Perpetual motion machine

[Gibsons]

Originally posted by: bobdole369
How about this idea:

wide cylinder on its side - Think massive fuel tank for the shape, or hamster wheel.

At the hub of this cylinder place holders that extend into the cylinder and hold a permanent magnet fast with N and S poles facing out of the device.

Now place another permanent magnet on the wheel itself. The repulsion should force the free magnet up the slope created by the floor of the wheel, creating potential energy released when gravity brings the magnet down.

Some form of ratcheting or grip tape or guides need to keep the potential energy from disappearing and force the free magnet to rotate the wheel. I'm sure it would reach a steady state.

Yes it would, and that steady state would be "not moving."

 

[QuantumPion]

Originally posted by: bobdole369

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

isn't that how ocean currents basically work?

ocean currents aren't perpetual motion, they are powered by thermal energy from the sun.

this idea is a real perpetual motion machine, as it extracts useful work based only on density differences between two fluids in a gravitational field.

the osmosis machine wouldn't work in reality but its fault is subtle and hard to catch

 

[Gibsons]

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

I think I see a problem.

 

[QuantumPion]

Originally posted by: Gibsons

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

I think I see a problem.

I'm not sure what you are objecting to, but that is not the flaw in the design.

 

[bobsmith1492]

Originally posted by: Veramocor

Originally posted by: bobsmith1492
A couple of inventors brought in a purported perpetual motion machine today. It consisted of two huge pistons sliding back and forth over two magnets. It made a ton of commotion and looked pretty cool, but since it was radiating a ton of heat and shaking their truck trailer back and forth, there's no way it was "generating more energy than it consumed" like they claimed.

I feel sad for the guys, though; they are so convinced. Somehow, if they think about it in a certain way, they can generate energy from nothing. I was hoping my boss could straighten them out but I think they were pretty stuck in their ways. They seemed to have been very emotionally invested in the thing which can good but not when it comes to science or engineering.

What type of company do you work at that crackpots bring their PM machines to you?

A contract engineering firm - this is perhaps the second time something like this was brought in. I don't know what the inventors expect from us... we tried to tell them how it was fundamentally flawed but they weren't listening.

 

[gsellis]

Originally posted by: bobsmith1492
A couple of inventors brought in a purported perpetual motion machine today. It consisted of two huge pistons sliding back and forth over two magnets. It made a ton of commotion and looked pretty cool, but since it was radiating a ton of heat and shaking their truck trailer back and forth, there's no way it was "generating more energy than it consumed" like they claimed.

Let me be the first to say, TTIUWP :camera:

That sounds like it was quite a show.

I guess the failure of would be inventors, besides the three laws, is that they focus on the wrong thing. Who wants a perpetual motion machine, I want a generator that uses some untapped force. So, it will go forever. I want free extra energy... jeez

 

[bobsmith1492]

I guess they think that if you make a good enough machine, it can run forever; then, make it a little better, and you can get energy out of it at the same time... kind of like "Well, if we just get to moving at light-speed then go a little faster..."

 

[Gibsons]

Originally posted by: QuantumPion

Originally posted by: Gibsons

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

I think I see a problem.

I'm not sure what you are objecting to, but that is not the flaw in the design.

It takes a lot of pressure to push water through the filter. Without that pressure, water will flow in the opposite direction, towards the salty side.

 

[QuantumPion]

Originally posted by: Gibsons

Originally posted by: QuantumPion

Originally posted by: Gibsons

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

I think I see a problem.

I'm not sure what you are objecting to, but that is not the flaw in the design.

It takes a lot of pressure to push water through the filter. Without that pressure, water will flow in the opposite direction, towards the salty side.

The containers are tall enough so that gravity provides sufficient pressure for the reverse osmosis to occur. In fact they are so tall that the difference in pressure between the fresh and salt side is enough for reverse osmosis. I believe the required height was something like 6 km tall. Outlandish, but physically possible.

