Re: Secondary recommendation

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 7/31/01 6:17:56 PM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "Stolz, Mark by way of Terry Fritz <twftesla-at-qwest-dot-net>" <
> Mark.Stolz-at-st-systems-dot-com>
>  
>  John, All
>  
>  I was looking for a fairly general answer.  Most websites I've looked at
>  give the impression that 19AWG is too large for a 4" and for that matter a
>  6" regardless of input power.

Mark,

The 19awg is a little thick for a 4" or 6" coil, but many folks use
20awg for a 6" coil, so 19awg is not much different and would
work fine.  Much depends on whether you're trying to get max
efficiency from this coil.  I've found the best efficiency using
somewhat thinner wire for more turns using those power levels,
but were talking about only a few percent difference.   Using
(2)  15/60's, you could get 90" sparks at 120 bps in an optimized
system, so the secondary should not be too short.

Then again, many folks get only 45" sparks from such as system.
It all depends on the overall design, quality of the caps, value of
the caps, bps, gap, toroid, etc.

But if you plan on an efficient arrangement, you'd want the
secondary to be at least 34" tall to prevent coil breakdown.
Perhaps 36".  A 6" dia is OK.  This would give you about 1000
turns using 19awg which would be OK.  Salt water caps will
hurt the efficiency some of course.  20nF will be a matched
cap for those (2) NST's in combo, so you'll have to limit your
main gap spacing to prevent NST destruction.  This will limit
the spark length greatly, and would permit a smaller secondary
to be used, if the cap value limitation is expected to remain.

John Freau

>  
>  For the record I'll be driving this with a single 15/60 initially but once 
I
>  have enough PFC scrounged up I'll be using two 15/60s.  If I can get enough
>  PFC scrounged up I might use my two 15/60s tied together with a 15/30.  I
>  could wind a short fat one with a piece of 12" PVC I have, but I'm saving
>  that piece of pipe for a future TC.
>  
>  The spark gap will be a static RQ/TCBOR type with 7 segments, the capacitor
>  will be the saltwater caps I'm using with my 2.5" (~20nf) and the toroid
>  size I'm unsure of at this point.  Since I don't know what my secondary 
will
>  be I can't plan the capacitance needed for the toroid.  Most likely it will
>  be a 6" dryer duct toroid, similiar to what I have on my 2.5" just bigger.
>  
>  Mark Stolz
>  Houston, TX
>