DDWFTTW - Tests.

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.

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).

spork said:

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.

Click to expand...

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.

spork said:

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.

Click to expand...

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.

spork said:

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.

Click to expand...

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.

spork said:

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).

Click to expand...

Not definitive either way but leaning very heavily toward sceptic.

ynot said:

Yep, same as I suspect happens with your cart.

Click to expand...

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.

Click to expand...

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.

Click to expand...

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.

Click to expand...

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

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.

Hey Ynot, was that typo in your OP subject?

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

casebro said:

Hey Ynot, was that typo in your OP subject?

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

Click to expand...

I think the first D stands for 'directly'.

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.

Michael C said:

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.

Click to expand...

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.

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.

Dan O. said:

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

Click to expand...

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.

ynot said:

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!

Click to expand...

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?

Dan O. said:

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.

Click to expand...

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.

spork said:

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

Click to expand...

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?

spork said:

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.

Click to expand...

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.

spork said:

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

Click to expand...

Prove it’s precession by getting a ball to travel in circular paths on your treadmill and post a video of it doing it.

spork said:

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.

Click to expand...

I would be very pleased if you did.

spork said:

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

Click to expand...

How is being “not definitive either way” denying anything.

H'ethetheth said:

I think the first D stands for 'directly'.

Click to expand...

“Directly” is the most important word in the sentence.

ynot said:

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?

Click to expand...

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.

Click to expand...

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.

sol invictus said:

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.

Click to expand...

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.

technoextreme said:

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.

Click to expand...

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!!!!

mhaze said:

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!!!!

Click to expand...

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

Ynot:

You guys have short or selective memories.

Click to expand...

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.

Click to expand...

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.

Click to expand...

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?

ThinAirDesigns said:

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?

Click to expand...

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.