Merged DDWFTTW in a “Real” Wind

[GlennB]

Oh, it's a little more than that. Without a lure, you will not give me the data.
But now you have.

Red alert!

He has the data!

This is no drill. He has the data!

 

[Jack by the hedge]

I can find a reel and thread that will roll backwards, and that will leave you to explain why.

I positively shiver with anticipation. Will this be before or after the video you promised someone a while ago?

 

[EHocking]

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

Here's a small gif to get him started.

 

[humber]

I positively shiver with anticipation. Will this be before or after the video you promised someone a while ago?

The intent is to show that you are tilting at windmills. You forget that any opponent becomes inured of any of the above taunts. Carters offer little else.

So far, you forgot about some side effects concerning the type of thread and the way it is wound, but did not hit on the fact that when you pull the thread, it is no longer parallel to the floor, and the normal force is no longer under the reel center. That completely escaped you. So what else did you miss?

 

[Jack by the hedge]

The fact is that only the opposing friction allows the reel to roll forwards. True. Yo seem to be getting a grasp of it now. In zero gravity, for example, the reel would just spin about its centre of gravity. If som eother way were devised to remove any friction between the reel and the ground it would do likewise. However that would not be analogous to the problem the reel was supposed to be representing, and is therefore irrelevant.
The torque from the thread will turn it CCW, so to the left - that is clear id you put the reel on a spindle. Only the opposing force of friction to the surface allows it to turn the other way. Yes. If you put the reel on a spindle, which is not part of the original problem.
It can readily be made to roll the CCW. Apply enough torque and it will.
So what use can it be? In the end you will find that its better to not use the reel idea at all. Or rather it would be a perfectly good analogy as long as you didn't introduce confounding elements which were never part of the original problem.
There can never be a gain in the work, so eventually, like all other vehicles, power will limit the top speed. In the case of the reel, that will be lower than a simple cart, because the rolling losses must be high enough to prevent the reel sliding or turning the other way.

Limiting the driving force would limit acceleration. Whether the reel has a lower top speed than "a simple cart" depends on other design factors too.

 

[humber]

Limiting the driving force would limit acceleration. Whether the reel has a lower top speed than "a simple cart" depends on other design factors too.

Post hoc modifications.
Power = work/time
Work in = work out.
The reel will reach a lower top speed than a simple wheeled cart, because amongst other things, it is less efficient.

 

[GlennB]

So far, you forgot about some side effects concerning the type of thread and the way it is wound, but did not hit on the fact that when you pull the thread, it is no longer parallel to the floor, and the normal force is no longer under the reel center.

My reel thread was totally parallel. On the flat test and on the uphill test. Stop being so damn lathophilic.

 

[Jack by the hedge]

So far, you forgot about some side effects concerning the type of thread and the way it is wound, but did not hit on the fact that when you pull the thread, it is no longer parallel to the floor, and the normal force is no longer under the reel center. That completely escaped you. So what else did you miss?

On a slope, the force of gravity acting on the reel can be resolved into one force acting from the COG of the reel to the point of contact with the slope and another perpendicular to it pulling down the slope. So the friction at the point of contact is reduced and the tension in the cord is increased. So far, no surprises.

It's fair to say that the result is that the accelerating force which can be applied to the cord without the reel slipping is reduced, but that is a world away from your flat out claim that it cannot work on a slope, which is demonstrably untrue if you merely bother to try it.

 

[Modified]

The reel will reach a lower top speed than a simple wheeled cart, because amongst other things, it is less efficient.

If the speed of the string (rather than the available force) is the limiting factor, then the reel will reach a higher speed.

 

[Jack by the hedge]

Post hoc modifications.
Power = work/time
Work in = work out.

Force is limited. Time is not.

The reel will reach a lower top speed than a simple wheeled cart, because amongst other things, it is less efficient.

What you are forgetting is that the power source is the wind or, in this analogy, a drive chain or cord, which is travelling at a constant speed. The simple cart cannot travel faster than the rope that pulls it. The reel can. QED.

 

[D'rok]

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.

So, the spool rolls up the incline after all, eh?

 

[D'rok]

Spool on an incline

Humber denies:

Take your silly under version of the reel. Tie the thread to the wall. Now try and move the reel when the thread is tensioned. You need to turn the reel, not pull the thread.
The only way it can travel, is if impulse causes the reel to roll along the thread so that the slack get wound up. doh. It always does that, but its hard to tell.
You can try and make it work up an incline if you like, or can't the cart go up hill?
Do let me know how you get on.

