Merged DDWFTTW in a “Real” Wind

[spork]

Rigorous test procedure to follow...

Classic! Good for you.

Now are those measurements ("steep angle" and "not as steep angle") precise? Perhaps humber can help you with that. I think there's a good impedance match there.

 

[I Ratant]

Even small surface imperfections will cause a light cart to lose traction, just like Spork's does. ...

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The initial sliding on the light carts demonstrates the initiating force is the surface of the propellor blades.
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I have a comment about the propeller.

[qimg]http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21643&d=1301700844][/qimg]

The prop will windmill in the >WS headwind, and turn CW. At all other times the air passes from the front to the rear, so that is expected. But no thrust will be generated without an engine, so the cart will not accelerate.
[/quote]
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My unpowered cart moves downwind with the propellor moving in the "usual" direction for a windmilling propellor. CCW looking at the front of the prop, from the direction the wind is coming.
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The engine/motor for the powered cart is the wheels.
As the sail (prop) pushes on the frame of the cart, that motion begins to rotate the wheels, which rotates the prop CW looking from the direction the wind is coming. That rotation is opposite what the unconnected prop to the vehicle.

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The only source of energy is the cart's KE. That may act for a short time as an "engine" but at the expense of a slowing cart.
Is that what you meant, rather than actually accelerating against the headwind?

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The energy... more like inertia... "remains in motion", Ike said... of the cart downwind is amplified by the prop blade area pushing and the wheels rotating, up to the point where the propellor "drag" becomes thrust, adding to the downwind speed of the thing.
A load cell on the prop shaft bearings would be interesting to see how the load shifts from pushing to pulling as the cart speeds up.

 

[A.T.]

The relevance of the spool and thread to the general theme of the OP is ????

That you have to deny even basic things like this, in order to "show" that DDWFTTW is impossible.

 

[Michael C]

The relevance of the spool and thread to the general theme of the OP is ????

The relevance of the spool and thread to the general theme of the OP has already been explained in detail. I can even show the mathematical equivalence between the spool/thread and the downwind cart, but if you want to know more about that you'll need to start by answering the little physics test question I set earlier.

 

[humber]

The relevance of the spool and thread to the general theme of the OP is ????

Mostly diversion from the sham trial, but exposing the Carteer's lack of respect or understanding of experimental control, reflects their acceptance of the trial and TM.

But anyway...
Rigorous test procedure to follow..
Propping the inclined plane.
Thread feed from the top of the spool. VIII-01
Thread feed from the bottom of the spool. VIII-02
The top feed spool will go to a much steeper angle before it begins to slide down the plane, than the bottom feed point.
At the slip/roll angles, the spool moves down, away from the tie point, different angles for the pulls, but the thread gets longer despite the direction the spool rotates.

Thanks. That confirms that the over the top spool will be the better climber.
The reel is something like a horizontal yo-yo. A yo-yo shows different behavior if slowly manipulated than if it has some momentum. Static tests are mostly a matter of dimension and friction.
Conservation of momentum means the 2:1 reel will never work as claimed.

 

[humber]

Classic! Good for you.

Now are those measurements ("steep angle" and "not as steep angle") precise? Perhaps humber can help you with that. I think there's a good impedance match there.

Define what you mean by "impedance", Chief.
You may phone a friend.

 

[Jack by the hedge]

It will not show a gain unless it is accelerating. Distance is not velocity.

I believe this is a basic misunderstanding on your part. When the hand pulls the string at a constant speed, the reel follows the hand at a constant speed. It does not accelerate.

With a 2:1 reel, if the hand pulls the string at a steady 1m/s, the reel follows at 2m/s (and so it catches up with the hand at a rate of 1m per second). Note that the reel moves at a constant 2m/s. It does not accelerate.

 

[spork]

Originally Posted by I Ratant
The relevance of the spool and thread to the general theme of the OP is ????

Mostly diversion from the sham trial, but exposing the Carteer's lack of respect or understanding of experimental control, reflects their acceptance of the trial and TM.

I knew we had a good impedance match there. It's a beautiful thing!

 

[spork]

I believe this is a basic misunderstanding on your part. When the hand pulls the string at a constant speed, the reel follows the hand at a constant speed. It does not accelerate.

With a 2:1 reel, if the hand pulls the string at a steady 1m/s, the reel follows at 2m/s (and so it catches up with the hand at a rate of 1m per second). Note that the reel moves at a constant 2m/s. It does not accelerate.

humber spent over a month on this topic. He is not capable of understanding that one object may move faster than another without it accelerating.

 

[humber]

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The initial sliding on the light carts demonstrates the initiating force is the surface of the propellor blades.

It will move without a prop if there is sufficient wind. There can be no torque without drag, but the sail force is not the only force at work pushing the cart downwind.

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My unpowered cart moves downwind with the propellor moving in the "usual" direction for a windmilling propellor. CCW looking at the front of the prop, from the direction the wind is coming.

