable that has two single wheel carts directly opposite each other that share the same tether for balance. The main thing I want to test is whether the carts are hovering or travelling relative to whatever surface they get their energy from with stored or sustainable energy.
The opposite-side carts design is an interesting touch, ynot, which is intuitively appealing to 'balance' the forces, but I wonder if it does that significantly in practice. The centrifugal force of the single cart moving in a circle would be balanced at the central bearing, but it probably wouldn't be rotating very fast (unless you get a really efficient design) - windspeed, of course, being when it is at rest w.r.t. the ground - so the force won't be very great. However, the fact that you have doubled the motive force by having two mechanisms with two props, your twin cart should have twice the power, even if none of the losses are offset by better balanced bearing forces.

I believe you are totally wrong. When the cart is prevented from travelling backwards only on the moving surface the propeller will develop enough thrust to allow the cart to "hover". When the cart is prevented from travelling forwards as well as backwards on the moving surface however the propeller will develop more than enough enough thrust to "hover" and it will travel forwards against the surface. In other words the cart will be able to travel faster than the moving surface that gives it it's energy. As I said above, the question I'm interested in is this "extra" energy stored or constant?
Like fredriks, I can't see that this is a correct analysis. For sure, when the cart is held still on the treadmill, the prop will generate whatever force it has to, whether that represents too little for FTTW travel or more, but then, when it is let go of, the fact that it progresses forwards seems conclusive unless it arrived at that position after first being driven forwards to accelerate the whole mechanism beyond belt-speed. This would be utterly impossible without being clearly visible, and would dissipate very quickly. It is not the same as the acceleration that the mechanism undergoes from being placed on the moving belt at rest and reaching windspeed.

It can help to translate back to a humberian 'real wind' scenario, assuming you believe in the equivalence. Then, we can imagine the land cart driven along, held next to a powered vehicle so the whole thing is going exactly windspeed, and uncoupled. If it moved off ahead of your powered vehicle, it's even more difficult to imagine that it could have gained enough momentum from the setup conditions to do so.

Ah, but I suppose I can imagine how the setup acceleration could give it momentum that is translated into further motive power (or how one could imagine such a thing), but it would require a significant mass, a flywheel, say, and very slow losses. Then, after the machine is driven up to windspeed and released, the flywheel's energy would return to the system.

Let's do this in imagination. If we imagine first doing this with just a simple cart with a flywheel driven by the wheels, pushed up to 10 mph in still air, we know that it won't just suddenly stop when we let go. It's momentum will cause it to continue into the headwind, a motive force against the resistance (indeed, any mass will, even just a cart freewheeling). So the question is, if we did so up to 10 mph in a 10 mph wind, downwind, would whatever momentum is in the machine cause it to continue accelerating and outpace the wind, if, for instance, it hasn't reached 'steady state' when we let go - we've given it a shove so far, does that shove continue?

I think this is the sort of principle you identify as a possible reason for temporary gains of velocity, and (as you say) it depends on how quickly the steady state is reached. In the treadmill situation, it could be tested by holding the cart at windspeed for a 'suitably' long time (whatever that is), before letting go.

However, imagining the land cart again, with no prop but a flywheel as big as you like, if we have acceleration forces of a tailwind and an outside force (push by the pilot vehicle), and resistance of friction only, when we reach windspeed and uncouple, there is now no driving force (we've uncoupled) and no tailwind or headwind. There is only the friction.

Now, here's the important consideration. While we were accelerating the machine, the flywheel was being accelerated (and the whole thing was harder to push). When we stop pushing, the flywheel is just going round without any acceleration, immediately. That seems to be how long it takes to reach that initial steady state before launching. So if we push a flywheel cart into a tailwind up to windspeed and let go, it doesn't outpace the wind just because of that pushing of a moment ago, or any amount of momentum so gained. Acceleration isn't translated into the next moment. Velocity is, but the moment you stop accelerating something (take the force away), it stops accelerating. Now we have a cart going windspeed and it will take longer to slow down because it has a ruddy great flywheel rotating, but it can't beat the wind.

Similarly, it seems hard to conceive that the prop could gain a sort of aerodynamic equivalent that is magically different. There is only its tiny plastic mass and the momentum of the air it is moving, which would very soon lose any excess energy.

In either frame, it seems even more impossible that holding it back could give it more momentum to do the trick. This is even more convincing in the treadmill videos, to me. The natural result for every other object (wheeled or otherwise) is to be slung off the back end of the treadmill, unless zero friction can be attained. The plastic spork pushes the cart that way, and then it repeatedly advances again. Clearly, the wheels are going slower when it is pushed back, so the only thing that could gain 'momentum' or other stored energy to cause it to come back (like a pendulum), is the prop or the propelled air (which is what you suggest, I think). But the free-spinning prop stops in 7 seconds. Besides, when this advance is balanced by the cart's own weight (component thereof) by tilting the belt, it generates an excess forward force to hold itself in position for minutes.

No, I really think all these momentum arguments are wrong. I value your experiment and expect it will verify the claim once again.

[spork]

Yes, the turntable was spun up by hand and was gradually slowing in the video. I was always fully aware of the consequences of this but I didn't mention it as I wanted to see if anyone would "spot the flaw" ...

This is the opposite of science. If it's true that you were aware of this flaw you're simply guilty of intentionally misleading the people to whom you're presenting your results and your argument. But I suspect the statement is simply a lie. You were obviously aware that the turntable wasn't powered, but you were somehow not aware that this would completely invalidate your results - or if you were, you hoped no one would notice or ask the question. You certainly ignored the question enough times.

You might note that we have done our best to outline the parameters of our tests in each video. That IS science.

[ynot]

This is the opposite of science. If it's true that you were aware of this flaw you're simply guilty of intentionally misleading the people to whom you're presenting your results and your argument. But I suspect the statement is simply a lie. You were obviously aware that the turntable wasn't powered, but you were somehow not aware that this would completely invalidate your results - or if you were, you hoped no one would notice or ask the question. You certainly ignored the question enough times.

You might note that we have done our best to outline the parameters of our tests in each video. That IS science.
Don't see how you conclude that I'm "guilty of intentionally misleading" when the OP presents no "results" and makes no "argument". I simply posted a video of a very quick experiment with a marble on a turntable. I said I shouldn't have called it a test. "Suspect" I'm a liar all you like it really doesn't bother me. Your "science" seems to be more interested in attempting to discredit people that don't agree with you with personal insults rather than intelligent debate. Perhaps you're miffed that you didn't "spot the flaw". I will ignore any future insults and will only respond to comments that address the issue. What you choose to do is up to you.

[ynot]

Double post

[ynot]

fredricks & John Freestone - (in laymans terms) How the cart moves relative to the moving surface is a "battle" between propeller thrust (combined with whatever amount of KE the cart develops) and rolling resistance. When the cart is "active" on the moving surface it has a "received" amount of energy and is continuously gaining energy from the moving surface at the same time as it is continuously losing energy to rolling resistance. Whether the received/continuously gained energy is sustainable against the continuous loss of energy to rolling resistance or not is what I hope to establish by testing on a turntable. If the battle is lost to rolling resistance then I believe it is far more gradually and slow than most people realise. An endless turntable is better to use for this testing than treadmill.

[spork]

Don't see how you conclude that I'm "guilty of intentionally misleading"

Let's look at your quote:

Yes, the turntable was spun up by hand and was gradually slowing in the video. I was always fully aware of the consequences of this but I didn't mention it as I wanted to see if anyone would "spot the flaw"






Your "science" seems to be more interested in attempting to discredit people that don't agree with you...

My "science" seeks to discredit voodoo and those that propose or practice it.

[ynot]

Let's look at your quote:
It's hardly possible to conduct a spot the flaw test by revealing the flaw. Besides, I didn't provide any information about anything in the video, not just whether the turntable was constantly powered or not. As I said earlier, I did more testing than was shown on the video and the rate of slowing of the turntable didn't make and noticeable difference to it being constantly powered or sped up. My next turntable will be powered at a constant speed and all relevant information that I can think of will be fully revealed.

[ynot]

The opposite-side carts design is an interesting touch, ynot, which is intuitively appealing to 'balance' the forces, but I wonder if it does that significantly in practice. The centrifugal force of the single cart moving in a circle would be balanced at the central bearing, but it probably wouldn't be rotating very fast (unless you get a really efficient design) - windspeed, of course, being when it is at rest w.r.t. the ground - so the force won't be very great. However, the fact that you have doubled the motive force by having two mechanisms with two props, your twin cart should have twice the power, even if none of the losses are offset by better balanced bearing forces.
The turntable cart I made had two props so I think the power would be much the same as two sided cart I will be building. I think this design will also be very easy to construct. I was surprised at the speed my cart achieved against the rotation of the turntable. One of the reasons I want to have a balanced cart is that the initial "unbalanced" cart seized up when the turntable was spinning very fast. The cart spinning around at the same speed as the turntable was a very unbalanced scenario and a potentially very dangerous bucking bronco. Both the cart and turntable were badly damaged and was one of the reasons I couldn't do more testing. When I rebuild the turntable and new cart design I will post videos and invite comments and critiques (I also expect a few insults ;-).

[spork]

It's hardly possible to conduct a spot the flaw test by revealing the flaw...

And it's not much of a "spot the flaw" test if it's passed off as a valid experiment and you refuse to answer the direct question about the turntable being powered - because you're hoping people will simply let the issue die.

You're welcome to peddle that "explanation" and see if it flies with anyone else. Personally, it tells me not to pay too much attention to any experimental results you post.

[Dan O.]

The change in rotation of the flywheel is visible in the video itself. It doesn't appear to be a significant factor. As the marble looses energy, it starts to move in an orbit (in the same direction as the rotation of the flywheel). If the disk didn't have a hole in the center, the marble's orbit would end up going around the rotation axis and then it would be clear to everybody that the marble is traveling slower than the disk.

[ynot]

The change in rotation of the flywheel is visible in the video itself. It doesn't appear to be a significant factor. As the marble looses energy, it starts to move in an orbit (in the same direction as the rotation of the flywheel). If the disk didn't have a hole in the center, the marble's orbit would end up going around the rotation axis and then it would be clear to everybody that the marble is traveling slower than the disk.
By "flywheel" you are obviously referring to the turntable. Using a heavier, better balanced and rounded metal ball bearing gave a better demonstration. The ball rolled much more smoothly, circled less and lost energy more slowly. It became a far more dangerous projectile however when it occasionally fell in to the spokes.

[Dan O.]

Using a heavier, better balanced and rounded metal ball bearing gave a better demonstration. The ball rolled much more smoothly, circled less and lost energy more slowly.

That's pretty much what I predicted back in post 10.

[sol invictus]

By "flywheel" you are obviously referring to the turntable. Using a heavier, better balanced and rounded metal ball bearing gave a better demonstration. The ball rolled much more smoothly, circled less and lost energy more slowly. It became a far more dangerous projectile however when it occasionally fell in to the spokes.


The ball behaved as expected - I don't understand what you think it shows that's at all interesting. It doesn't matter very much that the turntable wasn't powered, so long as it wasn't slowing down too rapidly.

This whole debate has gotten increasingly mysterious to me - we understand perfectly what are the forces acting on the cart either on the treadmill or in the wind. We understand why it goes DDWFFTW, and why a marble won't. It's obvious that this is nothing to do with "stored energy", because that alone cannot make the cart accelerate from wind speed to FTTW.

All of this stuff follows from Newton's laws, and it agrees with all the evidence. So really - what more is there to discuss?

[ynot]

The ball behaved as expected - I don't understand what you think it shows that's at all interesting.
I think it's an interesting effect to observe and not what not what some people may have expected (as they have commented). It is not so impressive that a cart with a propeller can hover on a treadmill when a ball can be seen doing almost the same on a turntable (or treadmill). Of course the ball can never travel faster than the overall speed of the moving surface because it doesn't have the facility to do this. A cart does in the form of a propeller.
It doesn't matter very much that the turntable wasn't powered, so long as it wasn't slowing down too rapidly.
I agree. Spork seems to be the only one that has an issue with it. I suspect that he will say that the issue is that I'm a liar, and an incompetent one at that.
This whole debate has gotten increasingly mysterious to me - we understand perfectly what are the forces acting on the cart either on the treadmill or in the wind. We understand why it goes DDWFFTW, and why a marble won't. It's obvious that this is nothing to do with "stored energy", because that alone cannot make the cart accelerate from wind speed to FTTW.
All of this stuff follows from Newton's laws, and it agrees with all the evidence. So really - what more is there to discuss?
Perhaps "achieved or developed energy" would be a better term than "stored energy". If the prop was sufficiently highly geared to the wheels and the speed of the treadmill was fast enough I imagine the cart could be made to fly vertically with the thrust of the prop. This doesn't mean it could do this continuously however. I have seen my cart both hover and progress against the turntable. My main question is can it do this continuously? If it can I don't currently see any reason why this doesn't mean it can travel DDFTTW. I am more interested in physically testing than discussing this.

[Michael C]

I have seen my cart both hover and progress against the turntable. My main question is can it do this continuously? If it can I don't currently see any reason why this doesn't mean it can travel DDFTTW. I am more interested in physically testing than discussing this.

Questions:

1. - How long did the cart keep progressing against the turntable?
2. - What was the speed of the turntable when the cart progressed against it?
3. - At this point, did you keep the turntable going at a constant speed, or was it freely spinning, so that it was gradually slowing down?

In order to test if the cart can progress continuously against the turntable, you need to have the means of keeping the turntable going for an indefinite time at a given speed. For any DDWFTTW cart, there will be a certain wind speed at which the cart will run exactly at the speed of the wind, that is to say it will "hover" on the turntable. At this speed the forward thrust from the propeller is just enough to overcome the losses due to friction. If the wind speed drops lower than this level, the cart will lose speed. For the cart to go faster than the wind, the wind speed must be above this level. For the cart to keep going faster than the wind, the wind speed must stay above this level.

[fredriks]

Ynot, the difference is in having a cart going at the same speed as the turntable or a cart that start to go faster than the turntable. It can look like the first one happen for some time with stored energy and low friction. The second cant simple happen with stored energy and low friction unless you change the cart after you release it with for example a gear box.

Take a wheel and go out to a road. Roll the wheel to some speed (the wheel in contact with road) and release the wheel. The wheel is definitely not going to accelerate but might be at almost the same speed for some time due to inertia.

The importance are the acceleration or force from gravity that we can see on the treadmill.

[spork]

This whole debate has gotten increasingly mysterious to me - we understand perfectly what are the forces acting on the cart either on the treadmill or in the wind. We understand why it goes DDWFFTW, and why a marble won't. It's obvious that this is nothing to do with "stored energy", because that alone cannot make the cart accelerate from wind speed to FTTW.

Actually, ynot has explained several times that he doesn't buy any of this.

All of this stuff follows from Newton's laws, and it agrees with all the evidence. So really - what more is there to discuss?

For those that understand and accept Newton's laws - nothing.

Spork seems to be the only one that has an issue with it.

Wrong. Several people asked whether it was powered, and you refused to answer.

I suspect that he will say that the issue is that I'm a liar, and an incompetent one at that.

That's not "the issue" - but happens to be the case.

I am more interested in physically testing than discussing this.

It seems you're more interested in bitching that JB and I won't do your testing for you. So go do your testing. Then come back and report your results. Feel free to leave out any important data such as using magnets or strings to make your cart do as you'd like to see it do.

[Dan O.]

I am more interested in physically testing than discussing this.

The discussion can help the testing. The Wright brothers didn't just slap together an airplane and try to fly like all the yahoos before them. They first developed the physics they needed so they would know what was required to make the plane work.

One of the most critical aspects for the cart is the propeller efficiency. If your propeller is not over 50% efficient, your cart cannot go faster than the wind. I posted a sketch of a simple gig to measure propeller efficiency in the other thread. Each propeller will have a speed where it achieves maximum efficiency. If you know what this is it will help you design the rest of the cart for the best performance.

[spork]

If your propeller is not over 50% efficient, your cart cannot go faster than the wind.

This depends on the advance ratio and efficiencies of the drive-train etc. I'm pretty sure it is possible to build a DDWFTTW cart whose prop efficiency is less than 50%.

[ynot]

By saying "I am more interested in physically testing than discussing this" I didn't mean I don't see a value in pre-test discussions and I'm very happy to do so. Here is my current test thinking and any constructive comments and suggestions are welcome . . . Build a turntable that can be run at a constant speed with an electric motor. Gear the motor to the turntable so different speeds can be tested. Build a balanced, double sided two prop cart. Hold the cart against the motion of the spinning turntable until it can progress against it with the thrust of the props and whatever KE is involved. Let it run unrestricted for a reasonably long period to see if it retains the ability to progress against the turntable or not. Rinse and repeat.

Having a balanced double sided cart helps ensure that the cart is not adversely affected by any lack of perfect leveling of the turntable. It also allows a test to be conducted where the cart and turntable are started together from scratch with no restriction on the cart and without having the whole thing turning in to a violent bucking bronco.

The tests I did before my first cart self-destructed displayed that the cart could easily be made to hover and progress against the turntable. I think a cart on a turntable may work more efficiently than one on a treadmill because as the cart turns the prop is continuously thrusting against "new" still air and not moving prop-wash air as it is on the treadmill. As long as the cart can be made to move against the motion of the surface that powers it then it should be able to retain the ability to do it indefinitely if it's energy is not being gradually lost to rolling resistance.

[ynot]

Questions:

1. - How long did the cart keep progressing against the turntable?
2. - What was the speed of the turntable when the cart progressed against it?
3. - At this point, did you keep the turntable going at a constant speed, or was it freely spinning, so that it was gradually slowing down?

In order to test if the cart can progress continuously against the turntable, you need to have the means of keeping the turntable going for an indefinite time at a given speed. For any DDWFTTW cart, there will be a certain wind speed at which the cart will run exactly at the speed of the wind, that is to say it will "hover" on the turntable. At this speed the forward thrust from the propeller is just enough to overcome the losses due to friction. If the wind speed drops lower than this level, the cart will lose speed. For the cart to go faster than the wind, the wind speed must be above this level. For the cart to keep going faster than the wind, the wind speed must stay above this level.
1. - Not long enough in my opinion to tell if the cart's energy was being gradually lost to rolling resistance. As I have said earlier I don't think the cart was good enough to use for credible testing. Hopefully the next one I build will be as I will have much more time to work on it.

2. - Fast enough for the cart to hover and progress against the turntable.

3. - Before the whole thing violently self-destructed I was able to briefly test with the turntable gradually slowing, being turned by hand at a relatively constant speed and being sped up. None of the testing was good enough to take seriously as the gears on the cart kept briefly binding and eventually locked up completely.

[ynot]

Ynot, the difference is in having a cart going at the same speed as the turntable or a cart that start to go faster than the turntable. It can look like the first one happen for some time with stored energy and low friction. The second cant simple happen with stored energy and low friction unless you change the cart after you release it with for example a gear box.

Take a wheel and go out to a road. Roll the wheel to some speed (the wheel in contact with road) and release the wheel. The wheel is definitely not going to accelerate but might be at almost the same speed for some time due to inertia.

