Re: topload problems

["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 7/14/01 9:46:11 AM Eastern Daylight Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "Will Daniels by way of Terry Fritz <twftesla-at-qwest-dot-net>" <
> tesla_is_god-at-37-dot-com>
>  
>  Hi all,
>       I just finished my six inch coil the other day but I cant seem to get
>  more than 1 foot arcs.  My secondary's winding length is 2 feet and my
>  power supply is two 12Kv/30ma NSTs with a six sectioned static gap and 24
>  beer bottle caps.  Soon I'm hoping to get a better capacitor so I can
>  enlarge my NST bank. 

Will,

That's a good size for the secondary for those NST's.  Such a coil
should be able to give about 59" sparks if everything is optimally
designed, and the system powered by a 140volt variac. 
      The bottle caps may cut the available spark length
drastically, especially if the total capacitance is a low value.  Did
you try blowing some air on the gap with a fan or blower?  Some
types of gaps tend to over-heat, and barely work.  I'm assuming
you have a few extra turns on the primary so you can tap outwards
to keep the coil in tune as you add larger toroids?  The largest
suitable toroid may be about 6" x 24" for that coil.  A 4" x 16"
will work OK too.
      If the cap value is small, this may reduce the spark length to
1/2 of 59" or about 30".  Since the bottle caps are lossy, this may
reduce the spark further to maybe 24".  For a 24" spark, a 3" by
12" toroid is big enough.
      I once observed a coil with a four-section static gap which gave
only 4" sparks from the coil.  When a small muffin fan was arranged
to blow upon the gaps, the sparks increased to 12".
      When a coil's output is weak, I first suspect a problem with
the gaps or with tuning.  I'm assuming your sparks emit from the
toroid.  You don't have to draw them off with a grounded metal rod
do you?  If your gap spacing is very very narrow, this will cut the
output spark length also.

John Freau
----

>  It seems that the larger my topload gets the shorter
>  my arcs get which goes against everything I've read.  I tried a dryer duct
>  toroid about 10" wide but I think the break out point must be too high
>  cause I get nothing.  I've tried everything from bolts to mixing bowls and
>  it seems that a bare wire some how works best.  Any ideas on how I can
>  improve my output would be helpful.
>       
>       -Will Daniels