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RE: Aluminum electrodes in TCBOR static gap

Hi Don:

Interesting observation, which begs a few further questions:

What is your power supply, and what is the geometry of your electrodes?  I'm
wondering if either is such that the electrodes get hot to the extent that
the aluminum undergoes something that makes it spew ions, making it more
difficult to quench.  But then that wouldn't explain the way it outright
refused to fire.  What was the individual and total gap spacing?  Could it
have been close to the firing voltage of your transformer?  I can't believe
that the minor difference in conductivity between Cu and Al would affect
anything here.

Regards, Gary Lau
Waltham, MA USA

		Original Poster: Don Allen <dona-at-amigo-dot-net> 


		Hi All,

		I tried an experiment the other day using aluminum pipe on
every other 
		gap electrode in my 11 gap static unit. It worked great the
first 30 seconds, 
		and then the streamer length went down to nothing until the
only sound 
		coming from the coil was just the noise from the gap unit.
I'm not quite sure
		what happenned. 

		Thinking that the unit wasn't getting quenched enough with
just the muffin
		fan, I elevated the unit and put an airhose from the
compressor. Same result. 
		The gap unit WAS firing and making a huge glow, but no
spark. I adjusted
		the electrodes a tad closer, thinking maybe that the firing
voltage was just
		too far. Same result.

		I removed the gap unit and dis-assembled the unit to do a
post-mortem. 
		The spaces between the electrodes were clean. Absolutely no
carbonization
		at all between copper and aluminum except a fine "spray"
like pattern on the 
		aluminum electrode, and nothing on the copper. I then
connected the gap 
		unit to just the NST. I could not get a spark to go all the
way around the 
		electrodes, like with all-copper electrodes. The spark would
actually stop 
		at the first series gap unit that contained aluminum. 

		Even blowing air on the electrodes would not get the spark
to "flare-up"
		and jump to the rest of the gaps, with the unit hooked up to
just the NST.

		This leads me to believe that aluminum is a very poor
conductor at high
		voltage levels. I'm still puzzled on why it worked well in
the first few
		seconds, but then stopped. I looked at the spray pattern and
it doesn't
		seem to have anything that would stop or impede spark
movement. 

		Comments, anyone?

		Don


		http://www.fwpd-dot-net/dona/tesla/teslacoil.htm