Would this work? (air filled tube inside a water filled container)

[TurkishFR]

Hey, I am from Turkiye, 17 yo and studying at high school. I have a project and would be better to know whether or not my project will work. I tried to draw it simply on paint and will tell you about some important points of it.

Image 1 is the main body, its something solid and waterproof. It has holes at the top and bottom.

Image 2, the red thing is a tube full of air. Its top and bottom is tied to the main body with a waterproof cloth or something else water proof.

Image 3, its a close look to what I am trying to tell above. The yellow things are waterproof cloth, to prevent water leak while red tube is moving vertically.My question is: Can the red tube move upward when its released in Image 2 position ?

 

[berkeman]

Welcome to the PF.

Your images are not loading correctly. Are you using the UPLOAD button in the lower left to attach them to your post? Be sure they are in JPEG or PDF format. Maybe try again? Can you describe what your project is about?

 

[TurkishFR]

Thank you. Okay problem fixed : )

 

[Drakkith]

My question is: Can the red tube move upward when its released in Image 2 position ?

Yes, a sealed tube of air will float when submerged in water and released. As long as the tube is relatively lightweight of course, and not tied down by the cloths. Just leave some 'slack' in the cloths.

 

[TurkishFR]

Yes, a sealed tube of air will float when submerged in water and released. As long as the tube is relatively lightweight of course, and not tied down by the cloths. Just leave some 'slack' in the cloths.

Yes, the red tube will be soo lightweigted when compared to the lifting potential of the air it keeps in. Yes the cloth will have enough slack to allow the tube to rise.

 

[Drakkith]

Hmmm. I just realized that the bottom is also sealed by the cloth so that there is no way for water to get underneath the tube. I'm not sure it would float now. @berkeman what say you?

 

[TurkishFR]

Hmmm. I just realized that the bottom is also sealed by the cloth so that there is no way for water to get underneath the tube. I'm not sure it would float now. @berkeman what say you?

Yes, both top and bottom is sealed with cloth. So there is a water pressure on the clothes and tube have to overcome this pressure too.

 

[berkeman]

Hard to say. If the cloth goes under the air tube, it's probably rough enough to allow water to get underneath and start the lifting process. No idea what the mechanism is for, though.

 

[Drakkith]

Well, if it's sealed to the tube, then there should be no way for water to get underneath the tube. In that case I don't believe that it would float.

 

[russ_watters]

Well, if it's sealed to the tube, then there should be no way for water to get underneath the tube. In that case I don't believe that it would float.

That is my interpretation.

 

[sophiecentaur]

Hard to say. If the cloth goes under the air tube, it's probably rough enough to allow water to get underneath and start the lifting process. No idea what the mechanism is for, though.

This proposed experiment is a really difficult mix of real and ideal components. If there is not way of water getting to the bottom face of the air-filled tube then there should be no upward force. It's a bit like when you stand in thick mud with Wellington Boots on and you can't drag your feet out. That 'suck' is all about greater air pressure down on the upper face of the soles, via the gaps between leg and boot and no pressure on the lower face. But, given time, water can seep in underneath and provide upward pressure.
How good are your seals? Only you (@TurkishFR ) can find that out.

 

[TurkishFR]

Thanks. I would like to be able to build such a thing to test it but I really have no idea how to build it.

 

[Merlin3189]

Since there is a hole in the bottom of the outer container, even if water can leak under the red tube, it can't exert more than atmospheric pressure at that level (- allowance for weight of the thin film of water) The tube must slide down under its own weight, unless friction keeps it in place.

That's my interpretation, but I must admit, I don't understand the role of the cloth, so I may not be seeing it right.

 

[russ_watters]

Thanks. I would like to be able to build such a thing to test it but I really have no idea how to build it.

Get a plastic bucket with a lid. cut a hole in the top and bottom, sized for a pipe to pass through. Instead of cloth, cut up a plastic sheet and duct tape it to the bucket and pipe. You'll need to support the bucket in a way that the underside is clear and support the pipe during construction and filling.

Fill the bucket, close the lid, and drop the pipe. Do this outside so that when the pipe drops straight through and rips off the plastic, the water doesn't spill on anything important.

