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Re: [TCML] new pig driven coil
Hi Joe,
As the builder of the 8 ft. tall Green Monster Tesla coil,
http://www.youtube.com/watch?v=H3pfStBx2qY, I have
to agree with Scott's summation. When there is plenty of
available raw power for running your coil (which a pole
pig can generously provide), an asynchronous, higher break
rate, a significantly STR primary cap and a huge topload is
the best way to extract long and bright sparks from your
coil system. My coil runs with a 14,400 volt, 10 kVA rated
pole transformer, a 0.1 uFd primary capacitor, and a 12"x
56" topload and the sparks regularly reach into the 11 to 13
ft. point/point range.
Also, when you mention that your ouptut sparks actually
start to decrease with additional power when the variac
knob surpasses the 80 mark, I am wondering if your SG
setup is reaching its limits in quenching. I personally have
never tried the propeller style RSG but it's pretty obvious
that the "propeller's" quenching ability is going to be limited
according to the power throughput, cross-section diameter,
length, thermal mass, ect. You mention that your runs are
pretty rapidly eroding the ends of your gap electrodes so
it sounds like proper quenching could be a definite issue
for you. When quenching starts to falter, the output will often
begin to deminish at that point. My ARSG is the disc type
with a 11.5" diameter x 1/2" thick G-10 disc, set with (8)
evenly spaced 3/8" x 2" long pure tungsten flying electrodes
and 2 pair of stationary 1/2" x 3" long pure tungsten electrodes,
with each pair set 180 degrees apart on opposing ends of
the disc. I originally had just a single stationary electrode pair
on one end of the disc, but ended up adding a second pair
due to improper quenching at the high power levels that I
run. My particular system seems happiest running around
350 bps.
Hope this helps,
David Rieben
----- Original Message -----
From: "Scott Bogard" <sdbogard@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, October 12, 2010 5:31 PM
Subject: Re: [TCML] new pig driven coil
Hi Joe,
Just a word of advice, using a SRSG on a high current system (which
depending on your ballast a PIG generally is) is going to really quench
your results with such a small cap, using Java TC you can calculate your
optimum BPS for a given cap size. You simply must build a variable ASRSG
(both for learning curve and for performance) unless you are so wealthy
you can buy enough caps for LTR on a PIG (or you use a high enough
multiplier in your sync BPS, so you might be Ok as I see now you are using
240 instead of 120.) I would still recommend it, they are fairly easy to
build compared to SRSG, high break rates give awesome effects, and you
don't need to change your cap size when you upgrade your circuit breaker
to allow more current flow (just run it faster!) My unballasted twin MOT
system (just raw AC, no doubler or other nonsense) runs 750 bps sweet
spot. The day I upgraded from SRSG I cut my power supply in half and
tuned it to the point I was getting longer sparks with half the power (by
almost a foot, 69-inches is my record with just 2 MOTs and ASRSG and 61
was my record for 4 with SRSG!) I've seen a pig coil running just a .05
cap do 15 feet using an ASRSG running a high break rate, it is the way to
go as far as I'm concerned, infinitely cheaper, more fun, just as long if
not longer sparks, I'll never run SRSG again, not even on little OBIT
coils (well I might, because now it sits around doing nothing, but I'm
going to try ASRSG with a small cap anyway...) Just my 2 cents, take it
for what is is (ramblings of an exhausted, half crazy man with nothing
better to do at the present moment...) Also note that if your current is
kept to about 250 mA or less you're actually Ok with a 240 BPS and that
cap, but someday you'll open up your ballast for 600 mA and be
disappointed when the sparks don't change AT ALL, this was my big mistake
with ballasted vs unballasted MOTs...
Scott Bogard.
On 10/12/2010 1:54 PM, Joe Mastroianni wrote:
I have built an anachronism. Of course, the very concept of the coil is
anachronistic, but through the tutelage and mentoring of Dave Leddon, I
have acquired and assembled the components necessary for a pole pig
driven srsg coil.
I got a 5KVA pig from Dave some months ago, and since then he's been
supplying me with various wisdoms though schematics, e-mails, and his
surplus parts. I have been beavering away diligently in my garage,
assembling the various components I get from Dave and a seemingly
endless stream of eBay auctions. No doubt I have assembled for a couple
hundred American dollars what would have cost thousands had I bought
everything retail (if that was even possible).
The spark gap is an SRSG propeller gap rotating at 1800rpm inside 8
stationary electrodes for 240bps. I am using a John Freau phaser on the
SRSG.
The power supply has 4 corcom-style 30A line filters in serial/parallel
arrangement. Using the guts from a cheepo adjustable 100AMP arc welder
as a current choke. An ABB EH175 serves as my contactor and I have a
2-phase superior electric 1296 powerstat for the main power Variac.
Also, I had my safety gap set too wide (obviously). With the tuning and
the gap set "correctly" or as close as I could get I was able to achieve
several runs, most of which at only 2/3 max on the current shunt. Spark
production was better than with my NSTs, as we would expect. The
propeller gap was brighter than ever, to the point I began to worry
about how quickly the electrodes would erode.
I also noticed that the max-output power occurred at about 80% power on
the variac output. Increasing the output past 80% actually DECREASED the
power output a perceptible amount.
I have come to expect that there is an issue with one of 2 things -
either 1) I have wired the variac wrong (though I have reviewed the
connections and I can't see how I did) , or 2) the inductance of the
variac is interacting with the primary windings and affecting f0.
And since writing the above, I am noting that I have connected my
current shunt to appear in the circuit in series between the power
source and the variac, instead of between the variac and the primary.
Perhaps that has something to do with it. I need to experiment to find
out.
Other things I have noticed - even at 15/240 my primary connections
never got hot (except when mistuned). Now they seem to get warm all the
time, which I suspect is just an expected artifact of the higher
currents. I do think I may have to reconsider the spring bronze and my
connection methodology for fear they present too high a resistance and
will eventually heat to the point of melting the polycarbonate supports.
Cheers,
Joe
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