Hi Gary,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 very low.
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?
Take care, Bart bartb wrote:
Hi Gary,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.Bart 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 try that?Regards, Gary Lau MA, USA_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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