? How to cast a ferrite core

[Gary Atkins]

We (son at school and dad) are playing round with a simple generator with 8
air coils on a static disk and 8 neo. magnets on a spinning disk.
Now, to get more power, it would be nice to make some sort of ferrite slurry
and pour it into the air gaps to make solid cores.
Has anyone tried this, or have any ideas?
I was thinking of iron filings mixed with epoxy glue. I have not seen any
suppliers of ferro-magnetic material in powder form.
ps I did not intend the corny pun on line one.
Gary

 

[John Popelish]

We (son at school and dad) are playing round with a simple generator with 8
air coils on a static disk and 8 neo. magnets on a spinning disk.
Now, to get more power, it would be nice to make some sort of ferrite slurry
and pour it into the air gaps to make solid cores.
Has anyone tried this, or have any ideas?
I was thinking of iron filings mixed with epoxy glue. I have not seen any
suppliers of ferro-magnetic material in powder form.
ps I did not intend the corny pun on line one.
Gary

Long ago, I tried making ferrite toroids by mixing ferrite powder of
various grain sizes with epoxy. At a consistency of damp sand, I
achieved a permeability of about 10, though my ferrite was not a
particularly high permeability type. So you might well get some
improvement in your generator by this route. Keep in mind that your
goal is to increase the permeability of the entire magnetic path from
one permanent magnet pole, through the coil window, and back to the
other permanent magnet pole, without giving the flux any better path
to go around the coil.

Are your coils and magnets mounted on iron disks or nonmagnetic
materials?

 

[Gary Atkins]

The coils and disks are mounted on thin mdf wood, but we might try perspex
as well
Gary

 

[Bullwinkle Jones]

Long ago, I tried making ferrite toroids by mixing ferrite powder of
various grain sizes with epoxy. At a consistency of damp sand, I
achieved a permeability of about 10, though my ferrite was not a
particularly high permeability type. So you might well get some
improvement in your generator by this route. Keep in mind that your
goal is to increase the permeability of the entire magnetic path from
one permanent magnet pole, through the coil window, and back to the
other permanent magnet pole, without giving the flux any better path
to go around the coil.

Are your coils and magnets mounted on iron disks or nonmagnetic
materials?

I remember reading a website almost two years ago. It had construction details
on a wind generator. They made ferrite cores for the coils using ferrous
material gathered from gravel roads/driveways/sandy beaches/whatever. They took
large powerful magnets, covered in plastic I believe and drug them around on
said surfaces to get the material needed. Then blended it with epoxy.

HTH.

 

[John Popelish]

The coils and disks are mounted on thin mdf wood, but we might try perspex
as well

Then there is little point in casting the holes in the coils with a
ferrite mixture till you poke holes through the backing board
(including behind the magnets) and cast a ring of ferrite behind both
magnets and coils as well. Otherwise you have not made the total
magnetic path around the magnets (from one pole to the other, through
the coil) much lower reluctance then it is, now.

You are beginning to find out why practical generators have all those
precisely punched and stacked iron laminations. Their only air gap in
the flux path is the one that allows the relative motion between the
rotating and stationary parts.

 

[Sir Charles W. Shults III]

I remember reading a website almost two years ago. It had construction details
on a wind generator. They made ferrite cores for the coils using ferrous
material gathered from gravel roads/driveways/sandy beaches/whatever. They took
large powerful magnets, covered in plastic I believe and drug them around on
said surfaces to get the material needed. Then blended it with epoxy.

Ah! Space dust! A lot of that stuff is burned up meteorite dust that
fell from space. Of course, these days, a significant part of it can be
from scrap steel...

Cheers!

Sir Charles W. Shults III

 

[Bullwinkle Jones]

Ah! Space dust! A lot of that stuff is burned up meteorite dust that
fell from space. Of course, these days, a significant part of it can be
from scrap steel...

I can't tell if you're being sarcastic or serious, or if this method would even
work. Would it work? I'm really not all that in the know when it comes to
these things. I just thought I'd mention it because it seemed plausable. I
would imagine that there is lots of ferrous material in gravel dug up from
quarries etc.. No? And, doesn't that material get created by forces inside the
earth?

Thanks!

 

[John Popelish]

I can't tell if you're being sarcastic or serious, or if this method would even
work. Would it work? I'm really not all that in the know when it comes to
these things. I just thought I'd mention it because it seemed plausable. I
would imagine that there is lots of ferrous material in gravel dug up from
quarries etc.. No? And, doesn't that material get created by forces inside the
earth?

With millions of iron vehicles and other man made devices rusting all
over the populated world, I think much of the magnetic bits in soil
are from man made sources. But iron is also a very common element in
the Earth's crust, and many iron bearing minerals are also
ferromagnetic, to some extent. The big questions are what exactly are
you going to gather by this method at any particular location, and
what are its magnetic properties?

Simply grinding on a piece of cast iron with a low speed abrasive
wheel (to reduce burning) and separating the magnetic particles from
the grit by this method would probably produce much higher quality
core filling. Not ferrite, but something capable of handling
considerable flux.

 

[cpemma]

I can't tell if you're being sarcastic or serious, or if this method
would even work. Would it work? I'm really not all that in the know
when it comes to these things. I just thought I'd mention it
because it seemed plausable. I would imagine that there is lots of
ferrous material in gravel dug up from quarries etc.. No? And,
doesn't that material get created by forces inside the earth?

One of the naturally-occuring oxides of iron is magnetic, appropriately
enough called magnetite:

"Magnetite is a member of the spinel group which has the standard formula
A(B)2O4. The A and B represent usually different metal ions that occupy
specific sites in the crystal structure. In the case of magnetite, Fe3O4,
the A metal is Fe +2 and the B metal is Fe +3; two different metal ions in
two specific sites. This arrangement causes a transfer of electrons between
the different irons in a structured path or vector. This electric vector
generates the magnetic field."

Slag from steel-making , sometimes used crushed for road-making, contains a
modest amount of iron oxides, but I doubt the permeabilty would match the
metallic form.

OK, that's more than you needed to know ;-)

 

[~^Johnny^~]

I remember reading a website almost two years ago. It had construction details
on a wind generator. They made ferrite cores for the coils using ferrous
material gathered from gravel roads/driveways/sandy beaches/whatever. They took
large powerful magnets, covered in plastic I believe and drug them around on
said surfaces to get the material needed. Then blended it with epoxy.

I should think they'd fair right...
--
-john
wide-open at throttle dot info

~~~~~~~~
"The first step in intelligent tinkering is to
save all the parts." - Aldo Leopold
~~~~~~~~

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

construction beaches/whatever.
They took around

Ah! Space dust! A lot of that stuff is burned up meteorite dust that
fell from space. Of course, these days, a significant part of it can be
from scrap steel...

I dunno about where you're at but here the heavier stuff gathers in the
eddies in streams, and can be picked up while panning for gold. Seems
like any magnet dragged thru dirt will pick up a substantial amount of
these iron particles.

 

[Rich Grise]

I dunno about where you're at but here the heavier stuff gathers in the
eddies in streams, and can be picked up while panning for gold. Seems
like any magnet dragged thru dirt will pick up a substantial amount of
these iron particles.

I work at a weld shop. You could probably pick up a pound of the stuff
dragging a magnet around the floor. Heck, I can drop a magnet on the
rug and pick the stuff up. But a lot'd be oxide(s), because it's slag.
But, who knows? Maybe the slag would improve something - I clearly
know less than nothing about ferrite!

Cheers!
Rich