Curious device

[Prajna]

10 minutes ago, sethoflagos said:

Pretty sure there's a x-post here with @exchemist so briefly:

If we're starting from your declared position of maximum attraction, we're moving against an attraction force for 90⁰; then with a weakened repulsive force (poles wide apart); then against the same repulsive force; then finally with the mirror image of the attraction of the initial power stroke.

In the absence of a proper mathematical analysis, by symmetry we have a nett zero sum. 

And then there's cam friction and the hysteresis braking mentioned earlier.

Granted I've ignored secondary effects of the movement of the magnets themselves but frankly, that's beyond my pay scale.

Suffice to say, if there was anything to see here, Faraday would have found it back in the day I think.

Looks right enough, so you've got the 180⁰ phase shift covered. Shall we leave the +/-90⁰ phase shifts to the OP?

Excellent analysis, both of you.  Sorry, I have no more reaction points available today or you'd both get a +1. This is exactly what I came here to explore. All I have to do now is re-read both comments carefully to make sure I understand. Thanks.

[Mordred]

6 hours ago, Prajna said:

Excellent analysis, both of you.  Sorry, I have no more reaction points available today or you'd both get a +1. This is exactly what I came here to explore. All I have to do now is re-read both comments carefully to make sure I understand. Thanks.

I gave them the +1 each for you.

[Prajna]

10 minutes ago, Mordred said:

I gave them the +1 each for you.

Thank you. Anyway, I hope there's nothing stopping me being able to do it tomorrow.

[Mordred]

1 minute ago, Prajna said:

Thank you. Anyway, I hope there's nothing stopping me being able to do it tomorrow.

No you get a daily allotment 

[Prajna]

2 minutes ago, Mordred said:

No you get a daily allotment 

There were very helpful comments today.

[Mordred]

6 minutes ago, Prajna said:

There were very helpful comments today.

Hence why I stopped adding to the mix. Once I saw you were progressing from their comments I didn't want to add any potential confusion. Threads can get too easily derailed.

[swansont]

Just FYI, the energy density of the earth’s magnetic field is about a millijoule per cubic meter. Scale up as necessary for a stronger magnet. The energy for doing stuff with magnets is not contained in the magnetic field.

https://brainly.com/question/17055580

[exchemist]

21 minutes ago, swansont said:

Just FYI, the energy density of the earth’s magnetic field is about a millijoule per cubic meter. Scale up as necessary for a stronger magnet. The energy for doing stuff with magnets is not contained in the magnetic field.

https://brainly.com/question/17055580

That's interesting. I had always understood that magnetic fields have energy, as for example in the stored energy in an energised electromagnet. If they do not, where does the energy come from when an object moves towards another under the influence of magnetic attraction? And you yourself say a magnetic field has an energy density. 

 

Edited April 19 by exchemist

[Prajna]

15 hours ago, exchemist said:

That's interesting. I had always understood that magnetic fields have energy, as for example in the stored energy in an energised electromagnet. If they do not, where does the energy come from when an object moves towards another under the influence of magnetic attraction? And you yourself say a magnetic field has an energy density. 

 

Sorry to have been quiet, I've been redoing my animation to better represent movement (or approximated movement) in the device. @exchemist, I do hope to ask for some more detail regarding your analysis, particularly regarding what you consider as Stroke 4 in your analogy. @sethoflagos, I am also interested to explore hysteresis further to estimate what part it plays in the dynamics of the device. @swansont, thanks for the further response. It seems to me that you make bare assertions, such as, "Magnets don't do work" and the above, "The energy for doing stuff with magnets is not contained in the magnetic field." Now, most likely you are right and it just remains for us to research deeply enough to understand your assertions but it would be much more helpful if you would offer some explanations to go along with your assertions. Thank you.

[exchemist]

33 minutes ago, Prajna said:

Sorry to have been quiet, I've been redoing my animation to better represent movement (or approximated movement) in the device. @exchemist, I do hope to ask for some more detail regarding your analysis, particularly regarding what you consider as Stroke 4 in your analogy. @sethoflagos, I am also interested to explore hysteresis further to estimate what part it plays in the dynamics of the device. @swansont, thanks for the further response. It seems to me that you make bare assertions, such as, "Magnets don't do work" and the above, "The energy for doing stuff with magnets is not contained in the magnetic field." Now, most likely you are right and it just remains for us to research deeply enough to understand your assertions but it would be much more helpful if you would offer some explanations to go along with your assertions. Thank you.

