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Re: [TCML] need help

On 2/16/13 8:54 AM, David Rieben wrote:

I'll leave a more thorough responses to your questions to some of the more knowledgable
resident member geniuses but to give you a brief rundown:

#1 - It doesn't take a large well-built and tuned Tesla coil to produce 20" discharges.
        A 4" x 16" secondary coil with a topload of approximately the same dimensions
         should handily do the trick, whether SG driven or of the DRSSTC variety.

I agree.. that's about the size of my little coil..

#2 - How much it cost is somewhat dependant on how advanced your "scrounging"
        skills are ;^) but I would think that you should be able to construct a spark gap
        driven coil of this magnitude for < $500 w/out much difficulty. The fully electronic
        DRSSTC may cost a bit more and is also considerably more advanced in
        design than a SG driven coil. I would recommend the plain SG driven coil
        for the beginner coiler. The main costs would be the transformer, capacitor(s),
        and the wire and/or copper tubing for the primary and secondary coils

I just bought 7.5 pounds (5900 ft) of AWG 24 magnet wire from Temco for $90 with free shipping.. You only need a pound or so, so figure $10-15 for wire.

A decent static spark gap is 3 pieces of 3/4" copper pipe about 2" long and a small "muffin" fan. Fans are maybe $5 (you want a 120VAC one). The copper tubing or fittings is probably another $5 total.

The neon transformer will be your pricey item.. figure $100.. you might be able to do much less if you can find one locally, but shipping is a killer: they're heavy. Here is where scrounging really pays off.

The form for the secondary can be either a piece of plastic pipe (don't use black ABS.) or a cardboard mailing tube.

The primary is, ideally, something like 1/4" copper tubing, but I think something like bare AWG12 house wire will work. You need about 50-70 feet.

The secondary top load is a metal pie plate and some of that expandable exhaust ducting.

The primary capacitor for something portable is probably a MMC (check the archives).. Cornell Dubilier 942 poly propylene capacitors. You need about 10-12 in series (2000V rating each). Last time I checked (last year) they were running about $3-4 each. You choose the value (say 0.15 or 0.10 uF) so that they have the right capacitance when seriesed up.

#3 - Plexiglas is NOT a good idea, as the heat of the discharges will start to melt
        and carbon track the plastic surface in a pretty short order. Tempered glass
        would be a better choice - avoid any plastic product for this purpose. Also,
        the sparks can pretty easily penetrate plexiglas.

I would look for something like a glass patio table top surplus..

#4 - Low pressure inert gases do make for interesting colors and effects with
        electrical discharges but obviously require air tight seals. Also, the discharges
        are nearly silent (think neon signs) and don't require near the voltage potential
        to bridge a given gap as opposed to open air. Sealed inert gas chambers for
        the discharges would certainly increase the construction complexity (and cost),

Argon is white..

#5 - Wood is a poor insulator for the high voltages and frequencies of typical
        Tesla coil discharges and will also quickly carbon track and give off copius

Fellow list member Jim Lux, as well as others, can give you a more thorough dis-
sertation on the liability issues of using TCs near other people, but I think the
bottom line is that it's quite a difficult task to operate them near people while keep-
ing it "OSHA" safe, from a legal liability standpoint.

Yup. They don't fit in a convenient category for most hazards and insurance.

 KVA Effects is a professional
special effects company in Southern California that specializes in Tesla coil/
high voltage effects and Jeff Parisse, their CEO, has voiced the exorbitant
insurance costs for them to do the Tesla coil effects for hire on this forum.

I believe that Jeff has sold kVA Effects to another TCML member in the Carolinas... But the point is well taken.. doing it as a "pro" on a regular basis costs a pretty penny in liability coverage. They did trade shows, tv and movies, etc.

(And they know what their doing!) I would suggest proposing your TC
idea to the school administration to see if they would even allow it before you
dive too deep into this project, unless you'd like to built a TC for your
own enjoyment.

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