Merged DDWFTTW in a “Real” Wind

[spork]

.
I don't have any problem with understanding the downwind stuff.

If I understood you correctly, you seem to think it's not actually going directly downwind faster than the wind. Perhaps I misunderstood your statement.

I wonder about its utility, being as mentioned, in the same "record class" as the "the world's largest collection of ball-point pens".

I'm still at a complete loss as to what you think it's utility is supposed to be. Are you in the market for one? If not, what do you care? We didn't build it for you. We built it for us, and we're happy with its utility.

The effort spent to achieve the modest result is somewhat disproportionate, to my way of thinking.

Proof positive that you don't understand it. What multiple of wind speed would you categorize as an acceptable result?

That so many people got so hot under the collar is amazing.
It ain't that important!

I'll watch now as you get hot under the collar.

 

[Jack by the hedge]

It's the one you chose.

You misunderstand. Your declaration of its being the worst choice is bad engineering. The under reel design is perfectly OK.

It's a total failure of an idea. Boyish.

Content-free hot air.

It's both a theoretical and practical failure. Not at all didactic, but misleading. It does not move faster than the force that is driving it, because that force is applied at the inner reel. Adding string to that does not make it go faster. Have you seen those dog leashes that wind into a reel? The dog may run at the same speed, but the distance increases as the leash unwinds. It's that, but the other way.

You twist and turn, but you are still wrong. Trying to explain how it works does not give you carte blanche to declare that it doesn't really work. A small child could understand the difference between the distance the string moves and the distance the reel moves in a given time.

The small child might, however, feel bold enough to ask you what you mean by "The dog may run at the same speed, but the distance increases as the leash unwinds". The dog may run at the same speed as what? And what distance are you talking about? If it runs at the same speed as the reel, then why would the distance increase or the leash unwind?

Wheels. Like a car. Has a long pedigree.

Oh. Wheels. Like a car. And how exactly do they demonstrate the principle of an object travelling faster than the thing which moves it?

They don't? Oh, well then I'm afraid they fail the basic criterion of the design brief and are useless. Sorry. Next please.

 

[I Ratant]

Well, no, though it depends on what you mean by important. It's one of those things that inevitably gets argued over until someone actually tries it and settles the matter. I'd liken it to the 19th century argument over whether a galloping horse ever has all four feet off the ground at once.

It's hard to imagine how, but you never know what practical use might be made of the principle in future.

.
I recall talking on some forum to a guy that wanted to use parasails to hoist wind "turbine" generators up to the jet stream where they could run 24/7.
Other than the enormous size of such a parasail required to lift the quite considerable weight of the propellor and generator, and the weight of the power transmission cables, and the amount of cleared space on the ground to permit movement in direction for the cabling etc. as the wind changed direction, this scheme had nothing to recommend it over the usual wind-farm, ground based, which needs much less area per each generator.
Even a low altitude device would require a lot of unusuable area relative to what it requires now, just sufficient room between the installations so one can fall down without damaging its neighbor.

 

[jduffy77]

.
I recall talking on some forum to a guy that wanted to use parasails to hoist wind "turbine" generators up to the jet stream where they could run 24/7.
Other than the enormous size of such a parasail required to lift the quite considerable weight of the propellor and generator, and the weight of the power transmission cables, and the amount of cleared space on the ground to permit movement in direction for the cabling etc. as the wind changed direction, this scheme had nothing to recommend it over the usual wind-farm, ground based, which needs much less area per each generator.
Even a low altitude device would require a lot of unusuable area relative to what it requires now, just sufficient room between the installations so one can fall down without damaging its neighbor.

I was just reading about a plan in the 1950's to extract oil from the Alberta tar sands using controlled nuclear explosions. But we're both a bit off topic aren't we?

 

[humber]

You misunderstand. Your declaration of its being the worst choice is bad engineering. The under reel design is perfectly OK.
Content-free hot air.
You twist and turn, but you are still wrong. Trying to explain how it works does not give you carte blanche to declare that it doesn't really work. A small child could understand the difference between the distance the string moves and the distance the reel moves in a given time.

