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Re: [TCML] Pictures of my Tesla Coil



Hi Dirk,

When you raise the primary and if you see racing sparks, start coming down in small increments until their gone. You may very well end up where you started. This arena will always be trial and error. One coil might handle 0.13 just fine and another coil may need 0.1. If it works out that 0.1 is your coils value, then so be it. But, do give some higher coupling a try.

Sparks will hit the strike ring from time to time, but they will also seek out the field around the toroid itself. I personally no longer use a strike ring. I got tired of strikes hitting it. Once I removed it, I had fewer strikes down to the primary area and more strikes in the air (this was most apparent as I increased power).

However, if a strike does run down to the primary, it can cause problems with the NST. So strike rings are certainly helpful to prevent unwanted voltages back at the transformer. I decided to risk it and this has been my personal preference for a few years now. So far so good. The TCML recommendation is still to use a strike ring.

Take care,
Bart

Dirk Stubbs wrote:
Thanks for the input. I have an additional neon transformer(15KV @ 30mA)
so I can just hook them up in parallel to gain the 60mA. I will also try
raising the primary 1" as you suggested. I would love to gain 30-36"
sparks from it but I do have a question. If you look at my primary I
have a safety ground ring(to avoid the sparks from hitting the primary)
that is about 2" above the primary which is about 20" from the toroid.
If the coil could deliver 30-36" sparks, why wouldn't it not just hit
the safety ground ring which is closer? Excuse my ignorance.
Anxious to try once the weather clears up in Kansas. I am not confident
with running the coil in the house as I have alot of computers and
afraid something bad will happen. Call me a chicken I guess. :)
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Barton B. Anderson
Sent: Sunday, December 23, 2007 3:31 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Pictures of my Tesla Coil

Hi Dirk,

Thanks for the specs.

Tuning looks good. Your about 4% high on inductance which is where I like to be. Coupling was slightly low at k = 0.11. You could probably do

some coupling adjustments if you can raise the primary or lower the secondary. A k of 0.13 is when the primary is about 1" above the secondary. The coil probably won't like going beyond that.

The coil could probably do about 30" to 35" spark length. But power is low with the 30mA supply. A 60mA or 90mA supply would certainly help on this coil.

These coils can handle rather high power with no problems as long as you

keep racing sparks away. About 5% more primary inductance above the resonant tune point is good to help with this especially when power is increased. The other item is to keep coupling high but not so high that racing sparks occur. Also, if high powers are used (say greater than 100mA transformer), you have to keep an eye on the lower secondary windings as they can begin to burn. I run a very similar coil but I had to lower coupling due to the bottom sec turn burning (no racing sparks, just burning). The transformer is a 12/60 NST with 1/2 the shunts removed. Since I fixed that I've done some rather long continuous runs on the coil (20 to 30 minute runs which is extreme for a coil, but it just keeps on going).

Here's some photo's of that coil for reference.
http://www.classictesla.com/photos/ba45/ba45.html

Take care,
Bart




Dirk Stubbs wrote:
Sorry I should have included some details.

Power: Neon Transformer 15KV @ 30mA
Capacitor: 14 doorknob capacitors 30KV @ 590pF  = 8.2nF
Secondary: 4" PVC with 22" total winding of 24-28 gauge(Don't remember
the exact gauge but do recall it was about 1000 turns)
Primary: 1/4" copper tubing, 13  turns, 22" overall diameter,
approximately 3/8" spacing(5/8" center to center), currently tapped at
11
Toroid: 2 - 8 pie pans with 4" flexible duct.

When I originally built my coil, I used TeslaMap to determine what I
needed.
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