The importance are the acceleration or force from gravity that we can see on the treadmill.
As different parts of a turntable surface travel at different speeds (slower toward the centre) it's obviously important that the cart always travels only on a particular circumferal (hope that's the correct word) path. This easy to achieve with a rigid tether to the centre. I will start by testing with the cart gradually progressing against the turntable but will test at several speeds including whether the cart can sustain a hover.

[Dan O.]

This depends on the advance ratio and efficiencies of the drive-train etc. I'm pretty sure it is possible to build a DDWFTTW cart whose prop efficiency is less than 50%.

You're right there. The 50% comes from the solution for the case where the air is expelled from the prop at the speed of the ground. Of course, if more air is accelerated less, you get the same momentum change with less energy and as it turns out requires less efficiency from the prop.

[sol invictus]

Of course the ball can never travel faster than the overall speed of the moving surface because it doesn't have the facility to do this. A cart does in the form of a propeller.

Precisely.

Perhaps "achieved or developed energy" would be a better term than "stored energy". If the prop was sufficiently highly geared to the wheels and the speed of the treadmill was fast enough I imagine the cart could be made to fly vertically with the thrust of the prop. This doesn't mean it could do this continuously however. I have seen my cart both hover and progress against the turntable. My main question is can it do this continuously? If it can I don't currently see any reason why this doesn't mean it can travel DDFTTW. I am more interested in physically testing than discussing this.


I'm all in favor in doing experiments, but I don't think you've thought through the alternative very carefully. Once you see the cart accelerate from wind speed to faster than the wind, it's over. That means the forces when it's at wind speed aren't balanced, and instead make it go DWFTTW. Done.

[ynot]

Precisely.



I'm all in favor in doing experiments, but I don't think you've thought through the alternative very carefully. Once you see the cart accelerate from wind speed to faster than the wind, it's over. That means the forces when it's at wind speed aren't balanced, and instead make it go DWFTTW. Done.
I don't agree. As I said earlier - " If the prop was sufficiently highly geared to the wheels and the speed of the treadmill was fast enough I imagine the cart could be made to fly vertically with the thrust of the prop. This doesn't mean it could do this continuously however."

There is no argument (from me at least) that the thrust of a prop can be made to exceed the rolling resistance by "artificially" holding the wheel(s) that power it against a moving surface until the prop develops enough thrust to do so. There is a doubt in mind however that this can be sustained in a closed system. Holding the prop against the moving surface isn't a closed system and enough time must be given to let any "advantages" gained by "artificially" holding the cart against the moving surface to dissipate. If I conduct the tests correctly the cart should be able to hover and travel against the turntable indefinitely. Jumping of the ground doesn't prove that you can sustain levitation.

[sol invictus]

I don't agree. As I said earlier - " If the prop was sufficiently highly geared to the wheels and the speed of the treadmill was fast enough I imagine the cart could be made to fly vertically with the thrust of the prop. This doesn't mean it could do this continuously however."

Sure - but so what? First, the situation isn't comparable, because if the cart lifts off it loses its power source, which doesn't happen in the normal configuration. It's obvious instead what will happen - it will accelerate until it reaches a speed where the forces balance, where it will come to a steady state at that speed. Second, the claim was merely that the cart will go DDWFTTW. Once you see that it accelerates from windspeed, the claim has been demonstrated.

And even if something somehow went wrong at a higher speed (like the wheels started to slip, and it fell back to slower than windspeed or something) that would merely demonstrate an engineering flaw in the design.

[ynot]

Sure - but so what? First, the situation isn't comparable, because if the cart lifts off it loses its power source, which doesn't happen in the normal configuration. It's obvious instead what will happen - it will accelerate until it reaches a speed where the forces balance, where it will come to a steady state at that speed. Second, the claim was merely that the cart will go DDWFTTW. Once you see that it accelerates from windspeed, the claim has been demonstrated.

And even if something somehow went wrong at a higher speed (like the wheels started to slip, and it fell back to slower than windspeed or something) that would merely demonstrate an engineering flaw in the design.
The claim is NOT merely that a thing can travel DDWFTTW. Anyone can make a brick travel DDWFTTW if they throw it hard enough. The claim is that that it can travel DDWFTTW using the immediate force of the wind only (no storage) and that it can do it continuously/sustainably. If this is not your claim please say so.

If the cart starts to travel against the turntable/treadmill it should continue to do so as the conditions remain the same. Any wheel slip should happen then if it's going to happen later.

[mender]

On the treadmill you're starting the cart at wind speed in a steady stats. If the cart moves forward at all for even a short time, it is moving faster than the wind. This is exactly the same as a cyclist holding on to the side of a vehicle while the vehicle gets up to a certain speed. When the cyclist is stationary relative to the vehicle, it doesn't matter how long he stays holding onto the vehicle before he releases and starts pedaling. If he can go faster than the vehicle by pedaling, he does it whether he has been holding on for five seconds or five minutes. There is no way that energy can be be stored to increase the speed of the cart simply by holding the cart in position.

Doing it for two seconds is sufficient to prove that the cyclist can exceed the speed of the vehicle after releasing. The cart isn't subject to "tiring out" (maybe seizing up but that's a mechanical issue), so one can say that five seconds is as good as five hours or five years as long as the cart stays mechanically intact. Continuing to test past the actual event is just showing how long it will go DDWFTTW, not whether it can or not.

My street car has reached a top speed of just over 150 mph. It went that fast for about five seconds before I backed off. Holding that speed for five minutes is a test of the cooling and lubrication systems, not the horsepower of the engine.

[ynot]

On the treadmill you're starting the cart at wind speed in a steady stats. If the cart moves forward at all for even a short time, it is moving faster than the wind. This is exactly the same as a cyclist holding on to the side of a vehicle while the vehicle gets up to a certain speed. When the cyclist is stationary relative to the vehicle, it doesn't matter how long he stays holding onto the vehicle before he releases and starts pedaling. If he can go faster than the vehicle by pedaling, he does it whether he has been holding on for five seconds or five minutes. There is no way that energy can be be stored to increase the speed of the cart simply by holding the cart in position.

Doing it for two seconds is sufficient to prove that the cyclist can exceed the speed of the vehicle after releasing. The cart isn't subject to "tiring out" (maybe seizing up but that's a mechanical issue), so one can say that five seconds is as good as five hours or five years as long as the cart stays mechanically intact. Continuing to test past the actual event is just showing how long it will go DDWFTTW, not whether it can or not.

My street car has reached a top speed of just over 150 mph. It went that fast for about five seconds before I backed off. Holding that speed for five minutes is a test of the cooling and lubrication systems, not the horsepower of the engine.
Stopping the cart from moving backwards with the moving surface is the essentially same as pushing the cart up to wind speed. Stopping the cart from also moving forward with the moving surface is essentially the same as pushing the cart to faster than wind speed. In other words you are saying that if you push the cart to a speed faster than wind speed it is going faster then the wind. This is self-obvious and has nothing to do with the claim being made.

The cyclist analogy is more relevant to the marble demonstration than a prop driven cart. Like the marble the cyclist can't travel any faster than the thing that is powering it. A cart with a prop can. Pedaling is not getting energy from the vehicle and is like fitting a motor to the cart.

ETA - Have you built your hi-tech turntable yet?

[Dan O.]

Ynot, I think I see what your concern is. You think that the energy stored in the rotating prop is enough to give the cart a slight boost after it is released and if the wheels also loose traction after the release there won't be any drag to slow it down again.

If this is what you think, you are right.

So how do you plan to determine if the cart is steady state or still running off excess stored energy?

[ynot]

Ynot, I think I see what your concern is. You think that the energy stored in the rotating prop is enough to give the cart a slight boost after it is released and if the wheels also loose traction after the release there won't be any drag to slow it down again.

If this is what you think, you are right.

So how do you plan to determine if the cart is steady state or still running off excess stored energy?
Not quite what I think. The "battle" is between the thrust of the prop + cart KE and rolling resistance. If the cart is held "stationary" (backwards AND forwards) on the moving surface that is supplying it with energy then (as long as the prop efficiency, gearing and surface speed etc are sufficient) it will develop more than enough prop thrust to merely hover and it will progress. This only represents sustainable DDWFTTW if it is self-sustainable.

If the cart is set traveling at a constant speed counter to the movement of the surface then whatever wheel slip, gearing friction, headwind or whatever other inefficiencies there are should be pretty much constant. If it starts moving it should be able to continue to do so if the claim made is correct. If not the claim is incorrect.

As I said earlier, I plan to have the turntable spinning at a constant speed that allows the cart to slowly progress against it and run it for a long period to see if it losses energy to rolling resistance. As the guys at NASA say - "It's not rocket scie . . . oh . . . yes it is!

[spork]

Just before releasing the cart you're holding it at exactly wind speed steady-state. At that point it had better already be pushing itself forward. If it is, it will go forward faster than the wind steady-state guaranteed. Any issue of wheel slip is a mechanical limitation, not a theoretical limitation. We can replace the wheels and surface with rack and pinion - problem solved.

Also, there is no way the cart can be pushing forward while held in place steady-state by your hand because of stored energy. Incidentally, both experiment and analysis shows that stored energy is not a necessary piece of the puzzle at all.

[ynot]

Just before releasing the cart you're holding it at exactly wind speed steady-state. At that point it had better already be pushing itself forward. If it is, it will go forward faster than the wind steady-state guaranteed. Any issue of wheel slip is a mechanical limitation, not a theoretical limitation. We can replace the wheels and surface with rack and pinion - problem solved.

Also, there is no way the cart can be pushing forward while held in place steady-state by your hand because of stored energy. Incidentally, both experiment and analysis shows that stored energy is not a necessary piece of the puzzle at all.
Do you think in the test I've outline in my last post that the cart will constantly progress against the turntable?

[mender]

Stopping the cart from moving backwards with the moving surface is the essentially same as pushing the cart up to wind speed. Stopping the cart from also moving forward with the moving surface is essentially the same as pushing the cart to faster than wind speed. In other words you are saying that if you push the cart to a speed faster than wind speed it is going faster then the wind. This is self-obvious and has nothing to do with the claim being made.


In a word, no. Stopping the cart from moving forward is keeping it from accelerating past wind speed. By keeping it at a steady state speed before releasing, you ensure that the cart can only go faster if there is an unbalanced forward force acting on the cart.

This is absolutely wrong:
"Stopping the cart from also moving forward with the moving surface is essentially the same as pushing the cart to faster than wind speed."

First of all, you are keeping the cart from moving forward against the direction of the moving surface. You are keeping the cart from moving in order to have a baseline speed. When you release the cart, the motion from that point indicates what the cart is capable of achieving steady state. If it moves forward, it can go faster than the wind. If it stays in position, it can only match the wind speed. If it falls back, it is no better than a big marble.

There is no way to store energy that could accelerate the cart despite what Dan O. said. If the wheels start slipping as soon as you release the cart, it will go backward, not forward.

No table yet, but we better establish what the results of the testing signify if we expect the test to be of any value.

[ynot]

In a word, no. Stopping the cart from moving forward is keeping it from accelerating past wind speed. By keeping it at a steady state speed before releasing, you ensure that the cart can only go faster if there is an unbalanced forward force acting on the cart.

This is absolutely wrong:
"Stopping the cart from also moving forward with the moving surface is essentially the same as pushing the cart to faster than wind speed."

First of all, you are keeping the cart from moving forward against the direction of the moving surface. You are keeping the cart from moving in order to have a baseline speed. When you release the cart, the motion from that point indicates what the cart is capable of achieving steady state. If it moves forward, it can go faster than the wind. If it stays in position, it can only match the wind speed. If it falls back, it is no better than a big marble.

There is no way to store energy that could accelerate the cart despite what Dan O. said. If the wheels start slipping as soon as you release the cart, it will go backward, not forward.

No table yet, but we better establish what the results of the testing signify if we expect the test to be of any value.
If the cart is being prevented from moving forward against the moving surface when it "wants" to move forward then it is "artificially" being held at wind speed as the prop develops even more thrust. For the period that the cart is being held stationary on the moving surface all rolling resistance is effectively being removed and the prop can develop more thrust than it could with that rolling resistance. If the moving surface had enough power and speed and the prop was sufficiently highly geared to the wheel(s) and the prop was large enough, then a brick without wheels could be made to progress against the moving surface for a short period. I may develop a test to prove this if anyone disagrees.

Perhaps before we establish what the results of the testing signify, exactly what the claim is should be specified.

[mender]

For the period that the cart is being held stationary on the moving surface all rolling resistance is effectively being removed and the prop can develop more thrust than it could with that rolling resistance.

No, the rolling resistance is the same for that speed. The prop doesn't develop any more thrust than it would when at that speed as it accelerates through that speed. The instant of release is essentially a snapshot of the cart when it is at wind speed.

When you spin up one of those little flywheel powered toy cars, the highest speed that it can get to is the same as the speed you pushed it to - no higher!

Same thing applies to the cart. There is no way to store any extra energy or force that can accelerate the cart past wind speed if the cart isn't already capable of achieving DDWFTTW travel. If the cart moves forward when released, the case is proven. It's as easy as that. Longer testing won't show a different result unless there is a mechanical problem that crops up during testing.

Is there any disagreement with that?

[ynot]

No, the rolling resistance is the same for that speed. The prop doesn't develop any more thrust than it would when at that speed as it accelerates through that speed. The instant of release is essentially a snapshot of the cart when it is at wind speed.

When you spin up one of those little flywheel powered toy cars, the highest speed that it can get to is the same as the speed you pushed it to - no higher!

Same thing applies to the cart. There is no way to store any extra energy or force that can accelerate the cart past wind speed if the cart isn't already capable of achieving DDWFTTW travel. If the cart moves forward when released, the case is proven. It's as easy as that. Longer testing won't show a different result unless there is a mechanical problem that crops up during testing.

Is there any disagreement with that?
I agree that when the cart is at a certain speed a particular amount of rolling resitance is established and is relatively constant. I'm talking about the cart being being able overcome rolling resistance to reach that speed however, not when it has reached that speed. When the cart "wants" to move forward it has reached it's ability to do so. If it is restricted from doing so it will develop more thrust than it needs to move forward and when released will move forward faster than it would have.

[mender]

If the moving surface had enough power and speed and the prop was sufficiently highly geared to the wheel(s) and the prop was large enough, then a brick without wheels could be made to progress against the moving surface for a short period. I may develop a test to prove this if anyone disagrees.

I disagree 100%. Think about what you wrote. If your brick has no wheels, the prop has no way of making use of the relative motion of the ground and the air. That's like saying that you can make a sailboat that has no sail and by towing it behind another boat then releasing it, can somehow have the sailboat move faster than the boat that was towing it.

In order for the cart (or a brick) to work, the prop has to be connected to wheels.

[mender]

If it is restricted from doing so it will develop more thrust than it needs to move forward and when released will move forward faster than it would have.


No. If it is restricted from moving forward, it doesn't develop more thrust as a result. It has exactly the same thrust at 10 mph when held as it does as it accelerates through 10 mph. The cart has only been interrupted in that process by holding it at 10 mph or more correctly placed into the exact same condition. When released it moves to the speed that it is capable of. No faster than it would have.

How could it?

[ynot]

I disagree 100%. Think about what you wrote. If your brick has no wheels, the prop has no way of making use of the relative motion of the ground and the air. That's like saying that you can make a sailboat that has no sail and by towing it behind another boat then releasing it, can somehow have the sailboat move faster than the boat that was towing it.

In order for the cart (or a brick) to work, the prop has to be connected to wheels.
It is possible to attach a wheel to a brick that powers a propeller but the brick doesn't ride on it. As I said I might build a working model to demonstrate what I mean.

[ynot]

No. If it is restricted from moving forward, it doesn't develop more thrust as a result. It has exactly the same thrust at 10 mph when held as it does as it accelerates through 10 mph. The cart has only been interrupted in that process by holding it at 10 mph or more correctly placed into the exact same condition. When released it moves to the speed that it is capable of. No faster than it would have.

How could it?
One of the factors that determines whether a cart can reach or exceed the speed of a moving surface is rolling resistance. A cart that could never reach the speed of the moving surface if it wasn't artificially held stationary to it can if it is. In other words, a wheel that is held against a moving surface has to reach the speed of the surface and the propeller has to reach it's full thrust potential at that speed. This not the case if the wheel has to accelerate up to the speed of the moving surface without being forced to do so by being held. Once again I think there are experiments I can conduct to demonstrate this.

[sol invictus]

When the cart "wants" to move forward it has reached it's ability to do so. If it is restricted from doing so it will develop more thrust than it needs to move forward and when released will move forward faster than it would have.


That's wrong, but it's good - now we know where your confusion is coming from.

When the cart's wheels are spinning at a certain speed, the prop will supply a certain amount of thrust. At the same time friction in the wheels will provide a braking force. At wind speed there's no air resistance, so the only other force acting is the one supplied by your hand holding it in place (if it's there).

So consider two situations - your hand was holding the cart in place but has just released it this instant, versus the cart started from a slower speed and is accelerating, and at this instant it is at windspeed. In both situations the wheels are spinning at the same rate, therefore so is the prop, and therefore the force from the prop and the friction in the wheels are identical. If the cart accelerates in the first case, it will accelerate in the second. There is no "stored energy" present in the first that isn't there in the second.

[John Freestone]

Mender, I'm glad you picked that up about the cart developing more thrust if it's prevented from moving. I think we've all be putting the same point to ynot in different ways. The bicycle example is good, as is the top speed of a car. I think this is just one of those things: ynot's imagination comes to different conclusions about the different scenarios. It is therefore quite valuable (to the cause) that his mistake, as I am confident it is, is rectified by empirical evidence. I don't believe Michael's cart goes faster than the ruler until he moves the damn thing, and the wheel 'definitely' doesn't rotate the way it 'should'.

I also have to say that I don't know enough about mechanics to be absolutely sure. I could imagine someone demonstrating a new type of kid's toy that, when pushed up to a certain speed and you let go, accelerates from there without any gear changes taking place. I would be dumbfounded, and before it's shown to me, I don't believe it, but there's Michael's cart again...

There is also a tiny bit of a suspicion about whether a prop suddenly accelerated to a certain speed gives the same thrust as one maintained at that speed, or more perhaps due to a sudden build-up of higher pressure air behind it, before that has time to dissipate and a steady flow develop. Again, even if there is something about that in the theory of propellers, I can't imagine that it lasts more than a fraction of a second, and would probably require an immense acceleration from standstill. (It would be a bit like the question of whether a rocket develops more thrust with a solid buffer behind it. They have them on Thunderbirds!;))

Anyway, I suggest you don't neglect your building time too much to answer these posts, ynot!

[ThinAirDesigns]

Yes, the turntable was spun up by hand and was gradually slowing in the video. I was always fully aware of the consequences of this but I didn't mention it as I wanted to see if anyone would "spot the flaw"

Oh sure -- the old "I'll do the test in an invalid manner, present it as valid and then when busted claim that what I was *really* testing was the audience." Really great credibility you're working on Ynot.

The video and "test" was put together very quickly and probably shouldn't have been called a test.

But it *was* a test and you have clearly said what the test was -- a test of the audiences ability to spot your inability to do a test to any degree of honesty.

