What to use for coil cores?

[captainpecan]

I was hoping some of you that have been making many coils, would have some good sources to come up with for core materials. I have been using steel bolts because they are easily available, and I have not had any luck finding a good source for iron to use. I have been thinking of using welding rods also, like Bedini does. Unfortunately, no place local that I can find is selling them either. I have also been debating on whether or not to order some black sand or iron filings and make my own cores. I figure if I'm gonna have to order something, I'd rather get the best stuff to use.

My question is this: I am currently working on a project that I would like a little better craftsmanship working with. I am looking for a core for my coils that is somewhat easy to make, but very magnetic, yet it will release it's magnetism very fast. I'm just afraid that using steel bolts will hinder the performance of my generator because they will not discharge the magnetic fields fast enough.

Can some of you give me your opinions on what is best to use for cores like this? I could swear I have seen some postings of cores that were hand made from some of you. Any tips? Many thanks!!!

[rave154]

Cap,

cant say for sure as i havent used mine (yet ), but apprently black magnetite (FE 304) has the properties you seek, highly magnetisable and quickly releases its magnetic field, i bought 2 KG of the stuff to do some Flynn / MEG cores with. Im going to mix it with fibreglass resin & hardner and pore it into molds, might end up using it with my coil that im using with my rodin coil (see Marko rodin thread )

hope this helps,

David. D

[cody]

captainpecan,

It would be easier to answer your question if we knew what kind of core you were making(e, toroidal, etc) Im just going to assume your making a bedini type coil and need a ferrous material for the center. The bolts you are using are not very good. The welding rods work very well, you can find them at any local welding supplier. They are also very easy to work with. Another good option is to chop up old transformer cores, microwave oven transformers work great, but they require more work than the welding rods. Magnetite doesnt have as high of magnetic/inductance properties as the former 2 solutions above, so you will have to adjust some parameters to make it preform as well, however it works very well at completely demagnetizing. I have a vid on making magnitite cores but it needs to be updated as i have a better way of doing it now. Basicly mix it up very thick if you use it, not runny, and ram it into a mold. If you really want some good stuff than check out metglass, however, judging from your current core material, i would recommend using the welding rods or transformer cores, they work great.

[morpher44]

welding rods

welding rods can easily be found at hardware stores ... ACE Hardware for example. You can also order online.

[boguslaw]

How to make magnetic shunt to prevent overload on primary ?
I'd like to build miniature neon sign transformer , just for 1000V at 20ma, that seems easy but I also want to have built-in current limit.

[nvisser]

I used lots of thin 1mm wire. Some of them I burned and varnished before compacting it into the bobbins. It looks like it gets magnetised after some time
Can anybody comment on this and is it necessary to electrically isolate the rods?
Are the welding rods that bedini are using isolated? From photos it looks like they are thick and you only need a few

[Karl_Palsness]

magnetite

hear are a few of my magnetite cores that I have made over the years. These where made over a year ago. I have had a lot of fun with them. Bedini self oscillators love magnetite. These cores are easy to make and are very fast cores.



Karl

[captainpecan]

captainpecan,

It would be easier to answer your question if we knew what kind of core you were making(e, toroidal, etc)

Well, actually for this project, it is just very simple coils wound like spools with a core in the middle. I will be making 14 coils, with cores about 3 inches long and about 5/16'' or so in diameter. Measurements aren't critical, just need all to be the same. I do however have plans for other stuff that will be quite different, so any info is appreciated.

When cutting welding rods for the cores, I assume everyone is just scraping off the flux? Or am I picturing the wrong kind of welding rods?

I am definitely interested in mixing my own cores also though, so all this info from you guys is priceless!!! Is there a special glue anyone recommends?

[captainpecan]

hear are a few of my magnetite cores that I have made over the years. These where made over a year ago. I have had a lot of fun with them. Bedini self oscillators love magnetite. These cores are easy to make and are very fast cores.

Karl

Nice work! What material are you using for the molds and glue, so you can actually get them out of the mold? Because I can already see me mixing some up and getting it all welded in the mold... lol...

[blackchisel97]

welding rods

I used lots of thin 1mm wire. Some of them I burned and varnished before compacting it into the bobbins. It looks like it gets magnetised after some time
Can anybody comment on this and is it necessary to electrically isolate the rods?
Are the welding rods that bedini are using isolated? From photos it looks like they are thick and you only need a few

Those used in Bedini coils are welding rods, Lincoln R60, 1/16 inch. They are copper coated. There is no need to varnish/isolate them from each other. They can be fixed in bobbins with a bit of epoxy, just to hold them in place. Such core works good with ceramic magnets but neos are too strong and will saturate core, resulting in retaining EMF thus preventing its sharp collapse. Neo magnets shouldn't be used in Bedini systems except air core Window Motors.


