Re: Arc Welders as Rheostats?? Variac Mod Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "marc metlicka by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>

Hello All,
The 10 amp variac core that i cut "DID" vibrate very nastily when
powered up. I shelved it for a long time thinking that i did something
wrong? Then i read an article about flybacks in one of the tech mags
that i receive (power electronics i believe) and it said a little
something about using a paper spacer between the cores, I coated a piece
of fish paper with epoxy and slid it into the gap. I then used two big
wire ties to hold it closed a little, when i tried it a couple days
later, no noise!
I think the noise was due to the core being made of laminates, They just
vibrated at the ends, but the main part is held by the windings (i
think).? I used two heavy wire ties on either side of the cut, wrapped
around the core section. This held the laminates in place while i cut it
with a hack saw. 
I wanted to cut it by hand, but i really suggest a band saw or better
yet, a porta-band saw. Oil for lube is a good idea. I suggest wrapping
the entire core with electrical tape before cutting! the little fillings
get into the smallest crevices and are very hard to get out! i kept
cleaning and then looking with a magnifying glass only to see more chips
stuck under the turns on the inside? I'm not sure it would hurt, but i
didn't like it! maybe the whole core could be dunked in wax before the
cutting, this would seal all the voids maybe.
 I gave that variac away about a year ago and think it is still being
used to limit a small pt in a table top type coil system.
Take care,
Marc M.

Tesla list wrote:
> 
> Original poster: "Jack King by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<speakernut-at-yahoo-dot-com>
> 
> I do like the idea of a simple, single band saw cut as
> opposed to notching out a chunk. Any magnetics experts
> care to comment?
> 
>