Re: New Coil?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 2/5/02 10:20:00 PM Pacific Standard Time, tesla-at-pupman-dot-com
writes:


>
> Hi everyone!
>
>     I just tried a new toroid on my existing coil, and upon re-tuning, got
> racing sparks and small sparks from the top terminal for a reward.  I
> thought that putting a larger toroid on the coil would lower the
> developed voltage (putting less stress on the secondary), and allow me
> to tune the primary out farther to lower gap losses.  It obviously
> didn't work.  I can't push the power up on this system.  Ed Sonderman,
> and many others helped me greatly with various suggestions, (Thanks
> everyone!) but it appears my coil is hopeless at over 1.8kVA :-(.
>
>     Anyway, I've had it with this coil.  As most of you who read the
> "Suicidal Secondary" post can agree with, it was badly designed.  I'm
> still disturbed that I can't figure out the racing spark problem
> enirely, but I want to build a new coil anyway.
>
>     I'd like to keep the 5 joule bang size the same, and possibly make it
> larger.  I want to do away with my 0.1 uF cap, and use a smaller unit
> with a higher stored voltage to keep the bang size up.  I still want to
> use a high inductance secondary, and a large toroid.  This time I should
> probably use a high inductance primary to balance out the system, rather
> than a large cap.
>
>     I'm not sure about the actual secndary design.  I want to use a static
> gap, and maybe a rotary gap later on.  The system will operate at 120
> BPS.  I don't now exactly what power source I'll use, but I'm thinking
> about using a rather high voltage supply this time.  Maybe MOTs with
> doublers, or 4 GE copier xfmrs in series.  I'd like to be able to shovel
> more power into this coil than I could with my previous one (5 to 7
> kVA).  I want to keep the size down, so I think I'll use a 6"OD
> secondary.
>
>     How does this sound?  I'm very much open to suggestions, since the
> badly designed coil was my first system.  Any help would be greatly
> appreciated.
>
> Thanks,
>     Winston
>
>     PS-Where can I get a pole pig or potential xfmr?  I live in the LA
> area.  I don't need one now, but since it appears that it is continually
> getting harder to obtain one (liability, etc.), I'd like to get one
> while I still can.  I called the power company, and after being
> transfered about for around half an hour, was told that they are
> contracted to sell their old stuff to some salvage company.




Winston,

Putting a larger toroid on an existing system will raise the output voltage,
larger radius of curvature will allow the voltage to build up higher before it
breaks out.  It is sometimes difficult to get just the right size toroid for a
given set up.  Too large and it won't break out, causing big problems at full
power, and too small and you get multiple breakout points instead of a single
breakout that we would like.  The upper toroid on my coil is too small,
allowing multiple breakouts.  I would like to make another one but need to be
careful and not go too large.  I am a strong advocate of two toroids.  The
lower one, right on top of the coil, will provide "shading" for the secondary
and prevent sparks from leaving from the top few windings.  The upper toroid
will then provide the major energy storage and the sparks will discharge from
there.  Increasing the toroid size will add capacitance to the system, lower
the resonant frequency ! and allow the use of more primary turns.

I would suggest going to a larger diameter secondary, like maybe 8.0" with a
36" or 37" winding length.

For a pole pig, you might ask them for the name of the salvage company that
they use and call them.  When I bought mine from the local utility company, I
found out the name of the individual in charge of all scrap (they call it
investment recovery), called him and did not have any problems.

Ed Sonderman