 

[TurkishFR]

Okay I will try to build it using a fridge bag (waterproof sheet), protein shaker (main body) and a pet water bottle (the red tube).

 

[TurkishFR]

Hey,

I tried to build something similar and seemed like it works, the problem is to mount waterproof sheet, I used a plastic bag but I could not stick it properly around the red tube. It needs a professional touch.

 

[berkeman]

What is it for? What is it supposed to do?

 

[TurkishFR]

Hey, whatsup. I ve tried to build somethings but I could not do it properly. It needs some professional touches, like as 3D printers to produce some parts etc.

As you said before, I think some water holes are needed in the inner tube to benefit from upthrust power of the water in the main tube.

 

[sophiecentaur]

Thanks. I would like to be able to build such a thing to test it but I really have no idea how to build it.

To make a good, reliable demonstration, you would need a pretty good machine shop facility - good enough to have the top and bottom tubes aligned and the same diameter within a fairly high tolerance so the 'piston' could move very freely without the water leaking. The movable piston would need to be a pretty good fit (more good machining) and the gaps would need to be filled with a lubricant (a fairly heavy grease, perhaps). The problem of a good enough seal is the critical one. Even with a 3D printing facility, I suspect you would still need to ream the two vertical tubes.
But you could get away with a much simpler implementation which could at least confirm your prediction or not. Have you actually told us what you think would happen and why? What would happen in the ideal case is pretty easy to guess, I think.

 

[TurkishFR]

To make a good, reliable demonstration, you would need a pretty good machine shop facility - good enough to have the top and bottom tubes aligned and the same diameter within a fairly high tolerance so the 'piston' could move very freely without the water leaking.

Yes, actually this is the biggest problem, as you say it requires professional tools to build a perfectly fitting tube and tube holes. Even If the holes become a bit larger than the tubes, it still creates too much problem.

The movable piston would need to be a pretty good fit (more good machining) and the gaps would need to be filled with a lubricant (a fairly heavy grease, perhaps).

I don't know it would not have to be a grease oil, it could be a pump bellows or a coat nicelly surrounds the tubes.

Have you actually told us what you think would happen and why? What would happen in the ideal case is pretty easy to guess, I think.

I will tell you if it works : )

 

[TurkishFR]

We could build it like this, to benefit more from the upthrust power power of water, so two seperatare air tubes to allow water to go under air tube.

 

[berkeman]

What is it for? What is it supposed to do?

Please respond to this question, or the thread will be closed. We do not discuss perpetual motion machines or over-unity mechanisms here...

 

[sophiecentaur]

I don't know it would not have to be a grease oil, it could be a pump bellows or a coat nicelly surrounds the tubes.

You still need to prevent water getting round to the bottom of the piston. You seem to be proposing a bellows 'somewhere'. I'm not sure where you mean but I could think of places where a long bellows could help perhaps.

I will tell you if it works : )

You should really have an opinion, based on some basic Physics. The answer is actually pretty clear - for an ideal setup.

We could build it like this, to benefit more from the upthrust power power of water, so two seperatare air tubes to allow water to go under air tube.

There is a problem with your logic there. There will be an upward pressure on the bottom of the top bit and an equal downward pressure on the top of the lower bit.
You can work out what your experiment should do if you just consider the pressures and weight involved. Would there be any net upwards pressure from the water, for instance? (Think like a Real Physicist. )

 

[TurkishFR]

Please respond to this question, or the thread will be closed. We do not discuss perpetual motion machines or over-unity mechanisms here...

Okay, close the thread and remove my account please.

 

[berkeman]

Okay, close the thread and remove my account please.

How come? What is the application?

 

[tech99]

Unfortunately there is a well known perpetual motion machine rather like this, where a series of floats on an endless belt enter a tank of water from beneath, via some sort of flap.

 

[sophiecentaur]

Ah well. PM is such nonsense in my mind that I just don’t spot it when it arrives[emoji206][emoji206][emoji206][emoji206][emoji206][emoji206][emoji206][emoji206]

 

[CWatters]

For the OP...

http://www.hp-gramatke.net/pmm_physics/english/page0550.htm

 

[berkeman]

Thanks folks. It looks like that was what the OP was trying to ask about. Since the subject is not allowed on the PF, this thread is now closed.