Re: First light, next coil

[FutureT-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 9/28/00 5:51:27 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

>   For my next coil, I've planned for a 15/60(modified to 120), a 4:1
>  aspect ratio with a secondary diameter of 4.25 inches/height 21.125(total:
>  24.5 inches), wound with 1676 turns of 28Ga magnet and lots of extra
>  (pancake)primary inductance.  Also, I will be using an LTR MMC: .028 or so
>  uF with a SRSG.  Any input on the dimensions or electrical specifications
>  would be greatly appreciated.  Thank you.
>  
>   Sam Beck

Sam,

When I used a 15/60 (unmodified) with a secondary which is
similar to yours, I got racing sparks when the sparks reached
61" long or so at 120 bps.  For a 15/60 NST, I would probably
use a 6.5" by 30" secondary or something similar, using
maybe 26awg or whatever gives 1600 turns.  Using the
modified NST, you'll have even more power so breakdown 
will probably be a problem at least at 120 bps.  (You may
be able to loosen the coupling enough to help stop the
racing sparks, but I'm not sure).   I'm not sure
just what the optimal size is though for your secondary, 
because most of my work was done with the 12/30 NST.
Your cap is just about matched size for reso-charging, so
you'll get quite a high voltage on the caps, possibly 32kV
peak or more.  A cap of about double the size (LTR) would
keep the voltage lower, but give the same spark length.
A higher bps will permit you to get longer streamers for
the size of your secondary, but will also limit the overall
efficiency of the system.

John Freau