I was there when David fried his Hipotronics cap. I know for a fact that I
saw a streamer hit the primary right before the cap went short.
We also tried running my 6" coil on his Green Monster control panel. It was
running very well, and fortunately the sucker gap was not overheating. Of
course it was just above freezing outside, so this is somewhat
unsurprising. What was surprising was then number of primary strikes my
coil was taking. I've never had a problem with primary strikes until I ran
it with a grounded primary. I do not run my coil with the strike rail
grounded, I just leave it floating because the primary will arc to it. I
ran my 6" coil on Cameron Prince's pole pig this summer and did not have a
single primary strike. This was not because the streamers could not reach
the primary either. Cameron's pig has two ears, and neither ear is
grounded.
http://www.flickr.com/photos/pslawinski I've got some pictures of the run
at David's home, and on the second page there is a video of the run at
Cameron's home.
On Tue, Dec 16, 2008 at 21:39, David Rieben <drieben@xxxxxxxxxxx> wrote:
Hi Bart, Jim,
If I'm not mistaken, I was the one who originally turned you on
to the grounding one of the ears of the pig to allow a single HV
transmission line from the pig to the primary circuit ;^) However,
after some recent discussion with one or two members, I am be-
ginning to wonder if this is the best configuration in light of suppres-
sing primary coil strikes. I have been running my Green Monster in
this fashion but have noticed rather excessive primary strikes. As a
matter of fact, I smoked my beloved Hipotronics pulse cap during
a recent firing of the beast for a mini-Teslathon ;^( (3 of us). I'm
not sure but it was mentioned that a large primary strike was seen
right before the Hipotronics caps gave up the ghost. Of course I
have an RF grounded strike shield ring and I was figuring that this
may be the main culprit for primary bound strikes. Do you guys think
that leaving the primary coil "floating" with not connection to RF
(mains ground) will suppress primary bound strikes from the
topload or is this a sure recipe for distruction of the primary circuit
components? Of course, I realize that one of the best methods of
suppressing primary strikes is to add an extra corona shield toroid
underneath the main topload. I have not done this in my design main-
ly due to the shear size of my main topload (12x56") in comparison
to the outer diameter of my primary spiral (about 40"). It seems to
me though that the RF grounded strike ring (which is about the same
diameter as the outermost primary turn - ~40", and sits on a horizon-
tal plane about 4" above the primary coil's plane, is the main culprit
at drawing the strikes toward the primary coil, regardless of whether
the primary coil is "floating" or grounded. What do you think?
Fortunately, I had a spare Plastic Capacitors BNZ custom made pulse
cap that I got as a spare from list member Bill Limeaux (Gomez
Addams), that was of the same capacitance as the now defunct Hipo-
tronics cap (.1 uFd) that I was able to swap out to get the Monster
breathing fire again ;^)
Anyway, sorry for the rather lengthy post but I am really curious
about this issue and thank you all in advance for your responses.
David Rieben
PS - I, too, have been tying the external tank of my pig to RF
ground via the transmission line from the tank circuit assembly
and if I disconnect the primary coil from the RF ground, then
the pig's external tank will also be floating (that just doesn't
sound good to me!)
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