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Rotary Modifications Update
---------- Forwarded message ----------
Date: Sat, 11 Oct 1997 18:14:56 -0500
From: Chuck Curran <ccurran-at-execpc-dot-com>
To: tesla-at-pupman-dot-com
Subject: Rotary Modifications Update
Hello All:
Thought I might share with you the last run for this year of my coil and
the current performance after modifying my rotary. Each spring for the
last two years I drag my winters project up out of the basement and set it
up in the garage, but I do need to park my truck inside during the
Wisconsin winter season!
I had been running with brass stationary electrodes that were effectively
about 3/8" across at the tapered end that conducted. In order to search
for better system performance by addressing the quench issue, I installed
1/8" diameter tungsten rods, heat sunk by the original 1" diameter brass
rod that is 1 1/4" long. System performance improved and initially things
looked good, but the real story was that 1/8" tungsten couldn't live long
with 14-16 Kw going through them. (There is also 7 stationary gaps in the
vacuum gap system in series.) The 1/8" tungsten simply died of fright.
My next effort was to obtain a sample piece of 3/16" diameter tungsten,
which by the way is referenced as a tri-metal non-thoriated material. A
farily new product that our local supplier had available. I installed the
3/16 and have run the system on four different nights now. Last night,
prior to setting up, I checked the gap whick was originally set at .025",
or quite honestly, as close as I could get it. I simply tried sticking in
a .030" feeler gage and it would not go. My short term results are real
encouraging at this point. The system was set up and I ran it for a group
of about 18 from work, three runs of 3-4 minutes each. The second run
gave one spark that hit the strike rail with several other forks, and then
the rotary motor started to slow down. What happened was a blown bridge
rectifier in the DC supply for the rotary motor. The arc to the strike
rail might have been a coincidence, the bridge rectifier should have been
on a heat sink, but I skipped that--mistake! I replaced it and was up and
running for the third run with about the best sparks I've gotten for this
night. The later it gets, the less wind there is outside and that must
help some. I wish I could run it inside once, just to see if there might
be an improvement. My next step will be to work on the moving electrodes
which are presently acorn nuts. I plan on trying tungsten there too, a
project for when the snow's on the ground. I'm wondering what diameter
tungsten others use and if it is heat sunk or not, along with how often
adjustments due to wear are needed--just curious.
Chuck