Merged DDWFTTW in a “Real” Wind

[Subduction Zone]

humber does not understand friction. That is why he does not understand how the cotton reel works.

 

[EHocking]

humber does not understand friction.

He has a fine grasp of fiction, though.

 

[humber]

humber does not understand friction. That is why he does not understand how the cotton reel works.

So you will be able to show me that you do.

A reel can be rolled towards the hand applying F, but may also turn counter-clockwise (CCW), and roll away from the hand.
Assuming that the force is applied parallel to the floor ( no lifting of the reel), which way will it go?

a = inner radius
b = outer radius
Fd = Friction
F = Applied force
m= reel mass
I = reel moment of inertia
v= linear velocity
w = angular velocity (radians/sec)

Linear component:
Net force to the right = F - Fd
Acceleration dv/dt = F - Fd/m

Angular Component:
Net clockwise (CW) moment = b*Fd - a*F
Angular Acceleration dw/dt = (b*Fd - a*F/)I

When a wheel rolls with out sliding ( pure rolling) the axle of the reel moves a distance equal to the circumference. So the linear velocity (the speed the axle moves) and the angular velocity ( the speed it turns) are related by (it travels 2pi*r with each turn)

v = b*w

The linear and angular accelerations are related as:

dv/dt = b*dw/dt

From a = f/m

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


Rearranging to relate Fd in terms of F

Fd( I + mb^2) = F( I + mab)


Fd = F(I + mab)/(I + mb^2)

If the reel moves to the right, then both the linear and angular forces will be positive (to the right). That depends on the friction to the surface and how the force is applied.
If pulled slowly, the reel will tend to roll with the hand, but a jerk may send it away.
It's a balance of the inertia of rotation and the friction to the surface, where the angular component is either positive or negative.

There is a third case, where there reel does not roll, but slides, so the angular component is zero. That may happen when the friction is very low. Wheels cannot roll without adequate friction.

The geared version is going to be bad. The most likely outcome, is that the gear will turn CCW, and move to the left. To move it forward would mean it would be dragged by the chain at the speed of the chain.

 

[I Ratant]

Unbe *********** believable!

 

[humber]

He has a fine grasp of fiction, though.

And you have avoided the matter of the streamer lift speed.
Airports use wind socks that are constructed to fly at a given wind speed.
That is a matter of their rigidity, shape and port dimensions.
Not random strands, which will have so many lift and drag components, that you can't tell one from the other.

 

[EHocking]

So you will be able to show me that you do.

A reel can be rolled towards the hand applying F, but may also turn counter-clockwise (CCW), and roll away from the hand.
Assuming that the force is applied parallel to the floor ( no lifting of the reel), which way will it go?

a = inner radius
b = outer radius
Fd = Friction
F = Applied force
m= reel mass
I = reel moment of inertia
v= linear velocity
w = angular velocity (radians/sec)

Linear component:
Net force to the right = F - Fd
Acceleration dv/dt = F - Fd/m

Angular Component:
Net clockwise (CW) moment = b*Fd - a*F
Angular Acceleration dw/dt = (b*Fd - a*F/)I

When a wheel rolls with out sliding ( pure rolling) the axle of the reel moves a distance equal to the circumference. So the linear velocity (the speed the axle moves) and the angular velocity ( the speed it turns) are related by (it travels 2pi*r with each turn)

v = b*w

The linear and angular accelerations are related as:

dv/dt = b*dw/dt

From a = f/m

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


Rearranging to relate Fd in terms of F

Fd( I + mb^2) = F( I + mab)


Fd = F(I + mab)/(I + mb^2)

If the reel moves to the right, then both the linear and angular forces will be positive (to the right). That depends on the friction to the surface and how the force is applied.
If pulled slowly, the reel will tend to roll with the hand, but a jerk may send it away.
It's a balance of the inertia of rotation and the friction to the surface, where the angular component is either positive or negative.

There is a third case, where there reel does not roll, but slides, so the angular component is zero. That may happen when the friction is very low. Wheels cannot roll without adequate friction.

The geared version is going to be bad. The most likely outcome, is that the gear will turn CCW, and move to the left. To move it forward would mean it would be dragged by the chain at the speed of the chain.

Wow.

After all you still came to the incorrect conclusion about the geared wheel and chain arrangement.

 

[EHocking]

And you have avoided the matter of the streamer lift speed.
Airports use wind socks that are constructed to fly at a given wind speed.
That is a matter of their rigidity, shape and port dimensions.
Not random strands, which will have so many lift and drag components, that you can't tell one from the other.

Stop it, please, before someone rings the RSPCA and reports this thread.

 

[humber]

Stop it, please, before someone rings the RSPCA and reports this thread.

Wow, and emoticons, are a poor substitute for analytical skill. We can assume that is the very best you can do. We all know it is.
If you wiki, you can find the performance data of wind socks. What happens when you attach them to a cart? Silence from you.