Vtech

[Joit]

Does anyone know, that a Core actually dont amplify the Magnetfield?

From Inherited waste of Physics - 1994, German Page - Altlasten der Physik

Electromagnet
Purpose:
The operation of electromagnets is said about it: shove it into a coil a soft -
into it, the soft iron is magnetized, it transforms itself into a magnet. The field of this
Magnet is added to the coil, so that a total of a stronger field than the result without an iron core.
Deficiencies:
The statement suggests the expectation that the magnetization of iron is greater, the greater the
Permeability μ is. One would therefore expect that the electromagnet has so much stronger field, depending
larger μ. Now this is not the case. Thus, a coil for the electromagnet, it is sufficient that μ
large compared to 1. It makes virtually no difference whether μ equal to 1000 is 10 000 or even 100 000.
Origin:
The electromagnet is easily explained and directly, using the first Maxwell's equation, a
Statement about the magnetic field H makes. Now it has become established throughout magnetic fields
to describe the vector quantity B. This restriction to B is often justified by arguments
which have nothing to look at the physics: B is the real or fundamental field, H other hand, a
secondary or auxiliary variable. Here's a mistake is made, we do not our students to look elsewhere:
We confuse physical size and physical system. The sentence "In the spring depends on a mass"
is not correct, because a physical quantity can not depend on a spring. Likewise, neither
B nor H be the field for B and H are physical quantities, the magnetic field, however, is a physical
System.
The description of the effect of the iron core is now with the size of H is much simpler than with B. For
one can define very easily with H, what is meant by a soft magnetic material: Inside
of such a substance is H = 0 A / m, regardless of how the field is outside / 1 /. (This property is lost,
if the material gets into saturation. There is then no longer soft magnetic.) Second, one can
with H formulate a size that does not change upon insertion of iron core of its value, an invariant
So: the path integral over a path that winds around the current-carrying wires just once. If
Now a part of the path of integration, namely the interior of the iron core, the field H made null
is so, the contribution to the integral on the rest of the way, that is outside of the coil, according
. grow
If the declaration without the magnetic field strength, ie, trying only to the flux density, it has been
firstly, difficult to describe the properties of soft magnetic material, and secondly
one lacks the invariant in the process of pushing the iron core.
Disposal:
For the explanation of phenomena that are related to the magnetization of matter, use the
magnetic field H. If we take H as a measure of what one wants to be understood by a lot or a little box
we can formulate the fact that soft magnetic materials in the interior of H = 0, then: Soft magnetic
Substances can be no magnetic field to penetrate into themselves, - as well as electrical conductors, the
not let electric field in itself. Thus one can now easily understand even the electromagnet:
Moves to one soft-iron into a coil, while holding constant the electrical current, so
the iron core pushes out the magnetic field from the interior of the coil.
/ 1 / Herrmann, F.: Contaminated physics (4), The Hysteresiskurve
Legacy of physics (36)

chased through a Translator, sorry for Errors, i didnt do a spellcheck.

[Karl_Palsness]

Mold release

Nice work! What material are you using for the molds and glue, so you can actually get them out of the mold? Because I can already see me mixing some up and getting it all welded in the mold... lol...

I make my molds out of Wood on my lathe or band saw ect... but the way I get them out is to use wax....I use a heat gun and put a generous coating of wax all everything I don' t want the core to stick to. Then I mix my magnetite with polyester fiberglass resin & hardener...finding the correct mix takes some time but when you find it you have a very dense core...also you have to make sure not to have any air bubbles in the mix. I also use a strong magnet under the mold in order to alien the sand to make a stronger magnetic field. Thanks to Peter Lindemann for that idea. after it is all dry I simply unscrew my mold and out comes my core and ready to cast then next. I also have extra rod cores ready to fill with my left over material as it is to expensive to wast it.

I find that with this cores I use the strongest magnets I can get to run on Bedini stuff as the core allow it to run stronger.

Karl

[gmeat]

zirconium is also said to be a good additive ala. Bill Muller.Cheers


-Gary

[captainpecan]

How about for use with an attraction motor? Is there materials that appear to attract stronger, but not really make a good core material? Or does it just seem to be the same either way?

[gmeat]

Capt.

laminated silicon steel is probably your best bet,And the thinner the better.If you look at Peters electric motor secrets thread and go back from the end of that thread a couple of pages there are references to different suppliers.Hope this helps


-Gary