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Author Topic: A bunch of questions regarding radially magetized ring magnet.  (Read 4130 times)

Offline PolaczekCebulaczek

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I'm interested with this kind of magnet geometry (for my generator project but not OU) and have some questions:

1.Is such magnet even possible to make at home? how to magnetize a ring like this?
2.Would such magnet loose it strength overtime?
3.How field lines would look like?
4.Compass inside the ring, would compass point in any fixed direction?
5.What if compass is not positioned in exact center of the ring, would it make any difference?
5.Can I induce current in coil when ring rotates? (coils inside/outside, near edge of ring)


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Offline gyulasun

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #1 on: August 11, 2017, 10:06:12 PM »
Hi,

Some answers:

1) Of course I cannot know your technical knowledge and means, no offense but I do not think that an average experimenter could make such magnets at home.  I mean in general, for any magnet shape.
2) The direction of magnetization is not known to define long term strength stability for permanent magnets that are manufactured correctly.
4) Yes, but the length of a compass needle would be important to consider, say the length of the needle is less than the thickness of the ring: I may be wrong but it would stay put in axial direction when put in the exact center (axle) line of the ring
5) Then it would turn towards the direction of the stronger pole at an angle which would come from the difference between the attract-repel forces ruling between the needle_ends and the inside pole of the magnet wall.
6) Well, not much at all because inside and outside the flux does not change much when such ring magnet would be rotated

Imagine your ring is placed flat onto the surface of the table as if it would be a cake and you cut it up to some pieces radially as cakes are normally cut.  You may wish to consider assembling such ring from some pieces of arc or trapezoid magnet shapes that has the correct and same direction of magnetization. Of course you need to create a strong hardware, a hoop, to keep the repel pole magnets next to each other in a safe position. 

I mention this because arc shaped or trapesoid magnets are not rare nowadays, after some search I found these:

http://www.greatmagtech.com/product_cat_list/Arc-Neodymium-Magnets-c21616/0/45.html and this shape for example:
http://www.greatmagtech.com/products_info/Arc-magnet-with-countersunk-hole-generator-magnet--335493.html 

Or   https://www.magcraft.com/arc-magnets 

Of course you can also search with such keywords like 'arc' or 'trapezoid' or 'special' shaped magnets.
I have no any affiliation with any of the manufacturers...  ;D

There would be another option for you. I know that most manufacturers gladly make such magnets for you but the cost can go skyhigh for the so called custom orders they force the buyers into by saying to pay for special tools etc.  At least  this has been so for years but maybe you can have some luck by seeing these free sample offers (probably for relatively small sizes) and the shipping should only be paid for.  See this link where even a single quantity, 1 piece radially magnetized ring magnets are offered:
https://www.alibaba.com/showroom/radial-magnetization-ring-magnet.html 

They call such magnetization direction for rings as radially magnetized or even uni-pole magnets.

Perhaps it would be worth for you to choose a few offers and write them with your needed magnet sizes, perhaps they would be willing to make it for you a single piece for free or at a minimal price and you pay only for the shipping what you can select as 'by Sea' too. 

Gyula


Offline PolaczekCebulaczek

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #2 on: August 12, 2017, 04:37:46 PM »
Hi,

Some answers:

1) Of course I cannot know your technical knowledge and means, no offense but I do not think that an average experimenter could make such magnets at home.  I mean in general, for any magnet shape.
2) The direction of magnetization is not known to define long term strength stability for permanent magnets that are manufactured correctly.
4) Yes, but the length of a compass needle would be important to consider, say the length of the needle is less than the thickness of the ring: I may be wrong but it would stay put in axial direction when put in the exact center (axle) line of the ring
5) Then it would turn towards the direction of the stronger pole at an angle which would come from the difference between the attract-repel forces ruling between the needle_ends and the inside pole of the magnet wall.
6) Well, not much at all because inside and outside the flux does not change much when such ring magnet would be rotated

Imagine your ring is placed flat onto the surface of the table as if it would be a cake and you cut it up to some pieces radially as cakes are normally cut.  You may wish to consider assembling such ring from some pieces of arc or trapezoid magnet shapes that has the correct and same direction of magnetization. Of course you need to create a strong hardware, a hoop, to keep the repel pole magnets next to each other in a safe position. 

