More triggered gap testing.

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi All,

	I built up a new triggered gap today.  I used 1/8 in. tungsten rods about
1 inch long.  I got some brazing rod from the home center store and tried
brazing on some scrape stuff, but decided I need more practice there ;-))
I need to visit the regular welding shop to get some better stuff...  So I
got some copper MIG wire welding contacts that the wire goes through in the
welder handle.  These are basically 1/4 in. dia. about 1 in. long solid
copper with a small hole through the center.  I measured the rod and found
an undersized drill bit and drilled the contact using the small hole as a
pilot hole for the drill.  I could then press in the tungsten rod into the
hole with a vice for a good tight press fit (safety glasses in case the
tungsten shatters!)

http://hot-streamer-dot-com/temp/MarcGap/P8120001.JPG
http://hot-streamer-dot-com/temp/MarcGap/P8120002.JPG

Then it was easy to solder the 1/4 in. diameter copper contact to a 1/4 in.
hole in the end of a copper pipe.  Thus, most of the copper contact was
inside the pipe in contact with the water.  The tungsten rod could even be
2 in. long and extend directly into the water too...  I mounted it an a
wood frame.  I had a little problem with getting the electrodes to line up
:-p but no big deal for the moment...

http://hot-streamer-dot-com/temp/MarcGap/P8120003.JPG

I then tried a wire ring around the gaps to get the arc to go across the
main gaps rather than through the trigger electrode. 

http://hot-streamer-dot-com/temp/MarcGap/P8120004.JPG

It actually worked very well.  The voltage on the ring is enough to fire
the gap quite nicely and the arc just goes straight across.  The frail wire
ring is not harmed nor does it heat up except a little from the nearby hot arc.

I fired the gap for a while playing with the ring and realized I never had
put water in the copper pipe to cool it!  I turned it all off and went
feeling around to see how hot it was.  Just barely warm :-))  I may have
gotten a little carried away with trying to cool it :o)  I added the water
and ran it hard for awhile.  The gaps seemed to remain cold given the time
it took to turn the power off before I could touch it.  There was no heat
discoloration of the tips.

Pressing the tungsten electrodes into the copper contacts and then
soldering them to the copper pipe seems to cool them very well.  The
contact extends well into the water so there is a lot of copper to water
contact right near the electrode.  Assuming the gap may cook off say 400
watts on a 900 watt coil, the electrodes may see 50 to 100 watts of heat
each since most of the heat goes to the air.  100 watts is fairly trivial
for this gap to cool.  It will be interesting to see if this vastly
prolongs the life of the tips.  They could be pulled out and new ones
pressed in too if they ever had to be changed.  Marc is sending me some
tungsten carbide disks that I would think would last forever.  They could
be copper plated using Mike's notes and soft soldered (probably best for me
since the brazing thing seems beyond me :-)) or I guess they could be
brazed to the ends of the copper pipe before it is all soldered up.  I
wonder if the brazing heat would burn up the copper pipe?  I guess it is
not hot enough to melt the copper but I would thing the black oxidation of
the copper would be really bad even with flux...  Maybe not, "I" really
don't know but it looks like the tungsten carbide can be soldered, brazed,
or press fit, so plenty of options :-))  With the faces soldered directly
to copper with water on the other side, even tin lead solder would never
melt.  It can simply cool the faces very well.

There are a bunch of people working on this stuff with all kinds of other
great ideas.  I think we are just seeing the early "model-T's" of the sync
triggered spark gaps right now, the best is yet to come!

Cheers,

	Terry