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Fine Tuning a Spark Gap and more

Hi Bart, All, 
 
Bart wrote:
"As for Q, if conductance is decreased, well... It may not be enough to be of
any real concern."

I agree with this fully. The way I understand the TC circuit, the Q while drop
like a rock anyway, as soon as the gap fires. So I donīt think this is of too
great a concern (unless you are stuck with a "X" amount of power and really
want to squeeze out that last drop).

Bart wrote:  Very likely, it has nothing to do with the aluminum and possibly
copper
 standoffs of equal positioning and size would do the same thing. 

I found this not to be true (but like I said I have no explanation), because I
tried a pure copper gap with a certain total width and then "rebuilt" this gap
using AL electrodes in between this time, but keeping the total gap width the
same. 

The Cu/Al gap was superior in performance. No further tuning of any other TC
component got me from 45-47 cm sparks to pretty constant 50-52 cm sparks. Plus
the output sparks where much whiter and thicker in apperance. The pure Cu gap
output sparks where more purplish in color. Its not much, but it IS an
improvement

Bart further wrote: 
I think only Reinhard could answer this with a similar comparison described
above.
 
Bear with me, please. I will experiment further. I am just getting ready to
wind my new 8" TC, so it may take a while, but I will keep you posted on new
results.

I am beginning to suspect it doesnīt really have to do with the AL (talking
about its electrical properties here), but rather it has to do with the
surface of the material. Like I have mentioned, the AL erodes fast in the
beginning and gets lots of pits and a very fine roughed up surface.

This may aid in breaking up the sparks within each single part of the gap (its
like having a TF similar gap within each single gap).
For this reason I will repeat the experiment using a pure Cu gap, but this
time I will knurl the copper. I know, this wonīt last very long, but if it
gets me the same results, Iīll be willing to bet its because of the surface
structure, which the AL aquires after a short time.

Now Mike wrote:
I have two, one inch aluminum spheres that were used for corona suppression on
a high voltage transformer's output connections, but never tried them as a TC
gap.  It seemed like the pitting would be severe and they wouldn't last long,
but now may have to try them out.

Hey Mike,
You donīt need to ruin those AL spheres (polished, I would guess). Just look
thru your junk, parts box,etc for a couple of AL stand-offs. For a test this
wouldnīt make a real difference. The Al has a pretty fast "starting" erosion
(it looks like being sandblasted after a few moments of op.). After that, the
erosion doesnīt go much faster than on Cu electrodes. You could just add a few
AL standoffs to the end of your normal Cu gap. Where you place the AL or if
you even go from copper to AL to another AL doesnīt seem to change the
performance at all.

Next Bill wrote:
One common trick has been to use 4 to 5
 > strips of equal width, and sandwich them together, then wind the
 > flat spiral.  Using this method, each individual strip had a thckness
 > of around 0.020 to 0.030"; therefore a composit thickness of 0.100" to
 > 0.150".

Someone else wrote something like: 
try adding PE in between the AL strips......

Now my question to this last comment: 

If you do this (add PE between AL), wouldnīt you effectivly be building a
capacitor "right into" the primary winding? This would/should affect
performance, I think.

Comments?


Coiler greets from germany,
Reinhard