Merged DDWFTTW in a “Real” Wind

[temporalillusion]

It is better are fooling knaves.

I think you meant "It are better is fooling knaves."

<oreilly>Plane goes up, plane goes down, can't explain that.</oreilly>

 

[Jack by the hedge]

Then he could have spent days finding an explanation of how it didn't really travel ddwfttw, but only looked like it did.

Like the cotton reel which catches up with your hand but only looks like it's moving faster. Priceless.

 

[ThinAirDesigns]

We found the forum's Platt.

JB

 

[I Ratant]

When free of the ground, and the rotor faces the tailwind, do the wheels turn as for forwards motion? If so, the cart is a downwind turbine.

.
Free of the ground today, the prop turns the wheels nicely. Either direction, depending on the direction the cart is pointed relative to the wind.
The drive-train friction is sufficient to hold the cart in place, on the ground, in the fastest wind available today, which wasn't all that fast.
The video frame rate on my camera doesn't show the rotational directions consistently.
The cart should move to the left, in these images.

 

[I Ratant]

Discussing this thing with a long-time aviation nut... pilot's license, life-time spend in aviation, full-scale and hobbyist, sail boat enthusiast, he expressed concern about the situation.
I was touched by his concern... as he felt my forehead to see if I was feverish, when I mentioned the point of the whole was to go ddwfttw.
He said that was not possible.
Only by.....dare I say it.... caution... bad word follows... tacking... would such a feat be done.
Which sailboats can do all the time.
But ddw.. nope.
Boy, is he wrong!

 

[humber]

.
The prop was installed on the driven cart in the same orientation as on the freewheeler when the single wheel is pointing in the downwind direction.
With the connection to/from the wheels axle to move the cart forward with the "wrong way" rotation... CCW as seen from the rear. The same rotation the freewheeling prop runs.
With a healthy wind, it drove off downwind, but the freewheeler caught up to it.

CCW prop = forwards wheels?
That still leaves the question as to how it is doing that. Which way do they turn if not on the ground and the tailwind is from the rear? Any variant can move either way dependent upon the balance of forces.
It sounds to me that it is a downwind turbine.
Are you saying the free-wheeler was slower at the start, but caught up?

.
Facing the driven cart into the wind, so the wind's rotation of the prop should move it upwind, it gave a couple of lurches towards upwind, but couldn't go forward.
Reversing the prop drive at the wheel axle so the prop goes CW viewed from the rear, as it is supposed to for this thing, in the light and variable winds today, which were more suited for thermal flying than anything steady, the wind at 1 foot up got to maybe 6 mph tops.

That does suggest that the previous version is a downwind turbine, and this one, a poorer upwind turbine.

.
The freewheeler would take off like a scalded ape, but the driven cart would move about 5 feet, given a nudge with the foot.

That makes sense if the that geared cart is back to the prop mode of the BB etc.

 

[humber]

.
Free of the ground today, the prop turns the wheels nicely. Either direction, depending on the direction the cart is pointed relative to the wind.
The drive-train friction is sufficient to hold the cart in place, on the ground, in the fastest wind available today, which wasn't all that fast.
The video frame rate on my camera doesn't show the rotational directions consistently.
The cart should move to the left, in these images.

If I see that correctly, that is the same Spork's small cart. The tailwind turbines the rotor and the wheels turn into the wind?
That is the one that would only run a few feet?

 

[3point14]

Yeah yeah ...whatever nonsense you like to make up. There is not one text that supports the intellectually puerile notion of a tacking prop.

As sail is a wing. An aerodynamic device that uses moving air to generate lift. That's how a sail works. Actually, a sail is a wing to such an extent that you can use a rigid 'wing' as a sail.

A prop blade [is] a wing. An aerodynamic device that uses moving air to generate lift. That's how a prop blade works.

How you fail to understand that two things that are the same thing will operate in the same way amazes me.

How you fail to grasp that the air moving over the ground is the same thing as the ground moving under the air amazes me.

How you could possibly believe that a balloon moving in air moves at anything other than the speed of the air amazes me.

You, my friend, are amazing.

 

[humber]

As sail is a wing. An aerodynamic device that uses moving air to generate lift. That's how a sail works. Actually, a sail is a wing to such an extent that you can use a rigid 'wing' as a sail.

And?
1) where are the text book references that suggest a prop is like a tacking sail.
2) Where do text books, or even general sailing references, liken a tacking sail to a prop?

A prop blade [is] a wing. An aerodynamic device that uses moving air to generate lift. That's how a prop blade works.

A wing is a device that gains lift as air decelerates against it. Same with a sail
A propeller accelerates the air, using power applied at the shaft.

And it is not possible to have more over-simplified view of fluid dynamics, than you hold. Hence, the balloon claim.

 

[3point14]

And?
1) where are the text book references that suggest a prop is like a tacking sail.
2) Where do text books, or even general sailing references, liken a tacking sail to a prop?

So? You want a text book to do your thinking for you?

You can't open your mind and just visualise an aerodynamic shape moving through air? Which is what they both are, you must accept?

Both are generating movement by creating a low pressure area on one side and using that to generate movement. You can't just draw the pictures in your mind and work out how to get from one to the other without a single hole in the logic? I described a thought experiment, could you tell me at what point it breaks down? You can't, you really, really can't.

