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Re: [TCML] Any one using a 7200 V pole pig?
Roger, I sure enjoyed your YouTube video's. Surfing across Youtube is
what "sparked" my interest in this endeavor. My collection of of big
old transmitter parts lends itself to a DC powered coil and I may well
explore that route especially if I build a bigger coil.
Thanks also to all the others too who replied to my questions. Dr
Resonance, I would like to see your "hyperbaric" design. I'll email
you.
I played with the piggie again today. I wound a new primary coil and
added some more capacity to the primary circuit which helped a bit.
Then I shorted out half the ballast resistance which made significantly
bigger sparks and melted the insulation off the jumper clip. So I read
up on ballasting pigs and ditched the resistors completely. I
substituted in a air core ballast inductor consisting of the remaining
3-400 feet on a spool of #14 house wire. Wow! Three foot angry
sparks! The increase in brightness was even more noticeable then the
greater length.
Unfortunately, the sucker spark gap looked like a ball of fire and the
gap was set so close that not much air passed through it so it quickly
got hot. The streamer length dropped off after only a couple of
seconds of operation. Just as everyone said, I probably need a rotary
spark gap. Or at least a real husky static gap. I'm not sure how much
power it was pulling from the 120V 20A circuit, but the #14 power cord
got warm so certainly well over a kilowatt input.
Building a rotary gap looks like a formidable task, so I may return to
the OBIT supply and simply add some more OBIT's. That is certainly the
easy path and better suits my capacitor bank. I'm not sure what
direction to take this project. Any suggestions or comments are once
again appreciated.
Charlie
-----Original Message-----
From: Roger Smith <rwsmith@xxxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, Mar 7, 2010 9:24 am
Subject: Re: [TCML] Any one using a 7200 V pole pig?
Hi Charlie, I got a 7200 volt, 5kva pole pig out of oil that I use to
run my large DC resonant charging Tesla coil. The pole pig drives a
DC voltage doubler circuit so the Tesla coil gets about 15000 volts.
One nice thing about this set up is that the charging choke takes all
the abuse so your rectifiers and pole pig will last forever.
Another thing you could do with it would be to get something like a
3CX10000A3 triode and build a large vacuum tube Tesla coil.
I couldn't resist looking you up in the ham radio call book
and I see you live in Bethesda Md. Cool, I use to live in Silver
Spring Maryland but I am livening in Ohio now.
Roger , KC8FTQ
----- Original Message ----- From: <cbroring@xxxxxxx>
To: <Tesla@xxxxxxxxxx>
Sent: Saturday, March 06, 2010 7:18 PM
Subject: [TCML] Any one using a 7200 V pole pig?
I've been messing with my first Tesla coil for several weeks now. It
has a 3.5" x 20" secondary, two OBITs in parallel for power, a sucker
gap, and 13nF beer bottle salt water primary capacitor. After fiddling
with it a lot, I managed 28 inch strikes between the break out point
and a metal tool chest, my official measuring technique.
Today I replaced the OBIT's with an old 7200V pole pig that weighs
nearly 100 pounds and has been out of it's oil for years.. I used 4.7
ohms resistive ballast, and ran it off 120V with the low voltage
windings paralleled.. I had to reduce the spark gap to about half of
what I was using with the OBIT's to get it to fire. The result was 8
inch streamers and a screech from the spark gap. I added another 6 nF
to the primary capacitor, re-tuned the primary coil, and the streamer
length doubled. The spark gap also sounded more normal. The ballast
resistors are rated at 450 watts and didn't get all that hot so I
wasn't putting much power through the system.
I think I understand whats going on here. The OBIT's were running near
resonance with the 12 nf capacitor and along with the wide spark gap
setting I was seeing much higher voltages across the primary capacitor
then I have with the pole pig. Now I have low voltage and lots of
current available now so I need a lot of capacitance and a small
primary inductor with high current capacity. It's also going to be
harder to cool the narrow spark gap.
My question is whether a 7200 V pole pig is worth using? I see that I
am going to have some issues to work around using this low voltage.
Also going to have to drink a lot more beer to provide bottles for
capacitors. I'm thinking it may be a better approach to find a higher
voltage transformer or even just a few more OBIT's
Any comments or suggestions?
Charlie
K3YA
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