So smug. Why do some wind vanes have two tails?

 

[humber]

Like the TM, the trial is the result of tinkering and bad science. Averaging the wind direction is a blunder.

 

[Llyricist]

Then point to the error. I do not accept bluster.

The problem is, the only nearly correct thing in that post is the definition section, and even it falls flat with the Fd term.

Not to mention adding a lot of terms that are entirely irrelevant.

 

[humber]

Yevgheni wrote this;
They are still baffled by the cotton reel? It’s a lever and that is all it is. Work in = work out. Let the outer radius be twice the inner radius. Furthermore, let a force of 1 Newton applied at the outer radius cause the reel to roll a distance of 1 meter in one second.

The work done is 1 Joule and the power needed is 1 Watt. Along comes a dunce and he applies that same 1 Newton of force on the inner radius and what happens? He has one-half as much leverage advantage as in the previous case. It is now one Newton acting over 1/2 meter. The work in is only 1/2 Joule and the power is 1/2 Watt. The output likewise is only 1/2 Joule and 1/2 Watt but he is applying the same force as before and the reel travels half as far! What has the dunce gained from his foolishness? Well, if he is applying the force through a string that is wound up on the spool, he will find that as the spool rolls over the ground a greater distance than the amount of string being wound up, he will need to keep on pulling the string backwards as he rolls the spool forwards. If he is really observant he might come to the conclusion that the reel is going faster than the string that is pulling it! That is only an illusion because the sum total of string being wound up on the spool and the amount the string is being pulled back is always equal to the distance the spool travels. It cannot be anything else! Of course, the dunce may amuse himself this way for hours on end, thinking he has discovered some wonderful new principle of physics, and may even think it has something to say about wind-powered carts. But what the dunce fails to understand is that the reel he has stupidly rigged up with the string on the center spool is moving only half as far as the reel with the string on the outer spool, for the same amount of force applied.. So the question is, what does the dunce think he has accomplished?

And what do you think you have accomplished? Mostly error, but the fundamental point still applies - no gain.

 

[A.T.]

To avoid the obvious , you have made the reel so inefficient that it will be useless.

That is the same trick spork used, right? He made his "failed upwind cart" so inefficient, that it goes downwind.

 

[Llyricist]

I love it, now it's irrelevant.

Their whole basis for objecting to the cart was that you can't outrun the source of power, when shown that you can, it becomes trivial, and the objection switches to their own hopelessly botched energy analyses.

 

[Modified]

And what do you think you have accomplished? Mostly error, but the fundamental point still applies - no gain.

What do you mean "no gain"? Why are you interested in gain when you claim it doesn't work at all? Finally admit you were wrong about that, then we can talk about gain.

 

[humber]

That is the same trick spork used, right? He made his "failed upwind cart" so inefficient, that it goes downwind.

That's right. But the idea is too much for you to consider. How could you be fooled?

I have two cotton reels. One will roll on an incline of less than 20 degrees and holding the thread won't stop it. The other can sustain 60 degrees without rolling. What's the difference?

Two un-braked cars are on a hill, one rolls down, the other does not. What is the difference?

 

[humber]

What do you mean "no gain"? Why are you interested in gain when you claim it doesn't work at all? Finally admit you were wrong about that, then we can talk about gain.

Work at all? Define at all. There are many variables that can cloud the result.
Gain is a matter of principle, and the other of experimental control or ignorance of other factors. So far, Carteers have failed at both.
As soon as I mentioned it, a lot of you tried it. Hence the remark "tell me how you get on". There are number of possible outcomes, but how many were tried and failed? There are reasons why some work and some don't.
Overall though, one way or the other, it will be friction that accounts for those differences.

 

[Llyricist]

And the lecture back telling us what we already knew, and have been trying to explain to him, as if it was us that didn't already know.

 

[D'rok]

And the lecture back telling us what we already knew, and have been trying to explain to him, as if it was us that didn't already know.

See, when he was vehemently insisting that the spool wouldn't roll up an incline and that you all were cheating and needed CGI effects to make a video of it, etc. - he was actually saying that it will roll up the incline but you silly carteers just don't know why.

 

[humber]

See, when he was vehemently insisting that the spool wouldn't roll up an incline and that you all were cheating and needed CGI effects to make a video of it, etc. - he was actually saying that it will roll up the incline but you silly carteers just don't know why.

Oh, it's a little more than that. Without a lure, you will not give me the data.
But now you have. I am sure I could make a video that would have you believe elephants can fly. After all, you do that to yourselves.
Carteers really missed their calling when The Inquisition ended.

 

[SOdhner]

I am sure I could make a video that would have you believe elephants can fly.

Right after all your other videos? Sometime in 2032, I would guess.