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Author Topic: Magnetic shield by use of a second magnet - A better way I think.  (Read 13579 times)

Low-Q

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Hi,

I hope you guys can look into this idea. The idea is to cancel a magnetic attraction or repell by using another magnet. I have some screenshots from the FEMM which I hope you will understand. The polarity is marked with small arrows inside the magnets.

In the first picture I show you how to cancel a magnetic influence by using two magnets close to eachother, but where the magnetic field points in opposite directions. The following examples are not fully correct, as I should have made them in 3D, but i will try to explain.


NOTE: The small magnets are magnetized horizontally with opposite directions, and the big magnet is magnetized vertically (north up). The big magnet is in the foreground, and the small ones are in the background.

Take the first picture "Cam-magnet-array-1"

The two magnets at the left side are suppose to be at the same distance from the big magnet at the right side, so you don't get confused about which magnets at the left side is most affected by the big magnet at the right side.

The big magnet does not see neither a south or a north pole from the small magnets. So there is no attraction between them, other than the attraction to the magnetmaterial itself.


In the picture "Cam-magnet-array-2", the two magnets on the left has slide apart vertically because they are locked horizontally. Now the big magnet will attract to respectively north and south, and wants to go to the left.


In the picture "Cam-magnet-array-final" I have made several small magnetsetups. As the big magnet X is moving to the left, a pushrod is forcing magnets in B together. This takes a huge amount of energy. However, the magnets in C are sliding apart with the same force. As both B and C are linked, it should not require energy to slide them in one direction or the other.

Now, A and B is attracting, and C and D is repelling the big magnet. This will force the big magnet to go to the left. Look close to this final picture, and see that the small magnets are not sliding across eachother, so the first of the two small magnets will allways be located in center or below - the opposite with the second magnet.

The sliding movement in the small magnets are suppose to be angular to the magnetic field from the big magnet. So there should not be any force from the big magnet to prevent these magnets to slide up and down. The idea is then to keep the directional force between the small magnets and the big one, and at no cost make an attracting magnet to the left, a neutral magnet in the middle, and a repelling magnet at the right side. NOTE: Each small magnet pair is suppose to act like one magnet that is altering in magnetic flux, just by sliding apart and together.

Those big green arrows in the last picture is the direction of movement of the magnets as the big magnet moves to the left.

I know I'm not a good "explainor", so please ask if there is anything unclear. For those who understand this, please let me know your thaughts.

Vidar

lumen

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #1 on: July 02, 2009, 12:56:32 AM »
I have been doing some testing along these lines and have found some unusual results. I have new magnets ordered to build a test device that previous testing has shown would be OU.
Of all the test setups I have done, only one other has shown any indication of OU, but this expanding magnet concept does show some unusual results.



lumen

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #2 on: July 02, 2009, 01:26:44 AM »
Could you also try your FEMM with the small magnets in attraction to each other?
You could achieve the same results without depleting the fields.
 

Low-Q

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #3 on: July 02, 2009, 08:27:21 AM »
Could you also try your FEMM with the small magnets in attraction to each other?
You could achieve the same results without depleting the fields.
You mean to test it when all the small magnet pairs are magnetized in the same direction, but still having the sliding function? And no change to the big magnet?

My idea was initially to use a magnetic field to attract another magnet, then collaps the magnetic field with the sliding function, and by the same function determine when and where the magnetic field reoccoured behind the big magnet.

My first thoughts about your request, is that the magnetic field will allways be present, and detected by the big magnet...I guess then you now will have a sticky spot somewhere, and in addition the big magnet will attract at the top, and repell at the bottom - forcing it to align horizontally with no movement sideways.

I'll do some simulations, so we'll see.

Vidar




broli

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #4 on: July 02, 2009, 09:56:27 AM »
Thanks for sharing. You idea seems interesting,
 
 I believe you have to watch out for the height of the big magnet. If it's too long it might not attract too good, even worse it might start repelling. It should be at all times be smaller than the "virtual" magnet you create by those two magnets. In most ideal cases it should be a very very short magnet almost being a single dipole. That way you're sure the attraction will win.

I also don't understand why you're using 2 sets of magnets. You can use a single set to attract and repel. At TDC the magnets should keep on moving which will cause the big magnet to repel.
 

onthecuttingedge2005

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #5 on: July 02, 2009, 11:34:49 AM »
Why don't you use the Halbach array

http://www.ian.org/Magnetics/Halbach_Arrays.html

you can add magnetic shielding as well to decrease the field even more on the sides and the back.

Jerry ;)

Low-Q

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #6 on: July 02, 2009, 12:15:19 PM »
Thanks lumen, broli and thecuttingedge2005. I will take time to simulate your ideas. I also will simulate an alternative idea I got, where all forces work with me. I must admit I'm a little exited :)

Low-Q

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #7 on: July 02, 2009, 02:36:59 PM »
Thanks for sharing. You idea seems interesting,
 
 I believe you have to watch out for the height of the big magnet. If it's too long it might not attract too good, even worse it might start repelling. It should be at all times be smaller than the "virtual" magnet you create by those two magnets. In most ideal cases it should be a very very short magnet almost being a single dipole. That way you're sure the attraction will win.

I also don't understand why you're using 2 sets of magnets. You can use a single set to attract and repel. At TDC the magnets should keep on moving which will cause the big magnet to repel.
 