It's the worst choice because it's an inefficient way of doing nothing.
And if the math and the drawing are not enough to show that, then I don't know what else can be done. I do not say it does not roll to the right, nor that the string does not wind onto the spool.

The problems are manifold, but the final speed will be determined by the power of the wind, and nothing will change that. It will never outrun the force that is driving it
Like the dog, no matter how long the leash is, the force is applied at the collar. And so just like the point at which the cotton meets the reel. It can do nothing else. It's partly illusion and partly word games.

Take the case where it rolls to the left as the result of a tug. I don't need to worry about the gearing. A full reel will readily move to the left. So, it's on its way.
It slows a bit, so I tug again on the thread, and that impulse drives it further, and so forth. Now, is the reel moving 10 times the speed of the small flick of the hand? Or does that have no meaning?

The string is wound on to the reel, so which way does the hand really move? The reel moves to the right as your hand moves to the right, and you don't notice that part of that motion, is the reel decreasing the distance between it and your hand. Looks like "faster"

Other than that, the top speed will be limited by the wind's power. Just like a simple cart, but less efficient, so slower.

 

[Modified]

It does not move faster than the force that is driving it, because that force is applied at the inner reel.

And for the dwfttw cart, the force is applied to the rotating prop, the effective surface of which is always moving slower than the wind.

 

[I Ratant]

Maybe. The wind generator sail does use wind.
I don't recall the name calling and general personal disparagement that this thread reeks of.
Not exactly the "friendly and lively" manner of discussion intended.

 

[D'rok]

A long time ago, some really smart people didn't believe that rockets would work in space. They proved it mathematically.
Oops.

The mathematicians are right.

Really?

 

[Jack by the hedge]

It's the worst choice because it's an inefficient way of doing nothing.

If you have a more efficient way of doing the same nothing then the floor is yours.

...the final speed will be determined by the power of the wind, and nothing will change that.

True

It will never outrun the force that is driving it

False. You will never admit it outran the wind that powered it. That's not the same thing.

Take the case where it rolls to the left as the result of a tug. I don't need to worry about the gearing. A full reel will readily move to the left. So, it's on its way. It slows a bit, so I tug again on the thread, and that impulse drives it further, and so forth. Now, is the reel moving 10 times the speed of the small flick of the hand? Or does that have no meaning?

It has no relevance. I'd like to see you try to demonstrate the "10 times the speed of the small flick of the hand" bit, though.

The string is wound on to the reel, so which way does the hand really move? The reel moves to the right as your hand moves to the right, and you don't notice that part of that motion, is the reel decreasing the distance between it and your hand. Looks like "faster"

Looks like faster? Travelling further in the same time looks like faster? What gibberish is this? Whether it's cord winding onto the reel, or a single loop rolling over the reel or even a drive chain only contacting a gearwheel at the bottom, the rope, cord or chain moves to the right at one speed while the reel or gearwheel moves to the right at a higher speed.

If the cord was in the form of a continuous loop, and you built a machine which followed the reel and payed out/pulled in the cord as required, then the reel could roll on indefinitely, pulled along by the cord, and travelling twice as fast as the cord that moved it.

Other than that, the top speed will be limited by the wind's power. Just like a simple cart, but less efficient, so slower.

You assume the relevant limiting factor is "efficiency" but you are wrong. The limiting factor for your "simple cart" is the wind speed. BB travels faster than that so wins outright.

 

[phunk]

Take the case where it rolls to the left as the result of a tug. I don't need to worry about the gearing. A full reel will readily move to the left. So, it's on its way.
It slows a bit, so I tug again on the thread, and that impulse drives it further, and so forth. Now, is the reel moving 10 times the speed of the small flick of the hand? Or does that have no meaning?

You still don't get it. It doesn't require a tug. It works perfectly fine at a constant speed. It can't slow down, because the string is always taut.

