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Re: [TCML] Spark gap assembly, acrylic?? and toroid size



Hey John...

Lexan is good to about 300 degrees before it starts melting ( nearly liquid state). At work we would use a 1000W hair dryer to heat the Lexan to a point as to where we could bend it over the edge of a table to form 90 degree bends in it... gives you an idea how "little" heat is required to make it bendable.

As far as the heat produced by the spark gap... depends on the amount of power you are putting into the primary. My original sparkgap for my polepig ( 240Vac @ 25A) would literally melt 3/16" dia tungsten rod in a static blown gap setup.... My latest spark gap ( SRSG @ 280VAC 60A) softens 1/8" tungsten rod enough to round off the tips of the electrodes...

Scot D



John Matok wrote:

Scot,

You said that Lexan is good for low temperature applications, but is it
suitable to use in a spark gap?  On the website that I provided, the plans
said to use Lexan.  How hot can the Lexan get if it's not in direct contact
with the copper?  How hot do spark gaps get in general?

Nicholas Goble


On Wed, Jul 16, 2008 at 7:56 AM, bunnykiller <bunnikillr@xxxxxxx> wrote:

Hey John...

I havent built the spark gap as shown with the aluminum holders but I did
build the one without the aluminum... I had it running on a coil that was
powered by 4 15/30 NST's in paralell and it worked quite well. Eventually
tho, I had to clean the surfaces of the tubes due to oxidation etc. I found
that adding a small fan to the unit increased its quenching too... see link
below for pictures

http://members.cox.net/bunnikillr/sprk.htm

As far as plastics, obtain a cutting board ( white plastic 1/4"+ thickness)
from places like Wal Mart etc. Usually they are made of HDPE
( Hi-Density-Poly-Eurathane).
acrylic,polycarbonate,lexan,plexiglass are ok for low temp applications but
can be either brittle or "gummy" when machined ( altho Lexan is great at low
speeds and cuts nice)  normally clear in color
Perfboard isnt really a plastic its more of a laminate/epoxy combo
MMC's are good on either HDPE, perfboard or G-10
Sparkgaps work best with G-10 due to the heat produced
Primary coil, once again HDPE

Toriod size "normally" is about the same over dia = to length of secondary
and smaller dia =to a bit less than secondary dia.
example, you have a 20X4.5    toroid would be good at  18-20 X 3-4

a second primary on a different power supply... ummm I would say no.  a bi
level primary on a single supply would work... someone on the list has done
so but I dont remember who did it... I dont know if it increased output tho,
seems to me it wouldnt..

A magnifier is a "2 coil system", it has a very tight coupling coeficient
on the 1st primary/secondary coil which drives a second secondary and
toroid. Special design considerations must be made to get this type of
system to work properly. Antonio has some great literature on this type of
coil...

Scot D



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