I mention this because arc shaped or trapesoid magnets are not rare nowadays, after some search I found these:

http://www.greatmagtech.com/product_cat_list/Arc-Neodymium-Magnets-c21616/0/45.html and this shape for example:
http://www.greatmagtech.com/products_info/Arc-magnet-with-countersunk-hole-generator-magnet--335493.html 

Or   https://www.magcraft.com/arc-magnets 

Of course you can also search with such keywords like 'arc' or 'trapezoid' or 'special' shaped magnets.
I have no any affiliation with any of the manufacturers...  ;D

There would be another option for you. I know that most manufacturers gladly make such magnets for you but the cost can go skyhigh for the so called custom orders they force the buyers into by saying to pay for special tools etc.  At least  this has been so for years but maybe you can have some luck by seeing these free sample offers (probably for relatively small sizes) and the shipping should only be paid for.  See this link where even a single quantity, 1 piece radially magnetized ring magnets are offered:
https://www.alibaba.com/showroom/radial-magnetization-ring-magnet.html 

They call such magnetization direction for rings as radially magnetized or even uni-pole magnets.

Perhaps it would be worth for you to choose a few offers and write them with your needed magnet sizes, perhaps they would be willing to make it for you a single piece for free or at a minimal price and you pay only for the shipping what you can select as 'by Sea' too. 

Gyula

Thank you such much!

well, it's quite tricky to magnetize a ring magnet like that using coil or another magnet(I don't know how...yet)
Is this a correct picture of field lines?

Offline gyulasun

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #3 on: August 13, 2017, 11:36:00 AM »
....
Is this a correct picture of field lines?

Hi,

Yes, for a six-pole radially magnetizatized ring it is correct.
The N and S poles alternate within the inside area (or space) as seen in the drawings here
for instance: http://www.aomagnet.com/radial-ring-magnets-c-19/  while for a unipole ring there is a single pole
(say South) in the total inside diameter area or space of the ring and the opposite single pole (the North)
on the total outside surface and nearby space of the ring.

Here in this link you can see some more field line distributions that includes the fields of unipole
ring magnets too (unfortunately their picture is rather small and blurry):
http://www.jjmagnet.com/f_products1.htm

In this pdf file you can see a clear picture on the fields of a unipole ring magnet as compared to a multipole ring:
http://www.aicengineering.com/files/2014328143328.pdf I copied this picture from the pdf file, see attached.   

Finally here is a large sized hence rather expensive (OD=70 mm) unipole radially magnetized ring magnet
with its nearly homogeneous South field inside and all North field outside:
http://www.materialhandlingzone.biz/product/aomag-uni-pole-radial-oriented-magnetization-neodymium-large-ring-magnets-diametrically-magnetized-od-70-x-id-62-x-20mm/   
 
Gyula
« Last Edit: August 13, 2017, 06:12:23 PM by gyulasun »


Offline phoneboy

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #4 on: August 13, 2017, 04:02:14 PM »
@ PolaczekCebulaczek, this was just an untried method I had come up with to try for a design I had.  I had read about people making weak magnets by heating iron and allowing it to cool oriented in the earths magnetic field, so I wondered if I could do something similar with a ferrite ring.  The idea was to make a two part mold as if i were going to cast a part.  You would need some wood, sand, sodium silicate, a co2 source, a ferrite ring magnet, and copper wire for the flat coils.  Once the form was made for the ring and the coils,  the magnet would be placed in an oven and the temp raised to past its curie point.  The ring would then be placed back in the form and the coils energized while the ring slowly cooled, hopefully reorienting the domains and creating a reasonably strong radial magnet.  See old vizimag pic for ref.

Free Energy | searching for free energy and discussing free energy

Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #4 on: August 13, 2017, 04:02:14 PM »
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Offline PolaczekCebulaczek

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #5 on: August 14, 2017, 12:33:31 AM »
Gyula thanks for pdf file, so in radially magnetized ring/unipole magnet there are almost no field lines extending , fascinating...

phoneboy your idea sounds interesting but I'm not sure if I understand the picture correctly, you meant something like this:

so two opposing poles-coils should produce N N outside and S S in the middle of the ring?

here is a method to make magnet using pancake coil but I cant see why this should work.

http://overunity.com/6856/how-to-simply-make-a-radially-magnetized-magnet-a-2d-magnetic-monopole/




Offline phoneboy

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #6 on: August 14, 2017, 02:26:32 AM »
This might help more, whipped up an image of the top half of the mold with the coil placed and the ring.

