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Re: [TCML] Newbe's First Coil



 I used to use #12 fine stranded wire with pvc insulation for flattish coned primaries.
Because I used quite a few turns, often 18 turns or more, voltage flashovers were not
a problem with the close-wound configuration.  I simply stuck a sewing needle
into the wire to create the tap point.  I then clipped an alligator clip to the sewing needle.
In some cases the needle glowed red hot, but it didn't seem to hurt the coil's 
performance because this resistance was only over a short distance.  This coil
was my old "research coil" which was a precursor of sorts to my TT-42 coil which
also uses a close-wound primary.  However the TT-42 flat primary uses 10awg telephone
solid ground wire for the primary.  Another small coil I made which is also shown
at my website uses either 12awg or 14awg pvc insulated solid wire (or is it stranded....
hmmm, now I'm not sure?) close-wound, for the flat primary.  The flat primary for
the TT-42 coil was tricky to wind however.  

   http://futuret.110mb.com

John

 


 

 

-----Original Message-----
From: Paul Brodie <pbbrodie@xxxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Mon, Feb 1, 2010 4:53 pm
Subject: Re: [TCML] Newbe's First Coil


I've considered using Monster speaker cable before, because of the really thick insulation. A major drawback has been the insulation and tapping the coil. Your idea of making a sharp probe sounds like a good, workable solution. I'm glad to hear it didn't present too many problems for you. 
 
Now that you have brought this up and pointed out how well it works, I think I might try using it with a flat spiral on a relatively low voltage coil I'm building. I don't really think it will save much money, though, if any. All of the Monster speaker cable I have ever seen was extremely expensive, certainly not less than 1/4" copper tubing. I will check to see how the price compares now. I haven't looked at any for a long time. One really good aspect of using this speaker cable is that it shouldn't have the problems with oxidizing and starting to look like poop, the way copper tubing does, which has been discussed at length here recently. :-) 
 
It appears to me that winding a flat spiral would be easier than making a helical coil. All I should have to do is wind it out flat on top of a piece of HDPE plastic. If I need to anchor it down, I can just spot weld it with a hot glue gun. If extra space is required between turns, in case the insulation isn't sufficient, it would be easy to add some by putting spacers between turns before gluing it in place and then removing them. 
 
I've often wondered about using multi-stranded wire for the primary coil because of the high frequency skin effect and the increased surface area of all the small conductors. Unfortunately, I think this is defeated by the fact that they aren't insulated from one another, like they are in Litz wire. 
 
Thanks for sharing your experience with this. 
Paul 
Think Positive 
 
----- Original Message ----- From: "Weinhold Shannon L" <Shannon.L.Weinhold@xxxxxxxxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> 
Sent: Monday, February 01, 2010 2:58 PM 
Subject: RE: [TCML] Newbe's First Coil 
 
I wind my primaries "helical" all the time and don't have any problems. 
I use heavy gauge monster cable speaker wire (probably 10 ga) with the 
thick rubbery insulation and it works great. I run the wire without 
spacing, because the insulation alone provides about 1/4" of spacing 
between conductors when two layers are stacked. 
One plus to doing it this way, other than obviously being much 
cheaper/having a much smaller footprint/less labor involved is that you 
can use a map tack (basically a long steel tack) to tune your primary. 
Just remove 3/4" insulation from your primary circuit lead-out wire and 
wrap it tightly around the top of the tack, then push the tack through 
the insulation to where its making good contact with the braided wire 
inside. Don't mess up here or you'll end up with a loud bang and a free 
swinging primary wire bouncing around like a down power line. Make sure 
that the tack is pushed in from an angle and has at least 1/2 inch of 
its length within the wire, and that its making good contact. (FYI, you 
can't do this with solid copper wire. It will heat up and melt the 
insulation and then you'll have the downed power line effect again. 
Surprising the braided cable is quite resistant to heating.) This makes 
for easy tuning, and when you get the tuning perfect you can simply 
carve out some of the insulation and easily solder the primary wire to 
the now exposed braided cable. 
Flat spiral coils look pretty, but they are spendy and take up a lot of 
space. Just be sure that your primary coil former is large enough in 
diameter to keep from over-coupling the secondary. If you get sparks up 
and down your secondary then you're over-coupled. You can always raise 
up the secondary a half inch at a time by placing something under it 
until you get your coupling right. 
Save the flat spiral for later when you know what the heck you're doing 
and you want a pretty coil. This works fine for functionality, and tesla 
map will tell you what size former you need if you enter in all the rest 
of the parameters. 
Just my two cents as someone who has some different experience. 
My coils can be seen on youtube here: 
http://www.youtube.com/watch?v=46ZcwyTUQPc 
 
Shannon Weinhold 
Klasdja Intelligent Innovations 
 
"The world we have created today has problems 
which cannot be solved by thinking the way we 
thought when we created them." 
-Albert Einstein 
 
-----Original Message----- 
From: mddeming@xxxxxxx [mailto:mddeming@xxxxxxx] 
Sent: Sunday, January 31, 2010 9:31 PM 
To: tesla@xxxxxxxxxx 
Subject: Re: [TCML] Newbe's First Coil 
 
Hi Charlie, 
 
I don't know anyone who uses a close-wound helical primary on a 
spark-gap coil. A 3.5 in. coil  could easily handle 500-800 watts, but 
not with 14 ga wire as the primary coil. 6-10 ga space-wound bare wire, 
or copper tubing would allow for higher peak currents for better power 
transfer and allow it to function as a heat radiator also. You might 
consider replacing the wooden rods with pvc pipe notched on the outer 
edge to hold the wire in place. The alternative is a flat spiral coil 
with 0.25 in spacing between turns. That should work up to 1 KW. 
It sounds like your new toroid may be a little large for your 230W OBIT 
to give consistant breakout without a point and ground rod. Be aware now 
that once you start making improvements, you will never be satisfied to 
the point of not wanting to change something ;^)) 
 
Matt D. 
 
(snip) 
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