 

[humber]

And for the dwfttw cart, the force is applied to the rotating prop, the effective surface of which is always moving slower than the wind.

That's a new deck, Modified. There is only one thing that contains more errors than the reel, and that is the Voodoo Van Test. Other than that gem, it's the king of wrong. If you should manage to sink any one argument, their is a flotilla of others. It's an illusion.
If there were two cars on the starting grid, and one moved 100m in a second and the other 200m, then you would say one was twice as fast as the other.
But, note that the faster car is ahead of the slower one, but the hand is always ahead of the reel.

 

[Llyricist]

How's that hole in your foot from your RMS miscalculation doing?

 

[Jack by the hedge]

If there were two cars on the starting grid, and one moved 100m in a second and the other 200m, then you would say one was twice as fast as the other.
But, note that the faster car is ahead of the slower one, but the hand is always ahead of the reel.

What if there were two trains which set off at the same time - one from 200 miles away and one from 100 miles away - on the same track, and they arrived nose-to-tail? The slow train arrived first by a few seconds. Was it actually faster, then?

In other words, that's a really desperately weak argument you have there.

 

[Jack by the hedge]

If you should manage to sink any one argument, their is a flotilla of others.

The flotilla is resting at the bottom of the lake, where it has been for quite some time. You merely decline to recognise this.

 

[humber]

What if there were two trains which set off at the same time - one from 200 miles away and one from 100 miles away - on the same track, and they arrived nose-to-tail? The slow train arrived first by a few seconds. Was it actually faster, then?

In other words, that's a really desperately weak argument you have there.

Errr...the one that is 200 miles away is 100miles ahead of the other. When you say "arrived nose to tail", I think you are assuming that the slower train is driving itself, rather than been towed by the train ahead.

The dog, JBTH. The force from the hand is applied at the collar. If you move the hand 1m, the dog will move 1m.
If the there is to be tension in the thread, then the hand must move further than the reel in the same time, so faster, not slower and just like the over the top version. String can wind on a reel or off a reel, but it's the same bit of string.

 

[D'rok]

Errr...the one that is 200 miles away is 100miles ahead of the other. When you say "arrived nose to tail", I think you are assuming that the slower train is driving itself, rather than been towed by the train ahead..

 

[spork]

I don't recall the name calling and general personal disparagement that this thread reeks of.
Not exactly the "friendly and lively" manner of discussion intended.

.
I don't give a **** about NALSA, whoever they are.
The "record" to me is as pointless as any of the Guinness "records", such as the "world's largest collection of ball-point pens".
...
That's not anything of any practical use,
Boeing lost the JSF contract because their vehicle, capable as it may have been, could not perform -all- the tasks the requirements listed
...
Special purpose vehicles like these carts are interesting to observe, but they have little more than a momentary diversion to offer.

Yeah, it's surprising that we're not more friendly and lively with someone that came just to insult the project and people that he knows nothing about.

 

[GlennB]

Errr...the one that is 200 miles away is 100miles ahead of the other. When you say "arrived nose to tail", I think you are assuming that the slower train is driving itself, rather than been towed by the train ahead.

Er, no. The train that started 200 miles away was behind the other from the pov of the race to the arrival point. It arrived at the same time, therefore travelled faster.

The reel started further away than the hand, they arrived together, so the reel travelled faster.

No physics or maths even required, just an understanding of the word 'faster'.

You really do suffer from lathophilia, don't you.

 

[humber]

The flotilla is resting at the bottom of the lake, where it has been for quite some time. You merely decline to recognise this.

No, as I said, it has so many embarrassing errors that it's best to spread then over time.

 

[humber]

.
Boeing lost the JSF contract because their vehicle, capable as it may have been, could not perform -all- the tasks the requirements listed, without major configuration changes, while the winner needed nothing extra to fly the envelope.

Could well be true, but supporters of Boeing's effort say theirs is more capable than Lockheed's X35, but the latter looks cooler. Either way, the "Blackbird"
is form over function.