Free Energy | searching for free energy and discussing free energy

Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #6 on: August 14, 2017, 02:26:32 AM »
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Offline gyulasun

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #7 on: August 14, 2017, 12:36:30 PM »

Gyula
thanks for pdf file, so in radially magnetized ring/unipole magnet there are almost
no field lines extending , fascinating...
.....


Your statement is misunderstandable how you mean so let me tell: field lines do extend
from an unipole ring magnet but the green viewing foil shown in pictures are somehow
mask them, not good quality pictures for unipole example, unfortunately. 
Magnetic lines of flux surely come out from the body of such ring magnets, especially
at the edges where the perpendicular sides meet but of course at the in-between surfaces too. 

You can imagine this when you consider a long rectangular bar magnet, magnetized length wise,
the lines of flux extend from mainly at the ends in quasi every direction from that 'uni pole' 
a long enough bar magnet has at its ends. 
In case of such radially magnetized ring magnets the smallest number of flux lines that extend
or come out from them can be found in the virtual center circle of their thickness.  (for a long bar
magnet this area can be found in the center or the middle of the full length as you surely know)

Gyula

Offline PolaczekCebulaczek

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #8 on: August 15, 2017, 07:26:50 AM »
phoneboy thank for 3d picture now I understand, NN poles would meet inside the ring and SS outside the ring.

gyulasun soo in very center of the ring there should be no magnetism ? (due to repulsion?) if I put a compass in exact center of the ring and if needle is not reaching field lines then the compass should point only to magnetic field of the earth, right??




Offline gyulasun

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #9 on: August 15, 2017, 07:07:11 PM »
...
gyulasun soo in very center of the ring there should be no magnetism ? (due to repulsion?)
 if I put a compass in exact center of the ring and if needle is not reaching field lines
 then the compass should point only to magnetic field of the earth, right??

No offense but I did not write, did not mean or did not imply that there is no magnetism in the
very center of a radially magnetized ring magnet.
Read my posts again, perhaps there is some language barrier?

Consider the following setup: you have say 4 identical bar magnets, each 5cm long, with 5x5mm
cross section, magnetized length wise. Say you fix these magnets onto a CD disk at 12, 3, 6 and 9 o'clock
positions so that their North pole ends point radially towards the disk center and each magnet North end is say
2 cm away from the very center point of the disk. Now try to increase in theory the number of bar
magnets you would also place radially to fill up all the space and get a radially magnetized ring
magnet that would have an OD of 7+7cm and an ID of 2+2cm, ok?

Now ask yourself: can the very center point or line of this setup free of magnetism?

My answer is no. There must be magnetism in the very center too. Very probably the strength of the
North pole fields in the very center is the smallest but not zero compared to any other point within
the virtual 2cm+2cm inner diameter area of this setup.

Generally speaking, maybe there are no lines of flux in some very narrow area between two
facing like poles (think of two block magnets in this example now) that are pushed together with a
strong force: the lines of flux are said to be pressed out from within the nearly or fully touching facing
surfaces of the two like poles BUT this is not an equivalent example to be compared to the very center of
a radial ring where there is always the 'distance' of just the inner ring diameter between any facing
like poled points, ok? And like poles cannot fully cancel within the inner diameter of a radial ring:
the squizing-out force of the like poled lines of force present in the ID area or space of the ring is not
enough to sweep them all out.

Now imagine that you have a radially magnetized ring magnet with an ID of say 5 cm, with an OD of say
7 cm and the thickness or height of such ring would be say 6 cm. If you could place a say 3 cm long
compass needle into the exact center line of this ring magnet, then I think the compass would stay in the
very center line.
A better example would be: instead of the compass you would use a say 3 cm long cylinder magnet
that would have an OD of say 2mm and would be magnetized length wise, then this cylinder magnet
would also stay in the very center line I think.