 

[Gibsons]

Originally posted by: QuantumPion

Originally posted by: Gibsons

Originally posted by: QuantumPion

Originally posted by: Gibsons

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

I think I see a problem.

I'm not sure what you are objecting to, but that is not the flaw in the design.

It takes a lot of pressure to push water through the filter. Without that pressure, water will flow in the opposite direction, towards the salty side.

The containers are tall enough so that gravity provides sufficient pressure for the reverse osmosis to occur. In fact they are so tall that the difference in pressure between the fresh and salt side is enough for reverse osmosis. I believe the required height was something like 6 km tall. Outlandish, but physically possible.

Make it as tall as you want to, the salt water side won't be lower than the fresh water side at equilibrium unless you apply some work/energy to the system.

 

[QuantumPion]

Originally posted by: Gibsons

Originally posted by: QuantumPion

Originally posted by: Gibsons

Originally posted by: QuantumPion

Originally posted by: Gibsons

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

I think I see a problem.

I'm not sure what you are objecting to, but that is not the flaw in the design.

It takes a lot of pressure to push water through the filter. Without that pressure, water will flow in the opposite direction, towards the salty side.

The containers are tall enough so that gravity provides sufficient pressure for the reverse osmosis to occur. In fact they are so tall that the difference in pressure between the fresh and salt side is enough for reverse osmosis. I believe the required height was something like 6 km tall. Outlandish, but physically possible.

Make it as tall as you want to, the salt water side won't be lower than the fresh water side at equilibrium unless you apply some work/energy to the system.

Well, supposedly it is the static pressure of the fluid forcing the system. If the static pressure of salt water at 6 km deep is ~15 psi greater then the static pressure of fresh water at the same depth, separated by a reverse osmosis filter, the salt water will flow through. This will in turn raise the level of the fresh water column.

 

[Gibsons]

Originally posted by: QuantumPion
Well, supposedly it is the static pressure of the fluid forcing the system. If the static pressure of salt water at 6 km deep is ~15 psi greater then the static pressure of fresh water at the same depth, separated by a reverse osmosis filter, the salt water will flow through. This will in turn raise the level of the fresh water column.

According to wiki you need more pressure than that, even for a relatively dilute salt solution.

 

[KIAman]

The only thing I can think of that comes close to a perpetual motion machine is something utilizing the tides. But even that doesn't really qualify considering the changing tides slowly bleed energy away from Earth's orbital spin.

 

[Paperdoc]

Originally posted by: QuantumPion
The best idea for a perpetual motion machine, which took me considerable time to understand its failings, is this:

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

Start from an understanding of Potential Osmotic Pressure. Let's use your structure of a large U-tube with a semi-permeable membrane across the bottom, salt water on one side, and fresh water on the other. Let it sit there for a long time. Water molecules can flow through the membrane in both directions, but the salt molecules cannot. Because the concentration of water on the two sides is different (higher in the fresh water side), the net exchange will be that more water flows from the fresh side to the salty side. This means the volume on the salty side increases, thus increasing the height of the column of salty water and reducing the height on the fresh side. That produces a higher static pressure on the salty side of the membrane, which tends to push water through the membrane from salty to fresh side faster than if the pressures were equal (as it was at the start of the experiment). So the build-up of pressure (from column height) on the salty side creates a flow preference that opposes the tendency for water to prefer to flow from the high-water-concentration (fresh water) side to the salty side. At some point these two driving forces just exactly match each other and the two column heights stop changing. They have reached an equilibrium state. The difference in pressure between the two sides (because of the difference in column height) is called the Static Osmotic Pressure for that salty solution. The process that got us to the equilibrium state is called Osmosis.

