TinselKoala's Magnetics Workbench

[Paul-R]

Now for the hard part.  Nathan Stubblefield used cotton insulation between his core and the
fe and cu wires and between the cu and fe wires themselves, and the layers too....

This is probably a rather facile question, but are you sure that he was not simply using
the best insulation then available? Is there not an easier and better solution nowadays?
Like the usual painting with varnish or some paper fibre based idea?
Paul.

[TinselKoala]

Bill, I for one am glad for your input. Please keep reading and commenting. I am truly interested in the Stubblefield bifilars, but they are different from what we are talking about here. I'm just trying to characterize these coils, and 0c has some specific things to look at with this configuration.
But I'll be winding some Stubblefield coils too. I have lots of strange wires, all different materials and insulations (enamel, silk, cotton single and double, rayon, gutta-percha, rubber, etc.) that might be interesting to examine in those configurations.
Please don't go away.

[Pirate88179]

@ TinselKoala:

Thank you, I appreciate that.  If I can help, just let me know.

@ Paul-R:

Yes, he used what was available at the time but the cotton use is very important.  I believe some of his coils used silk as well.  The key is to use an insulation that isolates the conductors and yet allows moisture to pass through.  Some of the experimenters attempted coils using modern materials and they did not work at all.  A few tried plastic mesh which allowed moisture to pass but still separated the conductors and I believe this worked, to a point but it did not hold moisture like the cotton does.  This is very important when placing in the ground.  Feel free to try some other things as we certainly did not try everything.  But we did see the need for the moisture holding properties of the cotton, or similar material in our experiments.

Bill

[0c]

@TK,

Whenever you are ready, could you see what shape magnetic field is produced with a small DC current? Is it evenly distributed above the coil? Does it intensify towards the center? Does a ferromagnetic core (steel washer) concentrate the field towards the center? Is there a difference in field intensity or distribution between the two coils?

Thanks,
0c

[TinselKoala]

I haven't had a chance to map the fields like you requested, 0c, but here is a video of a comparison I did that might be of interest.

http://www.youtube.com/watch?v=mvb39SwTXBE