A bunch of questions regarding radially magetized ring magnet.

[gyulasun]

...
yes by wide I meant inner diameter, big hole.

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

Only in case the inner diameter of a radial ring is high (big) enough so that when
you approach this magnet with a compass alongside the ring's center line axis,
then the presence of the inner unipole field cannot influence the compass needle
any more. Likely sizes to experience this I speculate you would need an unipole ring
with inner diameter of say 20 cm and needle length say 2 cm.
Suppose the ring has an ID=12 cm only, then the same needle would surely be influenced
by the small center field of the unipole ring and the needle would not show
true Earth North pole any more due to the presence of a stronger than the Earth's field.

....
I will buy some magnets online meanwhile can you tell me which of (7) induction methods
would generate current when coil or magnet rotate.
...

No, I cannot, you need to explore that by doing tests.

Gyula

[Magluvin]

I was looking into them for my resonant pendulum using the speaker coils as drivers and pickups. These magnets if pushed back and forth in the coil would have very dense field passing through the coil, with small tolerance. If we look at a speaker motor, the magnet is sandwiched between 2 plates, the top plate with a hole in the middle and the bottom plate with a post in the middle that is just smaller in dia than the top plate hole so the magnets poles have a path of shortest distance at that pole gap, saying that all the field of the mag is concentrated there. Well I say not all and the field is not as dense as it is directly out of the face of the magnet.

So possibly the best induction with one of these magnets is to pass the mag through a coil that is just bigger than the mag dia. And to increase the flux get another ring mag that the other can fit into the larger ones hole with a gap for the coil. So now you have magnets on the outside and inside the coil. very dense field and all of the winding is induced, not just portions of it like in motors.

Then you can get another pair of those rings, with opposite poles of the first 2 and put them on axis near the first set and have another coil in that to generate also. The point is now you can put a rod core in the holes of the inner mags, which would link them magnetically, and an outer tube core to magnetically connect the outer diameters of the mags to close the magnetic loop, making the flux in the gap that much stronger.

Like a rod magnet, when it is just in open air, the fields at the poles faces are not as strong and or dense as they would be say per sq mm as it would be if the field had a core to use as a more direct path back to the other pole. So there is a flowering out of the fields from the poles making them less dense at the time. Probably the best reason why is that like polls repel, once it is out of the magnetic medium.  When a polarized field is in say an iron nail, the iron seems to neutralize the effect of the field wanting to flower out and repel its near by field of like polarity. Like they are attracted to each other when in the iron and the iron just may not be attracting the field, it may just be a medium that the fields issues with its close neighbor are negated and they can live together there in the iron. But once out of the iron they spread like a colony of bats out of a cave hole

So when we examine magnets by themselves the N pole is not just coming out of the face of the pole, some comes from around the sides on that half of the magnet and similarly at the S pole. When the fields come out of the face of the mag, they immediately start doing this i hate my neighbor thing, thus the spread of the field and that is translated within the magnet where they are being pulled away due to what is going on outside the magnetic medium.  So adding the path core to shorten the loops from N to S, then at the faces the flux gathering in the iron core in close proximity helps to make the pole face field denser and feel stronger.

So by adding the cores to the double dual ring mag gen, the field at the gap should be incredibly dense and strong, all making for a very efficient gen or motor, like a speaker.

Since standard speaker motors use a gap in between 2 cores that carry each mag fields to the coil gap, there is leakage that Im afraid hurts the field at the gap. Like if you look at most standard speaker motors the plates that capture the fields are a lot less volume of mass than the surface of the mags have to give. So as you can see by bringing a speaker near a crt, that field is leakin jim.    But if the coil is directly in the gap of 2 magnets instead and just use the cores as outer an center field looping, Id say the field in the gap would be a way better use of the field than the standard speaker motor which are pretty eff already as is.



mags

[triffid]

test,just wanted a link back to this thread.triffid

[Magluvin]

I was asked to clarify some things in my last post..

Normal speakers have axially mag poles and they use the top plate and the bottom pole plate to bring the fields of the magnet to the coil gap.

Where in my post I would like to try these radially magnetized magnets, a large ring and a smaller ring that fits the hole of the larger ring with space enough for the coil to move within, both with same poles in and same poles out, N out S in for example. I believe that the field between the 2 rings( inner S pole of the large ring and outer N pole on the inner ring) would have a denser field in the gap, rather than just making cores(top plate and bottom pole plate to basically carry the fields of the magnet to the gap. I think there is a lot of flux wasted that way due to leakage, like I said when you bring a speaker near a crt, that flux didnt make it from the magnet through the cores to the gap. So I would like to reverse that and make the coil gap with the actual pole faces of the mags, where the inner ring is attracted to the outer ring, and then the inner rod core and the outer tube core to close the magnetic circuit. Even if there are loses in the circuit closing cores, the gap between the magnets will still be denser than having the core carry it to the gap.

mags

mags

[Magluvin]

here are pics

First is a normal magnet motor using the top plate and the bottom pole plate to bring the magnets fields to the coil gap

Second is closer to what Im getting at, but they only have 1 ring magnet on the outer side of the coil and just core on the inner side, of which the core just does not completely contain the field. Did like 5 vids on this subject. So I think the field would be denser if the inner pole had a ring mag too.

Cant get deep into it right now, but I believe there is a difference between flux density and actual field strength, where I think that expanded fields outside of a magnetic medium are weaker and possibly further more attribute to a weaker pole at the face, not just because of density at the face. Will be testing that theory.  If we have 2 mags in attraction with some measuring device to detect the pull force, and then we add a core to give the outer poles a shorter path to the other, will the pull force between the mags increase?  In that, without the outer return core, is the flux density between the 2 attracted mags any more when we add the return core( if not why), or is the field stronger because the flux loops are shorter rather than open air loops that can expand basically infinitely?  When the 2 mags are spaced face to face very close, there is little if any flowering of the field at the poles and the percentage of it all being there in the short gap is very high.  So if we add the outer return cores, and the force between the 2 mags increases substantially, can we only attribute that to the smaller percentage of flux density possibly added by adding the cores to have even less flowering at the gap?   I think its more of the shortening of the loop that increases field strength, along with density, naturally.

So that is why Im looking into this ring magnet idea also.  Like the 2 mags face to face to measure the pull, that outer core would have to be massive to contain the highest percentages of the return flux.  So in the sec pic example, Im betting on better flux density with an inner and outs mag ring around the coil will do better than core to core and even mag to core gaps. 

The mag pull test could be done with a short return core vs a longer larger return core to see if shorter loops create a stronger gap. dunno yet, gota git back to work work. As in making a living.

Mags