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[RE]Primary Coil
Original poster: "M G" <gt4awd@xxxxxxxxx>
I do not have a protractor right now, but after looking at the
primary, and actually thinking about it, would have to say the
supports are at 35 degree verticle. For the secondary coil I left 2"
of pvc to raise it above the bottom primary turn. The topload side of
the secondary has not been cut yet. It has nearly 5" of extra pvc
length. After looking at several pictures it seems that around 3"
would be about the right spacing?
Used some of the 1/4" copper tube, that I thought would never use,
for the strike rail. Purchased 10 feet of it before I had learned it
would need to be at least 3x the length. The inside diameter of the
primary is nearly 7", and the secondary diameter is only 4.05", so I
do not think overcoupling should be a problem. I did not varnish the
wood supports so we will see if they work out.
Buying an electrical fire extinguisher was one of the first things I
did before using the NST to make simple jacobs ladders. Eight
supports for the primary coil would help a lot if your using thick
solid wire. After adding the strike rail to the primary I found how
much easier it is to bend the 1/4" copper tube without problems.
Heres a few new pictures of the primary. One showing the secondary
and topload placed how they will be when it is finished. Worked the
primary into a little better shape. The topload is 4" aluminum
ducting covered in a aluminum tape. It has a diameter of about 8.5",
which is a little small, but I think should work?
http://img105.imageshack.us/img105/9636/1000125vt3.jpg
http://img105.imageshack.us/img105/1433/1000126rj3.jpg
http://img105.imageshack.us/img105/7031/1000128mw0.jpg
http://img105.imageshack.us/img105/7536/1000129ra3.jpg
I appriciate the replies. Thank you, Matt G.
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Original poster: FutureT@xxxxxxx
From the picture, it looks to me that the supports are 35 degrees
from vertical which may give tight coupling. But you can simply
raise the secondary enough to stop any racing sparks. Much
will also depend on the diameter of the secondary vs. the primary.
You can use Bart's JavaTC to figure out the actual coupling.
Personally I like to use flat primaries these days as can be
seen on my TT-42 coil:
http://hometown.aol.com/futuret/page3.html
By the way it was about 7 years ago that I built the TT-42 coil.
Interestingly (at least to me), the primary for the TT-42 was
taken from the VT-27 vttc project which never worked out well.
You should allow some provision for raising the secondary to
adjust the coupling. Just placing a spacer of some sort under
the secondary to raise it can be an adequate method.
Regarding the use of wood. It's true that the wood can conduct
depending on the humidity in the area, and the type of wood, etc.
Yet many TC projects have been built over the years using
untreated wooden primary supports and they have worked well.
Regarding fires. Be ready to shut off the power quickly and
use a fire extinguisher if needed. Usually the wood doesn't
actually burst into flames, it just carbon tracks some. The
volts per turn are not all that high really. Certainly since you
already built this primary I'd say go ahead and use it. You
have nothing to lose. If it shorts out or is too lossy, you can
always build another.
I like your style. That's mostly what I do... I use what I have
at hand for my projects. I knew a guy that used wooden
primary supports on his pole-pig powered coil that gave
8 foot sparks. He never had any problems with the wood.
I did have problems when I used wood for some rotary gap
projects. In one case I just cut out the carbon tracked area
and continued to use the rotary. I did use plastic or phenolic
for later rotary projects.
John
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Original poster: Mddeming@xxxxxxx
Hi again,
A 9kV RMS transformer will charge your primary cap to ~12.7 kV
peak.( 9 x sqrt(2)). I would play it safe and use HSPE strip as a
standoff and nylon wire ties. The angle can be checked with a
protractor. The angle between the supports and the base will be
either 35 deg. or 55 deg. If it's 55, it may give you some of the
problems mentioned.But, on a first try, you can learn more from what
goes wrong than from what goes right.
Good Luck,
Matt D.
"Experience is what enables us to recognize our mistakes the next
time we make them" Anon.
-----------------------------------------------------------------------------------
Original poster: "Gerry Reynolds"
If you want to get a nicer looking primary, you might want to try
using eight spokes of support instead of four.
BTW, I have used wood for primary support on my first coil using a
12KV 30ma NST. The wood was varnished before mounting the copper and
it never failed. Of course I decommissioned it to work on my 2nd and
larger coil. For that, I used HDPE for the supports. It is softer
than acrylic and doesnt have the tendacy to crack.
Gerry R.
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Original poster: "resonance"
Best to not use a 35 degree primary. At 4 inch dia secs and above a
flat spiral usually provides adequate coupling. Inverted V primaries
are not necessary until you are running a 1-3 inch dia. coilform or
running a DRSSTC design where increased coupling offers improved performance.
Dr. Resonance
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Original poster: otmaskin5@xxxxxxx
I have also built my primary for a 15/60 system out of wood (3/4 X
3/4 oak) & have been getting 50+ inch strikes without any problems in
the primary. At least so far so good...If it does eventually develop
carbon tracking, I'll rebuild with HDPE or some other serviceable
plastic. But if the wood keeps on working, I'm keeping what I
got. Dennis Hopkinton MA
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Original poster: gt4awd@xxxxxxxxx
Hi everyone, I finished making my primary coil. It has
eleven turns using 10 ga. solid copper wire. The turns
are spaced at least half an inch, and the coil is on a
35 degree angle.
The spacing is fine, but the coil is uneven at parts.
The 10 ga. wire was not the easiest to shape right.
I was wondering if this is going to affect the coil
performance a lot, or if my primary should be fine?
Is the perfect, circular, shaping of most well built
primary coils for performance reasons, or is it
just nice to look at?
http://img167.imageshack.us/img167/6384/1000122be1.jpg
http://img167.imageshack.us/img167/2487/1000121qa2.jpg
By the way, what should I do to hold the wire in place?
Right now its just pressed agianst the wood inside the
slots. If it were to fall the coil would be ruined. I could
use wood/metal epoxy but it is flammable. That is what
I used to attach the primary supports to the wood base.
Thanks,
Matt
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