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Re: [TCML] Secondary and Primary Assistance
I know of inks that would do much better than your graphite. Here in the
US, these inks are used for magnetic check magnetic ink character
recognition (micr) readers (versus simple optical readers) for the banks
and insurance companies, but in other countries where check the fraud
situation is "far more severe", they use US technology magnetic inks and
various other means of fraud protection (indelible inks, fused toners,
etc. (all US designed). I was one of a small handful of engineers that
spent a lot of time in South America and Mexico to get many countries
check systems up and running (Brazil, Peru, Colombia, Venezuela, Chili,
Dominican Republic, and all the major cities in Mexico). This is where
my experience is with inks.
If Sonotube or Quikrete suppliers used something like those toners and
inks, then we would certainly have a problem with coils. But the ink
stain on sonotubes is nothing more than a stain in my eyes. I just can't
see it as significant to the operation of coils (thinking about the
voltage between 2 inches of coil form). Thickness and density of
conductive inks and toners are just as important as is wire size to the
electrical guru's of the world. Sonotube ink is very thin and density is
Something to think about however, is the voltage between a section of
turns in which the ink might overlay a single conductive strip. Near the
bottom of the coil, voltages are pretty low within a 1" area of turns,
but as we progress towards the top of the coil, those voltages within
the same 1" area will get higher and higher. They can exceed 10 to 20 kV
within that 1" area at the last 1/3 of the coil. This is probably where
the concern should be focused and due to that, maybe "Megger's" or other
brand bond and dielectric testers are not capable of telling the tale
for Tesla Coils.
In the end, it may be wise to remove the ink before sealing and coating
the form. Basically, getting it ready for winding. After all, we are
dealing with uniquely very high voltage at low rf. Certainly can't hurt
to be safe.
Far more important than ink conductivity is moisture absorption
prevention. If anything will make a sonotube coil lossy, moisture will
and this is the "real" concern. I personally thinned out polyurethane
with paint thinner and coated the coil inside and out after heating and
drying. The mixture absorbed into the cardboard and sealed the entire
tube. Then after winding, I again added my normal exterior coating.
Worked great for my coil, but maybe raw sonotube coils might perform
with higher losses due to lack of preparation?
I tried it. Ran my 4.5" coil with a 30" length of sonotube. Got zapped
a couple of times, so decided to isolate myself a little better. I put
the sonotube near the coil (without me) and ran it. I saw no
distinction between ink or non-inked areas. This is an untreated
sonotube. The output is probably 200kV, but still nothing discernible.
However, in a coiled situation, there may be some losses. However, I
really doubt the losses are discernible.
Lau, Gary wrote:
As Scott suggested, I think the most revealing test would be to hold
a sample of the printed form up to a small sparking Tesla coil
topload and see if the sparks want to surface track on the printed
portions more-so than the unprinted portions. A real easy test if
one has a piece of Sonotube available; unfortunately I do not. I
don't know at what voltage a Megger (Meager?) operates, but probably
the closer to actual TC voltages, the better.
Using what I have, I just held a piece of 4" SDR PVC pipe with
un-cleaned printing on it, to the sparks coming from my bug
zapper-powered mini coil (http://www.laushaus.com/tesla/bzt_coil.htm
). I was unable to see any effect that the printing had to the
sparks. However, when I drew a line with a graphite pencil on the
PVC, the sparks made a very bright surface track along that line.
Similar behavior when I sprayed a water mist onto the PVC, though not
as bright as the graphite.
If someone has a piece of Sonotube and a small coil available, please
Regards, Gary Lau
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