Coating for bare steel wire?

Hi all,
I want to build up a magnetic core using a few hundred feet of 0.023" diameter ER70-S6 MIG filler wire. To limit eddy current, I need to make
the wire non-conductive to low voltage (ca. 5.0V AC @ 60Hz) up to 100 degrees F (38 C).
Right now, I'm contemplating a monstrosity full of pulleys and motors, to apply several coats of polyurethane liquid with intervening drying stages.
I am aware of McMaster 8867K25 which is a 0.062" diameter vinyl insulated mild steel wire. At only 249 feet per roll, I am concerned about the need for splices, though.
How would you approach this particular challenge?
Thanks!
--Winston
--

I'm still waiting for another sublime, transcendent flash of adequacy.

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Winston wrote: ...

Magnet wire. E.g., from a MOT. Bob
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Of no use, but interesting as all getout:
http://www.persiangig.com/pages/download/?dl=http://naserhashemnia.persiangig.com/the_j%26p_transformer_book_12e.pdf
or
http://naserhashemnia.persiangig.com/the_j&p_transformer_book_12e.pdf
ppgs 41-53
Dave
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XR650L_Dave wrote:
(...)

http://www.persiangig.com/pages/download/?dl=http://naserhashemnia.persiangig.com/the_j%26p_transformer_book_12e.pdf
Downloaded and saved. Very interesting indeed. Thanks, Dave!
--Winston
--

I'm still waiting for another sublime, transcendent flash of adequacy.

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On Wed, 7 Oct 2009 14:40:46 -0700 (PDT), XR650L_Dave

I dont read Arabic very well. Is there a translation available?

GUNNER'S PRAYER: "God grant me the serenity to accept the people that don't need to get shot, the courage to shoot the people that need shooting and the wisdom to know the difference. And if need be, the skill to get it done before I have to reload."
0
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On Oct 7, 4:37 pm, Winston @ bigbrother wrote:

Depends on what you are making -- relay, transformer, choke, electromagnet, vibrators for friends and loved ones, etc. Also on form factor. Which of the shapes in following is closest to what you want? <http://en.wikipedia.org/wiki/Magnetic_core
Most of those shapes are commercially available, some in lower-conductivity silicon steel laminations like in most commercial transformers, others in ferrites or powdered iron.
One light coating of polyurethane on your wire probably would be good enough. Have you thought about hanging the wire between two well-separated trees outdoors and painting it with a roller? Didn't think so. :) But seriously, if you string the wire back and forth 10 or 20 times between two headers 40' apart, it would be quite fast to paint it all with a roller.
<http://www.femm.info/wiki also may be of interest re finite elements magnetic modeling.
--
jiw

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It's a lot easier than that. The old Fordson spark coils of tractor mythology/fame used "stove pipe wire" for the core.
The trick is to anneal the wire in a slightly oxidizing fire (basicall, "blue" it). The oxide coating is not significantly conductive. And for what it's worth, the more thoroughly annealed the wire is, the greater the permability and the higher the saturation current of the transformer will be. Of course, the alloy plays a great part in this, with high- silicon steels being good in this respect.
LLoyd
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Lloyd E. Sponenburgh wrote:
(...)
Interesting!
I shall DAGS 'stove pipe wire' ASAP.
Thanks, Lloyd!
--Winston
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James Waldby wrote:

You guessed it! It's an electromagnet.

The 'ER' core is the closest. Unfortunately I need all pole pieces to be about 4 times longer than we see in the illustration.

Yup. My application is at 60 Hz so I don't really need ferrites. That is fortunate because this requires a 'full custom' treatment. The tooling charge would probably be awe - inspiring.

Funny you should mention that! I used a very similar method to coat the copper windings. They've been suspended in the back yard drying for the last few days!

Hmmm. Perhaps a tubular roller on both ends so that I can coat the unexposed side as soon as most of it is dry.
Food for thought.

Very cool! I will play with that.
Thanks, James!
--Winston
--

I'm still waiting for another sublime, transcendent flash of adequacy.

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    Check the second URL (quoted below). It gets you a PDF file in English -- with the sole nuisance that there is an '&' in the file name, which unix and linux need special command-line tricks to deal with.