What I was wanting to show was that a thing can be made to move in the opposite direction of a moving surface using stored kinetic energy alone, and that it can retain this energy for much longer than most may think.

What you showed, even with your secret cheating, was a device that was always going slower than the moving surface. Ours goes faster.

JB

[spork]

Do you think in the test I've outline in my last post that the cart will constantly progress against the turntable?

I know for a fact that it will. It's been shown in so many different ways. And if you manage to fail to show that result - I will perform the experiment correctly.

At the moment there is no compelling reason to perform the experiment since we all know the result. If you fail, then I will feel compelled to set the record straight, and will be happy to do so.

Incidentally, Bauer did exactly the experiment you describe. Why would you expect to get different results from his (aside from being less competent)?

[ThinAirDesigns]

I will start by testing with the cart gradually progressing against the turntable but will test at several speeds including whether the cart can sustain a hover.

Contrary to humber's position, this device isn't "balanced". You will never find a speed where sits perfectly still on the treadmill for any length of time. Too many variables in friction, level, voltage, etc.

JB

[ThinAirDesigns]

Having a balanced double sided cart helps ensure that the cart is not adversely affected by any lack of perfect leveling of the turntable.

No need to worry about adversely effecting the cart in that manner -- as we've demonstrated, you could tilt the turntable by several degrees and the cart will still happily chug around.

It also allows a test to be conducted where the cart and turntable are started together from scratch with no restriction on the cart and without having the whole thing turning in to a violent bucking bronco.

Why in the world go to all the trouble of a second cart -- ever hear of a counterweight?

JB

[ThinAirDesigns]

... will test at several speeds including whether the cart can sustain a hover.

What's this fascination with "hover"?

We have a device that will accelerate from below wind speed to above wind speed repeatedly. We have a device that will maintain a speed greater than the wind indefintely. Any decent turntable testing will show this.

Given the above, how could the device NOT be able to merely match the speed of the wind?

I just don't get your analytical skills.

JB

[ThinAirDesigns]

It is not so impressive that a cart with a propeller can hover on a treadmill when a ball can be seen doing almost the same on a turntable (or treadmill).

This one is one of my favorites -- you really should join up with the perpetual motion crowd ... they "almost" can make a magnet motor spin forever.

It would have been fun being around Ynot in the early days of heavier than air flight testing ... "it's not so impressive that a object can actually fly when you consider all the flawed designs that have almost done it."

LOL

JB

[Michael C]

ynot, you plan to "Build a balanced, double sided two prop cart". Do you know if this will be more efficient or less efficient than a single prop cart? The working DDWFTTW carts that I have seen so far (Bauer, Goodman, Spork) only had one propeller. Are there complcations with using two propellers? Could an aerodynmics expert give an opinion here?

[ThinAirDesigns]

ynot, you plan to "Build a balanced, double sided two prop cart". Do you know if this will be more efficient or less efficient than a single prop cart? The working DDWFTTW carts that I have seen so far (Bauer, Goodman, Spork) only had one propeller. Are there complcations with using two propellers? Could an aerodynmics expert give an opinion here?

As far as I can tell, he's planning on two complete carts on opposite sides of the turntable.

Whether he puts two props on each cart prop shaft may or may not effect the result. We put two props on our shaft at one point (offset by 90d) and the results were not as good. I can imagine that this would depend on the props used however.

His complete lack of understanding of the basic principles involved drives him to make the testing rig unecessarily complicated -- build a very light device (I could build one for a turntable lighter than ours and that's less than 6oz) and turn it loose for a minute or an hour or a day or a week while advancing on the treadmill at a speed that's not rocking the turntable around. -- DONE!

I love the fact that his device worked so well and accelerated to the point that it went so fast against the turntable that it turned the entire thing into a "bucking bronco" and then blew itself apart. His conclusion: 'I suspect it's powered by KE" and so I'll present a intentionally dishonest "almost" faster than the wind marble test to show how "unimpressive" the other test would have been had I done it properly and showed it instead.

Freakin' hilarious.

JB

PS: Know that I love people who build and test -- just remember my comments are in the context of Ynot's constant claims that we either aren't capable of conducting proper testing, or just didn't.

[John Freestone]

Could an aerodynmics expert give an opinion here?
Where's that bloody goldfish when you need him?

[ThinAirDesigns]

where's that bloody goldfish when you need him?

don't you dare!!!!

:-)

jb

[Dan O.]

Ynot's contention that holding the cart in place can add momentum to the propeller that will temporarily propel the cart forward when released is correct. BUT ONLY IF holding the cart provides additional downward force that increases the traction between the wheel and the rotating disk. Restraining the cart with a horizontal tether can only impart a horizontal force so will not increase traction.

[ThinAirDesigns]

Ynot's contention that holding the cart in place can add momentum to the propeller that will temporarily propel the cart forward when released is correct. BUT ONLY IF holding the cart provides additional downward force that increases the traction between the wheel and the rotating disk. Restraining the cart with a horizontal tether can only impart a horizontal force so will not increase traction.

Yes, and in that case all that would demonstrate is that increasing the friction between surface and wheel (even to the point of rack and pinion) would give the steady state result that the added downward force gave.

Interestingly enough, the way I tell if the wheels we have chosen (we tested with a lot of different wheels) are gripping the surface well enough it to push down on the front of the cart while holding it still. If I can hear the prop whine increase with downward pressure I know that the wheels are slipping on the belt.

We have found that any wheel with soft rubber on the rim (or a wide rubber band application to the rim) eliminates any slipping on our treadmill.

JB

[spork]

I love the fact that his device worked so well and accelerated to the point that it went so fast against the turntable that it turned the entire thing into a "bucking bronco" and then blew itself apart. His conclusion: 'I suspect it's powered by KE" and so I'll present a intentionally dishonest "almost" faster than the wind marble test to show how "unimpressive" the other test would have been had I done it properly and showed it instead.


Personally, I've had my doubts from the start that he ever built a prop cart that advanced on his turntable. The more I read, the more trouble I have buying that story. It's a bit like the Roswell incident in that there's no video or stills showing any such thing. The difference being that with the Roswell incident we at least are given some exceptionally poor stills of a small portion of the "wreckage".

[Dan O.]

Yes, and in that case all that would demonstrate is that increasing the friction between surface and wheel (even to the point of rack and pinion) would give the steady state result that the added downward force gave.

What if when the cart is placed on the treadmill/rotating disk and forced to make contact with the track, the traction against the wheels is greater than the thrust of the propeller? In this case, when released, the cart could move forward pushing the skidding wheel down the track until the propeller looses enough momentum that it falls back to traveling slower than the wind.

Just because some cart can travel faster than the wind doesn't mean that every cart will.

[Dan O.]

Why in the world go to all the trouble of a second cart -- ever hear of a counterweight?

A counter weight would be counter productive because when fully balanced there would be no normal force between the wheels and the track so no traction. You could always compensate by using magnetic wheels and a steel track but everybody would then know it was the power of magnets that was then moving the cart :)

[spork]

What if when the cart is placed on the treadmill/rotating disk and forced to make contact with the track, the traction against the wheels is greater than the thrust of the propeller? In this case, when released, the cart could move forward pushing the skidding wheel down the track until the propeller looses enough momentum that it falls back to traveling slower than the wind.

Just because some cart can travel faster than the wind doesn't mean that every cart will.


True, but this is a mechanical limitation - not a theoretical one. What you describe is clearly possible. That's why we imagine a rack and pinion (un-skiddable) interface. In such a case if the cart surges forward from steady state at wind speed when released, you can be assured it will find an average speed greater than wind speed downwind.

[spork]

A counter weight would be counter productive because when fully balanced there would be no normal force between the wheels and the track so no traction.

The counterweight could easily be canilevered from the axis so that it provided the desired counterbalance w.r.t. centripetal force, without reducing the traction of the real cart.

[ynot]

"I will ignore any future insults"

[ynot]

ynot, you plan to "Build a balanced, double sided two prop cart". Do you know if this will be more efficient or less efficient than a single prop cart? The working DDWFTTW carts that I have seen so far (Bauer, Goodman, Spork) only had one propeller. Are there complcations with using two propellers? Could an aerodynmics expert give an opinion here?
I built and tested a cart with two props on a single shaft. It worked fine.

http://forums.randi.org/picture.php?pictureid=498&albumid=116&dl=1228631624&thumb=1

[spork]

"I will ignore any future insults"

Good plan. I should have thought of that long ago when you were insulting our experiments and videos, and whining that we wouldn't do your work for you.

I will not ignore any future ignorance of the basic principles of physics.

[spork]

I built and tested a cart with two props on a single shaft. It worked fine.


It appears I've been proven wrong. I seem to recall seeing that picture in the main thread. My apologies.

[ynot]

Ynot's contention that holding the cart in place can add momentum to the propeller that will temporarily propel the cart forward when released is correct. BUT ONLY IF holding the cart provides additional downward force that increases the traction between the wheel and the rotating disk. Restraining the cart with a horizontal tether can only impart a horizontal force so will not increase traction.
The point I'm making is that when the wheel that powers the prop is held against the moving surface it is forced to reach the speed of the moving surface (wind speed) and the prop is forced to create the maximum thrust created by that speed. A cart that would never reach wind speed in an outside wind test can be forced to reach wind speed with a treadmill or turntable. Holding a cart against a moving surface is the same as pushing a cart up to wind speed in an outside test.

[ynot]

It appears I've been proven wrong. I seem to recall seeing that picture in the main thread. My apologies.
Accepted.

[spork]

The point I'm making is that when the wheel that powers the prop is held against the moving surface it is forced to reach the speed of the moving surface (wind speed) and the prop is forced to create the maximum thrust created by that speed. A cart that would never reach wind speed in an outside wind test can be forced to reach wind speed with a treadmill or turntable. Holding a cart against a moving surface is the same as pushing a cart up to wind speed in an outside test.

That's exactly right. But in that situation you would be holding the cart forward on the belt - not holding it back. If you release the cart and see it surge forward it tells you that you were clearly holding it back while it was trying to exceed the steady-state condition you are enforcing. In this case we can be sure it will find an average velocity greater than wind speed.

[Michael C]

I built and tested a cart with two props on a single shaft. It worked fine.

That doesn't answer the question: would a single prop cart be better?

As far as I know, a two-bladed prop is more efficient than a four-bladed one.

[ynot]

That doesn't answer the question: would a single prop cart be better?

As far as I know, a two-bladed prop is more efficient than a four-bladed one.
I have seen airplanes with two bladed props, four bladed props and some with even more bladed props, If two was significantly better why do they ever use four and more? All I know is that two two bladed props together on the same shaft (essentially a four bladed prop) worked fine on my cart and it was able to progress against the moving surface.

[Michael C]

I have seen airplanes with two bladed props, four bladed props and some with even more bladed props, If two was significantly better why do they ever use four and more? All I know is that two two bladed props together on the same shaft (essentially a four bladed prop) worked fine on my cart and it was able to progress against the moving surface.

There is always a compromise. For a given diameter, adding more blades should increase the thrust-producing surface but the prop will become less efficient since there will be more unwanted interaction between the blades. For a large aircraft a two blade prop capable of producing sufficient thrust might have to have such a huge diameter that it would become too unwieldy. For small-scale machines such as yours, a two-blade prop should be the most efficient. See for example this information on model aircraft propellers (http://www.airfieldmodels.com/information_source/model_aircraft_engines/propellers.htm):

Number of Blades

Propellers have one, two, three or four blades. Single blade propellers are counter-balanced and used on extremely high rpm racing motors. I've never seen these sold anywhere and suspect they are built by the user. You don't need to even think about these props unless you're building control line speed aircraft. In fact, they may not even be used any more. I haven't been paying attention.

In our realm, the most efficient propellers are two bladed. Because the diameter of our propellers is so small, multiple blade propellers disturb the air that the trailing blade is entering. Therefore, 3 and 4 blade propellers are less efficient.

In general, the only time a 3 or 4 blade propeller should be used is for a more scale appearance or when a smaller propeller disk is necessary.

For example, a scale, twin-engine aircraft may not be able to swing a 2-blade propeller of a small enough diameter to clear the sides of the fuselage. A three and four blade prop can be used here because it can be a smaller diameter and present the same load on the engine.

For best performance with sport aircraft, stick to 2-blade propellers.

[ThinAirDesigns]

A counter weight would be counter productive because when fully balanced there would be no normal force between the wheels and the track so no traction. You could always compensate by using magnetic wheels and a steel track but everybody would then know it was the power of magnets that was then moving the cart :)

A counterweight need not be installed in such a way as to lift the cart off the rolling surface. It can be mounted so that it places a side load on the center hub and no lifting force on the cart -- and still balance the rotation.

JB

[ThinAirDesigns]

I have seen airplanes with two bladed props, four bladed props and some with even more bladed props, If two was significantly better why do they ever use four and more? All I know is that two two bladed props together on the same shaft (essentially a four bladed prop) worked fine on my cart and it was able to progress against the moving surface.


For a given diameter, more blades will absorb more horsepower but less efficient as a whole.

If I have a lot of power but I don't have the ground clearance (or body clearance) to increase the prop diameter I would need to add blades.

Again, our tests showed better results with one prop but I don't insist that will be true with all props. I expect however it would be true if the correct prop is used.

JB

[Dan O.]

A counterweight need not be installed in such a way as to lift the cart off the rolling surface. It can be mounted so that it places a side load on the center hub and no lifting force on the cart -- and still balance the rotation.

JB

Or, if you fully balance the cart, you can then add a specific force from a spring to control the available traction to investigate how traction affects the operation.

[ThinAirDesigns]

...to investigate how traction affects the operation.

I pretty sure I know how traction affects the operation -- it's good for it (but I suppose I should check with the goldfish before I say for certain).

JB

[John Freestone]

Ynot, hi, continuing from your recent success with the cart on a turntable (tt):

I was a little surprised that you plan to do the double-sided cart after such 'amazing' speed, but I guess that suggests that your motives now aren't about proving the principle so much, and have become something else, like just doing something new for the sake of innovation or improving the performance as much as possible.

However, I would have thought it would be well worth your trouble doing tests, even fairly rough and ready ones, on the single cart before you add the second, for comparison purposes. (I'm just curious as to how much better the double is.)

It would also be best to make sure you get the constant turntable drive sorted out first, as that's fairly crucial to correct test results, I think.

I might be going on about things you already know, but you could get a pretty good test result just by counting the revs of your tt, then counting the counter-revolutions of your cart over a certain time. I guess actually the first is more difficult than the cart revs, because its so much faster. You might manage to count a mark on the circumference over a given time. I suppose it can't be taken from 'known revs' quoted on a motor, because that will vary with load. You really need the absolute revs of the tt. Otherwise, if it's too fast to count a mark, one way would be to hire a strobe light with a fairly accurately calibrated and variable pulse with a readout, and adjust the period until it coincides with your edge mark. I'd be interested to know how you decide the revs.

Then there'll be a simple formula involving those figures tt-revs and cart-revs and the radius that will give you the relative speed, or the 'multiple of windspeed' or whatever you want the performance as. Being slightly math-o-phobic, I'll set myself the task of working it out, since it can hardly be that difficult and I really should start my aversion therapy!

Do you expect approximately twice the performance from the double-cart? I can't see any reason why not....or maybe your testing will be more approximate or even 'yes-no' (although you surely can't have any doubts that it's a yes now).

Anyway, well done. I reckon at some point, if this principle continues to attract enthusiasts, there's going to develop a 'world record' in the form of a multiple of windspeed achieved (probably one for 'wild' wind and another for more accurate indoor tests on treadmills and turntables). You never know, your twin cart design might just set it.

I'm working on a DD cart using a completely different approach. It's in the design stages at the moment, top secret, and probably complete rubbish!

[CNY_Dave]

The heck with DDWFTTW, I think you could start a 60-page thread just on the balls oscillatory behavior and center tropism.

Very cool!


Dave

[huh34]

Do you expect approximately twice the performance from the double-cart? I can't see any reason why not....

You are not thinking clearly, J. The double-cart will be quite the same. If your car goes 100 mph and your friend's car goes 100 mph, you can't do 200 mph just by driving together...

(You can pull twice as much external load though, like a one-horse sled compared to a two horse sled...)

[Christian Klippel]

It would also be best to make sure you get the constant turntable drive sorted out first, as that's fairly crucial to correct test results, I think.

....

Otherwise, if it's too fast to count a mark, one way would be to hire a strobe light with a fairly accurately calibrated and variable pulse with a readout, and adjust the period until it coincides with your edge mark. I'd be interested to know how you decide the revs.


Hi John,

to get a constantly driven tt, i would guess that one of these electric drill's (not the ones using batteries, obviously) that come with electronic regulation would be sufficient. From my experience, the better ones maintain a rather constant RPM under slightly differing load conditions.

As to the RPM measurement, well, there is a rather simple way. Just use counter and a stopwatch. Have the counter count each revolution, and let it run for a given period of time. Preferably, for one minute to make calculations easy ;) A smooth going mechanical counter would be ok, but of course an electronic one would be better. Otherwise there are these hand-held RPM counters, which aren't that expensive.

There is another way using an LED, AC supply and a camcorder. If interested i can explain that as well. Just think of the reverse running spoke-wheel effect that you often see on TV......

Ynot, do you have some skills and equipment for doing electronics (using microcontrollers)? If so, building a constant RPM drive is a snap.....

Greetings,

Chris

[John Freestone]

You are not thinking clearly, J.It won't be the first time, huh34.

The double-cart will be quite the same. If your car goes 100 mph and your friend's car goes 100 mph, you can't do 200 mph just by driving together...

(You can pull twice as much external load though, like a one-horse sled compared to a two horse sled...)Ah, yes, after more thought, I see. My prediction couldn't be right without making the props move through the air too fast and not provide thrust, indeed retard motion instead. Thanks.

[ynot]

The main reasons I’m building a double-sided cart are as follows . . .

The cart/turntable combination are always balanced (good thing to have on a turntable I assure you).

Friction forces on the centre tether pivot are less.

It reduces any effects of the turntable surface not being perfectly level.

The combination of props on two opposite carts may give a more stable thrust.

One of the tests I will do is spin the turntable and cart from stationary and see if the created wind alone (cart won’t be restricted in any way) will cause the cart to travel against the turntable (faster than the wind).

The “sail” area of two props/carts will be better for testing when the cart isn’t held against the spin of the turntable (not that my new cart design has much area).

I already know that prop thrust can move a cart against the motion of the surface it’s running on if it is forced to do so by holding the cart against that motion. Hopefully these tests (and others) will show if it is possible when the cart isn’t forced and if it’s sustainable (both the same thing really).

[ynot]

Couldn’t resist posting a quick video of my new “Wind Cheetah” cart design prototype to show how well it works even though the turntable is buckled and still turned by hand. This is NOT a test and no claims are made. The prop is driven from the centre of the wheel by a flexible cable. After spinning the turntable and then picking up and switched on the camera to start filming it had slowed down quite a bit so was going faster than is shown. The video is not sped up and the cart is moving purely by the thrust of the prop.

http://www.youtube.com/watch?v=mXhxhPs0qZc

[ThinAirDesigns]

Couldn’t resist posting a quick video of my new “Wind Cheetah” cart design prototype to show how well it works even though the turntable is buckled and still turned by hand. This is NOT a test and no claims are made. The prop is driven from the centre of the wheel by a flexible cable. After spinning the turntable and then picking up and switched on the camera to start filming it had slowed down quite a bit so was going faster than is shown. The video is not sped up and the cart is moving purely by the thrust of the prop.

http://www.youtube.com/watch?v=mXhxhPs0qZc

Thanks for the post Ynot.