Now, to change the equilibrium and cause a preferential flow of water molecules from the salty to the fresh water side we can apply an external force (pressure) on the salty side so that the net pressure at the membrane on the salty side is greater than the Static Osmotic Pressure. Since that causes flow opposite to the direction of the original "normal" Osmosis, we call this "Reverse Osmosis". It is widely used in lots of processes. In the system proposed here, this could be accomplished merely by adding more salt water to the salty side and increasing the column height to accomplish the required pressure difference. But look closely at what we have now. The height of the salty water column at equilibrium was higher than the fresh water column, and now we've just increased that even more to produce Reverse Osmosis. Over on the fresh water side, how do you expect to get the height of that column up to the top of the U-tube so it can overflow back to the salty side? You can't without providing an external source of energy to do that work. That is just the opposite of what was proposed.

The original proposition postulated that the water column heights would just naturally make the fresh water column side higher than the salty water side so that work could be done as water flowed over the top. The facts deny that.

 

[Gannon]

Originally posted by: bobsmith1492

Originally posted by: IHateMyJob2004
Try to figure out a way to have gravity be the driver for a perpetual machine.

I got stuck at this:
feet per second squared. Convert that to the units of energy. I couldn't figure it out.

Hint: there's no such thing as a perpetual motion machine.

Feet/sec^2 would be acceleration - acceleration due to gravity. To get to energy, you'd need an object's mass and altitude; then energy would be height x mass (or weight...)

I've always wondered if you couldn't fill large balls with gas and release them down an open tube (gravity does most of the work) into the ocean and then open up the door and allow the ball to rise and use the difference in pressure to generate 'perpetual energy', not perpetual motion per se but it would be interesting experiment. You probably coun't get a lot of energy out of it for huge economies of scale but I wonder on a smaller basis if it would be worth it.

 

[Gibsons]

Originally posted by: Gannon

Originally posted by: bobsmith1492

Originally posted by: IHateMyJob2004
Try to figure out a way to have gravity be the driver for a perpetual machine.

I got stuck at this:
feet per second squared. Convert that to the units of energy. I couldn't figure it out.

Hint: there's no such thing as a perpetual motion machine.

Feet/sec^2 would be acceleration - acceleration due to gravity. To get to energy, you'd need an object's mass and altitude; then energy would be height x mass (or weight...)

I've always wondered if you couldn't fill large balls with gas and release them down an open tube (gravity does most of the work) into the ocean and then open up the door and allow the ball to rise and use the difference in pressure to generate 'perpetual energy', not perpetual motion per se but it would be interesting experiment. You probably coun't get a lot of energy out of it for huge economies of scale but I wonder on a smaller basis if it would be worth it.

Once it's full of water, you'll have to pump it out or remove the tube, whatever, mucho energy needed. Net loss. You could do something like this using tides, but that's not perpetual.

 

[Fallen Kell]

Originally posted by: QuantumPion

Originally posted by: bobdole369

Imagine a very tall U-shaped container, one side filled with fresh-water and the other with salt-water. The bottom is separated by a reverse-osmosis filter, and the top ends of the tube are touching with a lid. The containers are tall enough such that the weight of the water provides sufficient pressure for the reverse-osmosis process to occur. Since salt-water is denser then fresh-water, its level will be lower then the fresh-water given a fixed system volume. As the salt-water passes through the filter, the level of the fresh-water side rises, causing the excess to spill back over into the salt-water side, thus forming a self-sustaining flow loop from which work can be extracted.

isn't that how ocean currents basically work?

ocean currents aren't perpetual motion, they are powered by thermal energy from the sun.

this idea is a real perpetual motion machine, as it extracts useful work based only on density differences between two fluids in a gravitational field.

the osmosis machine wouldn't work in reality but its fault is subtle and hard to catch

Not really. Since the Fresh water is less dense than the salt water, the fresh water that is pouring onto the top of the salt water will simply pool at the top and not mix in to the denser water below it without external agitation. Thus the entire system will grind to a halt once the density of water on the one side of the filter decreases to the point where it does not have enough force to push through the filter (or the tops of the two containers spillover and thus the gradual contamination of the fresh water side with salt water could also occur).