Re: Maxwell 37667 dies interestingly...thoughts?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: DRIEBEN@xxxxxxxxxxxxxxx 

Aaron,

I'd say that your final sentence explains
it for the most part. 400 bps with a 14.7
kV pig is quite a bit more "rigorous" than
120 bps with an NST power supply. But it is
interesting that there was no apparent in-
ternal arcing damage and the "guts" of it
still seemed fully functional. I think others
have mentioned 37667 Maxwell failures with
15 kV rated NSTs, although they seem to
handle sub-15 kV voltages from NST's in stride.
For a 35 kVDC rating, AC RMS volages in excess
of 12 or 13 kV is "pushing" it for Tesla pulse
discharge work. Dr. Resonance opts for a mini-
mum DC voltage rating of 3X the working AC RMS
voltage input in his coils. I'd say the biggest
issue in this situation would be the current in
stead if the voltage though. It sounds like the
heavy currents may not have generated enough in-
ternal heating of the capacitor components to
melt the dielectric and arc over but DID generate
enough heat to create sufficient internal pressure
to crack the external plastic case.

David Rieben

----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
Date: Monday, July 17, 2006 8:59 am
Subject: Maxwell 37667 dies interestingly...thoughts?
To: tesla@xxxxxxxxxx

> Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
>
> I took my Maxwell 37667 to a friend's place over the
> weekend to see if it would help get his new 24" coil
> to put out some sparks.  Despite early indications
> that things were too far from complete to run the
> thing, we got enough wire stripped quickly enough to
> do a temporary lash-up before daylight failed.
>
> Things kicked off with the destruction of two homemade
> rolled caps that he'd spent a bunch of time on.  What
> a bummer (and boy did they look cool, too!).  I took a
> deep breath and offered to put the Maxwell on the
> cooker to see what would happen.  We were immediately
> gratified with 8- and 10-foot streamers as the break
> rate topped 400 bps.  Yikes!  We dropped a few
> different toploads on the thing and played around for
> a while.  In the end, the Maxwell probably had only
> two minutes of runtime spread over a ten-minute
> period.
>
> Then, Bad Thing #1 happened:  A streamer hit the wire
> between the Maxwell and the primary.  Due to the
> temporary nature of the wiring, the cap had been
> sitting relatively exposed a few feet from the base of
> the coil.  Doh!  A metal sawhorse was quickly placed
> over it.
>
> And finally, Bad Thing #2:  Shortly into the run
> immediately following placement of the sawhorse, a
> crack opened in the Maxwell, and the oil drained out
> rather quickly, leaving a nice puddle of Maxwell juice
> on the floor (VEERRRYY slippery stuff, I can now say!)
>
> What is quite interesting about all of this is that,
> due to the surpise of seeing the Maxwell croak, it
> took us a few seconds to kill the power.  In those few
> seconds, the coil continued to operate normally; there
> was no obvious dip in performance.  The contents of
> the Maxwell were quite warm, though not what I'd call
> "hot", and I neither saw nor smelled any sign of
> burning.  On top of that, measurement revealed that
> the capacitance was still 0.03uF, and no DC resistance
> would register on the DMM.
>
> So the mode of failure here is a little unclear to me.
>  Did thermal expansion of the contents simply pop the
> case, or was there most likely some kind of arcing
> fault, perhaps initiated or encouraged by the strike
> in the prior run?
>
> As the Maxwell's guts seemed in remarkable shape, my
> friend is going to try running them in a bucket of
> mineral oil and see what happens.  I'll report back
> with the results.  If they aren't serviceable, then
> perhaps we'll pry them apart even more and see what we
> find.  They were just too pretty not to get a second
> chance :-)
>
> Any other thoughts on "Why Maxwells Fail"?  I never
> even felt the thing get warm in my little coil running
> at 120 bps.
>
> Regards,
> Aaron, N7OE
>
>