Re: Secondary runners

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

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Robyn,
      12" is about all I've been able to get from a 9/30 NST also, and I too
am only building "small" (12" high) coils. I've met my original goal of
getting sparks as long as my coil is high, but had to go to higher powers
than the plans I made my first coil from indicated. Some day I will try
for 2X (ie 24" sparks from a 12" high coil), but not in the near future.

I too had arcs racing down my secondary until I went to a flat primary, so get
rid of the 30-degree conical.

Also, I make a fixed connection to the outside turn of the primary, and my
variable connection for tuning is on an inside turn. This way the coupling
between primary and secondary is minimized - which helps eliminate the racing
sparks some more.

If you try some other spark gaps let us know the outcome, I've only tried
static gaps so far, and not even a blown one (but I have experimented with
various gap materials, and so far tungsten-carbide is best by far).

If you ever do get longer sparks, let us know how, since there are always
more things to try than I have time for!

-Peter Lawrence.


>
>Hi List, 
>
>      What besides cupping can cause arcs to race down my secondary. It is
>happening with one of my smaller coils (1.75 inch by 10 inch winding length).
>The coil form is acrylic tube, and the bottom turn of the secondary is even
>with the bottom turn of primary. The primary is a 30 degree cone type primary,
>with 9 total turns at .5 inches apart. Torrid is 3 inch by 8 inches OD, and my
>capacitors are TDK UHV series Strontium Titanate pulse rated capacitors. The
>cap bank is right at .01uF, and that is perfect for my 9/30. All I can seem to
>get out of the coil is 12 inch arcs, and with those I get runners. Perhaps it
>is because of my single static non-quenched gap that I am using until I have
>time to make a better one. What do you think?
>
>