Re: Primary coil

["Tesla list" <tesla@xxxxxxxxxx>]

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


-----Original Message-----
From: tesla@xxxxxxxxxx
To: tesla@xxxxxxxxxx
Sent: Sat, 10 Feb 2007 11:47 PM
Subject: Re: Primary coil

Original poster: FutureT@xxxxxxx
In a message dated 2/10/07 7:59:19 PM Eastern Standard Time, 
tesla@xxxxxxxxxx writes:

>Hi, thanks for the replies. Matt D, I will only be using a 9kv 30ma
>NST for the coil. Should I still add the HDPE plastic or will it be
>ok? I think the supports are at a 35 degree horizontal angle, but I
>am not sure of the difference between the two. I cut the bottom of
>the supports to a 35 degree using an angle cutting table saw.

>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%3Ehttp://hometown.aol.com/futuret/page3.html>http://hometown.aol.com/futuret/page3.html>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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