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Re: Toroid Size?
> Date: Tue, 7 Jan 1997 23:25:31 -0700
> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Re: Toroid Size?
> Reply-to: tesla-at-pupman-dot-com
> > Subject: Toroid Size?
>
> Subscriber: ccurran-at-execpc-dot-com Tue Jan 7 23:01:06 1997
> Date: Tue, 07 Jan 1997 21:55:24 -0600
> From: Chuck Curran <ccurran-at-execpc-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Toroid Size?
>
> Tesla List wrote:
> >
> > Subscriber: rwstephens-at-headwaters-dot-com Mon Jan 6 22:25:48 1997
> > Date: Mon, 6 Jan 1997 20:07:27 -0500
> > From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
> > To: tesla-at-pupman-dot-com
> > Subject: Toroid Size?
> >
> > All, and Chuck Curran,
> >
> > Here's one to put in your collective pipes and smoke for a while.
> > Chuck, you should pay special attention to this post. It, and any
> > enlightening replies that it might generate from the experts on this
> > list may be just in time to save you some grief. I hope you haven't
> > built your topload yet.
> >
<mega-snip but no RFI generated>
Robert & All:
>
> Sometimes being slow/patient might be a benefit.
Yeah, but I urged you to go build something. After all, wouldn't it
have been a lot more personally satisfying to learn what I just
shared with you the hard way all by yourself? : )
> Your post is of great
> interest to me, specifically in how it relates to what I observed with
> the coil design by Resonance Research, Inc. or D.C. Cox. The last few
> weeks I have been considering whether that big toroid I mentioned in
> early December would ever be built. Seeing that 19" dia by 39" wound
> length coil spit out sparks in the 12 foot range with a 30" diameter
> toroid has at least made me think there is at least two ways to skin
> that poor abused cat!
> No Robert, I haven't even purchased the material yet for the toroid.
> It was planned for the end of this month or early February. I was
> planning to start up the new coil with my present 8" x 48" toroid and
> get things roughed in and then switch to a bigger toroid--now I might
> change those plans somewhat. My present coil, 8" diameter by 28" wound
> length using #20 wire ran with the 8"x48" toroid. The big difference in
> performance between my coil and the Cox coil was I had 5'-7' sparks that
> were not continuous. The Milwaukee Museum coil had continuous sparks
> that reached out and just sorta happily sat there two or three at a
> time, always one up to 12 feet long the others much smaller. They were
> inside on a stage,
Once you are processing enough power I find this appearance of streamer
behaviour is very dependant upon the beat frequency of your break rate with
the 60 HZ mains frequency. A variable frequency rotary is a great aid. Mine
on MTC is fixed with an 1725 RPM motor, but I had to go to 14
rotating contacts as the original 12 did not make a pleasing spark
display. To determine that I required 14 contacts, I buzzed the 60 Hz,
1725 RPM motor off a sinewave audio generator boosted in a big hi-fi
power amp and stepped up through a transformer (ad-hoc variable frequency
AC mains supply). I was able to push the motor up to about 100 Hz before
losing step. I measured the frequency of the power that ran the motor at the
most pleasing streamer pattern rate and did a simple math ratio conversion from
Hz to RPM. I fabricated a new disk and was very pleased with the results. I
now rep at 399-400 PPS. I _love_ the sound this machine makes now! It, most
of which comes from the large streamers, has a certain quality about it
which is really addictive. Especially the doppler effect as the
discharge wanders about the toroid.
> I was out in the driveway with the normal 9:00 PM
> summer night breeze. That pretty little spun aluminum toroid seemed to
> be plenty for that coil, so your comments Robert, are hitting a target
> over here by me. I already down-sized my cap, which I mentioned
> yesterday, to .05 mfd-at-30KVAC, for two reasons, resonant frequency
> dictated that was the perfect size, plus cost factors!
You can do big magic with just 0.05 mfd. My LTC threw an 18 footer
with just 0.05 mikes!
> Hope the damage done to your secondary wasn't too bad. A couple of
> questions on your coil--you mentioned the PVC coated #18 wire, I don't
> recall if you have a layer of varnish over it or anything elsed? Most of
> the standard hook up wire has about a 600 volt rating guess it wasn't
> too hard for that MTC of yours to pop chunks like it did--would of
> probably damaged any combination of materials under the cicumstances you
> described.
There were two painted on coats of varathane over the PVC wire jacket.
You're right, it didn't matter. There were many areas where the
varathane was blasted off, but the PVC wire insulation actually remained in good
shape, in addition to those deep crater sites. I've been able to repair the
secondary (thank goodness!) with spot cleaning with trichloroethane 1-1-1,
parting the turns with a knife blade, heating the damaged area with hot air gun,
and pressing in hot glue (LDPE) as a filler. A flat piece of teflon sheet is pressed
against the dab of hot hot glue for 60 seconds while it cools, then pulled away
leaving a spiffy, neat, flat repair. I heat the coil area again and the applied
hot glue with a hot air gun for a few seconds just after applying the
glue and immediately before pressing down on the teflon molding tool.
An interesting bit of information is that I had wrapped the bottom
half of the secondary with about 24 layers of 10 mil sheet poly
before this run in order to stop pri-secondary arcing near the
secondary bottom to enable me to increase K to 0.22. There were NO
strikes to the secondary under this poly. This would indicate that a
good layer of poly over the ENTIRE secondary might well be of help
when one is trying to push the outside of the envelope as I was.
> I will be ordering the 12" diameter flexible aluminum duct no matter
> what. The unknown at this point will be what exact size to make the
> whole thing.
I suggest the same size as my 12" X 48". Your secondary which is the
same diameter as mine and also a bit longer will likely handle it
just fine. You are going to need many primary turns however to tune
this beast with just 0.05 mfd though, no matter what size topload you
use.
> Since I don't have a clear path but alot of curiousity
> right now, I think I will build a slightly bigger toroid and learn what
> I can. I am anxious to check out the k of the new system, but that will
> be some time away--8 week lead time on the cap. I should have the
> primary coil system done by 1/18/97 and then I will finish my static
> gap. I have several photo's and I will post them when the primary is
> completed. Any constructive criticism would be appreciated from all.
> Tune for minimum smoke is always the goal.
> Let us know about that "bigger toroid to stuff underneath"--maybe 30" x
> 90"?? :-) Getting late here time to go to bed!
Did you say 30 feet X 9 feet?, yes, see my recent post. : )
> Chuck Curran
Good luck,
Robert