It roughly appears to be holding ~1.5x windspeed.

JB

[ynot]

And then I couldn’t resist going to the next step and test if the cart would develop enough speed to travel against the turntable when it wasn’t forced to do so. Very crude equipment and testing method but look at the result and draw your own conclusions . . .

http://www.youtube.com/watch?v=9zw2FJfBte8

[John Freestone]

That's an interesting design. It looks like you've got a cable or something from the axle straight to the prop shaft, bending 90 degrees, is that right? Nifty idea, if it's efficient enough.

I wonder what effect there is on the DDW physics of putting your prop at a greater radius than the wheel, as it seems to be. I'm trying to work out if it provides some unique advantage. I think the prop is travelling 2pi(Rprop-Rwheel) further than the wheel per revolution of the turntable, which means it's in a faster wind. I hope it's not setting you up for some criticism from nay-sayers, if you care about that.

Maybe it just acts similarly to a change in gear ratio. Or maybe it is equivalent to a cart with a prop high up, in a faster stream of wind than there is nearer ground level. I'm not clear on those points in my own head, what the difference is in practical terms, but the former would seem perfectly innocent, whereas the latter would seem potentially a cheat.

[Dan O.]

The prop radius to wheel radius just changes the gearing. But that flex cable from the wheel to the prop... that's going to store a lot of energy like a spring. :)

[ThinAirDesigns]

And then I couldn’t resist going to the next step and test if the cart would develop enough speed to travel against the turntable when it wasn’t forced to do so. Very crude equipment and testing method but look at the result and draw your own conclusions . . .

http://www.youtube.com/watch?v=9zw2FJfBte8

Well, based on your wording either I don't understand this test, or I don't understand the last test. What is the difference between the two?

What do you mean by "wasn't forced to do so"? and conversely, then in the other test, how was it "forced to do so"?

JB

[ynot]

Well, based on your wording either I don't understand this test, or I don't understand the last test. What is the difference between the two?

What do you mean by "wasn't forced to do so"? and conversely, then in the other test, how was it "forced to do so"?

JB
In the previous video (and all other videos I've seen) the cart was held against the moving surface until it reached the speed of the surface. In other words it was forced to do so. Holding the cart against the moving surface until it gains speed is essentially the same as forcing a cart up to the speed of the wind in an outside test by pushing it. In the last video however the cart wasn’t held against the turntable at all and it reached (and exceeded) the speed of the turntable/wind without being forced to do so. In other words it did it only using the speed of the wind. There is a small amount of “holding” due to inertia but I think this is so slight it doesn’t need to be considered.

The most “telling” part of the video for me is from around 18 to 24 seconds in. The turntable isn’t being sped up (in fact it’s slightly slowing) and yet the cart goes from travelling with the turntable to moving against it. It takes the cart a bit of time to “settle” to it’s speed.

I don’t see how the turntable's poor condition would have helped the cart’s performance, in fact it should have hindered it. I think this is the best proof provided so far in support of the DDWFTTW claim. In fact I’m not sure I need to continue testing but will wait to see what objections if any arise to explain how it wasn’t the wind alone that gave the cart it’s speed.

ETA - The latest video is the same as putting a cart on a very long stationary treadmill and then starting it up and not restricting the movement of the cart. Initially the cart will travel backwards with the moving tread. As the wind created by the cart moving through still air increases the prop will develop enough thrust to travel forward back up and against the motion of the tread (also against a headwind).

[ynot]

The prop radius to wheel radius just changes the gearing. But that flex cable from the wheel to the prop... that's going to store a lot of energy like a spring. :)
Sorry but the secret is actually in the vice grips - They have been sprinkled with fairy dust ;)

ETA - Hope people appreciate the danger involved with this test. I could have had my guts ripped open with the prop or my fingers torn off with the spokes. :eye-poppi

[Dan O.]

Sorry but the secret is actually in the vice grips - They have been sprinkled with fairy dust ;)

ETA - Hope people appreciate the danger involved with this test. I could have had my guts ripped open with the prop or my fingers torn off with the spokes. :eye-poppi

It sounded like you did catch a finger on something.

Why didn't you spin the flywheel from below or use a disk mounted in a drill to spin the tire.



If you have ambitions to build a bigger rotating disk: http://www.astro.ubc.ca/lmt/lzt/gallery.html

[spork]

I think this is the best proof provided so far in support of the DDWFTTW claim.

Finally I can rest. I was on the edge of my seat wondering whether DDWFTTW really was possible. I figured all the existing analyses and experiments, both outdoors and with constant speed belts, were pretty sketchy.

[Michael C]

Spork, you just attributed Ynot's words to John Freestone.

[John Freestone]

Finally I can rest. I was on the edge of my seat wondering whether DDWFTTW really was possible. I figured all the existing analyses and experiments, both outdoors and with constant speed belts, were pretty sketchy.
spork, I don't understand. You quote me as saying "I think this is the best proof provided so far in support of the DDWFTTW claim.", and I'm sorry if this offends your studies and experiments, as well as those of others, so to check what I was on about, I clicked the link, and I can't find where I said it, if I did. If I did, and if I said it about ynot's turntable, I apologise and retract it. I think your and JB's treadmill tests are by far the best empirical proof for those who, like me, are crap at maths.

I'm not bothered about trawling through for an in-depth spork-gate, I just want to clarify my position. I think for those who feel that the magic plastic spork pushing your cart backwards causes a problem with steady-state (much as perhaps ynot had/has), the turntable removes such an objection, although it adds different ones, particularly if you don't have it moving at a known speed. As I think the record will attest, I have said that I think different experiments are good for people with different ways of thinking about the problem and different sources of doubt. For the frames-of-reference deniers, there's only going to be road tests, etc...

When it comes to proof of DDWFFTW so far, for those reasonably educated on the discoveries of the last 350 years, AFAIK, yous the daddy.

[John Freestone]

Whoops, I see. You probably just cut the wrong quote tags, spork. I'll boil you in oil another time! ;)

[John Freestone]

The prop radius to wheel radius just changes the gearing. But that flex cable from the wheel to the prop... that's going to store a lot of energy like a spring. :)
Hi Dan. Can you help me with this a bit more. I can't get it out of my head that somehow it is the same as having a differential windspeed - like putting your 'sail' up to a greater height than where the cart is meant to be going faster than the wind. But then, when I think "where is the cart?", I'm stuck, with this angular, rotating analogue. The 'cart' goes from the prop tip at its greatest radius (to clarify, we're meaning the turntable radius, not the radius of the prop or wheel itself here, yeah?) perhaps right to its fixing to the centre of the TT. It's natural to think of the wheel as being in the stream of wind equivalent to that in which a land cart would be, just because it is a wheel and is in contact with the surface, and the bits further in as only part of the experimental requirement to keep the vehicle in place. I presume that I'm at least right in saying that the equivalent windspeeds are different - right at the centre, there is zero windspeed whatever happens. If we extended that cable and frame and stuck the prop out at twice the radius of wheel position on the TT, doesn't that represent putting the prop of a landcart into an airstream twice that of the vehicle at wheel-level? Or is it in the end 'nominal' where we say the cart is, and we can define it as where its prop is?

[Dan O.]

The prop does see more effective wind the further out it is placed. But it is also equivalent to spinning the disk faster. It's probably easier to analyze by considering the position of the prop as fixed and varying everything else.

The "wind" at the prop is ωdp where ω is the angular speed of the disk (in radians per second) and dp is how far from the center the prop is placed.

[note: radians are just a unit for measuring angles to make the math easier. If the disk rotates 1 radian, a point on the disk at radius r moves a distance r around the circle.]

If the wheel is at distance dw from the center of the disk, the disk will move under the wheel ωdw (assuming that the wheel is moving at the speed of the "wind". The wheel (and the propeller) will therefore be rotating at ωdw/2πrw (where rw is the radius of the wheel (2πrw is the circumference)).

The gearing which is the ratio of the speed of the propeller to the speed of the cart is dw/dp * 1/2πrw].

[ThinAirDesigns]

In the previous video (and all other videos I've seen) the cart was held against the moving surface until it reached the speed of the surface. In other words it was forced to do so.

All well and good, but that's not what you said the last time.

Above you say it was forced until it reaches "the speed of the surface". In the post I questioned you said "I couldn’t resist going to the next step and test if the cart would develop enough speed to travel against the turntable when it wasn’t forced to do so".

See the clear difference. Now you say it's forced to the same speed and previously you say it's forced to a faster speed. I couldn't understand why you were saying you had previously been forcing the device to go faster than the turntable. Now I understand.

We do force it to go the same speed as the belt when we place it there. We do not force it to go faster.

JB

[ynot]

Here’s another video of the cart being powered only by the wind on a repaired and motor driven turntable (electric drill). The turntable is fairly level but looks to be on an angle because of the camera angle. The cart ran against the motion of the turntable at a constant speed for over 5 minutes (then the drill chuck came loose on the shaft).

http://www.youtube.com/watch?v=MCB1Jczysrk

I was thinking of doing another test where the cart is held in a set position on the spinning turntable (spinning with it) so it’s like a cart not moving on the ground in a wind. Then the cart would be released so the wind could move it. Would this test have any added value?

[mender]

Yes.

Maybe we can get humber to look at it and tell us how an orange can do the same thing!:D

[ynot]

Yes.

Maybe we can get humber to look at it and tell us how an orange can do the same thing!:D

Here tis - http://www.youtube.com/watch?v=k4owZkoeGAU

Things are moving a bit fast to see clearly what’s happening but the cart is held to the turntable with a block that is removed at about 3-4 second in (if you’re quick you can see it flying through the air on a string).

Surely not an orange . . . But how about a ball bearing? ;)

[John Freestone]

Here’s another video of the cart being powered only by the wind on a repaired and motor driven turntable (electric drill). The turntable is fairly level but looks to be on an angle because of the camera angle. The cart ran against the motion of the turntable at a constant speed for over 5 minutes (then the drill chuck came loose on the shaft).

http://www.youtube.com/watch?v=MCB1Jczysrk

I was thinking of doing another test where the cart is held in a set position on the spinning turntable (spinning with it) so it’s like a cart not moving on the ground in a wind. Then the cart would be released so the wind could move it. Would this test have any added value?
Nice one. It looks like it's still accelerating by the end of the video, and is on its way towards 2x windspeed (rough guesstimate). I suppose this test, starting the TT with the cart free to do its thing, is just like 'a wind gradually getting up' when you're on the tarmac. The next one with the block, of course, demonstrates self-start in a constant wind.

I have to say that there is something very impressive about these TT tests. They combine the control of the treadmill with the ability to let the cart do its own thing, and it very clearly does not have any desire to hang about at that dawdling old windspeed, does it? The treadmill tests are great, but unfortunate in having to prod or retain the cart, or put the treadmill on a slope, which doesn't have quite the same emotional effect - or have I just forgotten how impressive that was; yes, that's certainly part of it. It was unbelievable to see it climbing a hill against the belt. I suppose people gawped at bicyles at one time. In a few years people might go "DDWFTTW, yeah, and?". Well done, ynot. Pity about all the wrangles, but I'm not going to take sides on this one.

Now, can you do that without the wheel slipping?:D

[John Freestone]

The prop does see more effective wind the further out it is placed. But it is also equivalent to spinning the disk faster. It's probably easier to analyze by considering the position of the prop as fixed and varying everything else.

The "wind" at the prop is ωdp where ω is the angular speed of the disk (in radians per second) and dp is how far from the center the prop is placed.

[note: radians are just a unit for measuring angles to make the math easier. If the disk rotates 1 radian, a point on the disk at radius r moves a distance r around the circle.]

If the wheel is at distance dw from the center of the disk, the disk will move under the wheel ωdw (assuming that the wheel is moving at the speed of the "wind". The wheel (and the propeller) will therefore be rotating at ωdw/2πrw (where rw is the radius of the wheel (2πrw is the circumference)).

The gearing which is the ratio of the speed of the propeller to the speed of the cart is dw/dp * 1/2πrw].
Thanks Dan. I'm going to chew on that for a while, and probably should try harder to get my head round the basic math for the straight-line cart to help me understand it. It sounds like you're saying that there's no need to be concerned about that 'cheat' of having the prop in a faster effective wind than the wheel, though. And when I think about that again, it's clear that 'the cart' is beating the windspeed at the prop as well as the wheel.

It's a weird kind of model to compare with the land situation, like a perfectly uniform gradient of wind from the ground upwards, which continues even higher. Not absolutely unlike real conditions, just more perfectly like them. Similarly, if we had a cart body and wheels a centimeter high, with a prop raised to a metre, we're not going to measure whether it beat the wind at the 1cm height.

[mender]

Surely not an orange . . . But how about a ball bearing? ;)

Have you tried the ball bearing on the powered tt?

[Dan O.]

Have you tried the ball bearing on the powered tt?

I'd wait for the Mark-II TT (see it in the background) that doesn't have a big hole in the middle. The ball or orange will be much more impressive then.

[Dan O.]

It's a weird kind of model to compare with the land situation, like a perfectly uniform gradient of wind from the ground upwards, which continues even higher. Not absolutely unlike real conditions, just more perfectly like them.

The real wind profile is a little bit counter intuitive. If you think of the air as like layers of paper with very low friction between them, you would expect to see that uniform linear gradient between the non-moving air at the surface and the fast moving air at the top. But when the actual air gradient is measured, it fits closer to a power law with an exponent of 1/7th (linear would be an exponent of 1).

[ynot]

If anyone is interested here are a few basic specs and mug shot

The wheel is 8.5cm diameter
The circle travelled by the wheel is 120cm diameter
The prop is 12 x 6 slow air
Shafts run on roller bearings that have been washed of grease
Cable is from my son's BMX brake system
Hose clamps are optional

http://forums.randi.org/picture.php?albumid=116&pictureid=548

[spork]

Spork, you just attributed Ynot's words to John Freestone.

D'OH! I tried to go back and fix it, but it's too late.

Whoops, I see. You probably just cut the wrong quote tags, spork. I'll boil you in oil another time! ;)

Hey, at least I didn't put your name on a humber quote! :D

As far as boiling me in oil... get in line.

[spork]

We do force it to go the same speed as the belt when we place it there. We do not force it to go faster.

But there are MANY places where we force it to go slower. It then reaches and surpasses the wind speed on its own.



I have to say that there is something very impressive about these TT tests. They combine the control of the treadmill with the ability to let the cart do its own thing, and it very clearly does not have any desire to hang about at that dawdling old windspeed, does it? Pity about all the wrangles, but I'm not going to take sides on this one.

There's no need to take sides at all. The powered turntable tests are great. I personally think both the treadmill and turntable have their place. I'm quite certain there are sceptics that will have a problem with this thing going in a circle - just as there are sceptics that complain about gravity, inertial reference frames, or the color of the sky. But the turntable does have the very real advantage of letting the cart achieve steady-state speed. That's why Bauer used a turntable for his cart many years ago.

The reason JB and I are giving ynot a hard time is because of his earlier demands on us, his attacks, and his subsequent posts that have been less than forthcoming about the limitations of his experiments.

I find it somewhat ironic that in one of his recent videos he goes to some trouble to explain that this is NOT an experiment, and no conclusions should be drawn from it, but it IS the best evidence yet for DDWFTTW.

[mender]

It appears to me that the cart in Ynot's experiment (!) is going 5.7 mph against a turntable speed of 13.5 mph in the opposite direction. That works out to .42 higher than windspeed (for those of us who can understand equivalence) on an advance ratio of .6, not bad!

So does that indicate an efficiency of 89% (1.42/1.6)? Ynot, what is the "balance speed" in turntable rpm of your cart? 17 rpm by some chance?

[ynot]

It appears to me that the cart in Ynot's experiment (!) is going 5.7 mph against a turntable speed of 13.5 mph in the opposite direction. That works out to .42 higher than windspeed (for those of us who can understand equivalence) on an advance ratio of .6, not bad!

So does that indicate an efficiency of 89% (1.42/1.6)? Ynot, what is the "balance speed" in turntable rpm of your cart? 17 rpm by some chance?
Sorry but I’m just a “hack” so you’re going to have to work out the technical specs yourself. The best turntable to cart rotation achieved is around 2 turntable to 1 cart if that helps. If I get around to building the double cart I think it will do even better.

I have also tested it running for more than ten minutes without any noticeable loss of cart speed. When I quickly step in and slow the cart down it returns to it’s “cruise” speed quite quickly. My sceptic side is now happy to fully accept the effect is sustainable indefinitely.

[Dan O.]

Cable is from my son's BMX brake system

I hope he doesn't discover it's missing at a critical time :eek:

[mender]

Well, your sceptic side has provided us with an excellent tool for investigating the cart's behavior when (all humbers should look away now) running the "equivalent" of DDWFTTW! As spork said, this proof is pretty solid! Nicely done!

17 rpm will be the same as having the turntable complete ten turns in 35 seconds. If you have an adjustable speed on your drill, I would really appreciate you checking this for me. The cart needs to stay more or less in one place while the tt is running. A slight tilt of the tt will likely show up as a low spot that the cart likes to stay close to on extended running. That's okay if it does that; might make it easier for now if it does that.

I don't think the double cart will do much different. The only external resistance is from the bearing on the shaft that holds the arm that holds the cart. I assume that amount of resistance is quite low; if so the double cart will be a very small amount faster than the single cart.

[ynot]

I hope he doesn't discover it's missing at a critical time :eek:
It was one of many spare cables he has, but he says brakes are for sissy’s anyway.

I’m trying to think of experiments to do using a fan or fans to create the wind and having the turntable stationary. Something like a heap of fans around a stationary turntable all angled in the same direction to create a circular wind. Throw in a stream of bubbles and see if the cart beats them.

[mender]

Ynot, I don't think you'll get much info from that but since it's your turntable and cart - ynot. Humber and that other guy would like it too since they wouldn't have to run around behind it (!) with a fan to see what is "happening"!

Any chance of doing the 17 rpm test?

[ynot]

Well, your sceptic side has provided us with an excellent tool for investigating the cart's behavior when (all humbers should look away now) running the "equivalent" of DDWFTTW! As spork said, this proof is pretty solid! Nicely done!

17 rpm will be the same as having the turntable complete ten turns in 35 seconds. If you have an adjustable speed on your drill, I would really appreciate you checking this for me. The cart needs to stay more or less in one place while the tt is running. A slight tilt of the tt will likely show up as a low spot that the cart likes to stay close to on extended running. That's okay if it does that; might make it easier for now if it does that.

I don't think the double cart will do much different. The only external resistance is from the bearing on the shaft that holds the arm that holds the cart. I assume that amount of resistance is quite low; if so the double cart will be a very small amount faster than the single cart.
Sure, I certainly didn’t mean to imply that two carts would give twice the speed or anything like it.

