Merged DDWFTTW in a “Real” Wind

[spork]

I was wrong. Apparently they do allow humber outside on a very short leash:
http://www.youtube.com/watch?v=rqtr_RvR3sY

 

[humber]

I was wrong. Apparently they do allow humber outside on a very short leash:
http://www.youtube.com/watch?v=rqtr_RvR3sY

Of course. Another thing not created by you.

I will be more than happy to support the DDWFTTW side at a moderated talk. Good luck getting a denier to take the other side.

You arrange that, and get then back to Yevgheni and me. OK?
Be prepared to answer to the chart you corrupted and show the results of all the trials, failures included.
Which of the above are you not prepared to do?

 

[humber]

The topic is the cart in the wind, and not a soapbox for Spork's attempt to evade the trials
If you support his debate proposal, then you should be asking him to explain the chart, and present the data. If not, what do you expect would change at a debate?

Lack of open disclosure is not only unscientific, but the hallmark of scientific fraud.

 

[A.T.]

As for his wrongness, he took the Rhett-Allain-escape-route by declaring himself incompetent and running away.

But you should have heard how astonishingly condescending he was with JB and I on the phone when he was explaining that he was in fact the expert, and we were a couple of morons.

It's funny how the lack of expertise doesn't prevent those people from shouting impossible at first, but prevents them from directly admitting that they were wrong afterwards. The problem which was so plain simple to them previously, suddenly becomes so complcated that they allegedly can't really tell the answer.

 

[humber]

It's funny how the lack of expertise doesn't prevent those people from shouting impossible at first, but prevents them from directly admitting that they were wrong afterwards. The problem which was so plain simple to them previously, suddenly becomes so complcated that they allegedly can't really tell the answer.

I didn't. I took about a minute of frame-stepping the video. Got the cart's mass and speed of the belt from the forum. Calculated the force based on the slew rate of the cart, result .04N. As measured by Mender.
Conclusion. Cart is stabilized by the prop, against that tiny force. Feedback, non-linear contact with the belt, and priming of the prop by hand explain how that is done. Elementary mechanics

 

[GlennB]

I didn't. I took about a minute of frame-stepping the video. Got the cart's mass and speed of the belt from the forum. Calculated the force based on the slew rate of the cart, result .04N. As measured by Mender.
Conclusion. Cart is stabilized by the prop, against that tiny force. Feedback, non-linear contact with the belt, and priming of the prop by hand explain how that is done. Elementary mechanics

Pseudo-scientific word salad.

What 'non-linear contact' and how would it explain the cart advancing up the TM?
What 'priming of the prop by hand'? There wasn't any.
'Feedback'? What is feeding back to where? Perhaps you're beginning to understand finally.

 

[Jack by the hedge]

The official run starts at UTC 588960. But if delayed by 10 seconds, the result is quite different.

If delayed until a windless day the result would be quite different too. In either case, so what?

The cart can travel >WS using momentum and the wind gradient alone. It uses the towers as sails...

I have never seen you explain how either of these claims would work. So, how about it?

 

[humber]

If delayed until a windless day the result would be quite different too. In either case, so what?

You are joking right? There is, and never was anything special about "going faster than the wind". It depends on the wind, and how you define it.

On a day with an average wind of 5mph, there is a bucket at the roadside.
It stays there most of the day.
Then, a big truck comes by, and blows it along the road. You film that as evidence of a faster-than-the-wind bucket.

I have never seen you explain how either of these claims would work. So, how about it?

But without the data, you will say it won't work. I get the data, and prove it that it will. On the other hand, the trial is proof of nothing other than a cart being blown along by some combination of gusts, sheer and gradient winds.
It travel 0.41 miles. The average speed is 13mph. without the push 8.5mph.
Big deal. If it were not such a pile of junk, it would do better.
DDW, in a constant breeze, steady state is something. Anything else is a bit girly.

STEADY STATE is important!
The red line is the BB, but another cart has less mass, so accelerates faster, meaning that at the point of measurement it is faster, but may have a lower terminal (steady-state) speed, yet steals the record from the BB.
That is a major flaw in the entire procedure.
But, it works the other way too. If the BB gains from some short term wind pattern, you may find it can't sustain that over time. In that case, the yellow cart is legitimate, but the BB is not.
The deal was steady-state ddw, not "whatever"

 

[Llyricist]

Of course, humber runs away from any challenge to actually show how the cart could benefit from a crosswind component.

 

[A.T.]

Of course, humber runs away from any challenge to actually show how the cart could benefit from a crosswind component.

Well, he tried once, you know. He even posted a vector diagram:

(axial force in red added by me)

 

[humber]

Well, he tried once, you know. He even posted a vector diagram:

[qimg]http://talkrational.org/attachment.php?attachmentid=2912&stc=1&d=1296766116[/qimg]

(axial force in red added by me)

And that is why it is wrong. Of course, it must be. You are a Carteer.

Related to that drawing, is an argument about Newton's impact theory and the Taylor Series. You seem to like the colored pictchas, though.
Now run along, little zealot. Spork needs to be consoled.

 

[Llyricist]

Which is why he runs away now.

 

[phunk]

Here's the part I don't get.

You're taking the momentum out of the cart via the wheels, putting it through several lossy steps, then putting it back into the cart via the propeller. How do you end up with more momentum than when you started?

 

[Llyricist]

And that is why it is wrong. Of course, it must be. You are a Carteer.

Related to that drawing, is an argument about Newton's impact theory and the Taylor Series. You seem to like the colored pictchas, though.
Now run along, little zealot. Spork needs to be consoled.

