On Oct 7, 4:37Â*pm, Winston @ bigbrother wrote:

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?

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