The reason why I use two sets, is because it should simulate a chain of these sets. Let's say all these sets are arranged circular, and a mechanism is arranging the magnets together where the big magnet is present so we can avoid a sticky spot. It can be hundreds of these sets, but also arranged tighter so the result will be a more uniform north and south pole the big magnet can attract or repel. If this big magnet is rotating and passes over these small magnet sets, and a mechanism will force the magnetsets together right in front of, and release the magnetsets behind the big magnet, the big magnet will allways attract in front and repel behind it without having a sticky spot that will stop the big magnet from runnig.

The question that remains is if there is the same energy spent to force the magnetsets together as the very same magnetset gets back when releasing (and expanding) again. Without the big magnet present, these two energies should be equal and cancel eachother out perfectly. However, in this case where the big magnet IS present, there will be a different event in front of the big magnet and behind it. So maybe that will be the dead end of this design. I don't know yet, but as you said, the shape and size of the big magnet will affect how the magnetsets will behave, and how they again affects the big magnet.

A different design of the big magnet might be a better solution. I'll see what I figure out.

Vidar

lumen

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #8 on: July 03, 2009, 04:09:24 AM »
The concept I have been testing is very close to Low-Q's design, with a few differences.
The testing at this point shows an energy gain of about 15%. The configuration had about the same gain using two different testing methods and I still can't believe it is really there.
I have some new magnets coming that should be even better for this process and if I can get the (what appears to be gain) up to over 20%, I will attempt to build a magnet motor based on this principal.
Anyway this is the concept I posted earlier in another thread but thought I would post again because it is so close to Low-Q's concept.




onthecuttingedge2005

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #9 on: July 03, 2009, 07:28:31 AM »
I think the "shielded Halbach array" is the closest you would get to creating a monopole effect with minimal field on the sides and the back. it is quite possible that nature itself provides such a Halbach array effect but in what material naturally.

Jerry ;)

Low-Q

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #10 on: July 03, 2009, 09:29:21 AM »
@lumen
In the example with magnet A and B upon eachother, the field from magnet C will be affecting magnet A as well as magnet B. So when you move magnet A to the right, it must fight against magnet C, because magnet C, which wants to go to the right is virtually going to the left when you move magnet A to the right. This energy, in fact a little bit less, is taken back when magnet C is moved to the new center. When you then move magnet A back, the rest of the energy is taken back. So left you have not gained anything.

That is my theory anyway. Because, if magnet C is forced to the left as soon as you move magnet A to the left, there simply must has been spent more energy to move magnet A than it takes to move it without the presence of magnet C.

Vidar

Low-Q

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #11 on: July 03, 2009, 10:11:20 AM »
I think the "shielded Halbach array" is the closest you would get to creating a monopole effect with minimal field on the sides and the back. it is quite possible that nature itself provides such a Halbach array effect but in what material naturally.

Jerry ;)
With a Halbach array you'll get two poles on one side, so you will allways end up with at least a dipole with both north and south. However, this array is interesting anyway, because you can shape the magnetic field to look like a monopole. But even if it looks like a monopole, it will not be able to push the uniform magnetic field in one direction to achieve force, as you will do with a wire in which a electric current is flowing and creates this circular magnetic field. That wire will move, but not the Halbach array. So back to the drawing board :)

Vidar

lumen

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #12 on: July 03, 2009, 03:38:00 PM »
Low-Q
Quote
when you move magnet A to the right, it must fight against magnet C, because magnet C, which wants to go to the right is virtually going to the left when you move magnet A to the right.

That is not actually what happens.
It is actually more like this:
Magnet C is moved into the center of what looks to be one magnet, then magnet A is moved expanding the magnet, leaving magnet C off center at a point of higher energy. Magnet C actually helps push magnet A to the new position because it is N to N.  The measured energy used to move magnet A is very close to moving A without C present.
The energy left in magnet C is 15% higher than what it took to move magnet A!

You think you could simulate this on FEMM?

Low-Q

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #13 on: July 03, 2009, 11:26:34 PM »
Low-Q
That is not actually what happens.
It is actually more like this:
Magnet C is moved into the center of what looks to be one magnet, then magnet A is moved expanding the magnet, leaving magnet C off center at a point of higher energy. Magnet C actually helps push magnet A to the new position because it is N to N.  The measured energy used to move magnet A is very close to moving A without C present.
The energy left in magnet C is 15% higher than what it took to move magnet A!

You think you could simulate this on FEMM?
I have done some simulations in big scale.

 Magnet C (N-S) feels a force to the right when it's close to magnet A and B (S-N). This force is approx 1300N in my simulation. Magnet A are forced to the left with about 600N - magnet B approx 700N.

Now I slide magnet A to the right so I have two full lengths. Now the force in magnet C is about 580N to the right.

Now I slide magnet C to the right so it fits in the middle if the new A-B positions. The force on magnet C is now 480N to the right.


Did this help you out? Clearly that magnet A must fight against a force in addition to the force from magnet B.

Vidar

lumen

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Re: Magnetic shield by use of a second magnet - A better way I think.
« Reply #14 on: July 04, 2009, 01:45:25 AM »
Thanks Low-Q for doing a simulation for me.

I was wondering how a simulation would compare to actual data taken along the same paths.
The actual data taken at .05" increments shows moving A with or without C present, to have nearly no difference.

It's interesting how the simulator does not seem to take into account that magnet A's N field is totally consumed into magnet B and should have no effect from magnet C. If magnet C had any connection to magnet A, it could only be to the back side of A and it would be the opposite field and should be pushed the opposite direction.

It seems to be right after both magnets A and B are separated and act as one longer magnet.

Thanks again for the interesting info.