Re: New to tesla coils

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

Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org> 

On Sat, 27 Sep 2003 15:04:11 -0600, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: sean <sean-at-nc.rr-dot-com> I will try to build thegeekgroup's 
>bucket cap, and maybe later get mmc.

I think that's a good plan :)

>I have no idea where to get a variac, so I'm probably not going to get
>one.  What is the purpose of the lightbulb in series with the
>transformer?  Does it protect it?

The lightbulb acts as a large resistor in series with the NST.  This will 
cause less voltage to be developed across the NST inputs.  Smaller wattage 
bulbs will cause the smallest voltage across the NST.  I suppose you could 
use a variable 100ohm, 225W or larger wirewound resistor, but those are 
expensive compared to a light bulb and receptacle.  Once you get the tuning 
pretty close you would then remove the light and run it "wide open."


>Also, is a filter absolutely required?  I looked at the Terry gap, is
>there an easier way?

A filter isn't required.  It helps protect your transformer and keep the 
RFI that makes it back to the house wiring at a minimum.  If you don't use 
one, just make sure you set your safety gaps well and often.

There are a multitude of static spark gap designs.  Gary Lau, I believe, 
has a vaccuum sucker gap that seems to get rave reviews and doesn't appear 
to be difficult to make.  For your first time, a couple of 3/4 inch copper 
pipe couplings side by side will be just fine.  Forcing air across the gap 
via a muffin fan, vaccuum, leaf blower, air compressor, or whatever will 
improve performance of a static gap.


>I'm going to make a static gap with a bunch of copper tubes (adjustable)
>
>I'll probably make a torroid from aluminum dryer duct.

Good :)


>I will probably try to make the primary adjustable.  What size copper
>tubing is best?

1/4 inch soft copper tubing is pretty good.  The primary current won't be 
too high, so you could get away with anything down to about 10 gage 
wire.  1/4 inch tubing is easier to make an adjustable connection (tap) to, 
IMO.


>For the secondary a 4" pvc tube, what type of glyptal should I use?
>Also, is there an alternative to ac-43 (they seem to be located in New
>Jersey)

The coating used isn't critical.  Dr R has been using the Glyptal for many 
years, and has found it works and looks great for his museum-class coils 
(30 year service life with daily use).  You can use plain varnish, but it 
will yellow over time.  There have been some great results using just about 
any two-part epoxy if the epoxy is mixed very well and the directions 
followed explicitly.  Use throw-away foam brushes with epoxy ;)  Some 
prefer not to coat their secondaries, but that has led to significant 
problems for me.


>Ok, I am bidding on a transformer on ebay, 12kv 60ma as brooksshaman
>(please don't bid on it)
>
>Am I forgetting anything?


You'll think of all kinds of things as you go along ;)


>Any other info is greatly appreciated as well.  Thanks for all the
>replies.


Just remember that building a functional Tesla Coil isn't really that 
difficult; building a work of art takes a lot of time and patience.  Don't 
feel compelled to make it absolutely perfect the first time around, since 
if you are like most of us, you'll continually want to upgrade or improve 
on something.  In a few years you may have a half dozen different 
secondaries, several types and values of capacitor, a couple power 
supplies, and several static and a rotary gap.  ;)

Cheers,

Mark Broker
Chief Engineer, The Geek Group