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Re: [TCML] New coil modeled after Green Monster
Hi Bill,
Yup, I'm still around, though I haven't really been taking
on any new projects in the last couple of years, mainly due
to personal economic restraints ;^(. However, the Green
Monster is still around and is still in working order (just
verified that this past July 4th). ;^)
Wow, I feel honored that someone would choose my coil
as a "pattern" to design theirs after, especially since the Green
Monster was not really patterned after any specific pre-existant
coil. Maybe I did something right on the drawing board with this
coil, eh? ;^) And yes, your listed specs of the GM are correct.
I'm also glad to see there is still some interest in the classic SG
coil system, in spite of the DRSSTC craze of today's coilers. :^)
As far as your problem with your current secondary turn/turn
flash over, John Freau addressed that issue quite well in his
response. I experienced the same problem with a previous coil
design and once I raised the bottom of the secondary a bit (by re-
moving 8 or 10 of the bottom turns and cleaning up the resultant
carbon track underneath), this problem was resolved. With my
current Green Monster system, the BOTTOM turn of the se-
condary coil sits about 1" ABOVE a plane that runs across the
very TOP of the primary coil's 5/8" copper tubing (primary is in
the classic flat Archemedian spiral form). IIRC, in the initial
"first light" of the Green Monster, I had started out with the
bottom secondary coil being horizontally even with the top of the
primary coil plane but had to raise it up about an inch to prevent
racing sparks, as well as secondary turn/turn flash over. So, yes,
the vertical placement of the secondary vs. the primary can be
fairly critical in the quest for optimal coupling.
Also (and some fellow coilers would take issue with me over this),
I tie both the bottom end of the secondary coil with the inner turn
end of the primary coil to dedicated RF ground. Many will say that
the primary coil should not be tied to the RF ground but should "float"
instead. However, I have tried it both ways and with my particular
coil, I ran into a few problems by floating the primary coil, namely
high voltage transients making it back into my control panel and
causing annoying and potentially destructive flash overs inside. Once
I returned to tying the inner primary turn back to RF ground, the
inner control panel flashovers ceased. So that's a no brainer for
me. ;^) Another benefit with the primary/secondary tied together
to RF ground is that there is no significant potential between the
inner primary turn and the bottom secondary turn, so horizontal
spacing of the inner-most primary turn and the bottom-most se-
condary turn is not at all critical.
Good luck with your project to emulate the Green Monster and
feel free to email me on-list or off-list if you'd like to get more
details on its design.
Happy coiling and happy 154th birthday to Nikola,
David
----- Original Message -----
From: "Bill Fuller" <bfuller@xxxxxxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, July 09, 2010 11:22 AM
Subject: [TCML] New coil modeled after Green Monster
Hello everyone,
It's been a while since I've been coiling and I'm ready to upgrade my
current coil.
Currently running a 10" coil with 6 to 8 foot sparks.
Looking to up-scale to a 12". I've had some issues with my 10" burning the
secondary about 3" up from the primary and hope to avoid this on the 12"
coil. Endless playing with primary to secondary spacing didn't tell me
anything. It's not a primary to secondary arc, it seems to be shorting
secondary turns after running for a few minutes. Been through 3 secondaries
and all had the same problem. Flashover perhaps, something geometry related
with this design I think.
That said, I was wondering if anyone can provide me with some core spec's on
the green monster coil so I can use it as a base model for my next. David,
still around???
I've looked at the YouTube videos and flickr pictures many times. This coil
makes long runs with minimum flashover and throws arcs quite a distance.
Nice work.
Anyway, I have been able to collect some specs (please correct if wrong);
Secondary: 12.5" x 54", 49" of #19 wire
Topload 12" x 56"
Cap BNZ 2500-104 0.1uF
Primary to secondary spacing 1.5"
Looking for some specifics to avoid flashover and burned secondarys.
Secondary height above primary:
Toroid height above secondary:
For a sanity check on my design it would be nice to know (you may or may not
have this info...):
Primary and secondary resonant freq.
Coupling factor
Primary and secondary inductance
Thanks in advance!!!
Bill
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