Sam Barros' Latest experiments:-)
Greetings Fellow Coilers!
Yep, it's me again... You probably remember my latest posting about a
High-Power Double Car Ignition Coil Driver which used two coils in
anti-parallel and could create arcs up to 10cm in length. I didn't
receive a whole lot of response on it and some of the few responses I
got were from people doubting the fact that it was outputting 1.1kW
and whereabouts. Hopefully that is cleared out now.
Well, I “teamed up” with another soon-to-become Coiler called
Reinars. He's on the list, but, like 95% of all users he seems to be
too shy to post anything (sorry Reinars:-)
Well, he's just a beginner and he wants to build a Tesla Coil, so I
suggested he built something smaller first, to get acquainted with
High-Voltage and general electronic building (I think all beginners
should do that). I learned trough several painful shocks that no
matter how much you study about it you can never have the same
knowledge as someone who has done the real thing…
I gave him my drawings and diagrams for the coil driver and now we
both have 2 working drivers. The best thing about having more than one
person working at the same project is money... I had wanted to try a
slightly modified driver for higher frequency and better frequency
control but now I just discussed it with him and he ended up trying
it:-) Also, we both tried a better pulse system.
Progress is slow. We now know how to increase the frequency of the
spark but that drastically decreases the length of the arc (as
expected). We also used a 70uF capacitor bank to pulse the coil (we
took caps from both devices and put it into one). Triggering had to be
done manually but the sparks definitely increased in power. Which
indicates that the coil is not saturating yet (good:).
I have decided that the next step really is a full-wave stabilised
voltage Doubler. We'll need some pretty big caps to keep the supply
voltage and consequentially the output arcs stable so we went out
searching for some surplus parts.
Now, Reinars found this army surplus shop, and that shop had things
you wouldn't believe! It would take a book to describe all the cool
world-war2 German, Russian, American, etc parts they have there, which
includes dozens of oscilloscopes, radar parts and such (the store is
MASSIVE!). Well, to make matters short, I picked up several goodies,
including a nearly 1-foot tall General Electric Pulse capacitor. Oil
filled weights more than a kilo. It has very large ceramic insulators
on top and is rated for 4kV 2uF. Not a whole lot considering its size
but now that I rigged up a MOT to run a cascade and charge the cap I
can finally conduct some cool water and wire exploding expts:-) I had
wanted to do this for SUCH a long time but I had never found HV caps
before here in Holland and my MOT cap bank couldn’t really do much
(just a few minor bangs).
Well, considering that my charging source (even though temporary) is
rated for 30kV DC, I am a bit wary of using the cap. The whole thing
is strongly built and will not explode in the event of a dielectric
breakdown (not enough energy either), but that is a one-of a kind cap
which I did not expect to find and I doubt I will see any other very
soon. While I search for a better charging source (something with more
juice too: the damn thing takes minutes to charge fully off the
cascade), I was wondering if anyone had ideas for a good spark gap.
First thing I considered was 2 bolts +- 4mm apart (my data for spark
length versus voltage is very unreliable, any help here would be
appreciated). But a few discharges would oxidise the bolts and allow
the voltage build up until the cap overcharged. Jim Lux once suggested
I used silver plated for a certain application (not really Tesla Coil
related but thanks, Jim!). He says the silver conducts even when
oxidised. That would be a good option but a single discharge will blow
the silver layer off. Pure silver spoons are bit expensive for a spark
gap, I think.
A gap in an oxygen-free atmosphere would be too complicated for such
a small and simple application. I was wondering if anyone has a good
idea... As well as a reliable table for distance/voltage breakdown
values of atmospheric air.
Other thing I got was a 20cm tall, 8cm diameter "Powerlithic",
maximum pulse voltage 300V, capacitance 10000uF... Another one of a
kind beauty! They don't sell those here in Holland either... This baby
will store over 400Joules so I want to devise something reliable
before I attempt to charge it up... Experiments at a similar voltage
with half the capacitance show well just how destructive those can
be... If the dielectric suffers punchtrough while fully charged
chances are I will be killed.
