Tracking

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ted Rosenberg by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Ted.Rosenberg-at-radioshack-dot-com>

Hello everyone. I need your thinking on a practical subject.

Last year, during use at The Hangman's House of Horrors, my 900W coil worked
very well for 2 to 3 hours at a clip. Then the 1.75 x 2 copper sweat
couplings became corroded, performance dropped by 80% and I had to stop the
show and "floss" the tubes with emory cloth. Then I was good for another 2-3
hours. We have discussed this on the list before.

To eliminate this, I decided to build a linear static gap using tungsten
carbide elements. Each is a donut cylinder about 1/2 diameter by 1/2 inch
high with a central 1/3" hole for mounting.
I am mounting each of the 9 carbide dies on the end of copper sweat fitting
for heat sinking and I'll probably use a fan as well.

But my big question deals with the potential for HV tracking where it is not
wanted: between the copper tubes and not the carbide cylinders.

The gap will look like this (sort of):

      -------------|
                   |-------------
      -------------|
                   |-------------
      -------------|
                   |-------------
      -------------|
                   |-------------
      -------------|

The horizontal lines are 3/4" copper tubes and the vertical lines are
carbide
doughnuts (which are actually parallel to each other) which will be the
sparking surface.
The above diagram is not to
scale, however, and each tube is actually slightly larger in diameter than
its doughnut.  Each tube will be mounted by its end (the end farthest from
the doughnut) to a slot in a melamine-coated particle board frame (using a
bolt axially through the tube) and adjacent tubes will have about 0.30" of
clearance where they are mounted to the frame.  I would be interested in the
List's observations on the possibility of the HV tracking across the
melamine or through the particle board instead of jumping the carbide to
carbide
~0.030" spark gaps it is designed for.  My unit will be composed of 8 gaps
of ~0.030" and will be driven by a 15/60 NST.

The current sweat coupler gap also has 9 tubes and each tube is .03 from the
next.

My belief is that the spark will jump the closest distance (.03) between
carbides and not the 10X distance .3 between the base of each copper tube.

I know marc metlika has had some experience here and I invite any and all to
offer their experience and opinions.

The schedule for using the coil at Hangman's is critical and I cannot afford
much of a delay.

Thanks for everyone's time. The list has been of great assistance in the
past.

Safety First (drill presses of course)


Ted in Fort Worth, y'all