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Jonathan Dennis

Thu Aug 13 2009, 09:29PM

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

Ok, so I finally finished my tesla coil and after an hour of tampering with it, still can't get it to work. I have lots of pictures for it so i'll post some pics, going to have to double post the pictures because It won't let me upload more than one at a time. Please let me know if you see any problems, I tapped at turn 8, and didn't really change the tap point because I assumed it would work at least a little bit even out of tune. I gave it like a 2-3" gap to jump out of the toroid to ground and nothing. Just really loud spark gap...

Jonathan Dennis

Thu Aug 13 2009, 09:30PM

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

rest of the pictures. *sorry for double posting*

Coronafix

Thu Aug 13 2009, 10:19PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Move the tap point. It's called tuning. The loud gap is a good sign, it means that the cap charge is dumping across it. Never assume a coil will work just because you think you have it all setup correctly. Try tapping it at 6 and moving out slowly until you get the best length. Good luck.

Jonathan Dennis

Thu Aug 13 2009, 10:41PM

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

thanks I will try that. So the tuning can prevent it from even jumping 2 inches? (btw freau said I should be able to get 32" streamers.)

brtaman

Thu Aug 13 2009, 11:19PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
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Posts: 247

If, apart from the primary, your coil is set-up properly, which it seems to be due to the loud spark gap.

Then as coronafix mentioned all you need is to start tuning and enjoy yourself this is the funnest part. Watching the sparks grow ;). Just to make sure everything is set-up properly bring fluorescent bulb into the coils perimeter to ensure RF is being generated (It will light up). Then start tuning away.

BTW Freau's equation assumes 100% efficiency, which is impossible with a spark gap. But you can expect some very nice performance from your 350ish VA? NST. :D Post up some pictures and a video or two when you finish tuning.

Thanks
brtaman

Jonathan Dennis

Fri Aug 14 2009, 12:22AM

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

Good news! I tuned to the 6th turn and immediately got streamers. Bad news! I had 2 secondary flashovers. I'm hoping I can fix that with several coats of polyurethane in the trouble area. It did get scratched several times on accident which might be the cause of the flashovers. One "corona discharge" from the bottom of the secondary jumped (dangerously close to the primary) to my grounded steel pole. Didn't measure but it looked like it was well over 2 feet! I'm curious as to why it did this when it would have been closer for it to jump from toroid to the top of the steel rod? Anyone have an idea? Unfortunately, i'm going out of town this weekend so I have to wait until I get back to tune it! :( But i'm realllllly excited it's working!

Steve Conner

Fri Aug 14 2009, 11:51AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Did you remember to ground the bottom of your secondary?

Jonathan Dennis

Fri Aug 14 2009, 12:50PM

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

Yes, I have an excellent ground that cannot be seen in the picture. It's a little more than three feet in the ground and I let a water hose soak the ground for a few minutes, the ground wire is heavy gauge copper wire bundled together.

Right now I need tips on how to stop the secondary corona and flashovers. It's doing it in 2 places near the bottom, jumping about 4 inches. It's not making it to the toroid. Will several coats of polyurethane fix this?

oucivileng

Fri Aug 21 2009, 02:00PM

Registered Member #1772 Joined: Tue Oct 21 2008, 05:23AM
Location: Athens, OH
Posts: 71

The polyurethane might stop some corona but not flashovers (i assume by flashovers you mean it's jumping to the primary coil). Raise the secondary a bit, make sure your secondary is grounded well, and watch out for any points or sharp edges on your primary coil. I had probs with the edge of the clips on the primary causing sparks.

HV Enthusiast

Fri Aug 21 2009, 03:17PM

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

Jonathan Dennis wrote ...

Yes, I have an excellent ground that cannot be seen in the picture. It's a little more than three feet in the ground and I let a water hose soak the ground for a few minutes, the ground wire is heavy gauge copper wire bundled together.

Right now I need tips on how to stop the secondary corona and flashovers. It's doing it in 2 places near the bottom, jumping about 4 inches. It's not making it to the toroid. Will several coats of polyurethane fix this?

Coatings on the secondary should never be relied on for preventing arcing and flashovers. If you have a high voltage gradient on the secondary, it will eventually pass through any dielectric material you have on there. Coatings such as polyurethane are only applied as a "mechanical" shield against nicks / bumps / etc... not for voltage isolation.

Your best bet for flashovers as previously stated is to reduce coupling by raising secondary above primary. If arcing is occuring at the base of secondary, then suspect the ground connection. If you are getting arcing from secondary to top turn of primary or strike rail, then you need to re-evaluate the geometry of primary or strike rail, or raise secondary.

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