The drill only has two speeds and it is currently running on the slow speed. I could alter the size of the small driving wheel but don’t have much spare time right now. Wish I had the multi-speed motor you said you have.

[ynot]

Ynot, I don't think you'll get much info from that but since it's your turntable and cart - ynot. Humber and that other guy would like it too since they wouldn't have to run around behind it (!) with a fan to see what is "happening"!

Any chance of doing the 17 rpm test?
Was actually thinking of a design where a fan chases the cart.

[mender]

Do you have a light dimmer in the house somewhere? If you can wire it into the box that your drill is running out of, that should allow you to vary the drill speed.

[ynot]

Do you have a light dimmer in the house somewhere? If you can wire it into the box that your drill is running out of, that should allow you to vary the drill speed.
So you want me to tear my house apart now? Good idea though. Don’t think I have a spare dimmer but they might not be too expensive to buy. Come to think of it I think I do have a spare dimmer but don’t where it is. So I know what you want, is it to run the cart in a hover for some reason?

[mender]

Yes; I want to see if the top speed of the vehicle when running in a decent wind is predictable based on the advance ratio and the "hover" speed.

The turntable speed that I'm after is one revolution every 3.5 seconds. If that can be maintained by hand, it might be easier than rewiring things. I know setting the drill would be more consistent.

Just had another thought: if you have another wheel like on the cart and a way of mounting that on your drill, you can vary the speed of the turntable by running the drill at a constant speed and moving the wheel in towards the centre or out towards the rim of the turntable to change the turntable speed. I don't know if that would get you in the right speed range though.

Unless you are already doing this of course!

[ynot]

I may have thought of a a design that will test the principle without using a treadmill or turntable (or maybe it‘s just a stupid idea) . . .

Build a cart with an onboard motor powered prop at it’s rear end so it‘s driven forward by the thrust of the wind it creates (wind powered cart). At the front end put the DDWFTTW prop and drive wheel but don’t connect them together. Run the cart in calm conditions and measure it’s top speed. Then connect the DDWFTTW prop and drive wheel and repeat the test. The connected cart should run faster than the non-connected. A valid test?

[John Freestone]

The real wind profile is a little bit counter intuitive. If you think of the air as like layers of paper with very low friction between them, you would expect to see that uniform linear gradient between the non-moving air at the surface and the fast moving air at the top. But when the actual air gradient is measured, it fits closer to a power law with an exponent of 1/7th (linear would be an exponent of 1).That's interesting, Dan. Thanks. Nice decision on the other thread, BTW. I might be close behind.

Hey, at least I didn't put your name on a humber quote! :D
Boiling in oil would be too quick.

Ynot - nice mugshot. While you've got that nice turntable, if you can see what speed is required to get different fruit and veg beating the wind, that would be a great boon to science. Well, you never know. I'm currently training cherries for an attempt on Everest.

[John Freestone]

I may have thought of a a design that will test the principle without using a treadmill or turntable (or maybe it‘s just a stupid idea) . . .

Build a cart with an onboard motor powered prop at it’s rear end so it‘s driven forward by the thrust of the wind it creates (wind powered cart). At the front end put the DDWFTTW prop and drive wheel but don’t connect them together. Run the cart in calm conditions and measure it’s top speed. Then connect the DDWFTTW prop and drive wheel and repeat the test. The connected cart should run faster than the non-connected. A valid test?
Isn't the front prop in a headwind?

[ynot]

Isn't the front prop in a headwind?
Sure but a “normal” cart travels in to a headwind after it reaches the speed of the wind as well (a lot less of headwind I know). The normal cart also progressively gets less power from the wind as it gathers speed but in the scenario I’m suggesting it always retains full power. I said it might be a silly idea but I think it’s worth thought and discussion.

[Dan O.]

So you want me to tear my house apart now? Good idea though. Don’t think I have a spare dimmer but they might not be too expensive to buy. Come to think of it I think I do have a spare dimmer but don’t where it is. So I know what you want, is it to run the cart in a hover for some reason?

Not a good idea unless you have a dimmer rated for inductive loads.

I do have a variac (variable transformer) that would do the job but it might be a bit difficult getting it to you. There is plenty of wind but I don't have a cart that can handle the weight :(

[ynot]

Isn't the front prop in a headwind?
Also the headwind has to effectively replace the tailwind so a puller rather than pusher prop would have to be used (or the prop reversed from “normal”).

ETA - But then the DDWFTTW prop would be thrusting against the motion of the cart. Begining to sound like a silly idea all round.

[mender]

Actually, Ynot, the connected cart will go slower. You'll be adding the drag of turning the propeller without adding more outside energy.

Dan O., I had this nagging feeling that the dimmer thing wasn't quite right but figured that someone would speak up.

[Christian Klippel]

Hello ynot,

congratulations to your DIY test-rig and the tests you did. You did a really nice job there.
And best of all, you actually did something, instead of simply complaining like certain other person(s). Kudo's to you for that!

As for the dimmer idea, yea, it usually has to be a "proper" dimmer to be used on a motor. Otoh, many in-line dimmers (that is, the ones you put in between a cable and not into the wall) are prepared for that. Also, certain wall-mount dimmers can handle that, if they are designed to dim a halogen light transformer.

The main difference between a simple "lamp only" and a "can do inductive load" dimmer is the snubber. That is, an R/C combination after the triac, that compensates a bit for the inductive load.

Greetings,

Chris

[ynot]

Hello ynot,

congratulations to your DIY test-rig and the tests you did. You did a really nice job there.
And best of all, you actually did something, instead of simply complaining like certain other person(s). Kudo's to you for that!

As for the dimmer idea, yea, it usually has to be a "proper" dimmer to be used on a motor. Otoh, many in-line dimmers (that is, the ones you put in between a cable and not into the wall) are prepared for that. Also, certain wall-mount dimmers can handle that, if they are designed to dim a halogen light transformer.

The main difference between a simple "lamp only" and a "can do inductive load" dimmer is the snubber. That is, an R/C combination after the triac, that compensates a bit for the inductive load.

Greetings,

Chris
Thanks Christian - Makes all the hard work worthwhile. This cart was actually a lot easier and quicker to make than the previous one.

I think Mender’s diabolical plan was to electrocute me with his suggestion. :D

[ynot]

Actually, Ynot, the connected cart will go slower. You'll be adding the drag of turning the propeller without adding more outside energy.

Dan O., I had this nagging feeling that the dimmer thing wasn't quite right but figured that someone would speak up.

Let’s forget both silly ideas then

I tested the hover/revolution rate by hand (a delicate process) and the constant turntable revolution rate for a hover was 8 - 9 rotations per 10 seconds second (almost 1 per second). I repeated it several times and made the cart hover at different positions around the turntable. Much slower than I expected and much faster than you predicted. Are you sure your figures are correct? One revolution per 3.5 seconds is very slow. The cart seems to be performing better the more I use it. Running in perhaps. Hope this has been of some help.

To answer one of your earlier questions I missed. Yes I have tried the ball bearing with the motor drive and it performed pretty much the same as hand driven. The turntable really does lose speed quite slowly. As I said the ball bearing performs much better than the unbalanced marble and it only takes a small downhill incline to make it advance against the turntable rotation.

If anyone has any test they would like me to do on the turntable I would be happy to do them if they make sense and are possible.

[Michael C]

Was actually thinking of a design where a fan chases the cart.

That won't be useful. Even if the machine is going at less than the speed of the air coming from the fan (i.e less than wind speed), it will be moving faster than the fan, since it will be moving away from it. It will move round the turntable out of the air stream of the fan before it can get to wind speed. You can make the fan go faster and faster around the turntable: all that will happen is that the cart will keep running ahead of the fan, at a point where it's getting just enough of the air stream from the fan to let it maintain the same speed as the fan around the turntable.

When I saw that Charles Platt had proposed such a test, and that Humber also thought is was a good idea, this brought to my mind the image of the tigers running round the tree in that strange children's story "Little Black Sambo (http://www.sterlingtimes.co.uk/sambo.htm)" (depending on where you live, this book may have been banned because of its racist content). In the story, the tigers chase each other around a tree until they turn to butter, which gets used for frying pancakes.

I still have a not-so-secret desire to see Humber desperately chasing the DDWFTTW cart around in circles. It would be a fitting punishment for his arrogance.

[mender]

I rethought the math and realized that I forgot a couple of things, but thanks for the test, Ynot. It shows a break-even speed of about 8.5 mph, which isn't bad for not being broken in yet. My cart still has some tuning left but is still about double the speed that JB and spork were able to achieve (only 2.7 mph!).

No accurate prediction of the top speed by my method yet. More tuning needed there too! I think that the rolling resistance may be too variable a number to base the top speed on. I think I still have quite a bit more testing to do on my cart before things start to form a pattern.

[Michael C]

The prop does see more effective wind the further out it is placed. But it is also equivalent to spinning the disk faster.

Moving the prop outwards further than the drive wheel isn't equivalent to spinning the wheel faster: the drive wheel will still be turning as the same speed as before, so the prop also keeps spinning at the same speed, but in a faster wind. This will change the ratio of prop speed to cart speed, so the relation between cart cruising speed and wind speed will also change.

It's probably easier to analyze by considering the position of the prop as fixed and varying everything else.

Yes, I think that's the best way of visualising it: the position of the prop defines where the wind is experienced.

In fact having the prop making a bigger circle than the drive wheel is equivalent to changing the gear ratio (or the size of the drive wheel, if you prefer). If you keep the prop at a certain distance from the centre of the turntable and move the drive wheel towards the centre, this will make the wheel, and therefore the prop, turn slower. You could create the same effect by keeping the drive wheel aligned with the propeller but increasing its size.

[ThinAirDesigns]

One thing to remember about Ynot's rig is the that prop is not operating in the same gradient as one on a straight treadmill.

As evidenced in our video's by the fact that the cart will hover at a lower speed with the prop off and away from the belt, I expect Ynot's cart performance to be better because of that design fact.

Of course I would also expect the inefficient cable drive to more than offset that advantage -- something born out by his break even speed.

Mender -- I would be surprised if you ever got your cart down to the break even speed that mine is ... I used a far more expensive and larger right angle drive on my first small cart and it feels much smoother and is more efficient than the "affordable" one's Spork used on the kits.

JB

[Dan O.]

Of course I would also expect the inefficient cable drive to more than offset that advantage -- something born out by his break even speed.

The cable drive system could be very efficient. I think he is just using the outer casing (essentially a spring) to make the bend. Most of the loss would be in the plastic coating which should disintegrate soon from the flexing (he did say he thought it was getting more efficient). There will be a small additional loss due to the extra loading on the bearings from the spring tension.

[mender]

The biggest problem is the single wheel, it has a persistent wobble that is slowing the cart but every now and then the wobble stops, resulting in a burst of speed. I'll be addressing that once I get the long driveshaft fixed again - too many prop strikes on a poorly repaired break makes for exciting times .:covereyes

A guy's gotta have goals though!

[ThinAirDesigns]

The cable drive system could be very efficient.

Well, perhaps it "could", but apparently it "isn't".

If I hang the prop off the back of the treadmill so like Ynot's it's not running in gradient, I get a break even of 2.3mph vs Ynot's 8mph+

The proof is in the pudding.

Now, for what it's worth I don't really see how that really matters ... his does the job he needed it to do. But it does tell me that if Ynot's is getting near 1.5x with that inefficient setup, I think ours would do closer (or over) 2x if he tied my cart on there with a string.

JB

[Dan O.]

The biggest problem is the single wheel, it has a persistent wobble that is slowing the cart but every now and then the wobble stops, resulting in a burst of speed.

It sounds like you either drilled the hub too big for the axel or the drill slipped and now you have a slot. The other possibility is that the axle wire is sometimes spinning in the hole in the frame.

[ynot]

I have made a couple of videos to demonstrate what I mean when I say a cart that wouldn’t normally advance against the turntable can be made to do so when it is “forced” up to speed by holding it against the turntable before releasing it.

Video 1 - The Little Cart that Couldn’t.
Pikachu’s friend Spork (another Pokemon character) told him all about DDWFTTW carts and Pikachu wanted to have a ride on one. There wasn’t enough room for Pikachu to ride on my Wind Cheetah cart so I added a block for WC to tow that Pikachu could ride on. But can WC towing a block of wood and Pikachu really travel DWFTTW? It appears not. No matter how long the turntable ran WC couldn’t oppose the motion of the turntable while towing the block and Pikachu. In fact Pikachu got so dizzy he threw up all over Spork.

http://www.youtube.com/watch?v=JX2mLQTHtw0

Video 2 - The little Cart That Could.
But all is not lost and Pikachu would have his DWFTTW ride after all. I held the cart against the motion of the turntable to allow (force) the propeller to get to full thrust and then WC happily chugged it’s way against the motion on the turntable towing the block and Pikachu (and it did it for enough time to indicate it was sustainable). Pikachu was so happy, not sure about Spork.

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

Disclaimer - All characters appearing in these productions are completely fictitious and do not represent any actual person or persons living or dead. ;)

[Michael C]

I have made a couple of videos to demonstrate what I mean when I say a cart that wouldn’t normally advance against the turntable can be made to do so when it is “forced” up to speed by holding it against the turntable before releasing it.

What these videos demonstrate is the difference between static and kinetic friction: the coefficient of static friction is usually higher than that of kinetic friction. This means that you need more force to start motion between two surfaces in contact than you do to keep the motion going once it has started.

You could do a similar demonstration with a bicycle towing something heavy in a wooden box: with a certain weight and surface area in contact with the ground, you could create a situation where the cyclist is unable to start unaided, but if given a push (being "forced" to get to a certain speed, as you might put it), it would be possible for the cyclist to keep going.

It's an interesting demonstration of a physical phenomenon, but doesn't have any particular signification for DDWFTTW. A DDWFTTW cart does self start, as you yourself have seen. All you're doing here is preventing the start. Why not put some wheels on Pikachu's block?

[spork]

Pikachu’s friend Spork (another Pokemon character) told him all about DDWFTTW carts
...Pikachu was so happy, not sure about Spork.

Interesting. Perhaps if you spoke "Pokemon" Pikachu's little friend Spork would explain some basic physics to you and clear up these little mysteries.

Also, I should say that your ill-concieved tests using such characters is an insult to the very well thought out and compelling videos Michael C has made.

I think you should be happy with your turntable, perform all the tests you like, post the results, and leave the explanations to folks that understand what's happening. The fact that you didn't believe it would work until you saw your own model doing it tells me everything I need to know.

[ThinAirDesigns]

I have made a couple of videos to demonstrate what I mean when I say a cart that wouldn’t normally advance against the turntable can be made to do so when it is “forced” up to speed by holding it against the turntable before releasing it.

What you have done is to demonstrate that a device can be built that will go "directly downwind, faster than the wind, powered only by the wind, steady state" (sound familiar) but depending on how much friction is involved, may not self start - it might require a push (and that push might be all the way to wind speed, it might not be all the way to wind speed.)

The above is something we attempted to figuratively pound into your head repeatedly. We explained over and over that we didn't include "self start" in our claim. Depending on the design and wind velocity, some can self start and some can't. Those that can't could be made to with the simple addition of some aero drag as below.

After the test, the "Spork" character responds by telling the Pikachu character to merely hold up a small parachute into the tailwind until the block starts sliding and then pull it in and stow it -- now it all self starts and Pikachu, quickly losing faith in the test designer wonders why Ynot didn't think of that in the first place.

Picachu is literally and figuratively sick of bad science.

JB

[John Freestone]

Ynot, can you clear something up for me, please? I watched the little cart that could first, because for some reason the ..couldn't didn't load properly at youtube and I clicked on the other. Now, first of all, I thought that was fairly obvious that the cart would accelerate from that held position. It's being made to keep at windspeed, but should theoretically be producing enough thrust to accelerate. You let go. It does.

But, I then watched the little cart that couldn't, and it doesn't run long enough to reach steady state, or not long enough for me to judge that. I take it that it is the same setup exactly, and I also have to take it from your report that however long it ran, the cart never reached windspeed. Now, I can't for the life of me think of any other explanation than that provided by Michael, which seems to suggest that not only did the cart not beat the wind, it never really set off from being stuck (by that higher static friction) to the TT.

Now you might think of something to test that - like perhaps handicap the cart in another fashion - if you want to check. From the few seconds we get, it seems to move slightly, but does not even cross the index mark. I think you would have a strange anomaly if it had a steady state that was some fraction of windspeed when set off from a standing start, but a multiple of windspeed if set off from windspeed. The physics of that would be very odd indeed - it should have a favoured speed - above it, it will slow down - below, it will speed up. See?

So the cart that couldn't may have just been stuck like a brick on a slope, but one that, with a tiny push, would slide down the slope. It's also my experience that such an object can slide a little way, but not quite get going and stop again.

The same design can't be a cart that couldn't and a cart that could other than by some unusual effect like the static friction you have introduced into the system. This is why your idea of the cart possibly only beating the wind when held so that it gains enough thrust to accelerate was wrong, I think. It is not being held so that it is forced to create sufficient thrust by being held, but prevented from developing more by going faster. At any speed slower than that, it will be providing more thrust than is needed for the speed it's going, so it accelerates. It's being held back, and if it's being held back, it can't be the cart that couldn't.

You might be able to hold it back to something slower, and then let go. But you've already done a standing start right up to beating the wind. I think you must conclude that your idea of what it can do being increased by being held must have been wrong. One test design - maybe tricky to find the bits - would be a trailer with wheels that are turning, but have a lot of friction in the axles. Another simpler (and truer) method might be to fit a more inefficient prop, so that it goes, but doesn't beat the wind. If you hold that cart at windspeed, I'm confident it will just slow down immediately you let go.

ETA: Whoops, in all that I forgot to ask the thing I wanted you to clear up: wasn't your point that a cart that would not 'normally' beat the wind could be made to by being held at windspeed? If so, the video of the cart that could isn't any use unless it slows down again to lower than windspeed and is actually a cart that couldn't. It seems to be a cart that could, but again the video isn't very long. So, after both videos, I don't know which it is, a cart that can or one that can't. Oh yes, I do, it accelerated from windspeed, so it isn't going to slow down again in the same conditions. You seem to have a view that the forces will be different depending on how they used to be at some time in the past, which is getting dangerously close to humberism for my liking. ;)

Keep up the good work.

[ynot]

As Michael C correctly says - “The demonstration shows the difference between static and kinetic friction“. And that’s all it was meant to demonstrate. It doesn’t prove that the cart with block and Pikachu can’t travel DDWFTTF (in fact the second video obviously shows it can). It shows the conditions of holding a cart against the motion of a moving surface are different than the conditions of not doing this (that’s it). It’s just a bit of fun from Ynot who is just a “hack” that wants to play with the expert Pokemon. But alas they don’t appear to like him and Squirtle keeps pissing on him. It’s so sad. But don’t worry, Ynot has broad shoulders and thick skin. But why does he keep dragging his knuckles along the ground? Perhaps he hasn’t heard about the evolution thing yet.

[spork]

Ynot, Michael C is correct in saying that your experiment shows the difference between static and kinetic friction. You're incorrect in stating that's all it shows. I can easily give you a scenario in which the block and surface have the same coefficient of friction for both static and kinetic, and yet they still show what your experiment shows - no self start, but it can sustain DDWFTTW if given a start.

