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Re: Monster Cap balanced by Monster Topload?

In a message dated 99-03-20 00:53:15 EST, you write:

<< Cap #2: 0.2uf 125KVDC. Manufacturer unknown. Used in some physics
> experiments
 
> Since I am in the process of building an 8.5" coil, I thought that the .2
> unit
> would work great there, until I ran the numbers, and found that even with a
> 6"x60" topload, I could only tap in about 4 - 5 turns. 


Michael,

Many coilers use only 4 - 5 turns in their primaries with excellent
results.  But I guess you're also saying the 6" by 60" topload will be
too big for your coil?

>If I recall, bigger is better on the primary inductor, so I can 
>control the surge impeadence of the primary tank.

If you use thick tubing, and heavy wiring, for primary and tank, 
losses will be acceptable with only a few primary turns.  Greg
Leyh uses only a few turns on his giant coil I believe.  You will
need a robust rotary to handle the heavy currents.

If you want giant sparks, I think cap size is more important than
the number of primary turns.  Big cap = big sparks.  To give an 
example, I built my sync gap coil using a .014uF cap, and 20 turns
on the primary, and got 64" sparks.  Skip Greiner built a similar
coil powered by the same sized NST, and obtained the same
spark length.  He used a  .015uF cap, but he used only 5
turns on his primary.  So the number of turns on the primary 
didn't seem to make any difference.  

However, I do prefer to use more turns on the primary if possible,
I acheive this by using a greater inductance in the secondary, rather
than greater capacitance.  Although you do want a large topload of
course.

> So. How do I boost the capacitance of the secondary without 
>having a topload larger

I would instead increase the secondary inductance by using a thinner wire,
and a larger diameter secondary.  Thinner wire is very acceptable in a
Tesla coil, and does not waste as much power as is often suggested.
Another way to lower the frequency
is to use more turns and make the secondary taller also.  In other
words build an overall physically larger coil if you have the room.  And if
you want to keep the power input reasonably low, use a lower break
rate of 120 to 180 BPS or so.  You may need a higher break rate if you
run outdoors to overcome air currents and wind.   Also, there's
absolutely nothing magical about using 1000 turns on a secondary.
1500 turns can be used to lower the frequency.  And of course a
wide secondary will also have greater capacitance and help to lower
the frequency in that way also.  Although too much capacitance in
the secondary (rather than the topload where it belongs), hurts the
performance.

John Freau


>in diameter than the streamers I would be throwing? I am 
>assuming something like stacking toploads, the questions then are:
 
> 1) Inter-toroid spacing - how close/far apart need I make them for the best
     capacitance, with breakout still possbile
> 2) How could I compute approximate C value for each additional toroid?
 
> [Even getting the cap size down to 0.1 shows I need only 7 turns :/]
 
> Charging system is capable of delivering 500ma at 14.4KV, so I don't think
> I'll have a problem running it (I could be wrong)
 
 
> Michael Baumann
> Coiler, Homebrewer, Nerd. mycroft-at-access1-dot-net
  >>