Yes, it would be good to understand exactly what @swansont means. I suspect it may be the simple point that a magnetic grab, once it is clamped onto an object, does no work when the crane lifts said object.

However, when a permanent magnet on a table top draws a nail towards it, against the force of friction, work is clearly done. That work, it seems to me, must be drawn from stored energy in the magnetic field. 

[Prajna]

Here is the updated animation. I have modified the cam groove so that it matches the cam pin movement and generally improved the animation so that it is smoother and less glitchy.

 

[swansont]

2 hours ago, Prajna said:

Now, most likely you are right and it just remains for us to research deeply enough to understand your assertions but it would be much more helpful if you would offer some explanations to go along with your assertions. Thank you.

You should open up a thread to ask questions. People could answer, or point you toward sources that would explain it. Of course, you could also pick up a physics textbook. You’d eventually find that a changing B field creates an electric field, and that can do work, and also that the energy in the magnetic field is fairly small, and is not the source of the energy. 

I’m explaining that the work in your device comes from whatever turns the rotor, not the magnets (which are just a substitute for a mechanical coupling, which would also not be doing work). You even acknowledge this, when you agreed that this device would not run on its own. Someone has to turn the crank. That’s where the energy comes from.

[Prajna]

4 minutes ago, swansont said:

You should open up a thread to ask questions. People could answer, or point you toward sources that would explain it. Of course, you could also pick up a physics textbook. You’d eventually find that a changing B field creates an electric field, and that can do work, and also that the energy in the magnetic field is fairly small, and is not the source of the energy. 

I’m explaining that the work in your device comes from whatever turns the rotor, not the magnets (which are just a substitute for a mechanical coupling, which would also not be doing work). You even acknowledge this, when you agreed that this device would not run on its own. Someone has to turn the crank. That’s where the energy comes from.

Well your expertise is (probably) physics and mine is more geared towards engineering. I could divert my attention to studying physics but really my interest is in approaching this from an engineering point of view. If you can help me to understand how the energy exchanges occur in this device, preferably in simple terms, then I will be very happy for that. I can understand any frustration you might have in dealing with a physics-naif who could resort to studying physics rather than asking questions the answers to which might be obvious and intuitive to one with a deep understanding of physics. I hope you will at least admit that this device presents an interesting problem of analysis and the energy exchange is far from obvious (to most people anyway and, I guess, even to some physicists).

[swansont]

46 minutes ago, Prajna said:

I hope you will at least admit that this device presents an interesting problem of analysis and the energy exchange is far from obvious

You’ve not shown a working device, only animations, so who is to say there is an energy exchange? I’m not convinced it will work as advertised.

[Prajna]

21 minutes ago, swansont said:

You’ve not shown a working device, only animations, so who is to say there is an energy exchange? I’m not convinced it will work as advertised.

True enough, it is only an animation, perhaps even a simulation though not necessarily accurate. I'm not sure I have advertised it in any particular way apart from being a curiosity. As a thought experiment surely I have presented enough to spark a discussion on (at least hypothetical) energy exchange. Thanks for continuing with your attention and thoughts.

[swansont]

1 hour ago, Prajna said:

As a thought experiment surely I have presented enough to spark a discussion on (at least hypothetical) energy exchange.

Energy goes in through the input, and some smaller amount goes out through the output.

You might note that after my initial commentary I stopped until there was an suggestion that this was an over-unity device; i.e. that stronger magnets would increase the power output in some way other than just reducing losses, and that turning the input rotor was not the source of energy in the device. 

You agreed that the system will not run on its own. These are contradictory statements.

[Prajna]

5 minutes ago, swansont said:

Energy goes in through the input, and some smaller amount goes out through the output.

You might note that after my initial commentary I stopped until there was an suggestion that this was an over-unity device; i.e. that stronger magnets would increase the power output in some way other than just reducing losses, and that turning the input rotor was not the source of energy in the device. 

You agreed that the system will not run on its own. These are contradictory statements.

You might note that an electric motor will not run until you flick the switch. Although it doesn't take much energy to flick the switch and the real energy that is running the motor comes from the power supply that switch needs to be turned on for it work. Here the operator is turning the rotor, effectively just switching fields in the magnet array, rather than any direct application of force to the rockers, which are what send work to the output. You may well understand how the linkage operates between the switching of the fields and output from the fields (and, apparently, the inviolable recovery of energy back into the field to balance it, if that is what happens) but it's far from clear to me. It seems to me that the connection is via magnetic attraction and repulsion of the switched magnets and by eddy current drag on the rotor tabs or fingers, but quite how that connection operates and how to begin to analyse it is beyond my current knowledge. If you can help me towards an understanding of that then I will be delighted. Leave aside any thought of it being any kind of perpetual motion/free energy/overunity device and look at it as just a transmission system: how is the work done on the rotor translated into work done on the output? You might like to analyse it in terms that a fellow engineer on the welding forum I frequent observed, "That's a very complicated system for what is effectively a brake."

