Merged DDWFTTW in a “Real” Wind

[humber]

Oh, I'm sure humber will soon produce a text-book reference saying that "towers can tack". And that "propellers gain efficiency through cross wind".

Well, I have asked you to prove what you say. Here is the diagram for the Newton argument. And what may be said about that, power and attack angle?

And pressure. Independent L/D ratios.

And the L/D ratio for small attack angles. Note the chart is normalised.

And why is the prop not now an airfoil? You do seem to be selective in the information you accept, dependent on the source.

 

[Jack by the hedge]

It has nothing to do with frames of reference. A boyish idea.

Can you explain why you think so?

You can try it yourself. Take a sheet of paper, put a cotton reel on it, and pull the paper. If the reel spins, it more or less stays in place.

Ah. Nope, I guess you can't.

So perhaps not "quite as fast as the wind" Is that right?

But you sure can sign of with a flourish of non sequitur.

 

[humber]

I think the lateral movement of the prop blades means they can tack a zero degree wind. (From their frame of reference, of course, it isn't a zero degree wind.)

I think the towers provide no power to the cart.

Which is to say it operates as a tacking sail. When ddw, the opposing turbine force retards the cart. Off wind it falls. It's not that is "does better" off wind, but worse when ddw.

 

[A.T.]

I Ratant has demonstrated that a turning rotor can make a sail.

The topic was "tacking". Show us with vectors how the performance of the BB increases, when off-DDW.

 

[Jack by the hedge]

The video shows a cart moving at 0.1m/s ( the visible motion) while the belt moves at 4m/s. So the cart "moves" 4.1m as 4m of ground passes by.

If you are citing this as proof that the cart's wheels are slipping on the belt, then either you are describing it really badly or it just isn't any kind of proof at all.

 

[A.T.]

Well, I have asked you to prove what you say.

I say nothing. Your picture says it all already:

Here is the diagram for the Newton argument. And what may be said about that, power and attack angle?

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21604&stc=1&d=1301418023[/qimg]

And pressure. Independent L/D ratios.

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21605&stc=1&d=1301418119[/qimg]

And the L/D ratio for small attack angles. Note the chart is normalised.
[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21606&stc=1&d=1301418268[/qimg]

All that adds nothing to the picture above. It's all already in there.

 

[jduffy77]

The video shows a cart moving at 0.1m/s ( the visible motion) while the belt moves at 4m/s. So the cart "moves" 4.1m as 4m of ground passes by.

If you are citing this as proof that the cart's wheels are slipping on the belt, then either you are describing it really badly or it just isn't any kind of proof at all.

I expect you know this already but Humber is even more out to lunch then usual on this issue. His "visible motion" is an absurdity. He is talking about the distance the cart outpaces the wind by, which of course would be the same on the ground if you had a balloon or something else in the wind.

 

[Jack by the hedge]

Which is to say it operates as a tacking sail.

Yes. Like people have been telling you for years.

When ddw, the opposing turbine force retards the cart.

Yes again. Ditto.

Off wind it falls. It's not that is "does better" off wind, but worse when ddw.

You are only considering the retarding force and declaring that this will reduce off-wind. Do you believe that the driving force would not reduce in similar proportion? If so, can you show why you believe this?

 

[jduffy77]

Which is to say it operates as a tacking sail. When ddw, the opposing turbine force retards the cart. Off wind it falls. It's not that is "does better" off wind, but worse when ddw.

There is no "opposing turbine force" on the cart we are talking about. What crazy ideas have come through your hat now?

 

[CORed]

Which is to say it operates as a tacking sail. When ddw, the opposing turbine force retards the cart. Off wind it falls. It's not that is "does better" off wind, but worse when ddw.

(bolding mine)

This is the kind of howler that makes participating in a thread involving humber worthwhile.

ETA: "Opposing turbine force" is pretty funny too.

 

[humber]

Can you explain why you think so?
Ah. Nope, I guess you can't.

Boy looks out of car window and giggles "the ground is going backwards"

But I am waiting for you to tell me that the cotton reel on the paper is not a GT of a cotton reel in the wind at almost WS. Why not?

It seems to want to stay in place, rather than be dragged back.

 

[humber]

(bolding mine)

This is the kind of howler that makes participating in a thread involving humber worthwhile.

ETA: "Opposing turbine force" is pretty funny too.

The cart is exactly like an uwpwind turbine. They too have a turbine to the wind and gears to drive the wheel into the wind. It moves one way or the other dependent upon the gearing, and the sail force pushing it downwind.
It has a large sail area and the gearing is "just so". Too little and the prop won't turn fast enough, too much and it goes backwards. Select by trial and error, and adjust according to the wind at the time. I told the TAD they would add a gear cluster. They didn't know why.

So yes, it is indeed funny that you have been championing the failed upwind cart. The new upwind cart will go through some BS modification to avoid direct comparison. That is the crank's way.