CW from the rear. The thrust leaves the rear, so incoming flow will drive it CW.

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The engine/motor for the powered cart is the wheels.
As the sail (prop) pushes on the frame of the cart, that motion begins to rotate the wheels, which rotates the prop CW looking from the direction the wind is coming. That rotation is opposite what the unconnected prop to the vehicle.

Yes it windmills CCW, but when the wind is from the rear.
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The energy... more like inertia... "remains in motion", Ike said... of the cart downwind is amplified by the prop blade area pushing and the wheels rotating, up to the point where the propellor "drag" becomes thrust, adding to the downwind speed of the thing.
A load cell on the prop shaft bearings would be interesting to see how the load shifts from pushing to pulling as the cart speeds up.

It's not inertia, but momentum. Kinetic energy is the integral wrt v
KE = int\mv = 1/2mV^2
Above WS, the headwind is a result of the rotor accelerating the slower air of the free stream. KE leaves the cart to do that, so it slows.

 

[ThinAirDesigns]

That's right. You were such good pals, that they gave you their data.

LOL -- I do understand that "Humberverse science" dictates that the "Humberverse scientist" doesn't get to look at a copy of the data after the test, but here on earth the scientists get to review it.

Just a simple thing to remember really -- we're on earth.

JB

 

[Jack by the hedge]

humber spent over a month on this topic. He is not capable of understanding that one object may move faster than another without it accelerating.

It appears so. This was exactly the same sticking point which finished Humber's previous discussion on JREF early in 2010.

 

[humber]

humber spent over a month on this topic. He is not capable of understanding that one object may move faster than another without it accelerating.

Take a look at the math, and if you can understand it let alone fault it, then you may see why acceleration is no different from increased velocity, but is change in velocity over time, Chief.

And what did you mean by impedance?

 

[A.T.]

Thread feed from the bottom of the spool. VIII-02

You heard humber. After initially claiming that the spool will never climb the incline with bottom bull, he is now back to safe-mode: His prediction will come true, only if the pull happens with absolutely constant speed. Which is of course impossible to achieve in the real world.

So, as usual, the predictions of humberphysics are not reproducible in reality.

 

[humber]

It appears so. This was exactly the same sticking point which finished Humber's previous discussion on JREF early in 2010.

Make one. A substantial reel. If it travels twice your speed, it will eventually overtake you. Or do you have a infinite string in mind?

The Chief has never done that, nor the math, but one would have expected such a "doing is all" guy to have tried it.

I think he threw in "impedance" to impress.

 

[Christian Klippel]

humber spent over a month on this topic. He is not capable of understanding that one object may move faster than another without it accelerating.

Block and tackle anyone?

 

[humber]

You heard humber. After initially claiming that the spool will never climb the incline with bottom bull, he is now back to safe-mode: His prediction will come true, only if the pull happens with absolutely constant speed. Which is of course impossible to achieve in the real world.

So, as usual, the predictions of humberphysics are not reproducible in reality.

Read again. I said the over the top would climb, when the under failed.
It's in the math.

 

[Jack by the hedge]

Take a look at the math, and if you can understand it let alone fault it, then you may see why acceleration is no different from increased velocity, but is change in velocity over time, Chief.

I suspect most of us already grasp A = dV/dT, thanks.

There is no increased velocity.
There is no acceleration.


Why don't you take a look at;

V_reel = 2 * V_hand

And tell us why, if V_hand is constant, you think V_reel will change over time.

 

[Jack by the hedge]

Make one. A substantial reel. If it travels twice your speed, it will eventually overtake you. Or do you have a infinite string in mind?

No. I have an analogy in mind, which demonstrates a particular point. Like most analogies, this one eventually breaks down. If you run out of string or if the dog eats the reel the analogy ceases to be an analogy. Do you find this concept confusing?

<edit> You could, of course, use a long loop of string and keep pulling and recycling it over and over. You'd have to swap hands every so often as the reel caught up, but there's no reason this wouldn't work.

 

[humber]

I suspect most of us already grasp A = dV/dT, thanks.

There is no increased velocity.
There is no acceleration.

From a = f/m
(F - Fd)/m = b(b*Fd - a*F)/I

Why don't you take a look at;

V_reel = 2 * V_hand

What I_see = what I_expect.

And tell us why, if V_hand is constant, you think V_reel will change over time.

From a = f/m
(F - Fd)/m = b(b*Fd - a*F)/I

There is no escaping the fact that if the reel is traveling twice as fast it will overtake the hand, so is utterly useless in practice. But, if both you and the reel start from a standstill, then both you and the reel will accelerate. Correct?
If at any instant the reel is traveling at twice your speed, it must be accelerating at twice what you are. Assuming steady state for one, and not the other is a mistake, and the source of the illusion.
The NALSA data will show what is really happening. A silly claim, with hyperbolic promotion.