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Re: Bottle Caps; First Firing
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: bert.hickman-at-aquila-dot-com
Sent: Saturday, November 15, 1997 10:17 AM
To: Tesla List
Subject: Re: Bottle Caps; First Firing
Tesla List wrote:
>
> From: ghunter-at-mail.enterprise-dot-net[SMTP:ghunter-at-mail.enterprise-dot-net]
> Sent: Friday, November 14, 1997 5:00 PM
> To: Tesla List
> Subject: Bottle Caps; First Firing
>
> Just fired up the little 4.5" x 23" TC for the first time. Tuning
> up was a pain. Took me an hour to find the sweet spot on the primary.
> Sparks were only 6 to 8 inches. A bit disappointing. I can see
> part of the problem right off. My foil-covered wine bottle caps
> (5 caps for .0056uF total) glow with lavender corona. The loss must be
> horrendous. I plan to paint them with melted parafin in an attempt
> to suppress the corona.
>
> I could see a bright corona halo coming from the top turn of the
> secondary winding. It was blowing right through the thick, sloppy
> coatings of gloss urethane. The top windings of my secondary are
> going to get the hot wax treatment as well.
>
> Another problem. My 5k, 50w series power resistors (one per
> transformer leg) are getting hot as pistols. Obviously, they are
> eating some power. I'm going to replace them with 100 turn chokes
> wound on 1" x 5" cylindrical ferrite forms. This will reduce ohmic
> loss while (hopefully) preventing raw RF from reaching my neon
> secondary.
>
> In frustration I opened the gaps up wide. The 15kv neon could just
> barely fire them. Sparks increased to about 12" and the noise was
> deafening. The safety gaps were firing like mad. Gave me the
> creeps. I know this treatment is hard on both the neon and my vino
> bottles. I put the gaps back to a sane setting. I'll pursue longer
> sparks through incremental improvements in efficiency instead of
> blowing up my neon & cracking glass. Sure was fun though. I wanna
> build a bigger one.
>
> Greg
Greg,
Congratulations on "first light" - now you're hooked! More power, more
power!! :^)
Although coating the winebottles with wax will reduce corona and ozone
production, it won't improve the cap losses in a major way, since most
of these losses stem from dielectric heating of the glass itself. If
you're getting corona from the top of the secondary winding, you need to
either increase the size of the top termial (toroid, sphere, etc), or
lower it so that it provides more E-field shielding of the winding.
Re: your damping resistors - try using a lower value (say like 3K) in
each leg IN ADDITION to your newly made chokes. BTW, make sure you've
heavily insulated the choke's winding from the ferrite core, since the
core's conductive enough to cause breakdown between the ends of the
choke and the core. BTW, the voltage developed across these chokes can
be truly awesome. You'll actually need the damping resistors MORE when
using the chokes to hel suppress ringing caused from the chokes
themselves.
Improve your caps, gaps, and add a good toroid and you'll be getting
multiple-foot streamers soon!
Safe coilin' to you!
-- Bert --