Hope this explains and puts an end for your dilemma... If still in doubt, please try to assemble such
radial ring magnet setup from cheap ceramic block magnets magnetized lenght wise and check it.

Gyula

Free Energy | searching for free energy and discussing free energy

Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #9 on: August 15, 2017, 07:07:11 PM »
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Offline Magluvin

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #10 on: August 15, 2017, 07:19:17 PM »
Ive looked for radially magnetized rings and only found these so far.

You would think they could magnetize a ring radially just by having one part of the magnetizing core in the inner radius and the other end of the magnetizing core on the outer radius. But so far i only see pies. magpies.

https://supermagnetman.com/collections/neodymium/products/rr0100n?variant=11410371011

https://supermagnetman.com/collections/neodymium/products/rr0090n?variant=11410370819

Mags

Offline gyulasun

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Offline PolaczekCebulaczek

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #12 on: August 15, 2017, 10:32:07 PM »
gyulasun ok I understand now, thank you for better explanation, you are right about repulsion however if the ring is wide enough there should be no magnetism in the center because filed lines wont reach that far?

and my last stupid question, how such magnet can be used as generator? I have one (from speaker) and only when I move coil (coil is inside the ring in vertical position) or magnet up and down then current is generated, is there any other method ?

Offline gyulasun

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #13 on: August 16, 2017, 12:47:55 AM »
gyulasun ok I understand now, thank you for better explanation, you are right about repulsion however
if the ring is wide enough there should be no magnetism in the center because filed lines wont reach that far?
 

What do you mean on wide?
IF you mean that the inner diameter of a radially magnetized ring magnet is high enough, then yes
the magnetic field strength should be at a very low level in the very center axis line of the ring.
IF you mean something else on wide then I do not understand your question, try to put it otherwise.

Quote
and my last stupid question, how such magnet can be used as generator? I have one (from speaker)
and only when I move coil (coil is inside the ring in vertical position) or magnet up and down
then current is generated, is there any other method ?

Sorry to ask but are you sure your speaker magnet is magnetized radially? 
Because most speaker magnets are magnetized through their thickness i.e. axially:
one of their flat surfaces is say North and the other flat surface is the South pole.

This would explain your current induction in a coil moved axially through the center line of the your magnet.
If your ring magnet would be indeed radially magnetized, the induction would be at a minimum level
when you move a coil in it as you described. I am not saying there would be no induction in it but it would be
rather small compared to a similar sized and strong ring magnet magnetized axially like most speaker magnets.

Is your speaker magnet made of ferrite i.e. ceramic? By the way, you can check very easily how the poles
are made for your speaker magnet by a compass. Did you check it?  Is your speaker magnet magnetized
radially indeed like your drawing shows for a radial ring in your first post above.
In attachment below I included an axially and a radially magnetized ring magnet drawing.

Of course I am not saying your speaker magnet cannot be a radially magnetized ring magnet, in this case
you have to find the best coil-ring magnets arrangement to utilize it in a generator.
I think however that with multipole radial ring magnets you could get higher output
versus an unipole one of same size and strength.

Gyula


Offline PolaczekCebulaczek

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Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #14 on: August 16, 2017, 03:54:40 PM »
Quote
Sorry to ask but are you sure your speaker magnet is magnetized radially?
Because most speaker magnets are magnetized through their thickness i.e. axially:
one of their flat surfaces is say North and the other flat surface is the South pole.

You are right, I just did some better tests and I found that my magnet is magnetized axially :(

Quote
What do you mean on wide?


yes by wide I meant inner diameter, big hole.

Quote
IF you mean that the inner diameter of a radially magnetized ring magnet is high enough, then yes
the magnetic field strength should be at a very low level in the very center axis line of the ring.

yet compass needle(that can't reach magnet field lines would still point to earth pole?

I will buy some magnets online meanwhile can you tell me which of (7) induction methods would generate current when coil or magnet rotate.(I know that some of the configurations have 0 difference between then when we consider induction law but I just want to be 100% sure)

Free Energy | searching for free energy and discussing free energy

Re: A bunch of questions regarding radially magetized ring magnet.
« Reply #14 on: August 16, 2017, 03:54:40 PM »

 

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