I was wondering if anyone has ever conducted experiments in capacitor
discharge (I know Bill has => Bill has done everything:-) Hey, Bill,
You reading this? You had a really kickass 25kJ pulse cap. It didn’t
explode when it broke down. How come? Strong metal casing or something?
Well, I just wanted to discuss some general capacitor expts with
someone who has done them... You know, exchange ideas, results, that
kind of stuff... No real help needed here though…
Well another thing is that they have HUNDREDS of transformers. Some
are really big, weighting over 20kilos, and others are much smaller.
The HV ones are very similar to MOTS but rated for 3kV or something...
They also have something that looks just like disassembled neon,
except it is 3 times as big... Low (3kV) voltage too...
What caught my attention were some funny-looking metal cans, like 8 X
6 X 12 cm and whereabouts... They were rated for HV (like 10kV and
less) and had ceramic insulators on them (nothing big). The schematic
on the bottom read DC High voltage transformer or something... Like
everything else in the shop, they were real cheap (I paid 2bucks for
the 4kV cap and 5bucks for the powerlithic), I almost got one, but
they have over 10 connections and I am unsure of what they are (old
stuff)... Anyone has seen those before?
Ah, back to the ignition coil driver, I connected an OSRAM 100W 12cm
diameter globe incandescent lamp to one of the coil’s output. As
expected the whole thing fills up with corona discharges. Now, if I
put the other coils output outside the glass huge streamers go around
the glass and several leave the filament. The strike zone quickly
becomes dangerously hot and glows green (!!!). I suspect the energy
might be sufficient to heat the anode by ion bombardment and the
voltage could possibly accelerate them enough for x-ray production...
I don't have a suitable Geiger counter but I do know that a green glow
is associated with x-rays. Anyone can shine some light on this?
Oh, also when I turn it off I can see it filled with a faintly
glowing blue gas, which soon fades away... Looks cool!!!
Well, that's about it... Oh, I also got 3 microwave ovens for free.
Only 2 had a MOT and only one MOT worked... One of the ovens was from
an unknown German manufacturer... REALLY old.. It has NO digital
components whatsoever. The power is full all the time and controlled
trough a spring-loaded timer with a small mechanical bell (also spring
loaded). It has no safety interlocks but it does have a high-voltage
(2.8kV 1A!!!) switch that has to be off in order for the door to open
(you press the switch, the HV is cut off and the door opens). It also
has a fan that's twice as big as a normal oven fan and looks like a
Well, anyway, analysis has revealed Magnetron short-circuit and MOT
overheating. Every time I plug in the MOT it makes a loud buzzing
sound and starts to smoke within seconds. Ballasting doesn't help. I
believe this is due to some insulation breakdown as the secondary will
make small sparks but they die off when you try to draw an arc...
Phey! That was a long message! I hope someone actually reads it:-)
Last news before I go is that I met this really AWESOME dude (“Downtow
Tiger” : also a silent reader from the List) He wants me to be his
mentor and is willing to make me a homepage... (Hey Tiger, hope you
don't mind me posting this... Just feeling proud of myself, that's
all:-)I don't expect to have it soon but it is a nice idea because
than you can all read about my non-Tesla Related expts...
I am buying a new meter (and this time I will keep the darn thing
away from that stupid ignition coil driver). I hope to have accurate
power measurements for my devices within a few days. I also intend on
obtaining a kV meter and hooking it up across the cap, so I can make
my OWN sparklength versus voltage table. The web seems to be in need
of one of those… I know there has being a lot of research into it and
all but I don’t have acess to the results so I will just have to make
"The Less You Know, The Better You Sleep"...
"Evolution Stops When Stupidity Is No Longer Fatal"
"If At First You Don't Suceed, Increase The Amperage"
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