You mean, incoherent gibberish that included the phrases "impact theory" and the "Taylor Series".

 

[Llyricist]

Here's the part I don't get.

You're taking the momentum out of the cart via the wheels, putting it through several lossy steps, then putting it back into the cart via the propeller. How do you end up with more momentum than when you started?

To put it simply, the extra momentum comes from the wind. The propeller only accelerates the air in relationship to itself, in the ground frame the air slows down, losing momentum, and transferring it to the cart.

 

[sol invictus]

Here's the part I don't get.

You're taking the momentum out of the cart via the wheels, putting it through several lossy steps, then putting it back into the cart via the propeller. How do you end up with more momentum than when you started?

Momentum is conserved, and it doesn't get lost at any of the "lossy" steps you refer to (energy does in the sense that it gets converted from kinetic energy to heat, but momentum does not). So if the cart is moving at a steady-state speed (regardless of whether it's faster than or slower than the wind), there's no obvious problem with momentum conservation.

However that argument obscures something important - to move at a steady speed the cart must extract energy from somewhere to overcome various resistive forces. It does so by slowing the air with respect to the ground - it leaves a trail of slowed (with respect to the ground) air in its wake. So even if the cart moves at a steady speed, the air does not - and the change in momentum is made up for by the a corresponding change in momentum of the earth. In other words, the cart is powered by the wind.

If the cart is accelerating, the above explanation continues to hold with the change that the the changes of momentum in air and ground don't quite cancel, leaving something for the cart.

 

[A.T.]

You mean, incoherent gibberish that included the phrases "impact theory" and the "Taylor Series".

And of course lack of any argument why the axial force component I indicated in his diagram is wrong:

 

[jadebox]

You're taking the momentum out of the cart via the wheels, putting it through several lossy steps, then putting it back into the cart via the propeller. How do you end up with more momentum than when you started?

That confused me for a while, so I did a little mind experiment to try to figure out where the energy comes from.

At first I thought of the cart as being like a parachute floating in the wind. If that were the case, it seems impossible (and it is) for any energy to be extracted from the wind to make the parachute move faster than the wind.

Then, I pictured having an elastic cord hanging from the parachute.

If the parachute is free to drift with the wind, the cord would hang limp.

But ... if someone standing on the ground were to hold onto the other end of the elastic cord, it would stretch. In a steady wind it would stay stretched. When the cord is anchored, the wind provides a steady source of energy.

In the case of the cart, the friction of the wheels on the ground is the equivalent of the person holding the elastic cord. The wheels take energy from the "elastic cord" and use it to turn the prop. The wind continues to supply energy so that the wheels can continue to turn the prop.

-- Roger

 

[ridgerunner]

Welcome ridgerunner. Whatever you do, don't confine yourself to this one thread. There's a wide, wonderful world in other parts of the forum.

Thanks for the welcome and sage advice!

Actually, I've been following this saga on and off for the past two years. Mostly lurking, but every once in a while I have something to say. Like for example:

If Humber makes a post which no one reads, is it still a troll?"

You guys have got to stop feeding this... this... (I don't know what he it is). Wait, yes I do, it is a troll! It thrives on the attention!.

My guess is that Humber knows perfectly well how the cart works. Either that, or it just doesn't care.

 

[humber]

Momentum is conserved, and it doesn't get lost at any of the "lossy" steps you refer to (energy does in the sense that it gets converted from kinetic energy to heat, but momentum does not).

Yes, and if you scramble an egg, the total amount of egg is conserved.

But momentum is not power is it? By your own argument about heat, unless the system is lossless, you're going to lose some.

So if the cart is moving at a steady-state speed (regardless of whether it's faster than or slower than the wind), there's no obvious problem with momentum conservation.

Tautology, and when is it NOT conserved. "The cart works on the same law of conservation that applies to a thrown brick"

However that argument obscures something important - to move at a steady speed the cart must extract energy from somewhere to overcome various resistive forces.

Yes. Like the air that is opposing it.

It does so by slowing the air with respect to the ground - it leaves a trail of slowed (with respect to the ground) air in its wake.

When above WS, the cart is traveling faster than the wind.
Hence the term "faster than the wind"
It will strike the air that is slower than it, and accelerate it. There goes some of the cart's momentum. The best you could hope to do - in a cartoon world - is to recover what is lost from the cart to that air. But even that cartoon does not allow for acceleration. The cart leaves a trail of accelerated air, and a vortex street in its wake. It does not gain from drag.

So even if the cart moves at a steady speed, the air does not - and the change in momentum is made up for by the a corresponding change in momentum of the earth. In other words, the cart is powered by the wind.

The wind gains energy from the Sun. Basic science. Discovery Chanel.
The wind moves around until that energy is dissipated against objects and the ground. There are large scale effects due to Coriolis etc, but for all practical purposes, the momentum of the Earth is not involved.

If the cart is accelerating, the above explanation continues to hold with the change that the the changes of momentum in air and ground don't quite cancel, leaving something for the cart.

Free lunch. The cart's Harrypothesis is blindingly wrong.

Firstly, when a car on the highway strikes slower air, the result is drag: an opposing force. There are few who see that as "slowing the air"

The cart faces the same problem. The claim is actually contradicted by Spork's own calculation. He has the drag force above WS as an opposing force, and subtracts it to get the net force. See the submission report. He uses Rayleigh's drag formula.

Now you are saying that when that same air hits the prop, it drives the cart. It adds to the net force.
It is little wonder that with that sort of loony-tunes theory as a basis, that the trials were not similarity tainted.