You claim to have thick skin and broad shoulders, but you launch these silly attacks as you've done with your description of your poorly conceived experiment, and hope not to be corrected. The simple recipe for avoiding attacks is to not attack others. The recipe for not being corrected is to avoid saying things that are wrong. 'mmKay?

[ynot]

Ynot, Michael C is correct in saying that your experiment shows the difference between static and kinetic friction. You're incorrect in stating that's all it shows. I can easily give you a scenario in which the block and surface have the same coefficient of friction for both static and kinetic, and yet they still show what your experiment shows - no self start, but it can sustain DDWFTTW if given a start.

You claim to have thick skin and broad shoulders, but you launch these silly attacks as you've done with your description of your poorly conceived experiment, and hope not to be corrected. The simple recipe for avoiding attacks is to not attack others. The recipe for not being corrected is to avoid saying things that are wrong. 'mmKay?
Sure, but you don’t seem to realise that works both ways.

I don’t mind being corrected when I’m wrong, in fact I would be disappointed if I wasn’t. I do mind however (but not much) that I’m accused of being “incorrect” by way of a misquote - Saying ‘that’s all it was meant to demonstrate” is not saying “that's all it shows”. You seem to employ misquoting/misinterpreting attacks in an attempt to discredit others quite often.

I will let forum readers reach their own conclusion as to who does the majority of personal attacking on this forum.

[ynot]

Ynot, can you clear something up for me, please? I watched the little cart that could first, because for some reason the ..couldn't didn't load properly at youtube and I clicked on the other. Now, first of all, I thought that was fairly obvious that the cart would accelerate from that held position. It's being made to keep at windspeed, but should theoretically be producing enough thrust to accelerate. You let go. It does.

But, I then watched the little cart that couldn't, and it doesn't run long enough to reach steady state, or not long enough for me to judge that. I take it that it is the same setup exactly, and I also have to take it from your report that however long it ran, the cart never reached windspeed. Now, I can't for the life of me think of any other explanation than that provided by Michael, which seems to suggest that not only did the cart not beat the wind, it never really set off from being stuck (by that higher static friction) to the TT.

Now you might think of something to test that - like perhaps handicap the cart in another fashion - if you want to check. From the few seconds we get, it seems to move slightly, but does not even cross the index mark. I think you would have a strange anomaly if it had a steady state that was some fraction of windspeed when set off from a standing start, but a multiple of windspeed if set off from windspeed. The physics of that would be very odd indeed - it should have a favoured speed - above it, it will slow down - below, it will speed up. See?

So the cart that couldn't may have just been stuck like a brick on a slope, but one that, with a tiny push, would slide down the slope. It's also my experience that such an object can slide a little way, but not quite get going and stop again.

The same design can't be a cart that couldn't and a cart that could other than by some unusual effect like the static friction you have introduced into the system. This is why your idea of the cart possibly only beating the wind when held so that it gains enough thrust to accelerate was wrong, I think. It is not being held so that it is forced to create sufficient thrust by being held, but prevented from developing more by going faster. At any speed slower than that, it will be providing more thrust than is needed for the speed it's going, so it accelerates. It's being held back, and if it's being held back, it can't be the cart that couldn't.

You might be able to hold it back to something slower, and then let go. But you've already done a standing start right up to beating the wind. I think you must conclude that your idea of what it can do being increased by being held must have been wrong. One test design - maybe tricky to find the bits - would be a trailer with wheels that are turning, but have a lot of friction in the axles. Another simpler (and truer) method might be to fit a more inefficient prop, so that it goes, but doesn't beat the wind. If you hold that cart at windspeed, I'm confident it will just slow down immediately you let go.

ETA: Whoops, in all that I forgot to ask the thing I wanted you to clear up: wasn't your point that a cart that would not 'normally' beat the wind could be made to by being held at windspeed? If so, the video of the cart that could isn't any use unless it slows down again to lower than windspeed and is actually a cart that couldn't. It seems to be a cart that could, but again the video isn't very long. So, after both videos, I don't know which it is, a cart that can or one that can't. Oh yes, I do, it accelerated from windspeed, so it isn't going to slow down again in the same conditions. You seem to have a view that the forces will be different depending on how they used to be at some time in the past, which is getting dangerously close to humberism for my liking. ;)

Keep up the good work.
It takes a long time to upload even short videos to Youtube so I try to keep them as short as possible. I tested the “cart that couldn’t” for quite a long time and I don’t think it would ever gain enough speed to advance against the turntable without receiving some sort of “prod“ to do so.

I’m not saying there’s anything wrong with a cart being helped up to wind speed as long as it doesn’t store excess energy in any way in the process. I once thought this might be happening but my experiments have proven (to me at least) it doesn’t. Other experiments I had seen didn’t prove this to me adequately and I have received feedback from others who also have been helped in this regard by my experiments. This is not saying that other experiments didn’t or don’t provide useful information.

My experiments have been so conclusive to me that I now pretty much accept that DDWFDDW is possible. I will always have an element of scepticism however for something that is so counter intuitive and will keep testing and may even build a cart for outside testing in actual winds or some form of wind tunnel. Have a ten speed bike design in mind as it would be cool to ride on the cart. Hope if others are doing the same thing they post videos of their results regardless of whether they are successful or not.

[Dan O.]

Because the efficiency of the prop is non-linear, it is possible for a cart that can travel DDWFTTW will not be able to self start. However, YNOT's videos don't clearly demonstrate this because the block in the two videos are in different positions. The can't-do cart has 15-20% more friction drag than the can-do card.

It is also possible for the block to start flying over the surface of the spinning disk much like the heads fly in a disk drive. Once the block takes flight, the friction goes to almost zero.

[spork]

My experiments have been so conclusive to me that I now pretty much accept that DDWFDDW is possible.

Have you posted video of any of these experiments? So far I think you've told us that everything you posted was a "find the flaw" game or specifically "not an experiment". Why haven't you tied weights to your cart and run them over pullies? Isn't that what you kept bitching at us for not doing? You were so upset that you would have to use your own time to perform your own experiments.

[spork]

Because the efficiency of the prop is non-linear, it is possible for a cart that can travel DDWFTTW will not be able to self start. However, YNOT's videos don't clearly demonstrate this...

D'OH! You gave away the ending. I'm sure ynot would have figured it out.

[ynot]

Have you posted video of any of these experiments? So far I think you've told us that everything you posted was a "find the flaw" game or specifically "not an experiment". Why haven't you tied weights to your cart and run them over pullies? Isn't that what you kept bitching at us for not doing? You were so upset that you would have to use your own time to perform your own experiments.
What a shame your main interests seem to be ego and limelight.

[ynot]

Because the efficiency of the prop is non-linear, it is possible for a cart that can travel DDWFTTW will not be able to self start. However, YNOT's videos don't clearly demonstrate this because the block in the two videos are in different positions. The can't-do cart has 15-20% more friction drag than the can-do card.

It is also possible for the block to start flying over the surface of the spinning disk much like the heads fly in a disk drive. Once the block takes flight, the friction goes to almost zero.
I filmed the “could” video first and when I did the “couldn’t” immediately after and the block spun in to the propeller with the centrifugal force (obviously). I tied a string from the side of the block to the center and made it too long by mistake. After filming I continued “playing” and did both “could” and “couldn’t” runs with the string attached. Same result each time and never any “flying“. Of course you will have to just believe me on this and I could be lying and cheating (again apparently).

[ThinAirDesigns]

What a shame your main interests seem to be ego and limelight.

Judging only by results, Sporks "main interests" of ego and limelight at least take second fiddle to making sure that test are what they seem to be.

Wish the same could be said for your tests. As he points out so far we have the following catagories of tests:

A: One round of trick "find the flaw" tests presented as real.
B: One round of tests that you have so little faith in that you introduce with "no claims are made" statements.
C: A last round of tests that pretty much everyone agrees don't demonstrate what you say they demonstrate.

JB

[ynot]

Judging only by results, Sporks "main interests" of ego and limelight at least take second fiddle to making sure that test are what they seem to be.

Wish the same could be said for your tests. As he points out so far we have the following catagories of tests:

A: One round of trick "find the flaw" tests presented as real.
B: One round of tests that you have so little faith in that you introduce with "no claims are made" statements.
C: A last round of tests that pretty much everyone agrees don't demonstrate what you say they demonstrate.

JB
The Spork & Co tag team strikes again. I will return to not responding to insults.

ETA - Let me answer your points first . . .

A: How is it possible to run a “find the flaw” test and not present it as real? That’s a question that isn’t rhetorical.
B: Not a lack of confidence but more an attempt to reduce insults. The attempt clearly didn’t work.
C: I don’t agree. But regardless, I never claimed to be perfect.

Lets see what Spork & Co have Offered . . .

A: Did they come up with the idea? No. it’s at least 60 years old.
B: Did they design “their” cart. No. they copied someone else’s cart.
C: Is using a treadmill their idea? No. They copied that idea as well.

But they have done very well to give this principle public exposure on several forums and boosting their egos and gaining some limelight in the process. It’s like you guys want something good to put on your CV.

At least what I’ve done has been fairly original.

[ThinAirDesigns]

The Spork & Co tag team strikes again. I will return to not responding to insults.
-
Now you're taking a simple statement of facts on record in this thread and calling them "insults".

JB

[ThinAirDesigns]

It is also possible for the block to start flying over the surface of the spinning disk much like the heads fly in a disk drive. Once the block takes flight, the friction goes to almost zero.

Same result each time and never any “flying“.

Unless you are prepared to show some pretty good resolution video to support that statement you're just barking on the wind -- not from a "lying or cheating" standpoint, but just from a "you can't know that so you shouldn't say that" standpoint.

The string on the front of the block angles up to the cart tether. Obviously this means that with tension the front of the block is receiving an upward pull. Once the boundary layer of air from the spinning surface gets under a ever so slightly raised surface, it would have a dramatic influence on the overall friction.

Only a very high resolution video taken from just the perfect angle could prove that Dan O's simple and perfectly plausible hypothesis is in fact not happening.

JB

[Dan O.]

I filmed the “could” video first and when I did the “couldn’t” immediately after and the block spun in to the propeller with the centrifugal force (obviously). I tied a string from the side of the block to the center and made it too long by mistake. After filming I continued “playing” and did both “could” and “couldn’t” runs with the string attached. Same result each time and never any “flying“. Of course you will have to just believe me on this and I could be lying and cheating (again apparently).

You would probably not see the flying because it is using ground effect. (<-= OMG, did humber write that!!)

To demonstrate if you have flight, spin it up so the cart & block are traveling faster than the wind then disconnect the drill so it will slowly spin down and watch for the sudden change when the block stops flying. Alternatively, tether the block to a force measuring device (without the cart) and look for a transition from low drag at high speed to higher drag at low speed.

[A simple force measuring device: hang a weight from the ceiling and run a horizontal tether from the weight to the block. Use a ruler to measure the displacement of the weight and calculate the force with simple trig.]

If you don't get flight with this block, try rounding the leading edge.

[ThinAirDesigns]

A: How is it possible to run a “find the flaw” test and not present it as real? That’s a question that isn’t rhetorical.
-
How is it possible to ever expect credibility after presenting tests as real and then days later, and only under challenge, admitting that they were intentionally flawed? That's a question that isn't rhetorical either.

B: Not a lack of confidence but more an attempt to reduce insults. The attempt clearly didn’t work.
-
Well, that's what you say *now*, days after the fact and again under challenge (see above)

Lets see what Spork & Co have Offered . . .

A: Did they come up with the idea? No. it’s at least 60 years old.
B: Did they design “their” cart. No. they copied someone else’s cart.
C: Is using a treadmill their idea? No. They copied that idea as well.

Wait, this is another game of "spot the flaw" and "I've left an important detail out that should be included" -- that detail is the flawless credit we've given to the designers who went before us. We throw credit around like Christmas candy.

JB

[ynot]

-
How is it possible to ever expect credibility after presenting tests as real and then days later, and only under challenge, admitting that they were intentionally flawed? That's a question that isn't rhetorical either.


-
Well, that's what you say *now*, days after the fact and again under challenge (see above)



Wait, this is another game of "spot the flaw" and "I've left an important detail out that should be included" -- that detail is the flawless credit we've given to the designers who went before us. We throw credit around like Christmas candy.

JB
You didn’t answer question A. When you have I will answer yours.

[ynot]

-
Now you're taking a simple statement of facts on record in this thread and calling them "insults".

JB
The old “my insults aren’t insults because they are facts” ploy.

[ynot]

You would probably not see the flying because it is using ground effect. (<-= OMG, did humber write that!!)

To demonstrate if you have flight, spin it up so the cart & block are traveling faster than the wind then disconnect the drill so it will slowly spin down and watch for the sudden change when the block stops flying. Alternatively, tether the block to a force measuring device (without the cart) and look for a transition from low drag at high speed to higher drag at low speed.

[A simple force measuring device: hang a weight from the ceiling and run a horizontal tether from the weight to the block. Use a ruler to measure the displacement of the weight and calculate the force with simple trig.]

If you don't get flight with this block, try rounding the leading edge.
The “block” thing is of no further interest to me. There are other things I may test and may start constructing a cart for outside wind testing. Or I may do something completely different with my time.

[spork]

What a shame your main interests seem to be ego and limelight.

Not only does that not follow in any way from the quote, there's nothing that suggests this other than your desire to attack us and our tests without expecting the same in return.


A: Did they come up with the idea? No. it’s at least 60 years old.

As I've said more than once - I did come up with the idea. I then learned I was not the first to have come up with it. Certainly that's common enough. I never claimed to have "invented" this thing. Nor have I ever claimed any different than the statement right here.

B: Did they design “their” cart. No. they copied someone else’s cart.

We initially copied Jack Goodman's cart to a large extent - and gave him full credit (watch our video). We then copied Mark C's cart to a large extent - and gave him full credit (watch our video). We never claimed any differently.

It’s like you guys want something good to put on your CV.

Really? You'd have to tell me what I plan to do with that. We've been completely up front with this from the start as well. We want to get the Mythbusters to do a segment on it.

At least what I’ve done has been fairly original.

Really!? By reproducing the tests the Bauer did many years ago? He put his cart on a turntable long before you copied him.

By the way - what Goodman did wasn't original. What Bauer did wasn't original.

The old “my insults aren’t insults because they are facts” ploy.

Facts are facts. If you find them to be insulting you should avoid doing things that are embarrassing.


I just hope you consider this entire post insulting - and therefore don't respond to it.

[John Freestone]

You would probably not see the flying because it is using ground effect. (<-= OMG, did humber write that!!)No, but I'm fairly sure he's trawling this thread for new phrases he can punch in to his random word generator and spew over the other one. Actually, what am I saying, he's used that one all along - that the cart on a treadmill is lifted on the boundary layer, by its wheels!

You're doing very well, BTW. One day at a time! :D

[John Freestone]

It takes a long time to upload even short videos to Youtube so I try to keep them as short as possible.I accept that, and I trust your integrity in honestly saying what you saw over a longer time. I think you may still misunderstand what I'm saying, since you haven't addressed the points directly. Maybe I was a bit quick to jump in and waffled a lot, and so confused you.

I tested the “cart that couldn’t” for quite a long time and I don’t think it would ever gain enough speed to advance against the turntable without receiving some sort of “prod“ to do so. That's fine, but the point was whether this was because it was a cart that couldn't self-start, as was put to you. If you observed it for a long time, it probably should have dawned on you that it was pretty much not going anywhere w.r.t. the mark on the TT. It seemed to me that your earlier hypothesis was something like the following:

A cart might be blown by the wind to less than windspeed (as almost any would without cleverly designed props and stuff if it has wheels and a fairly low rolling resistance in a good enough wind), and remain there, not beating the wind. However, if held at windspeed, the same cart might then beat the wind steady state (or even, perhaps, beat the wind for a time and then return to slower than windspeed).

That's the kind of thing I thought you thought, and that you posted these last two videos genuinely to demonstrate. It seems that you were wrong, because of the difference between the static and dynamic friction. If you have the same cart not starting in one video, and beating the wind in the other, it isn't a cart that couldn't beat the wind, just a cart that couldn't self-start, and not only did the original claim of JB/spork allow for that, but it means that your hypothesis was wrong. It could help the whole study, other people's understanding of it, and relations with other experimenters, if you were clearer in your retractions or where you stand on these things.

I’m not saying there’s anything wrong with a cart being helped up to wind speed as long as it doesn’t store excess energy in any way in the process. I once thought this might be happening but my experiments have proven (to me at least) it doesn’t.It is good of you to say that you changed your mind, but it is a different matter from the above, I think. But maybe we are a little at cross purposes. The phrase 'helped up to windspeed' is crucial: does it mean given a wee push to get over its static friction (or allow its prop to develop enough efficiency, as I understand is another possible reason not to 'start')? It sounds like it could be a way to try to bolster your earlier hypothesis, because another way to read it is as if it needed pushing all the way to windspeed, or holding at windspeed, for it to beat windspeed. You seemed to say that a cart that won't could become a cart that would by being held at windspeed. Clearly, your cart that wouldn't could be helped up to some small fraction of windspeed, if necessary, and continue to accelerate, beat the wind, and remain there steady state. That's a cart that could, to me, and could despite dragging a brick. Being held at windspeed had nothing to do with its success, and your experiment suggests, and you seemed to interpret it, otherwise.

Other experiments I had seen didn’t prove this to me adequately and I have received feedback from others who also have been helped in this regard by my experiments. This is not saying that other experiments didn’t or don’t provide useful information. You're definitely right there about your main demo, IMO. As I said before, if someone looks at the spork pushing the cart backwards on the treadmill and has a kind of intuitive feeling that that could somehow make it 'bounce back' and accelerate beyond windspeed, then your minutes and minutes of steady state counter-rotation is one method of helping people get over that, as is putting the treadmill on a slope (but that is hard to balance, etc.).

My experiments have been so conclusive to me that I now pretty much accept that DDWFDDW is possible.Gosh, reticence still!...

I will always have an element of scepticism...Ah yes, of course, this is scepticism, and good on you for that. I "pretty much accept" there's no God, I'm going to die, and machines can be blown faster than the wind blowing them directly downwind. I could wake up and realise some of that was wrong!:) You don't have to ever be 100% convinced.

however for something that is so counter intuitive and will keep testing and may even build a cart for outside testing in actual winds or some form of wind tunnel. Have a ten speed bike design in mind as it would be cool to ride on the cart. Hope if others are doing the same thing they post videos of their results regardless of whether they are successful or not.A ten-speed DDWFTTW bike - ace! You should turn some heads.

[Dan O.]

The “block” thing is of no further interest to me. There are other things I may test and may start constructing a cart for outside wind testing. Or I may do something completely different with my time.

That's unfortunate because designing of flying blocks is something that may be marketable unlike the curiosity of the downwind cart.

[ThinAirDesigns]

Ynot:
At least what I’ve done has been fairly original.
-
Spork:
Really!? By reproducing the tests the Bauer did many years ago? He put his cart on a turntable long before you copied him.
-
Yeah, in the context of his post that one killed me it was so ironic. And in Ynot's case he hasn't even given credit but rather claims it as "fairly original" work.

