Re: "I want bigger sparks!" (me too)

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

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

>  
>  Hello List,
>      I just finished my 3.5"X12" Tesla Coil and I am getting about 8-12" 
>  sparks from it. I am pleased with the output but I think it could do 
better. 

Kevin,

It's always great when you first see those sparks, but you
can definitely do better.  A friend of mine once built a similar
coil, but he used about 20 beer bottle caps, or so, and he got 16"
sparks at first, then he made some improvements and got 21".
But even more length can be obtained even with your relatively
small secondary.  You won't get coil breakdown until you reach
about 30" of spark or more depending on the breakrate.

For best results, you may need a lot more than 20 beer bottle
caps, since an 0.02uF cap would be ideal as Gary mentioned.
Bottle caps will probably cost you at least 15% penalty in spark
length compared to MMC's or other quality caps.

You don't want to make the safety gap and spark gap too wide, 
because it will stress the NST.  Since the secondary is short,
as your sparks get longer, they will tend to arc down and hit
the primary.  To prevent this, you can stack a number of toroids
of progressively larger sizes on top of the secondary.  The 
sparks will emit from the top toroid, and will be directed outwards,
from a higher position, and will have less tendency to strike the 
primary.

A 120 bps sync gap in combo with an LTR value cap can 
probably help some, but a well-designed static gap can come
close.  You may want to try experimenting with a triggered gap
too, since they seem to be getting more popular lately, and it
may outperform a plain static gap.

As the coil gets more and more powerful, a point will be 
reached where you'll need to build a larger secondary of about
6" x 28" or so.  This will permit the sparks to reach 65" in an
optimized design with your NST, if your NST is working OK.

John Freau