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Re: The big bad Mark III



snips

----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, August 12, 2000 8:48 PM
Subject: The big bad Mark III


> Original poster: "Troy Peterson" <highvoltage-at-mad.scientist-dot-com>
>
> Hi again list!
>
> I am about to begin scrounging parts for my 3rd tc, which I am
affectionately
> calling the Mark III (real original name eh?). There is good reasoning
behind
> this though: When I was into building Van De Graff generators it took me
three
> attempts to truly get it right. My first tc was a tiny (1.5" diameter)
coil
> that I played around with to get the feel for HV (1" streamers), my second
coil
> was a 4" diameter coil that I threw together just to see if I could make
it
> work, and now I am going to build a somewhat decent coil (I hope).

It seems to me you just need to do more homework on the project before you
play with deadly voltages and whatnot. I made my first coil two years ago
(I'm only 15 now) and I spent seven months gathering parts and getting the
best possible construction info. Set you homepage on your browser to a
random site on the TC webring, then read every page. Try to learn from
other's mistakes rather than wasting your own money : ) Now, that I finally
have a job, i'll be able to make a decent coil. My previous 4 coils used
leyden jars, unpotted NSTs, decks screws and other junk. Now, I'm looking to
build a "plug and play" model that will last. I've been to a megavolt and
back, and now I'm going to make one that looks good...
BTW- My first coil stood 14 inches tall and made arcs in excess of 30
inches... not *too* bad.


Anyway, a
> few questions.
>
>    I  was considering going to the ends of the earth and back for 2 15kv
60mA
> NSTs, but then I realized that, assuming 100% efficiency and 0% losses
this
> would draw 15A - not too good for a 15 circuit in the house


I wouldn't worry too much about that unless your house has really old
wiring. At one point, I was drawing 2.5kW from my 15A (1800VA) house
circuit. I've learned the value of a VA and how much you can stretch it.
However, don't go crazy, you can do some costly damage doing that. I like to
use a breaker from a power strip to protect the house wiring. It has an MOV
in it as well. If you use this method as well, you'll know that the breakers
in those things are small but, they trip about an amp less than a standard
15A breaker (which don't trip at 15A). If you have a current meter, hook up
two MOTs in parallel and then in series with a variac (using the primary as
current limiting) then measure the current it takes to blow your breaker.
Mine is around 21 amps! The wiring is pretty new, and can take this high
current intermittently (typo).  So, to conclude, 15 amps is not exactly
stretching the limits on a standard houshold circuit. Just make sure you
don't have anything other than 60w lightbulbs on the circuit at the same
time.




 In the end it
> will depend on what I can actually obtain - I am hoping for 15kv 90mA
total at
> least. I am not asking anyone to waste their time doing the calculations
for me
> (there are plenty of programs to do that...)


Wasting time? ... Never. WinTesla tells us that you'll need a .0159uF cap
for resonance. From there you can figure out how many caps you need by
multiplying the transformer voltage(15000) by two then divide that number by
the max dc voltage rating of the caps (2000)... Thet will be how many per
string (n)
Therefore; C=n(.068/15) and C is .0159
so you'll need between three and four strings of 15 caps giving you a grand
total of at least 45
See, that was simple : )

but can someone point me in the
> direction of what I would be looking at in way of a cheap MMC?

Hmmm... I wonder where you could get metalized poly caps at a decent
price?...
Oh yeah, ME! I'm organizing a MMC bulk buy this week. The final per-cap
price should be on the list by tomorrow.


I am looking for
> cheap caps that will handle the current and voltage at about 0.025 uf I
think -
> I just want to know what type of caps I should be looking at and how many.
I
> was going to go with the typical 1/4" copper tubing for my pri. coil until
it
> occurred to me today that copper ribbon would be more compact and perhaps
> easier to mount - along this line: Where could I get some?

All of us would use copper ribbon if we could find it. Copper tubing is
still the best choice as far as availablity goes. The only other thing you
could try, is to go to as many harware stores as possible in search of some.
I've been to about 20 stores and have come up empty. You could try an online
manufacturer, but you might have to buy like 1000 pounds or something...

Is it cheaper than
> tubing?

Depends on who you get it from ; )

does it suffer from corona problems?

not too bad

 and how do I figure out it's
> inductance?

whip out an inductance meter

Cost is the biggest concern (I am saving for college). Finally, my
> planned secondary is 6" od pvc wound 24" long with #24 enameled wire, does
this
> sound ok with the above system?

I've tried 6" x 24" with 26 wire and it really sucked. I'd lean more towards
the 1:6 (w:h) ratio so you won't need a strike ring above your primary.
Also, just look at the performance of John Freau, or Greg Hunter's coil...
The performance speaks for itself.

> I hope to design this coil to be fairly compact so I can take it with me
when I
> leave home. My last one was huge (for a small coil), having been built
with the
> tank circuit inside a TV stand and lots of bottle caps..

I've been there... My last coil had 24 wine bottles on the second deck of
it's stand which measures two feet square by three feet tall. If portablity
is an issue, just try and make everything close togather, and make sure the
stand has some good casters. (BTW- the "wheel barrow" approach doesn't work
well here)

I hope my little experience helps out here
Be careful and have fun,

    -Michael




Thankyou for any help
> you can provide.
>
> Regards,
> Troy Peterson [VE7SOK]
> <mailto:troypete-at-sunwave-dot-net>troypete-at-sunwave-dot-net
> <mailto:highvoltage-at-mad.scientist-dot-com>highvoltage-at-mad.scientist-dot-com
>
>
>
>