Re: I give up!! I regret building my tesla coil!

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Garry,
          I'm really sorry to hear your story. I'd like to 
have a look through your post bit by bit to see what might be 
rescued from the mess:

On 20 Aug 00, at 19:52, Tesla list wrote:

> 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.

Here is what I would advise someone who came to me and asked 
me to surpervise their building a coil. To prevent NST burnout;
- do not open the gap too wide. I know from experience what a 
gap will roughly fire at by observing the electrodes and 
spacing. For hemispherical 1/2" electrodes as a rough guide, 
count on around 6kV/mm. Double that for 1/4"
- minize the lead length between the transformer and gap (no 
more than 1 foot. Forget the chokes.  

> 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!

That secondary could still have worked but coupling to it from 
anything but a helical primary might have been too low.
     You never said what transformer you were using with this 
(or previous models for that matter).
  
> 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..

Nothing wrong with either of those IMO. Results speak for 
themselves. I don't think you could expect much more from that 
transformer without a more elaborate gap system. 

> 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 take it there were no changes other than the gap itself? Did 
the gap power arc or have a nice crisp rat-tat-tat to it? That 
result sounds to me like a power arc or a serious detune of 
the coil itself.  

> 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.

Definitions like pushpull really don't figure in a cap 
charging circuit for a disruptive coil IMO. Without seeing 
pictures or the real McCoy of the various configurations it is 
hard to know exactly what might have been wrong. 
     ALSO, nothing has so far been said about the primary cap, 
what materials it was made of and its value. Did you stick 
with the same transformer for all these expts?
  
> 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.

Be aware that output can change with atmospherics. I have 
observed a very noticeable difference in output between high 
and low humidity days.
  
> 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.

I can't see why that should be so.
  
> 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.

Another thing not said is what the gap firing looked and 
sounded like. Was it a steady staccato sound or a "fizz" of 
sorts?
  
> 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!

It would greatly help if you post each and every detail of 
where your project is currently at and freeze the design right 
there so we can give some advice on where to go from here.  

> 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 appreciate your frustration but do not agree with what you 
say in the preceding paragraph. I had to start on my own with 
no help from anyone but I did have the benefit of several 
decades of electronics practice under my belt. I still had a 
lot to learn about this particular subject. It need not cost a 
lot of money to build a coil. You can pick up used NSTs from 
sign manufacturers very cheaply (sometimes for free). 
    My first coil was a hit and miss affair wound on a 
varnished paper towel roll with a helical primary which 
eventually gave wispy 5-6" streamers from a crude MMC made 
from ceramic caps and an ignition coil. 
    My first mains coil was a frustrating affair - I wound 
three secondaries and got nil results until I hit upon the 
idea of getting an oscilloscope onto it to see what what as 
actually happening. Instant revelation - suddenly I realized 
tuning was involved and I never looked back. You're by no 
means the only one to start with next to no results. I had to 
look around for a suitable transformer, scrounge old pieces of 
PVC pipe from a building site, grab some old copper tubing 
from a scrap metal dealer etc.  

> 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, 

Nothing at all is said about tuning, tapping the primary, 
adjusting coupling etc. Presumably all this was done 
incrementally and the results noted if not recorded?
  
> 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!

Help is at hand. Please post every last detail of your current 
setup - every detail.

Regards,
Malcolm