ROFLAO

JB

[ynot]

Ynot:

-
Spork:

-
Yeah, in the context of his post that one killed me it was so ironic. And in Ynot's case he hasn't even given credit but rather claims it as "fairly original" work.

ROFLAO

JB
I knew nothing about the Bauer turntable tests before making my turntable. Of course you will claim that this is just another lie, but you are happy to accept Spork’s “I did come up with the idea. I then learned I was not the first to have come up with it” claim without question or criticism. Other than what has been mentioned about Bauer on this forum I know nothing about Bauer and what he did. Did he design a single wheel cart with a ridged tether that was powered by cable drive? Or did I copy all those things from someone else as well? Before you say all those things have existed in the past give an example of any invention that is totally original.

Still waiting for your answer to question A. Let me give you a hint - The answer is - “You can’t conduct a spot the flaw test by revealing the flaw up front”. That’s the obvious fact of the matter that you have been so reluctant to answer. Your accusations that I was lying are therefore based purely on your own opinion and are made without a single fact to support them.

In other words, just petty unsubstantiated personal attacks.

[Subduction Zone]

I just introduced this subject to my brother. He is a real life honest to goodness rocket scientist. He had an almost visceral reaction against it and refused to debate an "internet hoax" with me. Of course there were the usual claims of "perpetual motion" etc. I know how he feels since I was there once too.

[ynot]

I just introduced this subject to my brother. He is a real life honest to goodness rocket scientist. He had an almost visceral reaction against it and refused to debate an "internet hoax" with me. Of course there were the usual claims of "perpetual motion" etc. I know how he feels since I was there once too.
Can you at least get him to look at the video evidence and comment on that?

I think the only way to put this thing to bed once and for all is to build a cart and conduct conclusives outdoor tests in "real" wind. The only thing I lack to do this for my ten speed bike design is a large enough prop (and time).

[CNY_Dave]

I just introduced this subject to my brother. He is a real life honest to goodness rocket scientist. He had an almost visceral reaction against it and refused to debate an "internet hoax" with me. Of course there were the usual claims of "perpetual motion" etc. I know how he feels since I was there once too.


Until you can mentally model it (with the cart at windspeed) with the prop as a sail that's moving backwards rel. to the cart, it's tough to see how energy could be added into the system.

That is, that there is indeed part of the cart that moves 'below windspeed'.

As soon as you see how energy can be added to the system, it becomes a matter of feasibility (which at this point has been well demonstrated).

Relative to ynot's comment on showing him the videos, I've found they do little to help convince someone who doesn't believe its possible.


Dave

[Subduction Zone]

I am going to let him stew in his own juices for a couple of days over this. I started to argue frame of reference equivalences between the treadmill and a wind on the road and he did not even want to argue that, he realized instinctively that if he conceded that then he would have to concede DWFTTW. At least he wasn't as bad as humber. His college age sons were there also and one seems to be a bit taken by it.

[John Freestone]

Can you at least get him to look at the video evidence and comment on that?

I think the only way to put this thing to bed once and for all is to build a cart and conduct conclusives outdoor tests in "real" wind. The only thing I lack to do this for my ten speed bike design is a large enough prop (and time).
I don't see it like that. What 'puts it to bed' for one person won't for another. For some the most clear proof comes as a maths formula, if they have sufficient knowledge of mechanics and aero. I guess when you say that, and talk about doing 'conclusive tests' you mean for the general public or something. You don't have doubts concerning the validity of inertial frames of reference, do you? You don't think your cart that can on a TT can't on the road outside in a 'real wind', surely?

[ynot]

I don't see it like that. What 'puts it to bed' for one person won't for another. For some the most clear proof comes as a maths formula, if they have sufficient knowledge of mechanics and aero. I guess when you say that, and talk about doing 'conclusive tests' you mean for the general public or something. You don't have doubts concerning the validity of inertial frames of reference, do you? You don't think your cart that can on a TT can't on the road outside in a 'real wind', surely?
Before my turntable tests I thought the odds were that it would be proven wrong. Before conducting outside tests I would now think that the odds are that it would be proven correct. (I‘m only talking about me). The trouble with equivalence tests is even although they might represent the real thing with 100% accuracy, they just aren’t the real thing. If a cart was travelling downwind and obviously beating bubbles floating in the wind then to most people it would be conclusive proof that the cart was travelling downwind faster than the wind as long as it could be shown that no cheating was taking place. You will never be able to convince some people with any amount of credible proof but those people aren’t of any importance to me. In fact proving or disproving it to other people isn’t that important to me.

[spork]

I knew nothing about the Bauer turntable tests before making my turntable.

Two problems with that theory. First of all, we discussed Bauer's turntable in the very thread you were participating in BEFORE you did your tests. It doesn't exactly take much research to be aware of it when you read it right here.

Secondly - whether you were aware of it or not doesn't seem to mean anything to you. You try to denigrate me for "copying" someone elses work when I (A) never claimed is as original, and (B) did arrive at it independently. You then claim that what you did WAS original. How very pathetic!

Of course you will claim that this is just another lie

Easy enough to do when we can show that you were discussing this in the very thread where we describe his turntable experiments!

... but you are happy to accept Spork’s “I did come up with the idea. I then learned I was not the first to have come up with it” claim without question or criticism.

JB was there to see it unfold. He also knows me plenty well that he would never question such a silly thing. And frankly I don't care if YOU question it.

Before you say all those things have existed in the past give an example of any invention that is totally original.

I can list 25 that I hold patents for.

Still waiting for your answer to question A. Let me give you a hint - The answer is - “You can’t conduct a spot the flaw test by revealing the flaw up front”.

This is maybe the most pathetic thing you keep spewing. Quite the contrary. You can't conduct a "spot the flaw" test if you don't tell people to "spot the flaw". What we call that is simply lying. If in fact you were conducting a "spot the flaw" test of course you wouldn't tell people what the flaw was, but you'd tell them to find it. Instead you continued to evade the question after several people had in fact spotted the flaw. You hoped it would go away. When the truth about your misrepresentation just wouldn't die, you decided to re-brand your lie as a "spot the flaw" test!

Pathetic.

[spork]

I just introduced this subject to my brother. He is a real life honest to goodness rocket scientist. He had an almost visceral reaction against it and refused to debate an "internet hoax" with me.

Just for the record, many (most?) of us "real life rocket scientists" don't insist this is an internet hoax and refuse to discuss it.

The trouble with equivalence tests is even although they might represent the real thing with 100% accuracy, they just aren’t the real thing.

How sad for you! You honestly don't understand what "the real thing" is.


Incidentally, you keep promising that you're done responding to insults, but you just keep insulting us. What's it going to take to get you to hold to your word?

[ynot]

Two problems with that theory. First of all, we discussed Bauer's turntable in the very thread you were participating in BEFORE you did your tests. It doesn't exactly take much research to be aware of it when you read it right here.

Secondly - whether you were aware of it or not doesn't seem to mean anything to you. You try to denigrate me for "copying" someone elses work when I (A) never claimed is as original, and (B) did arrive at it independently. You then claim that what you did WAS original. How very pathetic!



Easy enough to do when we can show that you were discussing this in the very thread where we describe his turntable experiments!



JB was there to see it unfold. He also knows me plenty well that he would never question such a silly thing. And frankly I don't care if YOU question it.



I can list 25 that I hold patents for.



This is maybe the most pathetic thing you keep spewing. Quite the contrary. You can't conduct a "spot the flaw" test if you don't tell people to "spot the flaw". What we call that is simply lying. If in fact you were conducting a "spot the flaw" test of course you wouldn't tell people what the flaw was, but you'd tell them to find it. Instead you continued to evade the question after several people had in fact spotted the flaw. You hoped it would go away. When the truth about your misrepresentation just wouldn't die, you decided to re-brand your lie as a "spot the flaw" test!

Pathetic.
Obviously TAD and yourself have been examining this principle much longer than I have. In the process you have been examining works previously done by other people including Bauer. If I knew that Bauer had used a turntable surely you two would have known that as well.

When I first suggested the idea however (Post #105 of the other thread) your first reaction was - “Shoot! I do like that idea” (post1520). TAD’s was - “Ynot, that's a really great idea. Hadn't thought of it.” (post #1509). Obviously neither of you new that Bauer had used a turntable or thought of doing it yourselves. Some other member first mention that Bauer had use a turntable for testing much later in the thread.

This and other attempts to discredit me by a series of lies and false accusations is no better than your attempt of post #94 of this thread . . .

“Personally, I've had my doubts from the start that he ever built a prop cart that advanced on his turntable. The more I read, the more trouble I have buying that story. It's a bit like the Roswell incident in that there's no video or stills showing any such thing. The difference being that with the Roswell incident we at least are given some exceptionally poor stills of a small portion of the "wreckage".

You were forced to quickly apologise when I reposted a photo of the cart I had built and you were conclusively proved wrong.

You continuously insult people on this forum and other forums. I guess it just reflects the type of person you are. I suspect that TAD is a better person but has been affected by “If you lie down with dogs you get up with fleas”.

This is your real purpose on this forum and others . . . Spork - “The only practical application it has is to start pissing matches on internet forums. And for that it has no equal.”

This is the last time I will reply to any of your posts. I feel sorry for people that are directly involved with you and can’t get you out of their lives as easily as I can.

[spork]

This and other attempts to discredit me by a series of lies and false accusations is no better than your attempt of post #94 of this thread . . .

I know you like to accuse us of lies - but you can't give an example because none exists. The facts are this... you knew Bauer had used a turntable BEFORE you made the claim that your work was original. Not only is that a lie; it's an insulting lie, because clearly we all know better.

You were forced to quickly apologise when I reposted a photo of the cart I had built and you were conclusively proved wrong.

I wasn't "forced" to do anything. I apologized because I was wrong. That's what grown ups do. You really should try it sometime.

You continuously insult people on this forum and other forums. I guess it just reflects the type of person you are.

Yup. I'm the kind of person that doesn't stand for being attacked and lied to. I guess lying and attacking others without basis just reflects the type of person you are.

This is the last time I will reply to any of your posts.

Another lie. How many times have you made this claim!? You can't drop it - despite that fact that you started the attacks and continue to perpetuate the lies. It's all here in black and white, so it really doesn't come down to your word against mine.

Pathetic.



Lets see what Spork & Co have Offered . . .

A: Did they come up with the idea? No. it’s at least 60 years old.
B: Did they design “their” cart. No. they copied someone else’s cart.
C: Is using a treadmill their idea? No. They copied that idea as well.

But they have done very well to give this principle public exposure on several forums and boosting their egos and gaining some limelight in the process. It’s like you guys want something good to put on your CV.

At least what I’ve done has been fairly original.

Quick recap: we were careful to credit everyone in our video and elsewhere. You claim as your original work something that you KNOW not to be original.

Pathetic.

[John Freestone]

Before my turntable tests I thought the odds were that it would be proven wrong. Before conducting outside tests I would now think that the odds are that it would be proven correct. (I‘m only talking about me). The trouble with equivalence tests is even although they might represent the real thing with 100% accuracy, they just aren’t the real thing. If a cart was travelling downwind and obviously beating bubbles floating in the wind then to most people it would be conclusive proof that the cart was travelling downwind faster than the wind as long as it could be shown that no cheating was taking place. You will never be able to convince some people with any amount of credible proof but those people aren’t of any importance to me. In fact proving or disproving it to other people isn’t that important to me.
Yes, I see. That makes sense. My question assumed that equivalence was the same as identity, and it's not quite that simple, and I agree with the probabilities view - like I said, it's rather what being a sceptic is about. Someone could at some time in the future show me why all of this was mistaken and DDWFTTW isn't possible after all. It occupies that 0.0something% in my head. I'd have a lot of humber-pie eating to do! I'd go further and say that the equivalence isn't even 100%, so there is some margin of possibility that the differences of scale, limits of moving surfaces, etc. could render it impossible (again, I have to estimate that with reference to more educated heads than mine and pure gut instinct, and it's darn small). So at the end of the day, for me, the cart on a treadmill, once I (re?)-learned the physical principles, trusted the equivalence and trusted the experimenters, was enough. If it can climb a backward-moving treadmill, it'll beat a tailwind. End of. Anyway, I'm just rambling now because I'm a bit bored. I really can't imagine how mental someone has to be to look forward to seeing a bicycle version, but that's how mental I am!:) Greetings from the proper up-side of the planet, BTW.

[ynot]

Given this principle has been around for at least 60 years I wonder why more outdoor “real wind” testing hasn’t been done. I know winds created by natural forces are rarely if ever constant and smooth, but given the results on treadmills and turntables show a significant increases over wind speed, I would have thought that conclusive outdoor results should be relatively easily to achieve. Why hasn’t the testing done by those that have done outdoor testing been conclusive?

[CNY_Dave]

Given this principle has been around for at least 60 years I wonder why more outdoor “real wind” testing hasn’t been done. I know winds created by natural forces are rarely if ever constant and smooth, but given the results on treadmills and turntables show a significant increases over wind speed, I would have thought that conclusive outdoor results should be relatively easily to achieve. Why hasn’t the testing done by those that have done outdoor testing been conclusive?


Probably those of the type to be so rigorous are also the type that would tend to be satisfied proving it to themselves, and not really caring to share the results.

Especially since this internet-thing is a relative newcomer compared to how long this has been kicking around.


Speaking of such, has anyone attempted to do this with a boat?


Dave

[Subduction Zone]

Given this principle has been around for at least 60 years I wonder why more outdoor “real wind” testing hasn’t been done. I know winds created by natural forces are rarely if ever constant and smooth, but given the results on treadmills and turntables show a significant increases over wind speed, I would have thought that conclusive outdoor results should be relatively easily to achieve. Why hasn’t the testing done by those that have done outdoor testing been conclusive?

Since we are discussing this on the internet the best sort of proof for this medium is one that would be accepted by people learning about it on the internet. I like the idea of a Lawrence Welk type champagne bubbler machine that would make a continuous supply of bubbles. The streamer on the cart is not my favorite since the cart moves some air you could claim that you are having a false positive test before you actually hit wind speed. If you accurately measured the wind speed and accurately measured the cart by radar there would still be naysayers who would claim that the data was faked. It would be pretty difficult for them to argue that the cart passing up a flock of bubbles was not going faster than the wind, unless like humber, you believe that a hot air balloon does not move at wind speed. Physically not as accurate, but as the saying goes seeing is believing. Of course the bubbles could always be claimed to be CGI but that is a stretch.

[Michael C]

Speaking of such, has anyone attempted to do this with a boat?

I don't think so. Mark Drela did an analysis of DDWFTTW (http://www.boatdesign.net/forums/attachments/boat-design/27991d1230779009-wind-powered-sail-less-boat-ddw2.pdf) where he looks at both boats and land vehicles. He concludes that for wheeled vehicles DDWFTTW is achievable "without too much difficulty", but for a boat it "would be quite difficult, but possibly doable
with careful component design and matching." It would be great if somebody takes up the challenge.

[ynot]

Probably those of the type to be so rigorous are also the type that would tend to be satisfied proving it to themselves, and not really caring to share the results.

Especially since this internet-thing is a relative newcomer compared to how long this has been kicking around.


Speaking of such, has anyone attempted to do this with a boat?


Dave
I’ve thought of testing in water. You don’t even need a boat. Just a prop in constantly flowing water connected to a wheel or wheels on “dry land” would do the trick.

ETA - Now where can I find a long trough of constantly flowing water?

[ynot]

Since we are discussing this on the internet the best sort of proof for this medium is one that would be accepted by people learning about it on the internet. I like the idea of a Lawrence Welk type champagne bubbler machine that would make a continuous supply of bubbles. The streamer on the cart is not my favorite since the cart moves some air you could claim that you are having a false positive test before you actually hit wind speed. If you accurately measured the wind speed and accurately measured the cart by radar there would still be naysayers who would claim that the data was faked. It would be pretty difficult for them to argue that the cart passing up a flock of bubbles was not going faster than the wind, unless like humber, you believe that a hot air balloon does not move at wind speed. Physically not as accurate, but as the saying goes seeing is believing. Of course the bubbles could always be claimed to be CGI but that is a stretch.

Why do I get a strong felling of déjà vu? Or is it just an echo from another forum? :D

What do you mean by CGI? I only know it as Common Gateway Interface.

[Michael C]

Given this principle has been around for at least 60 years I wonder why more outdoor “real wind” testing hasn’t been done.

I'm sure that the outdoor tests done by Bauer and Goodman were perfectly sufficient to convince themselves. Since there seems to be no commercial application of this device, and there are no prizes to be won, presumably they didn't want to invest in more expensive tests to convince those who refused to believe them. DDWFTTW does not represent any revolutionary physical principle: it's perfectly explained by analysis using well-established classical mechanics, so a detailed mathematical explanation together with the treadmill tests is all that is necessary to demonstrate that the thing works.

Having said that, it would be nice to see an outdoor demonstration on a large scale. I hope that Spork and JB will continue to create a ride-on cart. Hopefully filmed by the Mythbusters team, somebody would release a helium-filled balloon in the wind, let it get a head start, then get in the cart and catch up with the balloon. Even then there'd be idiots who'd cry "fake" or pretend that the balloon doesn't travel at the speed of the wind (Humber...), but that's unavoidable. This test wouldn't prove anything that hasn't already been proven, but it would be far more impressive than the treadmill or turntable videos for the average hobo.

[Michael C]

I’ve thought of testing in water. You don’t even need a boat. Just a prop in constantly flowing water connected to a wheel or wheels on “dry land” would do the trick.

ETA - Now where can I find a long trough of constantly flowing water?

I don't think you're talking about the same thing as CNY Dave. I take it that he was talking about taking a boat go DDWFTTW, while you seem to be talking about making a vehicle go beside a stream of water faster than that stream of water. It should certainly be possible to do this; to test it you could use a stretch of river with a level path beside it.

[ynot]

I don't think you're talking about the same thing as CNY Dave. I take it that he was talking about taking a boat go DDWFTTW, while you seem to be talking about making a vehicle go beside a stream of water faster than that stream of water. It should certainly be possible to do this; to test it you could use a stretch of river with a level path beside it.
Whatever way you do it there has to be some form of “stationary ground” for a wheel to run on and power the prop. The point I’m making it that the "water-cart" doesn’t have to be a boat floating in the water. The water speed can easily be indicated by small things floating on it.

[Michael C]

Whatever way you do it there has to be some form of “stationary ground” for a wheel to run on and power the prop. The point I’m making it that the "water-cart" doesn’t have to be a boat floating in the water. The water speed can easily be indicated by small things floating on it.

A DDWFTTW boat doesn't need wheels any more than an ordinary boat needs wheels. You're talking about a cart that runs "next to the water faster than the water", using the difference in velocity between the water and the ground. I'm taking about a boat that sails downwind faster than the wind, using the difference in velocity between the air and the water. Such a boat would have a propeller in the air connected to a turbine in the water.

[CNY_Dave]

<snipped>

Hopefully filmed by the Mythbusters team, somebody would release a helium-filled balloon in the wind, let it get a head start, then get in the cart and catch up with the balloon.

<snipped>



A combination of lead balloons, party balloons, weather balloons, a dirigible covered in thermite, supporting a small child and a man in a lawnchair holding a BB gun, I would hope!


