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Another Capacitor Order

Quoting Scott Myers <scotty-at-wesnet-dot-com>:

> I have built several homebrew capacitors.  Considering the 
> price of the materials required, time involved, quality 
> achieved and the chance of capacitor failure in a homebrew 
> unit, it is my opinion that is is cheaper to buy a pulse 
> capacitor made commercially. 

I have built literally dozens of homemade HV capacitors:
saltwater/glass, saltwater/plastic, glass/foil, waxpaper/foil
liquid oil dielectric, Aluminum/poly/oil, Al/poly/air, air
dielectric (HV electrostatic air filters), rolled, stacked... 
I currently have about $2000 in materials alone invested in
working homemade capacitors, not including the many hours during
many weekends in construction time. 

Good quality "off the shelf" capacitors that can withstand the
abuse that the Tesla tank circuit dishes out are rare. Many of
the units I have used that can stand the abuse (transmitter
micas, paper/mica HV filter caps, and HV PCB caps for example)
are not designed to pulse and have low Q factors; they get hot
and/or fail eventually; the spark is not that good, even from
transmitter micas costing hundreds of dollars. A well constructed
homemade plastic/Al/oil capacitor looks damned good by compar-
ison, but it really takes a lot of HV capacitor design and
construction experience to put together a first class unit. 

Having built many failed or half-failed capacitors when I was
younger (I started building pulse caps as a sophomore in HS over
20 years ago), and being heavily invested in decent quality
homemade Al/poly/oil caps now, I can honestly say that I can
build a cap that will match the performance of a commercial
plastic film pulse unit. The only problems will be that my
homemade cap will be considerably larger and heavier, and the
retail material costs for the project will be nearly the same as
the total cost for the commercial cap. This totally ignores the
time that it would take me (many many hours) to design, obtain
the materials and build. When I am done my cap will not have a
warrantee. Only the experience I have gained in previous designs
and construction (at what cost?) and the expense of quality
materials and quality time assure me that the cap will hold up.

These days I would only build homemade capacitors for
educational/demonstration purposes. I freely admit that I am a
pack-rat Tesla coiler, which means I never have enough high
quality capacitors (or anything else) and I can always justify
the need for more.  But I am very selective these days. I can be
very selective because I have good capacitors (homemade and
commercial) and I am experienced with the quality of what is
available and what I am capable of building. 

If I could go back and do things over I would not have been so
impatient (why wait six weeks for commercial caps when I can
build and have the coil firing in two), nor so hard-headed (I am
saving money because I am not paying professional skilled labor
rates). I would have been better off if about $1500 of the
materials investment in my homemade capacitors had been spent on
commercial caps. I could have had the same total capacitance, and
spent the time developing very high Q spark gaps that you can't
buy commercially.

Learning is an on-going process. I stop learning the day I die. I
spend a fair amount of time trying to help people avoid the
mistakes I have made in this hobby, and everybody learns as we
exchange experiences and knowledge. Building homemade caps is
perfect for those dipping their toes into Tesla coiling, up to
the intermediate coiler with a few neons and a few feet of spark.
If you are shooting for reliable spark over 3 - 4 feet in length
then you are gearing up for some serious coiling, and this is
going to require a "base line" investment that many here are
freely willing to make. Commercial capacitors are part of that
bottom line investment.

I guess the good news is that once you are "in" the hobby the
cost really drops for most of us. Heavy equipment like pigs &
powerstats don't get used up, RF grounds last for years, properly
built coils don't burn out, and good capacitors have a long
service life. You can settle down to a point where the largest
expense for processing peak powers in the megawatt range is going
to be an extra $10.00 a month on the kilowatt/hour meter.

I wish I could settle down to this point, but to sit on the
sidelines and watch a reasonably priced capacitor deal, or
variac, or another pig go by...


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12