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Re: MMC question

    Greetings Terry and everyone.
It's michael again.

Here are the full specs of my ineficient coil. Once again, i'm looking for
reasons I can only get 12" sparks from 1350 VA of input power.
Primary:
16turns 3mm Iron fencing wire, Neatly wound with 7mm spacing at 30 degrees.
2nF (sorry i said 20 last time, it was typo) rolled poly cap

Secondary:
4.33" PVC. sanded, varnished, sanded, varnished.......
22" winding of 22 Guage wire.

Grounding:
either an electric fence ground pole 2' in ground, or a pile of metal rods not
in the ground (results were the same using either)

Power supply:
3 X 15Kv 30mA NSTs (I used the "poor schoolboy doing science project" method
and scored 7 NSTs of which 6 worked, all in 1 afternoon).

No torroid yet.. I'm just using a bolt for now.

I've found that best rtesults are acieved at around turn 12 on the primary.
this being around 12" arcs to a grounded pole.

Another interesting note is that it works almost as well using any one of the 3
NSTs as it does using 3, and i have tested that each work and are all in phase
and well matched.

Thanks all,
    from michael.




Tesla List wrote:

> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
> At 04:13 PM 6/7/99 +1000, you wrote:
> >    Hi all.
> >My name is michael and I am new(ish) tp this list.
> >
> >I would like to know if standard metallised polyester greencaps will
> >work at all in a coil. I was recently given a few hundred (like 500) of
> >these each rated at 100Vdc and 0.49uF.
>
> I don't know what cap value you want but these caps look like they would be
> very difficult to use.  You need a lot in a string to get to a reasonable
> voltage but then the capacitance is pretty high.  Polyester will heat
> quickly and you will only be able to use one or two strings which means
> they will see very high current.  For example:
>
> 250 caps in two string gives a 25kV 4nF cap.  The current will really be
> too high for just two strings.  I fear you would wire up 500 caps and it
> would fail quickly.  I don't know all the variables but I would really be
> careful...
>
> >
> >I understand that these are probably undesirable, however it's all i've
> >got at the moment (other to a 2nF rolled cap that's too small for my
> >coil).
> >
> >I would also like to know if  "Plastic film Boxed casing MKT 250V" caps
> >will work. I have made a few bricks (5" X .5") of 360 each, but am
> >worried about blowing them when they have other uses. They are each
> >rated 250V and 0.022uF.
>
> The key is if they are polypropylene or not.  If so they have a good chance
> of working.  Just don't let them heat up.
>
> >
> >My other question is this.
> >I am running a 4" coil with 16 (30 degrees incline) turns of 3.5mm Iron?
> >fencing wire for the primary.
> >My spark gap consists of up to 10 X 0.5mm gaps.
> >I'm using 3 15Kv 30mA NSTs and am only getting 12" discharges.
> >My cap is a 20nF (about) rolled PE type.
> >I've raised the secondary to reduce coupling but to no avail.
> >Does anyone have any suggestions??
>
> It definitely sounds like something is out of tune.  The primary and
> secondary my be working at different frequencies.  I would guess you
> primary circuit is running around the 100kHz region but your secondary
> probably wants to run at a much higher frequency.  Try tapping in the
> primary.  Maybe to as little as five turns.
>
> The fence wire is not the best but that is not the main problem here.  With
> more info I could tell your much more about were the tuning was at.
>
> >
> >Thank you very much for your time.
> >
>
> Cheers,
>
>         Terry