Dave

[ynot]

A DDWFTTW boat doesn't need wheels any more than an ordinary boat needs wheels. You're talking about a cart that runs "next to the water faster than the water", using the difference in velocity between the water and the ground. I'm taking about a boat that sails downwind faster than the wind, using the difference in velocity between the air and the water. Such a boat would have a propeller in the air connected to a turbine in the water.
Yes I’m talking about travelling down river faster than the river (DDRFTTR) and didn‘t realise you weren‘t. Good luck with trying to work exactly how fast the wind and the water is travelling at any time. Just one is hard enough

As far as I can see a successful DDRFTTR test is every bit as good as a DDWFTTW test to prove or dsprove the principle.

[Subduction Zone]

What do you mean by CGI? I only know it as Common Gateway Interface.

A movie special effects term. I don't remember exactly what the acronym stands for it is either computer generated images or something on the order of computer graphic imagery, I like the second a bit better.

[John Freestone]

Yes I’m talking about travelling down river faster than the river (DDRFTTR) and didn‘t realise you weren‘t.Yes, that was something I mentioned in the main thread, and maybe others did before me (in case anyone cares). I suggested that it might be useful to test the principle in a long watercourse, having a water-cart (same, just probably heavier and with low prop to keep below waterlevel) moving along the bottom - a steady speed of water flow could be checked more easily, I thought, than wind. Buoyancy might be a bit of a problem, causing wheel slip. I didn't think of the wheels outside the water, though: that's a better idea.

I also suggested it as a version of my 'pipe-racer', if the pipe were filled with water or another fluid instead of air. Air is just a fluid, technically speaking, IIRC. I have a feeling I might have been the first to propose the pipe-racer (named by JB), which is just the same as the cart except you put wheels radially so as to contact round the inside of a pipe. I haven't bothered with detailed plans for the same reason people haven't done more extensive testing and proof of the cart, probably - it's a curiosity. If anything does turn out to have commercial application, it's more likely to be a pipe-racer, to my mind - maybe I should get my patent application in. Damn, now I've told the world.

As far as I can see a successful DDRFTTR test is every bit as good as a DDWFTTW test to prove or dsprove the principle.Yes. Relative speeds of a fluid and a surface, or two fluids - two surfaces is kind of too uninteresting (unless one is a piece of paper and the other a ruler, with little characters sitting around the place....;))

A movie special effects term. I don't remember exactly what the acronym stands for it is either computer generated images or something on the order of computer graphic imagery, I like the second a bit better.
Computer Generated Imagery usually...or Image/s.

[John Freestone]

Someone even suggested a cart that travelled directly down-magma faster than the magma. I hope they were joking. :)

[ynot]

Someone even suggested a cart that travelled directly down-magma faster than the magma. I hope they were joking. :)
Here's a torpedo that travels Down Wire Faster Than The Wire! :eye-poppi

http://en.wikipedia.org/wiki/Brennan_Torpedo (http://en.wikipedia.org/wiki/Brennan_Torpedo)

[Christian Klippel]

A movie special effects term. I don't remember exactly what the acronym stands for it is either computer generated images or something on the order of computer graphic imagery, I like the second a bit better.

Hello Subduction Zone,

you were pretty close. It means "Computer Generated Imagery" (http://en.wikipedia.org/wiki/Computer-generated_imagery), and is probably as old as computers that are capable of producing graphics.

Greetings,

Chris

Edit: Here (http://de.wikipedia.org/w/index.php?title=Datei:Yafray_example_image.camera. jpg&filetimestamp=20061020233848) is great example of how realistic modern CGI can look like, here (http://www.yafray.org/forum/viewtopic.php?t=1286) is another one.

[spork]

Probably those of the type to be so rigorous are also the type that would tend to be satisfied proving it to themselves, and not really caring to share the results.

I was satisfied when I worked out the simple vector analysis. It wasn't until JB insisted we build one that we actually did. I was amazed that people questioned the analysis (it really is quite simple), and am even more amazed that they question the demonstrations. For me, I'm pefrectly keen on sharing the results, I just can't believe how hard it is to get people to accept them.


The streamer on the cart is not my favorite since the cart moves some air you could claim that you are having a false positive test before you actually hit wind speed.

This is a common concern about Goodman's cart, but if you look carefully, you'll see that his streamer is well out to the side of the prop. Still, I agree that smoke or bubbles would be better because they provide a wind history of sorts.

If you accurately measured the wind speed and accurately measured the cart by radar there would still be naysayers who would claim that the data was faked.

There could never exist evidence so strong that all naysayers will accept it. Sad but true.


Having said that, it would be nice to see an outdoor demonstration on a large scale. I hope that Spork and JB will continue to create a ride-on cart.

Yup. That's still our plan. Not that I expect to change many more minds, but it should be fun. Hopefully I won't procrastinate nearly as much as I did with the model. I'll let JB take charge of the schedule. That's what's worked so far.

[ynot]

For those that missed or didn’t understand how the Brennan torpedo works, I think it’s a very good working example of DDWFTTW, only in this case the W stands for Water. The wires want to pull the torpedo backwards and at the same time they also spin the props that want to push the torpedo forward. The props win and the torpedo moves forward. Essentially the same as cart’s prop thrust winning the battle against the moving surface.

The Brennan torpedo - http://en.wikipedia.org/wiki/Brennan_Torpedo

I accept this as a working, undeniable proof of DDWFTTW (patented in 1877)

[ynot]

Personally I think this debate is over and thank most for participating and the very helpful information they provided. I think any intelligent (self-honest) person has to conclude that DDWFTTW is possible and there is a practical working example in the Brennan Torpedo.

If anyone DOESN’T accept that the Brennan Torpedo is an actual, practical working example of DDWFTTW (no treadmills or turntables required), that is essentially the same as the carts in the videos, I would appreciate an explanation why it isn‘t.

I suspect (but don’t know) that Spork & Co may have known about the Brennan Torpedo all along and were only here for the thrill of the “pissing match” and the limelight.

If Spork & Co build a “real wind” cart and travel DDWFTTW in to the limelight then it merely proves that they were after the limelight all along. Proof of the principle already exists in the Brennan Torpedo.

[Michael C]

Personally I think this debate is over and thank most for participating and the very helpful information they provided. I think any intelligent (self-honest) person has to conclude that DDWFTTW is possible and there is a practical working example in the Brennan Torpedo.

The Brennan torpedo is certainly analogous to the DDWFTTW vehicle. So is a cotton reel being pulled along the ground, which was the inspiration for the Brennan torpedo. So is my machine that goes under the ruler. All these machines illustrate the same principle of using the relative movement between two surfaces, or media, to make a vehicle go faster than this movement relative to one of the surfaces, or media. If the Brennan Torpedo clinches the argument for you, fine. But you cannot claim that it actually is a downwind faster than the wind machine, any more than I can claim this for my ruler-powered cart.

The Brennan torpedo is actually a machine that goes in the opposite direction to the wire (in fact it has two wires, but that is for steering purposes: you could make one with only one wire, but you wouldn't be able to guide it). If you look at the torpedo from the frame of reference moving at the same velocity as the wire, you see that the velocity of the torpedo relative to the wire is in the same direction and greater than that of the water relative to the wire. So somebody who understands frames of reference will recognise that it is a "down water faster than the water" device. But somebody who understands frames of reference will also recognise that Spork's cart on a treadmill is a downwind faster than the wind device. Moreover, it isn't just an analogy of a downwind faster than the wind device, it really does go downwind faster than the wind, exactly as Bauer's and Goodman's carts did.

Because you hit on something that has convinced you that DDWFTTW is possible, you announce "I think this debate is over". Other people have been convinced by other means: somebody who understands the analysis of the DDWFTTW principle can be convinced by that alone, another person will have their eyes opened by one of the analogies, another person will be convinced by treadmill tests... Each of these people could say for themselves "the debate is over" at the moment when they were convinced. For others, the debate goes on. If you're now totally convinced, you can have some fun trying to explain to determined skeptics why you think the Brennan torpedo is such a good example.

As for Spork and JB being only "after the limelight", I think you're mistaken. They have never made a secret of the fact that others had done this before. They are not claiming to have invented something new. They have tried, here and in many other places, to explain how the thing works. They have presented analyses and analogies. I don't know if they'd already seen the Brennan torpedo, but I'm sure of one thing: if they had shown everyone a detailed explanation of how it works, that wouldn't have convinced the hard-core skeptics any more than the other arguments they presented.

[fredriks]

Proof of the principle already exists in the Brennan Torpedo.


Some people actually believed that this was proved by the treadmill videos or even by some theoretical argument or from all other mechanical systems that has been discussed. Good that you finally explained for everybody else that it is proved now.


I suspect (but don’t know) that Spork & Co may have known about the Brennan Torpedo all along and were only here for the thrill of the “pissing match” and the limelight.

edit: the post above says much the same thing that I q

If Spork & Co build a “real wind” cart and travel DDWFTTW in to the limelight then it merely proves that they were after the limelight all along. Proof of the principle already exists in the Brennan Torpedo.

You seems to be a very strange fellow. You first start as a die hard skeptic even though you didn't seem to understand the basic physics involved or the explanations. Then when you finally find something that you think prove that is can be done you seems to think that other people hold back that information for some reason just to fool you and other people.

Theoretical explanations not good for you.
Treadmill don't good for you

Turntable quite good but the other people didn't want to help you and didn't want to build one.

Brennan Torpedo very good but people didn't want to help you so they must have some kind of agenda.

edit: Michael C post say much of what I was thinking.

[ynot]

The Brennan torpedo is certainly analogous to the DDWFTTW vehicle. So is a cotton reel being pulled along the ground, which was the inspiration for the Brennan torpedo. So is my machine that goes under the ruler. All these machines illustrate the same principle of using the relative movement between two surfaces, or media, to make a vehicle go faster than this movement relative to one of the surfaces, or media. If the Brennan Torpedo clinches the argument for you, fine. But you cannot claim that it actually is a downwind faster than the wind machine, any more than I can claim this for my ruler-powered cart.

The Brennan torpedo is actually a machine that goes in the opposite direction to the wire (in fact it has two wires, but that is for steering purposes: you could make one with only one wire, but you wouldn't be able to guide it). If you look at the torpedo from the frame of reference moving at the same velocity as the wire, you see that the velocity of the torpedo relative to the wire is in the same direction and greater than that of the water relative to the wire. So somebody who understands frames of reference will recognise that it is a "down water faster than the water" device. But somebody who understands frames of reference will also recognise that Spork's cart on a treadmill is a downwind faster than the wind device. Moreover, it isn't just an analogy of a downwind faster than the wind device, it really does go downwind faster than the wind, exactly as Bauer's and Goodman's carts did.

Because you hit on something that has convinced you that DDWFTTW is possible, you announce "I think this debate is over". Other people have been convinced by other means: somebody who understands the analysis of the DDWFTTW principle can be convinced by that alone, another person will have their eyes opened by one of the analogies, another person will be convinced by treadmill tests... Each of these people could say for themselves "the debate is over" at the moment when they were convinced. For others, the debate goes on. If you're now totally convinced, you can have some fun trying to explain to determined skeptics why you think the Brennan torpedo is such a good example.

As for Spork and JB being only "after the limelight", I think you're mistaken. They have never made a secret of the fact that others had done this before. They are not claiming to have invented something new. They have tried, here and in many other places, to explain how the thing works. They have presented analyses and analogies. I don't know if they'd already seen the Brennan torpedo, but I'm sure of one thing: if they had shown everyone a detailed explanation of how it works, that wouldn't have convinced the hard-core skeptics any more than the other arguments they presented.
I agree completely with everything you say relevant to DDWFTTW. You misquote me however when you remove “Personally” from the start of “I think the debate is over”. I fully realise that this debate will continue and some people will never agree with DDWFTTW regardless of how conclusively it‘s proven. For me it’s “game over“.

Thanks for your contributions.

[fredriks]

And this sentence?


I think any intelligent (self-honest) person has to conclude that DDWFTTW is possible and there is a practical working example in the Brennan Torpedo.


Was that also included in the personally?

I cant see how Michael C misquoted you in any way. You wrote a post with a clear meaning and he responded to that. You are now trying to back pedal. I don't believe that is the first time you do that...

[ynot]

Some people actually believed that this was proved by the treadmill videos or even by some theoretical argument or from all other mechanical systems that has been discussed. Good that you finally explained for everybody else that it is proved now.



You seems to be a very strange fellow. You first start as a die hard skeptic even though you didn't seem to understand the basic physics involved or the explanations. Then when you finally find something that you think prove that is can be done you seems to think that other people hold back that information for some reason just to fool you and other people.

Theoretical explanations not good for you.
Treadmill don't good for you

Turntable quite good but the other people didn't want to help you and didn't want to build one.

Brennan Torpedo very good but people didn't want to help you so they must have some kind of agenda.

edit: Michael C post say much of what I was thinking.
I’m happy that you reach your own conclusions regarding events in the matter and most of what you say I may agree with. People often tell me I’m “different”. From some it’s an insult. From some it’s a compliment. From some I’m not sure. As The believer brigade say - “ We all travel different paths toward understanding”.

Thanks for your contributions.

[ynot]

And this sentence?



Was that also included in the personally?

I cant see how Michael C misquoted you in any way. You wrote a post with a clear meaning and he responded to that. You are now trying to back pedal. I don't believe that is the first time you do that...
What's not personal about "I think"?

[spork]

I suspect (but don’t know) that Spork & Co may have known about the Brennan Torpedo all along and were only here for the thrill of the “pissing match” and the limelight.

I suspect that you're a little man with a little life that simply wants to continue to attack JB and I as you have from the start. You should definitely stop lying, and your conjectures about what we knew and what are motivations are, aren't much better.

If Spork & Co build a “real wind” cart and travel DDWFTTW in to the limelight then it merely proves that they were after the limelight all along. Proof of the principle already exists in the Brennan Torpedo.

Ah yes, at first you were all pissy that we wouldn't do the tests you TRIED to describe because they didn't make a lick of sense. There are plenty of people that still don't accept DDWFTTW for any number of reasons. As ludicrous as it is, MANY don't accept the treadmill as a valid demonstration. And now you attack us because we do plan to provide the further proof that people are looking for.

Still pathetic.

[spork]

As usual, you're right on the money Michael. Everyone thinks they've hit the one true and final explanation the moment they finally see the light. I've learned the hard way there IS no one right explanation, just as there is no such thing as convincing proof for many people.

More frustrating, is that MANY people, once they come to believe in DDWFTTW, go on to explain how it "really" works and how all the explanations up to that time have been poor. Without exception I've found all of their "really good" explanations to be fatally flawed. Along those lines, I hope that ynot will use the example of the Brennan torpedo to convince other sceptics. But I hope he doesn't try to go into much detail on how this works. He will be doing science a disservice.

I don't know if they'd already seen the Brennan torpedo...

The first I ever heard of the Brennan torpedo was from the link ynot posted. Frankly I'm astonished that this example has never come up.

As to the "limelight" question, that's just silly. Consider this - I've never even posted my name in association with this thing! I love brain-teasers. I collect them. I've got a word document that has pages of them. I've posted many of them on the R/C heli and kitesurfing forums. This one just happens to be a sort of explosive one. It's that simple.

[fredriks]

The first I ever heard of the Brennan torpedo was from the link ynot posted. Frankly I'm astonished that this example has never come up.


I have heard about it before. Jason Roders talked about it on the ozreport forum.

I haven't read about it yet but it sound like it is really a "treadmill" experiment. The torpedo go forward in the water when you pull a string in the other direction. The "real" experiment should be done in a river with fixed lines. (Jason Rogers wrote this)

Those are of course equivalent but it still show the problems for those people that don't believe the treadmill is a valid evidence.

[Michael C]

I cant see how Michael C misquoted you in any way. You wrote a post with a clear meaning and he responded to that. You are now trying to back pedal. I don't believe that is the first time you do that...

In French that sort of back pedalling is called "mauvaise foi". I can't find a neat English phrase that translates the exact meaning: "bad faith" doesn't really work. It's a particularly annoying form of dishonesty that goes like this:

A person first says something stupid, insulting or just simply wrong. When the blunder/insult/mistake is pointed out, the person pretends that it wasn't meant that way: it should be perfectly clear to anybody with half a brain that they meant something completely different, or that they were just joking. They'll pick on little details of phrases that (they claim) make their real intent clear, or imply that others are lacking a sense of humour because they missed the obvious joke.

Once somebody has back pedalled like this, it becomes doubly hard to admit the original mistake or apologise for the original insult.

[spork]

In French that sort of back pedalling is called "mauvaise foi". I can't find a neat English phrase that translates the exact meaning: "bad faith" doesn't really work. It's a particularly annoying form of dishonesty that goes like this...

Interesting that the French would have a word for that! :D

O.K. just kidding; but we really should have a word for that in English. It is a classic ploy that's used all too often (not unlike the "I was conducting a spot the flaw test"). Perhaps we can call it a "ynot" going forward. I think it has an ironic accuracy to it.

[spork]

Did a few minutes of googling this term and learned some interesting things. It seems "bad faith" is actually the right translation, and has a deeper and more subtle meaning than we typically ascribe to it. The wikipedia article indicates that "bad faith" actually comes from this French term.

This was another interesting quote:

mauvaise foi: "Sartre's French term for "bad faith," the culpable self-deception involved in declining to accept responsibility for one's choices. "

I find the "self deception" aspect to be very interesting, and probably quite apt.

[ynot]

I’ve designed a “Brennan Boat” that uses the same principal as his torpedo except it uses the flow of water as the power source instead of pulling the cables. Or to put it more correctly, the water pulls against the cables. The cables (red) are simply anchored to a fixed point and as the boat moves away from that point the cables unwind from the spools and spin the prop. One cable feeds from the top of it’s spool, the other from the bottom of it‘s spool so they both turn in the same direction. The spools can be either directly attached to the prop shaft or via gearing if required. Hopefully the images make it clear how it works. The same setup could be used for wind tests.

http://forums.randi.org/picture.php?albumid=116&pictureid=558

[spork]

I’ve designed a “Brennan Boat”

Very nice. Is this more "original work" or did you copy someone that you might not even be aware of? Are you sure?

[ynot]

Some have been concerned about what air movement is created by the turntable. Here is a short video with bubbles to show air movement while the cart and turntable are operating . . .

http://nz.youtube.com/watch?v=vvrf78dNihk

[ThinAirDesigns]

I present that the primary value of that video is in demonstrating how difficult it is to present a video that demonstrates something of value.

Ynot will defensively take that as in insult and none intended -- people just don't realize how hard it is to present testing videos that don't raise more questions than they answer.

A good example of the above in our library is our video showing the cart self starting in the wind. For this test we didn't care about DDWFTTW -- we only wanted to show the cart taking off from a standstill in a tailwind. All over the internet we now see comments regarding that video saying "it wasn't faster than the wind -- there were leaves passing it" etc. Of course there were leaves passing it ... it was taking off from a standstill and we couldn't run along side and film it on a busy street with cars coming. It proved one point, but just provided opportunity for more doubt in another.

We should have never released that one as it just adds to the DDWFTTW confusion while only proving a point that isn't central to our claim.