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Re: [TCML] can you help my son and i with this Please



With relatively small coils like these, I have had really good luck using heavy duty banana jacks with pieces of 1/8" tungsten electrodes I bought from a welding supply company. I use 4 jacks and 4 pieces of tungsten making two sets of spark gaps and wire them in series. I mount the jacks on a piece of plastic I cut from a kitchen cutting board. It only requires a single 7" piece of tungsten for both gaps. I take a rotary tool, like a Dremel, and grind part way through the tungsten and then snap it. After that, I grind the ends smooth on a grinder. The gaps are super easy to adjust simply by loosening the jacks and slipping the electrodes in or out, while the coil is off. :-O
It wasn't my idea but it works like a champ and it isn't expensive at all!
Paul
Think Positive

----- Original Message ----- From: "jimlux" <jimlux@xxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, November 22, 2009 5:57 PM
Subject: Re: [TCML] can you help my son and i with this Please


Jon Danniken wrote:
Roger Smith wrote:
I would recommend starting with a small one especially if cost is a
factor. In some ways the small Tesla coils can be more fun than the
big ones. You can get closer to them and see more corona and the
finer sparks and smell more ozone.    Start with one based on a small
neon sign transformer or oil burner transformer and save the 10" pvc
pipe for later.   A piece of 3" pvc won't set you back much.

I would concur with this advice. You could use a capacitor made from clear glass bottles,

Google "beer bottle capacitor" ... just need a 5 gallon plastic bucket, some salt, and a 6 pack's worth of beer bottles.


an oil burner transformer (or a small neon from a
sign shop), a couple of brass screws for the gap,

Ooh. I wouldn't do the "bolt gap" even though you see it in lots of beginner designs. It gets hot, it's hard to adjust, etc. Better to do the 3 pieces of copper pipe in parallel gap. 1/2" or 3/4" couplings, or just 2" long pieces cut off the end of a piece of pipe with a tubing cutter work just fine.
Scrounge a muffin fan to gently blow on it and it works even better.




 and a three to four
inch section of PVC (or ABS or cardboard) for the coilform. Copper tubing makes a good primary, but so does some bare copper wire.

For a small coil, start with bare AWG 14 or AWG 12 house wire in a flat spiral (aka pancake). Use pieces of cardboard with slits about 1/2"-1" apart to hold it. You'll need about 50-60 feet to make the right size spiral. Once you get it working, you can scrounge up some copper tubing for a performance boost.

A fancier support uses strips sawn off the end of a white polyethylene cutting board.


The
magnet wire for the secondary can be purchased from a local motor rewinder for a few bucks if you can talk them into selling you a partial spool, or you can buy a small amount from ebay if the price isn't too much).

You buy by weight, normally, so google up a copper wire table to find how much you'll need.

800 turns on a 4" diameter form is about 800-900 feet. For a small coil, awg 20-24 works nicely, although you can go bigger if you like. AWG 24 gives you about 35-40 turns/inch, so 800 turns is about 20 inches long.. a bit skinny for the desired 4:1 or 5:1 length/diameter ratio, but close enough. If you have a 5 or 6" form, all the better.


If you scrounge well, you can come up with a respectable coil for under $20.


That would be a lot of scrounging.. when you're down in that territory, the little stuff like bolts and wire nuts adds up.



Jon

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