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Re: Dwell time, etc



Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Kevin,

You will probably get varying answers on this issue, but my
opinion is that at the "modest" power levels that you are pro-
posing to run, you could get by with smaller diameter electroes.
D. C. "Dr. Resonance" Cox may tell you that you would need
even larger electrodes but remember, he builds them to pro-
fessional museum quality where they are expected to run seve-
ral hours a day, 7 days a week, for many years, without a hitch.
I'm reasonably sure that you want be putting that kind of demands
on your coil ;^) Take a look at the 8th picture down of my coil
at: http://dawntreader.net/hvgroup/david/gm.html. Those are
1/2" x 3" long stationary electrodes and 3/8" x 2 1/2" long
flying electrodes in my rotary gap and I am running this sys-
tem with a 15 kVA pig. At the time, I was also using a
4 segment, 3 gap stationary, forced air cooled RQ style of
stationary gap in series with the rotary gap, but have recently
removed the RQ gap. I haven't had a chance to fire it yet since
this newest modifiation but I suspect that it will work the same
if not better, since I'm sure there was increased gap losses
with the additonal seriesed gaps. I've seen RSGs desinged
to handle 10 or 15 kVA with only 1/4" diameter electrodes
although I think that 1/4" electrodes may be a bit "whimpy"
for that much power.

Are you planning on running synch or asynch? I run asynch with
my big coil and I have personally always had problems with
extremely erratic firing when I would try to series 4 gaps on
an asynch rotary gap, as opposed to just 2 gaps. This erratic firing
would occur no matter how well I had the electrodes aligned at
presentation and no matter how close I could get the flying elec-
trodes to come to the stationary electrodes without collision.
This dosen't seem to be a problem with synch rotary gaps
though. Others seem to have had success running seriesed
4-gapped asynch rotary gaps but "I" personally have never
been able to get it to run right in this setup. YMMV.

Also, if you plan to run asynch, .2 uFd will probably be too big of
a capacitance for your transformer to fully charge in each cycle. I would
just use "one" of those .1 uFd Condenser Products caps and
hold on to the other one for a spare. OTOH, if you are planning
on running synch, then go for the .2 uFd, or even bigger!

David Rieben




----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, March 28, 2006 6:21 AM
Subject: Dwell time, etc


Original poster: "MakingLightning" <MakingLightning@xxxxxxxxxxx>


What is dwell time and how does it affect your coil?

I always thought that nice big electrodes on a spark gap was a good thing,
but was recently told that it would increase your dwell time.

I just wound an 8" coil
and am planning on using 2 big 0.1 uf 90kv (20kv working voltage) custom
made Condenser Product caps in series (I bought them about 12 years ago when
they actually sold things like that to us, then went through a divorce and
am finally getting around to using them, they were about $1000 apiece
then!),
a 5kva 14.4kv pole pig,

and was planning on making a 12" rotary gap with 8 - 1/2" electrodes and 4 -
9/16" stationary electrodes in series (better for quenching?).

I have a 60a 240v variac and a 200a welder for controlling the power.

Anyone have an idea of what length of sparks I should expect from this
setup? (free air and to a ground rod)

Any other comments that you guys have on this setup would be greatly
appreciated.

Kevin