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New Testing done and my 8" secondary
Hi All,
I just got finished with the testing of my florists plastic.
Here are the results so far:
Material thickness per sheet: 1.5mils
I goofed on this (in my first email, I wrote 3 mil per sheet). I guess my
micrometer had dirt or something between the measuring points)
Testing was done at 50 Hz:
Cap#1
AL
Plastic
AL
You can apply approx 3kV before it arcs through. The plastic doesn´t melt like
PE, but simply shrivels up around the point where it arced through. No fire,
no smoke.
Cap #2
AL
Plastic
Plastic
AL
Now you can apply 5.8kV across the cap before it arcs through. Seems to me as
if you could say (for starters) about 800V per mil at TC frequency would be a
safe value. Shortly before the "cap" dies (i.e arcs through) sparks will jump
from one terminal to the other via the plastic´s surface (starting at approx
5.5kV). It seems as if the plastic allows the voltage to creep over the
surface. However (in defense of the plastic) I have to admit I took it
directly from the flower pot. Who knows what stuff (probably conductive) the
florists pour on the flowers to keep em fresh longer.
Anybody out there who thinks I should get a roll of this stuff and make a TC
cap?
BTW: I just finished my 8" secondary:
Specs:
Wire: 0.85 mm = AWG "19.5"
Wire spool weight before/after winding: 22lbs/12lbs
i.d:0.850mm=0.0334567"
o.d.:0.908mm=0.0357395"
Secondary former:
Total weight with wire: 21 lbs.
Diameter:20 cm=7.8722"
Total length:106 cm=41.75"
Chosen winding length:82.85 cm=32.61"
h/d ratio: 4.12
Turns:940+1.2 (space wound from end of winding to end of former)
Aprox wire length: 590m=1937 ft.
DC resistance= 17.0 ohms
Calc´d inductance: 37.86 mH
Measured 35.6 mH
(pretty damn close I would say)
Cself=14.68 pF
Ctoroid should be somewhere between 14.68pF and 58.73 pF
So, I chose a Al dryer duct toroid with:
Tube diameter: 4.271"
Outer toroid diameter:31.8"
which gives me a Ctoroid of 30.78pF (about midway between)
My loaded resonance frequency should be around 121 khz, which should be good
for some long sparks. We will see, however. (Calcs where made with my homebrew
tc program)
I glued a piece of 2mm thick copper plate (2" high x 4" wide) to the bottom of
the coil´s base. I soldered a nut to the copper, hammered the lower end of the
copper wire nice and flat and soldered this to the copper plate.
The coil form was sanded thoroughly (wet and dry grit 60 to grit 150 in
steps), dryed (3hrs total) coated with clear varnish (inside and out), wire
wound, coated with 2 coats of epoxy resin (sanding in between coats), final
smooth sanding (180 grit) and coated with 2 coats of clear varnish again. It
looks pretty and it is as smooth as a baby´s butt. Now on with the
work..................
Coiler greets from Germany,
Reinhard