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Re: I give up!! I regret building my tesla coil!
First off...
1) Never believe the advertising with respect to spark length (just like
MPG, your mileage may vary, and will usually be less). Coiling is
frustrating... there are so many things that affect the spark length, and
most of them interact. Be happy with 1" at first, and then gradually make
it longer.
2) The only homemade cap that I'd fool with is a beer bottle cap. For the
hassle, any sort of poly/aluminum foil version is stomped into the ground
by a MMC. For quick and dirty, get it working... get some transmitting
doorknobs. Sure, they aren't the best, but they DO work, and they are
readily available, and easy to connect to. If you are truly poverty
stricken (like your budget is < $25, and you have lots of time to
scrounge), the beer bottle (or wine bottle or whatever) is the way to go:
salt, aluminum foil, and cooking oil are awfully cheap (if not free).
All coiling (or maybe everything) is a tradeoff.... The cool, slick,
compact system isn't going to be cheap. Cheap is generally bulky, heavy,
fragile, or clunky (or all of the above).
This all said, it is possible to easily get 12 inch sparks from a 15 kV/30
mA neon transformer ($80 brand new retail, much much less used or
scrounged), a pair of 2700 pF, 40kV doorknobs (about $25 each at an
"expensive" surplus place), bare #14 AWG house wire for the primary, 3
pieces of 1" copper tubing 2" long as a spark gap, and a secondary wound on
a 3" cardboard mailing tube with #21 enameled wire, and a toroid made with
4" flex dryer vent tubing and two pie pans. No chokes, but the wiring is
short, and the gap is across the NST, so I figure the gap shunts all the
RF. It may not be fancy, but it works. You'll need a few scraps of plywood
to hold everything, and some sort of insulating standoffs to hold things
like the spark gap.
It shouldn't take more than 8 hours to put it together, starting with all
the parts lying on the table in front of you until you get "first light",
which will be sparks a few inches long to a grounded rod. Then, you'll
spend the rest of your life trying to make them longer...
----------
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: I give up!! I regret building my tesla coil!
> Date: Sunday, August 20, 2000 6:52 PM
>
> Original poster: "Garry F." <garryfre-at-pacbell-dot-net>
>
> I have built tesla coils when I was in high school, in college and
recently. My
> biggest problem was a continual burning out of the NST over and over
because I
> could never understand the hieroglyphics that were presented to me
instead of
> plain english as to how to build a choke to prevent feedback.
>
> Finally I get some plans from
<http://www.sciencefirst-dot-com>www.sciencefirst-dot-com
> and I build according to their plans and it was supposed to produce 18"
sparks
> but produced only one and a half inch sparks. The plate stack cap plans
were
> defective, the dimensions of the coil was 1.5" by 40! This is the WOUND
area!
>
> By fooling with it I eventually got sparks near 8" but the toriod had no
break
> out at all. Well, being broke from buying a brand new NST for this and
tools, I
> had to wait some weeks before I had some more money to spend (Waste).
>
> So, I spend more money and make another secondary and this turns out to
be 3"
> by 24" using #29 magnet wire. Better, but not short enough. Still it
produced
> nice 12" sparks easily. I am using a 9kv .2 MA NST and produced 14"
streamers
> off the toroid..
>
> Ever being interested in improving the output, I tried various spark gap
> designs. One suggestion was use two rounded brass doorknobs in an air
cooled
> system. The results were abysmal! Lousy 1" streamers off the toroid that
were
> so sporatic, I could eat a sandwich between streamer appearances.
>
> I built a spark gap that was made of aluminum flashing rooled up at the
ends to
> provide a make shift cooling fin design. This worked pretty well.
>
> Then I stated my design here and they said I almost had a Push-Pull
circuit and
> I could have a true push-pull circuit if I added a grounded electrode in
my
> spark gap letting both branches spark into this. I tried this. The
results were
> again dismal. I tried retuning. It was HALF the output I had from the
previous
> design.
>
> Then I tried that J. Quick spark gap design and the output from that was
even
> worse!!
>
> So, I try to revert back to my rolled flashing air cooled design and no
matter
> how much I fiddled, I did not get quite the output I had before I tried
the
> push-pull thing.
>
> Then I heard that the electrodes should be absolutely flat and so I built
one
> Thursday night and it was producing better sparks. Not like what I had
before I
> tore it apart for the push-pull design, but close.
>
> The next morning, the spark gap would not fire reliably, so I took it
apart and
> adjusted the gap smaller and I got lousy output of 2" streamers off the
toroid.
>
> So, I buy some 1/4" refrigeration tubing and try another primary. It's
amazing
> how difficult it is to wind this stuff. What a nightmare of kinking and
> tangling the likes of which I've never seen before!
> I finally get it built in a desparate hope that it will solve the lousy
> stinking results I am getting and I put it on and it absolutely stinks!!!
The
> sparks are not steady, the sparks are half the thickness I expected!
>
> Then there are the caps. Mine are not soaked in oil. Maybe I should do
this but
> I don't want to have to haul around two five gallon buckets of oil and a
cap
> inside. That's like having a hearing aid the size of an ice-cream truck!
>
> Well, after trying the tubing, I and looking in disgust at $35 worth of
tubing
> and other stuff that was a waste of money, I realize I could have bought
their
> 18" spark model NEW and all built from Information Unlimited for LESS!
Sure it
> would have cost $499 but I've spent more than that already!
>
> I don't have a machine shop! I hadn't been busted financially for years
but
> now, I can barely afford a soda! I do programming full time for a company
that
> does financial reports and processes transactions.
>
> I didn't buy the one from information unlimited because I wanted the
feeling of
> accomplishment but after three months of spend spend, all I managed to
buy
> myself was weekend after weekend working in a sweaty back room, sick from
not
> eating all day till 11PM because I got to get whatever failed
modification
> finished and then when it doesn't give the expected results and I can't
figure
> it out and I've tried everything I can think of I give up and revert only
to
> find LESS results when I revert and wishing I hadn't tried the
modification in
> the first place.
>
> So, here I sit, I possibly have spent $700 bucks and what do I got but a
truck
> load of defeat!!
>
> Sorry for the rant, but I feel the need to warn those out there who are
> considering trying this fine hobby out, you better be prepared to spend
> thousands on tools and have a machine shop to make something that looks
good
> and operates well and loads of money and a whole lot of luck and once you
get
> one that seem to work to your satisfaction DON'T mess with it. Build
another
> coil and keep the one you got. You might like me have to budget your
buying for
> half a year but at least you won't mess up what you have.
>
> I've been working on this it seem forever, and what do I got to show for
it?
> Some gain in knowledge and NO TESLA COIL AT ALL!! Every time I tried to
modify
> it, I was sorry,
>
> I wish I had bought one pre-made from somewhere. Sure I couldn't say "I
built
> it" but at least I'd have something to show instead of something that
makes me
> sick at heart just to look at it!!
>
> Thanks for letting me blow off steam. I hope I got the sense to give up
and not
> continue trying this but I have the feeling that I will just keep on
trying to
> the injury of my wallet and my self respect!
>
>
>