Source for 1/4" thick Alnico bar magnets?

[Freekmagnet]

Anyone know a source for some 1/4" thick A5 bars? Just like the typical humbucker bar, but thicker. 1/2" tall, maybe 2.5"+ long magnetized in the 1/2" direction.

I want to try building a pickup with a thick blade. I can't seem to find any wider that 1/8".

Thx!

[bajaman]

as an additional question, does anyone know a source for 1/16" thin alnico bars ?

[rjb]

Are you planning on making a bobbin - or just flatwork?

Maybe you could use two 1/8" magnets side-by-side.
They would try to push away from each other, but I bet you could make a bobbin core strong enough to hold them together.

-rb

PS- Why do you want to make a fat blade?

[J M Fahey]

Agree.
They will repel , which is good because that means the magnetic field is pushed forward, where itīs useful.
You might want to make a small guide, wood is strong enough, so they are pushed together , well aligned. and epoxied to each other.
Once it cures, mutual repulsion will not be enough to crack the epoxy and pull them apart, let alone damage the bobbin spool.
Slightly warming them will help epoxy stick better.

Remember to degrease them well before epoxying.

[Freekmagnet]

Are you planning on making a bobbin - or just flatwork?

Maybe you could use two 1/8" magnets side-by-side.
They would try to push away from each other, but I bet you could make a bobbin core strong enough to hold them together.

-rb

PS- Why do you want to make a fat blade?

Agree.
They will repel , which is good because that means the magnetic field is pushed forward, where itīs useful.
You might want to make a small guide, wood is strong enough, so they are pushed together , well aligned. and epoxied to each other.
Once it cures, mutual repulsion will not be enough to crack the epoxy and pull them apart, let alone damage the bobbin spool.
Slightly warming them will help epoxy stick better.

Remember to degrease them well before epoxying.

Gluing two together might work. I'm currently casting my bobbins, so I'd just have to make one to fit the two together.

I actually thought about putting two together before - would putting them side-by-side eventually cause the magnets to weaken or discharge?

I'm looking to experiment with different width blades. I've been making some bass pickups making ceramic blades. I have some .20" blades and some .125" blades and the thinner blades seem to have a smoother attack. I want to make some comparisons. I have some .125" A5 magnets already.

[Mike Sulzer]

Gluing two together might work. I'm currently casting my bobbins, so I'd just have to make one to fit the two together.

I actually thought about putting two together before - would putting them side-by-side eventually cause the magnets to weaken or discharge?

I'm looking to experiment with different width blades. I've been making some bass pickups making ceramic blades. I have some .20" blades and some .125" blades and the thinner blades seem to have a smoother attack. I want to make some comparisons. I have some .125" A5 magnets already.

I glued a couple with Gorilla glue. I do not think they are coming apart.

The conductivity and permeability of a blade (inside the coil) matter much more than when the same magnet is used outside the coil. So the type of alnico is more important, and of course you can use two different types.

[John Kolbeck]

Agree.
They will repel , which is good because that means the magnetic field is pushed forward, where itīs useful.

The magnetic fields never really change shape, push forward, or however you look at it. The magnetic fields just overlap. Even a single, solid magnet is pushing against itself, which is why when you drop, one and it breaks, it sort of explodes, as it finally becomes free to push apart. Then the little pieces of broken magnet reform as a clump, but now the shards are north beside south, south beside north.

[Mike Sulzer]

The magnetic fields never really change shape, push forward, or however you look at it. The magnetic fields just overlap. Even a single, solid magnet is pushing against itself, which is why when you drop, one and it breaks, it sort of explodes, as it finally becomes free to push apart. Then the little pieces of broken magnet reform as a clump, but now the shards are north beside south, south beside north.

What you are saying about the fields not changing shape is almost perfectly true for neo magnets, but alnico has a high enough permeability so that the field it produces is significantly affected by a similar magnet placed close to it. So the field of two magnets is not exactly the sum of the two individuals.

[John Kolbeck]

What you are saying about the fields not changing shape is almost perfectly true for neo magnets, but alnico has a high enough permeability so that the field it produces is significantly affected by a similar magnet placed close to it. So the field of two magnets is not exactly the sum of the two individuals.

How significantly is the shape effected by the permeability of the AlNiCo, though? They are permeable, but not nearly to the degree of steel.

[Mike Sulzer]

How significantly is the shape effected by the permeability of the AlNiCo, though? They are permeable, but not nearly to the degree of steel.

Well, the permeability is something like 6. That can make a difference, but you have to solve a differential equation to get a number in a specific case. FEMM could do the job in 2D. Just in general, in power handling applications such speakers and motors, you need a lot more alnico than, say, ceramic in order to avoid saturation.

[J M Fahey]

The magnetic fields never really change shape, push forward, or however you look at it. The magnetic fields just overlap. Even a single, solid magnet is pushing against itself, which is why when you drop, one and it breaks, it sort of explodes, as it finally becomes free to push apart. Then the little pieces of broken magnet reform as a clump, but now the shards are north beside south, south beside north.

Sorry but magnetic field DOES change shape, thatīs what we do all day long, either to focus it where we need it, to modulate it with varying distance from a magnetic object (what pickups do) , etc.

Single magnet, well away from any other magnetic object, active or passive:


2 magnets, axially aligned, same orientation:


2 magnets, axially aligned, opposite orientation:


2 magnets, parallel, same orientation (what the OP is asking here)


see the magnetic field changing shape.
Now if they get closer and closer, eventually touching each other, they will become "a single larger magnet" and we are back to square one, it becomes a single fatter magnet, what the OP is trying to make.

Just as an extra note, see a smaller magnet perpendicularly 1nserted in a larger homogeneous field, see the wild twisting around it:

[John Kolbeck]

Those depictions of magnetic fields changing shape are just the result of adding together those two fields. You mentioned "focusing" for example, I think it's more accurate to say that flux is "concentrated" in some way that is useful. You couldn't, for example, make a static magnetic shield, because there is nothing in physics that says you can steer a magnetic field in some direction other than what it would naturally go. The best you can do is create yet another magnetic field that is polar opposite of the magnetic field that you don't want, so that you have a zero sum magnetism. You're never redirecting or focusing anything, you're just creating new magnetic fields in order to end up with a desired concentration of flux in a certain place or places.

Mike Sulzer mentioned permeability of metals, but there again, you're really just creating yet another magnetic field with the free spinning domains of the metal, and adding that to your stack of existing magnetic fields. The end result might make it appears as though something has changed shape under iron filings, but it's really just the result of static fields adding and subtracting within the same area of space. That's why you get an energy product from a permeable core, you're getting a higher sum of magnetism, not merely redirecting it.

Now if they get closer and closer, eventually touching each other, they will become "a single larger magnet" and we are back to square one, it becomes a single fatter magnet, what the OP is trying to make.

That was what I was getting at, but it sounded like you meant something else when you said this:

Agree.
They will repel , which is good because that means the magnetic field is pushed forward, where itīs useful.

The fields aren't pushing outwards, you're just seeing the return paths of the side-by-side magnets attempt to repel. This is why magnets are strongest at the edges, because even with a solid magnet, the return path of all the constituent domains are still attempting to repel each other. The edges of the magnet are strongest because they have fewer neighboring domains trying to cancel them out.

I realize that using words like "focus" is a useful abstraction for more complex magnetic circuits, but then it seems that people don't realize it's just an abstraction, it's not what is really happening.