It might not be in a textbook, but that doesn't mean it's not true. A very, very, very large number of things that you know to be true were, at one point, not in textbooks. This is relatively new technology and is, I believe, not considered to be particularly useful (but I'm still very glad some people have done it) technology, why would it be in a textbook? It might be one day. Actually, is that what it would take to change your mind? It being in a textbook? I think you might want to think about that for a while.

Now, about that thought experiment, can you tell me at what point it breaks down? It might well do, I don't know.

 

[3point14]

A wing is a device that gains lift as air decelerates against it. Same with a sail
A propeller accelerates the air, using power applied at the shaft.

You can't see how they're the same thing? Which one is a helicopter rotor-blade?

And it is not possible to have more over-simplified view of fluid dynamics, than you hold. Hence, the balloon claim.

Oh, I don't claim to be an expert, which is why I'm amazed that you can't get it as you seem to have all the book learnin'.

Now, about that thought experiment..

 

[Jack by the hedge]

1) where are the text book references that suggest a prop is like a tacking sail.
2) Where do text books, or even general sailing references, liken a tacking sail to a prop?

I don't know. But, since it's obviously a big deal for you, I'm curious to know how many such textbooks you've checked so far.

A wing is a device that gains lift as air decelerates against it. Same with a sail
A propeller accelerates the air, using power applied at the shaft.

You do realise, I'm sure, that the wing, sail and blade all have torque applied at their root. And you also realise, I have no doubt, that all three obtain thrust in the same way by deflecting the air passing over them in the same direction.

And it is not possible to have more over-simplified view of fluid dynamics, than you hold. Hence, the balloon claim.

Sure. Explain to us again why a balloon, released at above windspeed, would slow down to below windspeed.

 

[ThinAirDesigns]

There's a damn good reason that this particular version won't be establishing any DDWFTTW records anytime soon.

JB

 

[humber]

You can't see how they're the same thing? Which one is a helicopter rotor-blade?

1) Where are the text book references that suggest a prop is like a tacking sail.
2) Where do text books, or even general sailing references, liken a tacking sail to a prop?

NONE. The tacking props is a fabrication.

Oh, I don't claim to be an expert, which is why I'm amazed that you can't get it as you seem to have all the book learnin'.
Now, about that thought experiment..

Because I do.

 

[3point14]

1) Where are the text book references that suggest a prop is like a tacking sail.
2) Where do text books, or even general sailing references, liken a tacking sail to a prop?

NONE. The tacking props is a fabrication.




Because I do.

Sorry, I must have missed the bit where you tore apart the thought experiment. Are you going to?


While you're at it, could you explain why this doesn't work either?

http://www.youtube.com/watch?v=IMEerIkOVZ0

 

[humber]

....

1) Where are the text book references that suggest a prop is like a tacking sail.
2) Where do text books, or even general sailing references, liken a tacking sail to a prop?

Every post from now on.

 

[I Ratant]

If I see that correctly, that is the same Spork's small cart. The tailwind turbines the rotor and the wheels turn into the wind?
That is the one that would only run a few feet?

.
The first image, if the cart was set on the ground, with the small wheel at the front, facing downwind, would have the propellor and wheels turning in the proper direction for forward motion, downwind. It would be facing to the right, relative to that image.
Howsomever, when set on the ground facing to the right, it really is reluctant to move at all, without a gentle nudge from my foot, starting it to the right, which is downwind (today). Then it moves lethargically, and stops within inches or a few feet.
Not enough wind today to keep it going.
When that powered cart moved downwind with some enthusiasm a couple nights ago, the propellor rotated in the opposite direction.. CCW as seen from the rear, and the gear connection from the wheels to the prop were such that forward motion downwind would use that CCW rotation.

 

[I Ratant]

There's a damn good reason that this particular version won't be establishing any DDWFTTW records anytime soon.

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21822&stc=1&thumb=1&d=1302820388[/qimg]

JB

.
That image just shows the normal rotation of the propellor and the wheels, when not the cart is not on the ground.
When it's on the ground, the cart should move off to the right, relative to that image, if the wind force can overcome the rolling friction.
The propellor and wheels will then be moving in the proper direction to get to wind speed.
As for any "record" I don't expect that at all.
I want to see the driven cart when released, and moving as fast as it can, -not- be caught and passed, or paced, by the freewheeling prop cart.
If this never occurs, then....

 

[spork]

Oh, I don't claim to be an expert, which is why I'm amazed that you can't get it as you seem to have all the book learnin'.

humber may appear to have some book learnin' when he's talking about areas you know nothing about, but I can assure you he gets almost nothing right in any area. Just draw him into a conversation in an area of interest to you. In no time he'll tell you he's an expert, and you'll watch him get it all wrong.

.
That image just shows the normal rotation of the propellor and the wheels, when not the cart is not on the ground....

Yeah, JB gets that. His point is that you've made a glaring design error. Now he'll sit back and watch.

 

[ThinAirDesigns]

That image just shows the normal rotation of the propellor and the wheels, when not the cart is not on the ground.

Yep -- got that.

I repeat: there's a damn good reason that this particular version won't be establishing any DDWFTTW records anytime soon (or even make reasonable DDW progress).

JB