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RE: Aluminum electrodes in TCBOR static gap
At 06:57 PM 10/14/1999 -0600, Tesla List wrote:
>Original Poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
Hi Gary, All,
>
>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
The power supply is a 15/60 NST. The gap spacing is .030, using 4"
long electrodes. Total gap is .030 x 11 = 0.33. I haven't encountered
this phenomena before using all copper electrodes, even when I
intentionally widened the gap between each electrode to .050 with
a second gap unit, using the same TCBOR construction and with
11 gap units.
I have no doubt I could remove the Al pipes, clean the fine carbonized
pattern with sandpaper, re-install and it would perform identically to
the first test - good performance for 30 seconds and then fizzle down
to nothing. I believe you might have touched on the point why - the
Al pipes may get much hotter than the copper and are harder to
quench, even with a muffin fan and an air-assist under the bottom
from the air compressor. This might be the actual reason, but I fail to
understand why, even with all the added air for quenching. It could
differering HV characteristics between the two metals.
I tried this, based on reading last year's archives from the list, where
Reinhard had used 6-sided Al standoffs in his unit and reported good
results. I didn't go the stand-off route, but wanted to see what would
happen with an alternating combo of Cu-Al electrodes.
My thinking now is that aluminum is a very poor choice as an actual
gap electrode. It could be different with a stand-off.
Don
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