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Re: Pictures of my 2KW coil and the 8x32 concrete toroid

Original poster: "Mark Broker" <mbroker@xxxxxxxxxxxxxxxx>

About 18 months ago I made a similar toroid, only using 4" ducting. I made the toroid the size I wanted, and then wrapped a single layer of 2" wide fiberglass mesh tape (drywall joint tape, actually) taking care to not deform the thing too much. The tape added quite a bit of rigidity, which made the next steps a lot easier.

Using a putty knife, I completely coated the thing with a lightweight, fast-drying vinyl spackle. The mesh tape kept the stuff from falling out of the grooves. After it was dry (a day due to the deep grooves), I sanded with 100grit, and then reapplied to fill in any gaps and whatnot. When that was dry (a couple hours), I started to wrap 1" wide strips of Aluminum duct tape around it. When wrapped, I used a soup spoon wetted with a little WD-40 to burnish the surface.

I ended up using two pie pans screwed together to make the center support.... get ones without teflon if you can!! :o

My results are not as good as yours, but a significant improvement over standard drier duct or even ducting wrapped with several layers of masking tape, and a whole lot easier than fiberglass/epoxy. The toroid feels stronger, and doesn't dent as easily as an uncoated one does. But the thin layer of spackle does deform rather easily when pressed on with a fingernail, so handling care is required.

Cheers!

Mark Broker


On Wed, 28 Sep 2005 00:09:03 -0500, Tesla list <tesla@xxxxxxxxxx> wrote:

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Everyone,

I finished building the 8x32 toroid using the mcmaster ducting
material (5 mil stuff) and grout to make a smooth surface.  The
following are my experiences:

1. Grout sands easier than bondo (that's why I switch) and the work
time is very good.  Before curing, grout is very chalky. Full curing
takes many days

2. Sanding to get a smooth surface worked fairly well but my results
were not as good as D&M's work.  I attribute this partly to: grout
sands maybe too easily.  I was able to reapply grout to fill in but
if the depression was too shallow, it was hard to get the new grout
to stick to the old grout thru the sanding process.

3. Adhesion to the AL duct was not perfect and sometimes cracks
formed and small pieces flaked off requiring reapplication.  This
problem was not major and added only a small portion to the time required.

4. There was some shrinkage with the first application of grout and
generally required a second application and in some parts a third
spot application.

5. After I was satisfied with the surface, I gave the toroid two
coats of varnish.  This gave it an excellent surface for taping and
greatly reduced the vunerability of the grout to damage.

6. Taping went very well.  I purchased 2 inch wide AL tape that I cut
length wise into 1 inch strips.

7. After taping, the toroid seemed very dent resistance although I
wont test this on purpose.  The final weight was 15 lbs that seemed
acceptable to me.  I probably wont use this method for much larger
toroids, but for this size and smaller, I think the weight is not a problem.

8. It took me two weeks to grout and a week to tape.  The grout time
seemed higher than I expected but grout is inexpensive.

9. Total cost $85:
     a. duct = $30
     b. Al center sheet = $20
     c. Grout = $15
     d. Al tape = $20

Now for the pictures:

http://www.hot-streamer.com/temp/GerryReynolds

Go the the directory for the 15KV_120ma coil.

There are pictures of the toroid during each stage of construction
and the other components of my coil.  There are also pictures of the
coil in operation both with a breakout point and ground target, and
with no breakout point.  The longest power arc was 86 inches and the
wall power was 2100 watts.  Exposures are 4 seconds at ISO of 400,
800, and 1600.  The picture names make a story board sorta and are
numbered in chronological order.  Enjoy.

Gerry R.