core rods and insulation

[faramog]

I used copper clad welding rods cut up and placed in the centre of the coil. They were not insulated. I just read that they should be... why ? My multicoil ssg is working fine.

Any knowledgable folks with views ?

Thanks

[Farmhand]

Hi faramog, I think the welding rods with the copper coating should be fine.
My understanding is that the core rods only need to be magnetically insulated not electrically insulated, the copper coating would acheive that I think.

Another suggested method ( I think ) is to use normal iron or steel rods but let them rust up a bit outside first.

The only conclusion i can come up with is that magnetically insulating the idividual core rods would reduce "eddy currents" .

Hope this helps

Cheers

[dragon]

If you put a stack of magnetic plates loosly in a magnetic field they will magnetize opposing each other - the plates will repel the ones next to it.

JB shows this in a lot of his drawings using opposing magnets where the field is extended. This is used in industry for separating heavy sheets of steel as well. If they are magnetically connected the field is more concentrated in the core ( such as a solid core ). I believe since the rods have a smaller surface area connected to it's neighbor it would tend to create this opposing field inside the core even if they were not insulated but the insulation would enhance the effect. Painting or coating them will also isolate the coupling.
________
LANDLORDS INSURANCE FORUM

[elias]

Take a piece of conducting metal and try to slide it over a strong magnet, you'll see that there is a drag to it. because the magnetic field of eddy currents in the metal opposes the magnet's magnetic field. So in order to minimize this effect, you need to use an electrically insulated cores, or ferrite non-conducting cores. Your machine would work but would be less efficient.