Reality prevails:

Tie it to a wall? Why not tie it to a cat? Or throw it in the ocean? Or fire it into the heart of the sun. Does it work now? Huh? Huh? Does it?

What are you, five?


OK. I still have my trusty reel and cord right here. It works uphill and it works downhill too. Are you bored of being wrong yet?

When the math tells you the opposite of easily demonstrated reality, you probably have a mistake in the math. There's certainly no mistake in reality.

You can do the experiment with the spool outrunning the string slowly and uphill to prove that it's not the inertia of the spool making it wind up the string. Maybe I'll make a video when I get home tonight.

Will you accuse me of using special effects when I show it doing what you claim is impossible?

Well, I just hauled my spool of line up quite a nice slope. Try it yourself.

What is you enjoy here, humber, the thrill of the attention or the actual fact of being relentlessly wrong in public?

Humbe denies more strenuously:

You will need CGI to make that reel move up the incline.
How embarrassing for you! A simple trick, performed by a powdered monkey, had you believing in magic reels.

Reality prevails:

No, you don't understand. No tricks, I wasn't fooled by anyone else. I've done this already, it works.

Humber denies using very strong language:

Oh yeah. On a smooth surface, with the thread underneath. Up an incline. BS

Reality prevails:

Yes. On my kitchen table, with the string underneath, with one end of the table propped up on a chair.

Humber denies with an extra helping of ridicule. Is he starting to get desperate?

No little ones, it won't work on an incline. It's a show-stopper in neon, that will be hard to deny. I doubt that you will get many to share your vision on that one.

Reality gets real:

Do try to keep up, humber. You're supposed to say it's impossible before it's been tested and found to work. Doing so afterwards is a little infra dig even for you.

And the backpedalling and obfuscation begins:

And what error has the Carteer made? He's wrapped the thread, such that the force between the turns prevents it from unwinding. Isn't that right?

I can then say that it rolls down the slope when released, but will not when you hold the thread. Why not put chocks under it?
Once again. its down to the balance of friction. To avoid the obvious , you have made the reel so inefficient that it will be useless.

Try again.

Result: Lurkers highly entertained.

 

[A.T.]

I can find a reel and thread that will roll backwards, and that will leave you to explain why.

Poor experimental control

 

[humber]

Force is limited. Time is not.

P = f*v
v =d/t
Work = f*d.
Power = w/t
The limit is still power, even if force is also limited.

What you are forgetting is that the power source is the wind or, in this analogy, a drive chain or cord, which is travelling at a constant speed. The simple cart cannot travel faster than the rope that pulls it. The reel can. QED.

It's a non-starter. There are machines which use shuttles that travel faster than something else. They are of no use in a car. Cotton reels are of no use in the wind. Never tested as far as I know.

The wind is not a chain, and you will need to use a sail or propeller, so back to square one. The final speed will be no different from a simple cart, except for the additional angular KE, for the same mass. It's not a good idea, but a bad one.
But the trial does not support your claim, so you have nothing.
The averaging of the wind direction simply invalidates the result.

 

[humber]

Poor experimental control

And how is that done. I pointed out your errors, so you can do the same?

 

[humber]

Humber denies:

I have posted the calculation that says it will stay on the incline.
Funny how you did not point that out to me.

 

[D'rok]

I have posted the calculation that says it will stay on the incline.
Funny how you did not point that out to me.

Gosh. You must have been right all along.

 

[Jack by the hedge]

Cotton reels are of no use in the wind. Never tested as far as I know.

The wind is not a chain, and you will need to use a sail or propeller, so back to square one.

Humber now appears to have forgotten what an analogy is. Clue - an analogy to a thing is not the thing itself.

The wind is not a chain. It does, however, provide a driving force, in a particular direction and, with care, at an approximately constant velocity. A bit like a drive chain, in fact.

A cotton reel is not a land yacht. However it does helpfully provide a trivial demonstration of the principle that an object can be driven forwards faster than the thing which drives it.

 

[Jack by the hedge]

I have posted the calculation that says it will stay on the incline.

Remind me - was that before or after you posted "No little ones, it won't work on an incline"?

 

[A.T.]

Cotton reels don't roll down hill in Carteerland.

I have posted the calculation that says it will stay on the incline.

Welcome in the club.