 

[humber]

Yes. Like people have been telling you for years.
Yes again. Ditto.
You are only considering the retarding force and declaring that this will reduce off-wind. Do you believe that the driving force would not reduce in similar proportion? If so, can you show why you believe this?

No, a whole cart that tacks, not a tacking prop.

If I wanted to hide that, I may use the tacking prop idea, with the assurance that none of you would consult a text book to see if that were true.
Not one word in any text book.

 

[humber]

I say nothing. Your picture says it all already:

No can do, eh? If you re-post a my diagrams be prepared to back that up.
A picture may say a thousand words, but you add none.

 

[CORed]

The cart is exactly like an uwpwind turbine. They too have a turbine to the wind and gears to drive the wheel into the wind. It moves one way or the other dependent upon the gearing, and the sail force pushing it downwind.
It has a large sail area and the gearing is "just so". Too little and the prop won't turn fast enough, too much and it goes backwards. Select by trial and error, and adjust according to the wind at the time. I told the TAD they would add a gear cluster. They didn't know why.

So yes, it is indeed funny that you have been championing the failed upwind cart. The new upwind cart will go through some BS modification to avoid direct comparison. That is the crank's way.

Yes the cart is exactly like an upwind cart.

Except the gearing.

Oh, yeah, and a rotor that's optimized to act as a propeller, rather than a turbine.

Yes, the downwind cart is exactly like an upwind cart, except for the parts that aren't.

 

[humber]

Yes the cart is exactly like an upwind cart.

Except the gearing.

Oh, yeah, and a rotor that's optimized to act as a propeller, rather than a turbine.

Yes, the downwind cart is exactly like an upwind cart, except for the parts that aren't.

And that is why it spins up very quickly CCW, when the chain comes off ?
That force "goes away" when the chain is re-attached? Something stop it from turning.
Optimized as prop? What does that mean? The lift is reversed?
There is a video that shows the prop produces <<10 W at 15rpm, probably 3W. Why don't you show me that is not correct?

And the cotton reel on the sheet of paper. A real wonder.

 

[CORed]

And that is why it spins up very quickly CCW, when the chain comes off ?

You do know that an airplane propeller rotates the opposite direction if the engine fails and it's allowed to "windmill"? Probably not

That force "goes away" when the chain is re-attached? Something stop it from turning.

That would be the wheels and the chain driving it in the opposite direction.

Optimized as prop? What does that mean? The lift is reversed?

It means it's designed for maximum efficiency in producing thrust when driven to rotate.

There is a video that shows the prop produces <<10 W at 15rpm, probably 3W. Why don't you show me that is not correct?

Because it's irrelevant. And you wouldn't understand anyway.
Besides, most likely you just made that up.

And the cotton reel on the sheet of paper. A real wonder.

Huh?

The gearing, or more correctly, the prop pitch gearing and wheel size, are the critical factor in determining whether it's an upwind cart or a ddwftw cart. The design of the rotor for optimum efficiency will be different for a propeller versus a turbine, but that's a fairly minor factor. I'm by no means an expert (or even close) in the finer points of propeller or wind turbine design.

Humber loves to cite "Newton" or "physics", in spite of the fact that he understands next to nothing about either of them.

 

[EHocking]

Afraid not. If a real cart is moving at 10m/s, after one second it will travel 10m.
That is 10m of road will pass by. Same for 11m/s etc.
On the belt set at 10m/s the belt moves 10m, but the ">WS cart moves say 10.1m. The video shows a cart moving at 0.1m/s ( the visible motion) while the belt moves at 4m/s.

Since I have no idea which video you are referring to, where is it stated that the cart is doing 10.1m/s?

So the cart "moves" 4.1m as 4m of ground passes by.

And if this was so, the cart would move "up" (ie in the opposite direction the treadmill belt) at 1m in 10sec.

Uh. So? This merely demonstrates that the cart is capable of >WS DDW.

 

[jduffy77]

And that is why it spins up very quickly CCW, when the chain comes off ?
That force "goes away" when the chain is re-attached? Something stop it from turning.

The wheels turn the prop when the chain is attached.

Optimized as prop? What does that mean? The lift is reversed?

Could this be your whole problem? You don't know what a prop is! A prop uses the wind as a power source to create thrust. A turbine is driven by the wind to provide a power source. Don't tell me that was all you needed to know. Are you saying you wasted 7 and 3/4 million words?

There is a video that shows the prop produces <<10 W at 15rpm, probably 3W. Why don't you show me that is not correct?

Your hero, Yev, already did that.

 

[EHocking]

Boy looks out of car window and giggles "the ground is going backwards"

From his frame of reference, it is.

But I am waiting for you to tell me that the cotton reel on the paper is not a GT of a cotton reel in the wind at almost WS. Why not?

Because I have no idea how to pass that sentence.

It seems to want to stay in place, rather than be dragged back.

Wholly dependent on the speed at which the paper is whipped out from under it. Slowly enough, and it will stay in place on the paper and be dragged with it (backwards wrt the ground), fast enough, the paper is whipped out from under it (forwards wrt the paper).