956 total pages.
    First publication 1925, last shown in the usual information is 1998 (12th edition).
    Total file size is 5.8 MB.
    Enjoy,         DoN.
--
Email: < snipped-for-privacy@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
  Click to see the full signature.
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Thanks!
At one time I started teaching myself Arabic but lost interest before long.
Gunner
GUNNER'S PRAYER: "God grant me the serenity to accept the people that don't need to get shot, the courage to shoot the people that need shooting and the wisdom to know the difference. And if need be, the skill to get it done before I have to reload."
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Transformer Iron cores depend on Iron with a Oxide surface (black). I don't know if your MIG wire is suitable for that treatment.
Bill K7NOM
Winston wrote:

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Bill Janssen wrote:

The MIG wire is >97% iron so I'm hoping that will be sufficient. I suppose the oxide surface acts as an electrical insulator to limit eddy current flow between laminations. For the prototype, varnish would take that role.
Thanks!
--Winston
--

I'm still waiting for another sublime, transcendent flash of adequacy.

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And steel is 99.9-99% iron. It's the little details that will get you. My old, OLD electrical how-to from the teens and twenties shows them using iron, not steel, wire for solenoid cores. The reason being is that soft iron, not steel, wire will have little or no remaining field once the current is turned off. You want it magnetized only when the current is on. And eddy currents are only there if you're running AC through it, which sounds like some kind of choke, if that's what you're doing. In which case you might want to rethink your choice of magnetic core. At 60 Hz or so you can salvage the silcon iron out of old transformer cores. Insulate with varnish, the induced voltages are low. For higher frequencies, hit one of the remaining ham radio supplier sites and look for powdered iron or ferrite cores, they have much better properties at higher frequencies. Then you need a book to tell you the formulas to get the performance out that you want with the magnet parameters of those cores.
Stan
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snipped-for-privacy@prolynx.com wrote:
(...)

I DAGS on 'iron wire' and 'steel wire'; came up with bupkis.

Yup. A.C. electromagnet is what I'm building.

I'd really like some enamel insulated iron wire, but none of my sources carries it. I have a query into a supplier of ferromagnetic tape suggested by Kevin Gallimore but I'm concerned that they deal in much larger quantities than I need. I'm not expecting a response from them.
MIG wire is the nearest thing available.
Suggestions?

Not really. This is a 10" long part. I'm not going to spend a few hundred dollars for transformers to disassemble.

I've looked into those and discovered they measure just a few percent of the size that I need and don't have nearly the proper geometry or chemistry. They are perfect, otherwise.
Thanks Stan.
--Winston
--

I'm still waiting for another sublime, transcendent flash of adequacy.

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Winston wrote: I have a query into a supplier of ferromagnetic tape suggested

Tempel Steel sells it in coils. I have called the application engineering departments of many companies, explained a problem and had the applications guy sample me the quantity I needed. If all else fails, why wouldn't you stack some thin mild steel sheet to the required thickness, clamp it down and mill out the core shape you want? Dip each new lamination in thinned laquer, restack, and you are good to go. If you described the function of what you have in mind, (I'm seeing a giant 60 Hz tape recorder head), perhaps some of the fellows could offer more suggestions.
Kevin Gallimore
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axolotl wrote:

http://www.tempel.com/home.asp Thanks, I will check with them.

Maybe if I spoke nicely with Tempel? Good idea!

That'll work, especially if I could get my hands on some silicon steel sheet or the tape you mentioned. Obviously, I could use regular old HRS as well.

You intuit well. I hope to shrink small sheet metal dents from the 'accessible' side.
--Winston
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Winston wrote:

(...)
Like this:
http://www.youtube.com/watch?v=zSz87hChfe8&feature=related

--Winston
--

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On Thu, 08 Oct 2009 16:07:40 -0700, the infamous Winston

OK, cool (but not nearly as cool as an electronic 10-incher.)
My across-the-street neighbor can use one of those right now. He backed into something and rolled a dent into the left rear QP. I told him to find a local "paintless dent removal" shop, guys who use suction cups and balloons to pop panels back into shape. I guess they also can use this type of technology nowadays.
Is this called induction shrinking?
-- Adults are obsolete children. --Dr. Seuss (Theodore Geisel, 1904-1991) --
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Larry Jaques wrote:
(...)

Mine will *hum*.

Could be! Hope there is no frame damage.

Dunno. I expect it's equal parts induction heating and attraction. (Can't wait to find out how you riff on that!)
--Winston
--

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