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Re: [TCML] How reliable will this coil setup be?
I like the way you did the video - pausing the frame at each major
component and putting up text to describe the components.
I think I see the problem that's causing you to burn through caps. I
don't think it's related to using 940 vs. 942 series caps.
The problem is your spark gap. The text states: Ten 1" diameter
copper pipes in series, 3mm between. So 9 x 3mm gives you about a
27mm total gap spacing. Way, way, WAY too wide. It's not obvious,
but a 15kV NST is capable of charging the caps to a far higher voltage
than is safe. Because your gap is too wide, you are over-volting your
caps, as well as your NST. You're lucky your NST didn't die. It's
possible that the caps that haven't blown may still be compromised
(may want to try measuring the uF value of each with a capacitance
meter). And the insulation in the NST may also be compromised.
There's no way to tell, but it doesn't bode well for long term
reliability.
The width of a static spark gap is very critical. If it's too wide,
it will permit the voltage to rise above what's safe for the NST &
caps. If it's too narrow, performance will be hobbled. If and when
you reduce your gap width, you're sure to find that performance will
be a good deal LESS than what you see now. That's the tradeoff - less
sparks, but you won't be destroying caps. The width must be set so
that the gap _just_ begins to fire with the NST wired just to the gap
(no caps present). This is why I like using a single sucker gap -
there's only one gap to adjust and it's presumably easy to move. With
a multi-stage cylinder gap, all you can do is change the number of
segments. I think the width for 15kV might be around 3/8" as a
ball-park figure, but always needs to be set individually,
experimentally.
I also second Dave's assessment of the hot strike rail - it needs a gap.
Regards, Gary Lau
MA, USA
On Thu, Sep 1, 2011 at 10:39 PM, James Hutton
<b-u-r-t-o-n-boy@xxxxxxxxxxx> wrote:
>
> Hey, so someone is buying my tesla coil off of me for a show he does. My tesla coil is very prone to failure at the moment because I bought the 940c series from cornell dublier.So I have ordered 12 x 942c20p15k (1 row of 10 in series and 2 extras).Hopefully this will make my coil run flawlessly and for long run times.
> I might get rid of the strike rail above the primary. The streamers never seem to hit it, but it gets so hot that it melts its way through my supports.It's more of a hazard then an aid. But for now I'm going to leave it in case I get rail strikes with the new caps.
> Here is a video of the build: http://www.youtube.com/watch?v=3c6LghhD43sIt is crap, but cut me slack. its my first ever build :P
> The only real problem right now is the caps.When I get the new caps, It should run fine.
> I was just hoping if someone could confirm a few things for me though.I just need this coil to be reliable... since it is going to be used in a world class show! (I dont know why they chose me... This is my first ever tesla build!)So could someone confirm that this setup will be reliable and work almost flawlessly?
> Theoretically, how long of a runtime could I push out of it before something failed.... and what do you think would be the first thing to fail?Will these caps pop at all? I am so used to those damn caps popping every 30 seconds of coil run, it seems almost too good to be true to me that the caps wont fail.I heard somewhere they have an average lifespan of 75hours!
> If anyone has any quick tips on how to make this more reliable, let me know!thanks _______________________________________________
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