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Re: First run 6.5" coil- odd results? (fwd)
Congrats on the sparks, Scott. Even 8" is a nice accomplishment for a 1st coil
running off a wimpy transformer :-)
Looks like Terry took care of the technical stuff, so i will advise on NSTs
(Neon
Sign Transformers) and caps.
1. The absolute best source of NSTs is old sign shops - not the kind that
sells
small neon signs and lives in some strip mall. You want the old grungy
warehouse
type that fixes signs for businesses and such. Find out who is in charge and
explain to him that you are doing this great science project for SCHOOL.
Take a
few good color printouts of coils in action. Take a pic of your coil to
show what
you have done so far. Know enough about Tesla to have a conversation about the
history of the Tesla Coil
Assuming that this guy has some old NSTs in the shop, you should either get
them
free or for about $20 each. Really play up the broke high school kid
thing. I am
25 so I don't have a chance - younger coilers can claim to be students, older
coilers can claim to be helping their kids with a science far, I just have to
admit to being a high voltage weirdo...
You want to look for 12 or 15KV models at 60ma. The sign guys will
typically call
these "twelve-sixty's" or "fifteen-sixty's". 120 ma models are in
existance, but
extremely rare. 30 ma models are OK if that is all you can get.
2. You will probably want to consider better caps. Rolled LDPE caps are
the old
standby. There are lots of text files out there describing how to build
these. I
think that I have links to some of them on my page.
The new caps are referred to as MMC and are series / parallel strings of
commercially available caps. People are having great results with these,
but they
are not as well understood as the rolled LDPE. (My next cap will be MMC,
mainly
b/c I am tired of lugging around 50 lbs of 6" PVC containers full of oil.)
Good luck. Always remember safety. Don't get so caught up in worrying
about the
HV that you forget about all the 120V on the input side of the NSTs, it has
killed
before...
Making arcs in Huntington Beach,
Ross Overstreet
http://www.geocities-dot-com/CapeCanaveral/Cockpit/3377/tesla/index.html
Tesla List wrote:
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
> Hi Scott,
>
> At 10:33 AM 6/6/99 -0600, you wrote:
> >Date: Sun, 6 Jun 1999 11:58:19 EDT
> >From: LUGNUT00-at-aol-dot-com
> >To: chip-at-pupman-dot-com
> >Subject: First run 6.5" coil- odd results?
> >
> > Since I'm new to the list, let me introduce myself. My name is Scott,
> >or "Lugnut" and I am very new to coiling. I wanted a good start, so I made
> >and bought everything for my coil, except for Xformer...:_( Chances are I am
> >doing something wrong but don't know it. I heard that my results were
odd due
> >to my Xformer, tell me what you think.
>
> Welcome to the Tesla list!
>
> >
> >
> > Well, here's my stuff: right now I'm getting 8" sparks maybe 9".
> >
> > secondary-6.5" OD PVC 1/4" thick wound to 26" 22 or 24 gauge...I
> >forget...
>
> Assuming your wire is around .024 inches in diameter, your coil is around
> 44mH with a self capacitance of 12 pF. There are around 1100 turns on it.
>
> >
> >
> > primary- flat pancake, 1/4" copper tubing spaced 1/4"
> > 13 turns total.
>
> Around 54 uH.
>
> >
> > capactitor- salt water type, 15 totally assorted bottles in a 10
> > gallon fish tank-no oil and I'm not getting flashover. Probrobly
due to
> > my transformer's lack of power.
> >
> > Xformer- right now I have a horrble, beat up, but working 4000 volt
> >-at-
> > 30mA..
> >
> > Spark gap- 4 gaps at about 1 millimeter each.
> >
> > There are no bypass caps or safety gaps.
> >
> > Discharg terminal- Use everything from a nail to a 7" sphere. After
> > tuning, I get the best results from the sphere, about 8" sparks. I
have
> > to use a nail to get sparks to the air, they get about 6" in the dark,
> >(really dim, but I can feel, them <ouch!>.
>
> Go with a sphere or any large smooth object. You need something with a
> large surface area on the top of the coil for best sparks. You coil (the
> secondary) is probably running around 160KHz
>
> This system seems to need a primary capacitance of ~18nF. I don't think
> your salt water cap can get this high. Your primary may be tuned to a
> higher frequency harmonic like 320KHz. I think you may need around twice
> the capacitance in the primary. Your system sounds like the primary and
> secondary are not tuned to the same frequencies.
>
> I would not try to touch the output arcs. In an untuned system, no telling
> what is going on. In general, touching output arcs is avoided these days.
> The voltage does not go along the outside of the body as thought for many
> years. I goes right into you. The nerves don't react to the high
> frequency but all the heating and cooking is the same as if it were DC. It
> is not considered safe.
>
> >
> > Problem- I have no real idea if I am doing well or not because nobody
> > that I've heard of uses the weak transformer that I have. If I buy two
> > 12kv-at-30mA NST's, will I get 12x the sparks? That almost sounds
> >insane...
> > 12x9!
>
> Well running systems with 12kV 60mA get about 36 inch arcs. It is
> generally a square law thing. To get twice the distance you need four
> times the power. But there are many variables...
>
> > By the way, I'm 14 and showed my science teacher, she looked at it
like
> > I was doing something wrong...hmmmmm...maybe I am. Please help me out
> > or even comment on my coil. I even need a name of sorts...you people
> >are the best!
>
> Science teachers always like to se "safe and sane" experiments. Like
> growing beans or something. :-(' High voltage arcs tend to scare people.
> She is probably worried that you will hurt yourself. She will get used to
> it :-))
>
> I can't be completely sure of the numbers here, but it is my best guess...
>
> Welcome and Cheers,
>
> Terry
>
> BTW - Write your posts to "tesla-at-pupman-dot-com" instead of "chip-at-pupman-dot-com".
> Chip probably already said this...
>
> >
> > Thanks,
> > Scott
> >