Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Magnetite cores?  (Read 5993 times)

antimony

  • Sr. Member
  • ****
  • Posts: 265
Magnetite cores?
« on: December 15, 2015, 09:04:28 PM »
Hi,  i am interested in making some magnetite cores for my coils,  and other stuff.  Firstly, becouse it is so nice that i can custom-make molds in various shapes and sizes, but also i heard that they do a pretty good job.
One guy compared it to Metglas, but im not sure thats right.

So,  what i wanted to ask was, have you any experience with this that you would like to share?

And the second question is about what i read in a swedish electronics forum, so i may have some trouble with translation,  but i hope you get it.  :)
Its about the mesh size of the powder, that the finer it is, the higher work frequency.
Do anyone know this?

Thanks in advance guys. :)

Paul-R

  • Hero Member
  • *****
  • Posts: 2086
Re: Magnetite cores?
« Reply #1 on: December 16, 2015, 04:03:54 PM »
What are you trying to do with these cores?

forest

  • Hero Member
  • *****
  • Posts: 4076
Re: Magnetite cores?
« Reply #2 on: December 16, 2015, 08:43:38 PM »
How to effectively crush ferrite core into ferrite dust ?

antimony

  • Sr. Member
  • ****
  • Posts: 265
Re: Magnetite cores?
« Reply #3 on: December 16, 2015, 08:50:14 PM »
What are you trying to do with these cores?

Well,  i am in the process of making my first magnet pulse motor, and i have made two coils already,  both of them Bedini style cores, but im not satisfied with them becouse my rods are about 3 mm in diameter and i cant find any better here where i live.
Another project that i would like to try to replicate is the Thane Heins BITT, but also other transformer projects like Lawrence Tseungs magnetic frame, and others that dont come to mind right now. 

Also,  i forgot. Thanks for your reply. :)


Jimboot

  • Hero Member
  • *****
  • Posts: 1407
Re: Magnetite cores?
« Reply #4 on: December 17, 2015, 10:41:11 AM »
I have a big chunk of it here. It does have a crystalline structure but I have never tried using it in cores.

Paul-R

  • Hero Member
  • *****
  • Posts: 2086
Re: Magnetite cores?
« Reply #5 on: December 17, 2015, 04:03:30 PM »
Well,  i am in the process of making my first magnet pulse motor ... Bedini style cores, but im not satisfied with them because my rods are about 3 mm in diameter and i cant find any better here where i live.
It is material that counts, although he diameter is important. John B recommends R45 or R60 gas welding rods. They can be obtained from people like British Oxygen and others. They take on magnetism rapidly and shed it rapidly.

sm0ky2

  • Hero Member
  • *****
  • Posts: 3948
Re: Magnetite cores?
« Reply #6 on: December 24, 2015, 09:35:26 AM »
ideally you want semiconductor-grade ceramic-ferrite inductors
you can buy these in all shapes, sizes and parameters
or reuse them from old electronics.
(don't use the rubber pegs, they burn tons of energy!)

However, if you want to make your own....

there are mechanical crushing tools, most are noisy, messy and cause heavy losses in material..
I prefer to use a mortar and pestle of a very hard stone. crush the magnetite (obtainable from sand with a magnet)
into a fine powder
(in theory yes, finer the powder the faster the response time, i.e. frequency)
and mix with a two-part epoxy resin, and cast into a mold

you can cut, file, sand this down after it hardens to perfect the shape

now: the amount of the powder you mix into the resin will determine the inductance of the core.
and there IS a maximum that the resin will hold, before it just hardens into crumbs.....

hope this helps, I gave up making them a long time ago, the computer guys are much better at fabricating these things

antimony

  • Sr. Member
  • ****
  • Posts: 265
Re: Magnetite cores?
« Reply #7 on: December 24, 2015, 08:11:16 PM »
ideally you want semiconductor-grade ceramic-ferrite inductors
you can buy these in all shapes, sizes and parameters
or reuse them from old electronics.
(don't use the rubber pegs, they burn tons of energy!)

However, if you want to make your own....

there are mechanical crushing tools, most are noisy, messy and cause heavy losses in material..
I prefer to use a mortar and pestle of a very hard stone. crush the magnetite (obtainable from sand with a magnet)
into a fine powder
(in theory yes, finer the powder the faster the response time, i.e. frequency)
and mix with a two-part epoxy resin, and cast into a mold

you can cut, file, sand this down after it hardens to perfect the shape

now: the amount of the powder you mix into the resin will determine the inductance of the core.
and there IS a maximum that the resin will hold, before it just hardens into crumbs.....

hope this helps, I gave up making them a long time ago, the computer guys are much better at fabricating these things

Your post helped a whole lot actually.  You adressed aspects of these cores that i havent thought of before.

I was thinking about getting a smaller amount of magnetite, and experiment a little bit with. 
Do you think that you can substitute the casting epoxy with glue,  or something else?

Thanks m8

sm0ky2

  • Hero Member
  • *****
  • Posts: 3948
Re: Magnetite cores?
« Reply #8 on: December 25, 2015, 03:54:27 AM »
Your post helped a whole lot actually.  You adressed aspects of these cores that i havent thought of before.

I was thinking about getting a smaller amount of magnetite, and experiment a little bit with. 
Do you think that you can substitute the casting epoxy with glue,  or something else?

Thanks m8

sure, the medium can be anything that's not electrically conductive, and non-ferrous.
you could use playdough if you want to,.. however
in practice, the harder the substrate (like in a ceramic inductor), the faster the response time, and lower reluctance to induction.
also, if the substrate is too soft, particles can migrate or cluster over time, resulting in changes in the induced field.