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Jonathan Dennis

Tue Jul 07 2009, 02:51AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
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Posts: 69

I am getting close to the completion of my FIRST coil! I am so excited to see how it will run. I just finished winding my secondary, and have one question. I have a 4" diameter PVC and 24" of coil so far. I know that the 5 to 1 ratio means I should stop at 20", but I thought 4 extra inches couldn't hurt. I have not cut the wire yet, and wondered if I could wind even more, seeing as how my roll still has plenty of wire. I don't know how making the secondary longer will affect my performance. Will it hurt or help?

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Corey

Tue Jul 07 2009, 03:08AM

Registered Member #1902 Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75

i would stop at where you are right now. The max ratio for a sec seems to be around 1:6. i could be wrong so wait for other opinions. GL w/ ur coil.

Jonathan Dennis

Tue Jul 07 2009, 03:53AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
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Posts: 69

Thanks, I'll keep that in mind. I'll stop for now, and wait for some more opinions before I proceed. If there is anyone that has experience through trial and error, I would greatly appreciate the passing on of that knowledge! :)

StevenCaton

Tue Jul 07 2009, 04:48AM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

Making your secondary 4 inches longer may be a wise idea, depending on several things. Firstly, if you are powering the coil from a NST that is equal to, or more powerful than 15KV at 30ma, or 12KV at 90ma, then yes, make the secondary longer. This will keep the sparks from constantly hitting your strike rail. 24 inches is pretty short, and with a somewhat powerful NST, you will have lots of sparks that will go down to the rail. For example, my spark gap coil, powered by a 12KV 90ma NST has a secondary that is 4'' by 27''. The sparks on that coil have actually hit the strike rail. (That coil does 58 inch sparks) However, that coil has a small toroid under the larger toroid, which keeps sparks away from the primary.

Jonathan Dennis

Tue Jul 07 2009, 04:57PM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Ok. My NST is 12kV, 30mA. So, not quite as powerful as the one you described. I guess that means I should probably stop where I am at. Freau says I can get 32" sparks, but I estimate about 28", if I am lucky. So 24-25" sound good?

StevenCaton

Tue Jul 07 2009, 05:27PM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

Yes, that sounds fine. Having sparks constantly trying to hit the strike rail really isn't much of a concern after all with spark gap coils. It looks cool when they hit the rail. Doing everything one can to keep them from hitting the rail is only important in solid state systems, where the spark can kill the control electronics below. Good luck

HV Enthusiast

Tue Jul 07 2009, 07:01PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

As Richard Hull once said, "Don't get hung up on magic ratios, equations, and other advice." Just build your coil and the sparks will come.

1:5, 1:6 - It ain't gonna make a difference.

However, adding the 4" does give you a bit more flexibility. You can always chop some down if you need to change the fres etc... Just another variable in the game of tuning.

Arcstarter

Tue Jul 07 2009, 09:17PM

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

I made my secondary like this, it is 4 by 24 inches (actually, around 4.5 diameter...) and i did that to allow larger sparks without strike rail/primary hits. Little did i know, the new coil worked so much better than my 4 by 16 inch one. I had 6 inch sparks with a 6kv 30ma nst with the 16 inch tall one, and i had 2 foot sparks with the new one (untuned in both instances).

Also, don't forget you can have sparks that strike a foot or two below the secondary and avoid the primary or strike rail. Not often enough to take a chance and remove the strike rail, but i had ground strikes with my coil with like 600 watts, and the topload added 6 inches to the 24 inch height, and the bas added another foot or foot and a half. Spark length is very dependent on the quality of your coil, make it good and never accept less than perfect! If you see bumps or overlaps, you need to get them out. It is very satisfying having a nice coil (mine had gaps though, due to the pitch black room with a blindingly bright reflection from the halogen i used).

I go for longer, and i use a thicker wire. Double built when possible, because insulation is good :P.

Jonathan Dennis

Wed Jul 08 2009, 02:04AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Thanks for the awesome advice. I will go with my current 4x24". My secondary is finished. Unfortunately, there are a few small bumps in the windings, caused by some kinks due to the manufacturers poorly wounded spool! I tried to get them out, but it was impossible without starting over, so I just left them.
I am now working on my primary, and trying to measure the distance between each spiral is killing me. Also the 1/4" tubing I am working with is a real pain in the arse. If you know what I mean. Any suggestions on any easy way of measuring out the layout of the spiral? I have 50 feet of 1/4" copp. tubing. Should come out to about 14 turns, according to wintesla. Thats with .25" spacing, however I think to avoid primary strikes, I should make the spacing a little wider. Input...please!

StevenCaton

Wed Jul 08 2009, 02:26AM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

The spacing isn't critical for a low power spark gap coil. 1/4'' spacing is fine. You could make the primary slightly conical if you want, but not too much.

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