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Re: FREE NST's


>
> Original Poster: "Trent Mullins" <neontrent-at-earthlink-dot-net>

Hi Trent, comments intersperced, 
  
>
> Okay, this is what I have.... 
>
> 1.   A helical primary 60 degrees from horizontal, 8 turns of .25 copper tube
>
> spaced .5 inches between turns, 
>      17"OD and 11"ID.

This is termed an Inverse Conical Primary due to the 60 degree angle from the
horizontal plane. A helix is parallel (strait up and down). 

Due to your secondary "loaded" resonant frequency of 122kHz (not 175kHz -
unloaded) due to the added capacitance of your toroid, I'm calculating you'll
need more like 13.7 turns. It's always wise to add a few more turns than you
calculate. Calculations get close often, but if there is a build up of
tollerances, the calcs can be off a bit and you may need more turns to tune to
the loaded resonant frequency. 

You've got 2.5 inches of clearance between secondary and primary. Conicals and
Helix have tight ratios of inductive coupling. I've built only flat spirals but
2.5 inches may not be enough clearance and may require raising the secondary up
to lower the coupling coefficient (if too tight, it causes racing sparks along
the surface of the secondary - a bad thing). 

Helix and Conincals are also closer to the top terminal and primary strikes are
more likely to occur. Why not build a flat spiral and reduce coupling problems
and increase the primary to top terminal distance? 
>
> 2.   A 36" tall, 6" OD hollow secondary wrapped with 1615 turns 44.8
> turns/inch 
> of 24 gauge magnet wire. 
>  

It will work, but that's a lot of wire. Your H/D ratio is 6:1. Again it will
work, but why not reduce to a 5:1 ratio (30" length) and increase to a 21 or 22
guage wire? This will increase your power handling, reduce the secondary wire
length by about a 600 feet, and pull your primary turns down to around 9.5 if
you stayed with the conical primary. This design will work good to (and cost
less). (well, unless you already have the magnet wire - then use it). 
>
> 3.   Two 15kV 60mA NST's wired in parallel for 15kV 120mA.

Sounds good. Should get you 70" sparks or so. 
>
>   
> 4.   Two .01uf 100kVdc caps from Fair Radio Sales wired in parallel for .02uf
>
> total.

Sounds good too. You may want to think about MMC's if for nothing else, to have
the ability to change capacitance values to meet future needs. Can't do that
with 2 caps very well. Trust me on that. I use CSI professional caps (three
.02uF in parallel). I can only do so much. Next cap buy for me is a pig powered
MMC. 
>
> 5.    A 13"x4" brushed aluminum torroid. 
>  

Should be fine and no problem of breakout. If polished smooth, this may be a
good size. If not, you might want to go a bit bigger (best to experiment within
your turning capabilities). 
>
>  These are my questions... 
>
> 1.     Will this work?

If you build it correctly, and understand the potential hazards as well as how
to keep you and others safe, it will work. 
>
> 2.     How do I attach the primary coil to the base that the secondary is 
> mounted to?

Anyway you want. Use a non-conductive form (even wood will work). I keep my
secondary and primary seperate. (primary base center is cut out - a seperate
inner base is used to set the secondary onto). The secondary bottom should be
as close to a perfect cut as you can get. You don't want a leaning secondary).
The primary needs to be attached from the bottom, so if you intend to use a
full base, just make sure you have easy access for attachment and tuning of the
primary. 
>
> 3.     Is there enough spacing between the primary and secondary?

mentioned this somewhere above. 
>
> 4.     Explain to me where and how I tap the secondary?

The bottom wire connects to an RF ground point (whatever you decide to use for
that). The top wire attaches to the toroid. No tapping occurs on the secondary
for tuning purposes. This is done at the primary because it's practicle. The
secondary can be considered the "fixed" LC circuit, and the primary is the
"tuning" LC circuit. 
>
> 5.     How do I ground the secondary?

Best to use a good RF ground for RF currents. A good RF ground can be as easy
as using copper welding cable (due to the many strands) which connects at the
RF connection for your secondary and runs out to ground rods pounded into the
ground. I use three rods spaced 8 ft apart in a triangular pattern. The rods
get buried a couple feet down under the lawn. I also run the line from the rods
to a point at the edge of the garage where the welding cable connects. This
way, I don't run over anything when mowing the lawn. 
>
> 6.     How do you coat the secondary with polyurethane?

I mount the secondary horizontally to wind it up. Then I coat it with Marine
Spar Varnish which is a heavy coat and is tollerable to temperature changes
(has a bit flexibility and doesn't crack easy). The last time I did this, I
hooked up a DC motor turning it slowly to wind and to coat the secondary. Helps
prevent runs during drying. 
>
> 7.     What is the easiest and cheapest way to build a spark gap for this?

Easiest and simplist is 2 bolts. Heats up quick, eats the bolts, etc.. A RQ gap
or rotary is better to use. Many NST's run great on RQ gaps or simple parallel
copper pipe gaps. You should use a fan. I use a G10 disk with tungsten
electrodes now. In my opinion, the best gap type if using a rotary. 
>
> 8.     How do I attach the torroid?

mentioned above. You can mount it on whatever form you wnat. I've put a plate
of plexiglass on the secondary and simply set the toroid on it and connected
the top secondary wire to it. Worked just fine. Nothing real criticle there
except maybe how far to put the toroid up from the top of the secondary
winding. If you have corona at the top of the secondary winding, then you may
need to bring it down closer to the top winding. 
>
> 9.     Is there anything else I need?

Money, time, try not to rush. Read read read - ask ask ask. Maybe some PFC's
for the NST. Safety gaps for the gap / cap and the NST's. How to phase the
NST's properly. There's lots more info to obtain. Hard for anyone to do it in
one shot like this. Too many email hours due to the large volume of posts these
days. Seach the archives. All this info is there for your access. 
>
> 10.    And finally, explain in LAYMAN'S terms how to hook all of this
> together. 
>          Example: connect one lead off the transformer to the cap, hook the 
> other lead to the...

Got to say, "find a schematic on the internets Tesla Web Ring". Lot's of them
out there. The circuit is simple but a schematic is what you need for this.
BTW, you don't want to put the cap in parallel with the NST. Look for a
schematic with the gap in parallel with the NST. 
>
> Thanks in advance, 
>
> <<mailto:neontrent-at-earthlink-dot-net>mailto:neontrent-at-earthlink-dot-net>neontrent-at-
> earthlink-dot-net

Hope I helped a bit. BTW - I don't need the NST - just felt like replying.
That's what this list is for. 

Take care, 
Bart