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Re: Toroid Size?
In a message dated 97-01-08 02:52:55 EST, you write:
<<
> Robert & All:
> Sometimes being slow/patient might be a benefit. 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, 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!
> 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.
>snip
> 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!
>Chuck Curran
>>
Chuck,
I read with interest your descriptions of your work and of the DC Cox coil.
The smaller Cox coil here in NJ gives similar but shorter "hanging in the
air for awhile" type sparks. My only suggestion for your project is; make it
modular so anything and everything can be easily and quickly changed, this
way you can find out what works best, by trial and error. A lot of work, but
there's no substitute.
BTW, I have here a back issue of TCBA News from 1984, vol. 3, # 2. There's
an article starting on page 11, by DC Cox concerning coefficient of coupling.
Cox mentions in the article that his model 150 Tesla coil, which uses a
secondary winding length of only 34", draws 5.5 kW and produces 13' sparks.
There happens to be an article by Bill Wysock in the same issue. Here's
the specs on Bill's Model Nine Tesla coil; pri. is 4 (?) turns of .375"
copper tubing, sec. form is 21" dia. x 60", 1/4" thick phenolic, the wire is
mil-spec mylar-jacketed thick-wall PVC insulated #16 AWG stranded silver
plated copper, 560 turns. Ten coats of shellac are applied in a controlled
environment. Toroid is 30" dia, polished, with 8" cross section. Capacitor
is 0.1 uF. (polypropylene). The 1800 rpm synchronous rotary has 0.50" dia.
tungsten electrodes. Bill claims that using no more than 5 kW, it produces
in excess of 15" sparks.
Good luck with your system!
Happy and effective coiling,
John Freau