I particularly like the way @exchemist has approached analysing the device, I find it clear, logical and easy to relate to. Perhaps his specialisation is not physics but, for me anyway, I appreciate the way he has stated things.

[swansont]

26 minutes ago, Prajna said:

You might note that an electric motor will not run until you flick the switch. Although it doesn't take much energy to flick the switch and the real energy that is running the motor comes from the power supply that switch needs to be turned on for it work. Here the operator is turning the rotor, effectively just switching fields in the magnet array, rather than any direct application of force to the rockers, which are what send work to the output

A motor needs to be connected to a source of electricity, which provides the energy to run it. It’s not from anything stored in the wires.

[exchemist]

22 hours ago, swansont said:

You should open up a thread to ask questions. People could answer, or point you toward sources that would explain it. Of course, you could also pick up a physics textbook. You’d eventually find that a changing B field creates an electric field, and that can do work, and also that the energy in the magnetic field is fairly small, and is not the source of the energy. 

I’m explaining that the work in your device comes from whatever turns the rotor, not the magnets (which are just a substitute for a mechanical coupling, which would also not be doing work). You even acknowledge this, when you agreed that this device would not run on its own. Someone has to turn the crank. That’s where the energy comes from.

Right. But, to be clear, there is energy in the magnetic fields, which can be made to do mechanical work, for instance in my example of the nail being drawn towards a permanent magnet, against the force of friction with a table top.  

My attempt at analysing the operating cycle of this reciprocating machine was to show how energy is alternately drawn from and returned to the fields generated by the pair of opposed magnets, so the net effect, over one operating cycle, is as you say, no net work done by the magnets and a mere  transfer of input mechanical work to output mechanical work. 

Edited April 21 by exchemist

[swansont]

3 hours ago, exchemist said:

Right. But, to be clear, there is energy in the magnetic fields, which can be made to do mechanical work, for instance in my example of the nail being drawn towards a permanent magnet, against the force of friction with a table top.  

The energy is insufficient to do that, and that’s not the source of the work - the magnetic field does not get depleted by attracting something. As I’ve pointed out before, something is holding, pushing or pulling the magnet. The magnet is like a chain used to lift something; it exerts a force, but that’s not where the energy comes from.

[exchemist]

44 minutes ago, swansont said:

The energy is insufficient to do that, and that’s not the source of the work - the magnetic field does not get depleted by attracting something. As I’ve pointed out before, something is holding, pushing or pulling the magnet. The magnet is like a chain used to lift something; it exerts a force, but that’s not where the energy comes from.

If a nail is attracted towards a permanent magnet, doing work against friction, where does the energy come from?

[swansont]

1 hour ago, exchemist said:

If a nail is attracted towards a permanent magnet, doing work against friction, where does the energy come from?

Depends on the configuration, but one question to ask is how the nail and magnet got close enough for this to happen. Permanent magnets don’t turn on, and these objects don’t magically appear close enough to each other for this to happen.

[Mordred]

Just a reminder I did post the related mathematics using Maxwell equations to describe what Swansont is stating in this thread previously

[exchemist]

1 hour ago, swansont said:

Depends on the configuration, but one question to ask is how the nail and magnet got close enough for this to happen. Permanent magnets don’t turn on, and these objects don’t magically appear close enough to each other for this to happen.

I don’t think that matters. But let’s say it has been brought up from infinity (a concept physicists seem to like), held in place on the table and then released. Work is done against friction as the nail moves towards the magnet. What provides the energy?

[Mordred]

16 minutes ago, exchemist said:

I don’t think that matters. But let’s say it has been brought up from infinity (a concept physicists seem to like), held in place on the table and then released. Work is done against friction as the nail moves towards the magnet. What provides the energy?

The E field not the B field. Doesn't matter if it's a permanent magnet or an electromagnet it's still the same.

To help understand the permanent magnet if you look at inductance it does have both the E and B fields .

The reason why the B field has less energy and doesn't do the work involves how the field diverges as opposed to the E field coupled with the Lorentz force law via the right hand rule. That directly relates to Swnsonts previous statement with regards to the cross product for the B field as opposed to the inner product of the E field

Edited April 21 by Mordred