Rotary Gap Electrodes - A first-hand experience

To: tesla-at-poodle.pupman-dot-com
Subject: Rotary Gap Electrodes - A first-hand experience
From: open_minded <bturner-at-apc-dot-net>
Date: Wed, 23 Oct 1996 01:27:25 -0700

Hi all...

  Well, I had a very successful, and eye-opening experience tonight. Lit
up my larger coil system with the new, 3600 RPM sync. motor. The coil
sure came to life...I had frantic, white, energetic discharges waving
into the air. Physically measured strikes came out to 67" to a metal
ladder near the coil. (Hey, whatever works.) Not shabby for a secondary
with only 22" worth of windings.

  One interesting thing though - I sure vaporized the tips off the
stationary electrodes in my rotary gap! Whoooeeeee. I had 1/8" tungsten
rods fixed into brass holders. At full poop, the stationary rods
achieved a nice, brilliant yellow after about 20-30 seconds. The rotating
electrodes (same stuff) stayed nice and cool.

  Pre-ionization was quite evident as the discharges initially started
out very long, then after about 5-7 seconds, shrank back as the electrode
tips got exceedingly hot. At least I think it was pre-ionization. After
the gap cooled for a few seconds, it would again light up with long
discharges that again would shrink back a bit as the tips heated up.
Anybody experience this phenomenon? (BTW - this same coil *didn't* have
this behavior with it's old 1800-RPM gap with other electrodes, so I am
rather sure that everything else hasn't changed.)

  Looks like a quick retro-fit is in order here. I will replace the 1/8"
rod in the stationary holders with 1/4", and cut some rather massive
and heavily finned brass heatsinks. Hopefully, this will help to keep
the (fixed) electrode temperature down below the 'nasty' point.

  Aside from dwell times and such, one must be careful to match the
electrode size and shape to the operating power levels! Either that, or
I will need to figure out a way to liquid-cool them....!!!!

- Brent