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First Coil, some questions

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LAN_403

dsheller

Thu Oct 02 2008, 10:11PM

Registered Member #1735 Joined: Thu Oct 02 2008, 08:02PM
Location:
Posts: 7

So I've done some research in the past, and know the basic schematic for a spark-gap coil, and the basic theory behind it. However, theory doesn't mean I know what to do in reality. So rather than babble... here's what I'm up to:

I have 3'' PVC for a form, haven't decided on a length yet but I am thinking somewhere in the 26'' to 36'' range.
10ft 1/4 inch copper tubing as a primary winding
Beer bottle caps -- those were fun to collect =)
Bolts to use as an adjustable spark gap

Now I know I need a source, so I was thinking a NST would be a cheap place to start -- however I have no idea what constitutes a good NST. Does anyone have any suggestions on where I could get one? Also... where do you find long spools of 24 or 26 gauge magnet wire? Any particular place? I haven't checked digikey / mouser yet, but if you guys know a cheap source for it that'd be great.

- David

Arcstarter

Thu Oct 02 2008, 10:17PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, i have an nst i tried to sell. It is 6kv and 30ma. Parawire is a good place to get wire. Also, you can ask for whatever color you want so you could have the first blue tesla coil on this forum... Just send them an e-mail.

TheBoozer

Thu Oct 02 2008, 11:09PM

Registered Member #1535 Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117

Sticking to recommended secondary aspect ratios is probably strongly suggested. 3:1 to 5:1 ratio is typical for a small coil. This means 9" to 15" winding length on a 3" O.D. form. I'm certainly no expert, but I've wound at least a dozen secondaries. This rule of thumb seems correct. The ones wound with high aspect ratios didn't perform well. I've only wound one with a 2.5:1 ratio, it seems ok. Tesla coils typically work better with short fat secondaries...

Rich

dsheller

Sat Oct 04 2008, 03:38PM

Registered Member #1735 Joined: Thu Oct 02 2008, 08:02PM
Location:
Posts: 7

I just thought of something else -- when I make the primary winding, how am I going to keep it from oxidizing? It's exposed copper and from all my work with veroboard I know it oxidizes pretty quickly.

Ryan

Sat Oct 04 2008, 06:01PM

Registered Member #1606 Joined: Fri Jul 25 2008, 02:40PM
Location:
Posts: 71

You need to use magnet wire, it comes coated so your wire wont oxidize. Regular copper wire (once stripped of its shielding) is not coated.

-Ryan

coillah

Sat Oct 04 2008, 06:25PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Hi dsheller,

You asked, what constitutes a good NST:

A good NST is one built without GFI or secondary ground fault protection. If your NST has that built in it will not work with your coil.

You were wondering about your primary tubing:
Yes it is true your copper will oxidate, and there is not much you can do to stop it, short of finding an appropriate cleaner/ may sealant. Handle your copper tubing with gloves when you are building your primary and let me know if you find something good to seal it with, cause I want mine shiny too.

Another Note on NST's:

There are a few good websites out there which contain calculators for guesstimating your spark length from your NST specs.

You may have already run into this one. Notice there is a spark length calc on the page for you to use. Essentially what it comes down to is just determining the power output of you NST. That will give you a rough estimate of where everything else should be on the broad power scale. I found my NST's on Ebay. Franceformers and Allanson, but make sure the allanson does not have GFI!!!!

As a closing note, make sure you go and READ. Most people like to help others on this forum with interesting, fresh ideas. I have seen a trend that is one such that if you have an innovative coil idea it gets people to reply to your thread much more easily. Noobish posts tend to be ignored as most of the questions have already been answered either in other threads or somewhere on the internet.

Use Google! It knows everything. Here's a couple of main sites to get you started:

All right, GL Happy Coilling

...

Sat Oct 04 2008, 07:48PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I would just spray the complete primary with polyurethane, although you have to make sure that you have finished tuning and won't need to tune it again later (ie, finalized topload and everything).

dsheller

Sun Oct 05 2008, 01:07AM

Registered Member #1735 Joined: Thu Oct 02 2008, 08:02PM
Location:
Posts: 7

Yeah I was hoping to be able to protect it and still be able to tune it... don't think that's going to be possible. Anyway, I'm thinking of a way to coil the form -- I'm thinking a gearmotor with a wooden jig where the PVC is able to freely rotate on one, and some method to attach the gearmotor to the PVC.

Mads Barnkob

Sun Oct 05 2008, 06:05AM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

If you do not run the primary hot, you could apply a thin layer of oil to protect it, or just give a good shineup once in a while if you are still tuning it.

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