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Re: Primary construction



Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi MCP,

Tesla list wrote:

>Original poster: The MCP <ejkeever-at-comcast-dot-net>
>Oh... Well, there's nothing special about the primary wire either. The
>connection to the caps is a fat red wire, with 1 or 2 mm of stranded wire in
>the middle. The primary coil is around 22 gauge wire, nothing special. It
>starts getting slightly warm after 20 seconds.

All losses end up as heat, so that is telling you something right there. 
Need to get heavier gauge wire. I personally would go with #18 or larger.

>The topload, I mentioned, is the remainder of wire coming off the secondary.
>It's roughly 6 inches long, wound around a 3/8" dowel rod as a form, coming
>out to 7 or 8 turns. It seems to give the same results as the original copper
>tube topload (1/2" pipe, ~2" diameter)

Ok. I'd try a larger topload. Any old thing would do. It would be nice to 
form a toroid shape if possible, but really, even a pepsi can would 
suffice. If pepsi can, try a primary about 3.2 turns range within a 2.2" 
botttom to top height. Set can upright on top of coil.

>However, although people are telling me this thing is in fact in tune, I still
>get absolutely no sparks exceeding 3 inches - ever. Do I need to connect the
>bottom of the secondary to a spike hammered into the ground? Do I need to use
>a "real" topload?

Couldn't hurt. Also, I've mentioned this in a past post and just noticed it 
again. Your coupling coefficent is low at 0.065. This will result in 
smaller sparks. If you were to place the primary center to the secondary, 
you "still have a low coefficient" at 0.085. This is the maximum you can 
possibly obtain without winding a primary coil closer to the secondary. 
This is probably the area I would work on along with the topload and 
primary size. I would go to larger primary wire also for the reason that 
#22 will not only heat up, but it will also be prone to pri to sec arcs 
(unwanted arcs) if you were to get too close. Increasing the primary 
diameter would increase the radius of curvature and in so doing, increase 
the voltage of arcover, thus allowing for a decrease in proximity between 
coils (needed to increase the coupling coefficient). Try to get k at least 
to 0.12 and then adjust coupling up or down by raising and lowering the 
primary (or secondary, whichever is easiest for your coil).

As coupling increases, the coil may want to arc out of the top of the 
secondary. At that point, it's time to decrease coupling until it stops. A 
pepsi can won't do well at shielding the top of the secondary, so you may 
not be able to run as high a k as you would like. If you can build a toroid 
out of something (again, anything will do), the shape of the toroid 
provides excellent sheilding and helps relieve the top terminal stress. At 
this point, you would have to double your coupling to even get to this point.

All these types of adjustments/modifications are all part of the fun to 
make the coil more efficient at producing longer sparks for a given input.

Take care,
Bart



>On Saturday 20 September 2003 09:19 am, Tesla list wrote:
> > Original poster: Bart Anderson <classi6-at-classictesla-dot-com>
> >
> > Hi MCP,
> >
> > Nice when you get things like that! But, the #32 is secondary wire. I was
> > curious about the primary wire and topload.
> >
> > Take care,
> > Bart
> >
> > Tesla list wrote:
> > >Original poster: The MCP <ejkeever-at-comcast-dot-net>
> > >Well, the wire I'm using is an interesting story... I got 8 rolls of #32
> > > gauge from mpja-dot-com to be used to wind a *load* of small electromagnets
> > > in an attempt to build a maglev. I ended up using, um... 2 of them. So
> > > I've got about 3 miles of wire, and I wanted to build a tesla coil! And
> > > I've *still* got almost all the wire I started with...
> > >
> > >Having this huge amount of wire available was one of the things that made
> > > me consider making little "play-thing" size tesla coils.
> > >
> > >On Friday 19 September 2003 06:47 am, Tesla list wrote:
> > > > Original poster: Bart Anderson <classi6-at-classictesla-dot-com>
> > > >
> > > > Hi MCP,
> > > >
> > > > 2 turns sounds about right with a slight topload (maybe a point or your
> > > > coiled wire?). Could you do us a favor and give more info as to the
> > > > wire type used for the primary? We are still not clear on what your
> > > > actually using. The topload would also be much needed data. This type
> > > > of data seems to be very limited from coilers (full specs with center
> > > > heights).
> > > >
> > > > Both John C. and I truly enjoy crosschecking against the programs. We
> > > > love doing it or we wouldn't. Your coil is pretty cool to run through
>Msnip...........
>
>
>
>