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magnifier coil form
In 1980 I Built a secondary coil form drum from two 3/4 plywood ring ends
30" I.D.,33" O.D. and 23 (3/8")inch diameter wood dowel's 36" long .
Drilled circle of holes 31" diameter spaced 4.2" apart.
I notched the dowel's with a round file so that the turns would stay in
place when wound on.I wound the drum with (rgu58)? coax cable.Turns were
wound basket weave style(lorentz coil), coax alternating inside/outside every
other dowell.
turn spacing was 1/2 inch between outside of coax.This took a buddy to help
me weave the wire between the dowel's,so if you want to make one of these
beasts first calculate the wire length needed,as you have to thread the whole
length through every other dowel each time you go around the form.
the reason I decided on winding a basket weave coil was from reading Teslas
Colorado Springs notes.He said that coil cap' was to be as small as
possible,and with this thick of cable it would be substantial. as the turns
only cross between the dowel's the coil had very low cap'.the ends of the
coax were stripped and the center wire was soldrerd to the shield.
Test run: I had on hand a 7KV neon sign transformer,and a .002 10KV AC
transmitting Glass mica capacitor.Primary was 1 turn 33" diameter level with
the bottom turn of the secondary.A rotary gap was made from a 4.5" diameter
72 tooth gear and a 1750 rpm tape recorder motor, gear put right on motor
shaft.
No corona shield or toroid on secondary just a 3" long brass bolt pointing
up.
Results,no corona from coil into air, but when a ground wire was put
within 6" of the brass bolt (blue white) discharge 1" diameter consisting of
25-50 multiple threads resulted.The discharge had a really
interesting(singing)quality to it.
There was no corona or spark between turns.
Summary : after reading numerous posts at pupman,
# 1 coil should have had a large toroid on top to lower secondary
frequency,and a larger primary capacitor to bring it into resonance with the
coil/toroid combination so as to load the NST to full output.# 2 the rotary
gap was way to fast for the amount of power the NST could supply.
I still consider this coil a success as i have never seen another tesla coil
that put out a (blue white) discharge with so many threads to it. Someone
said "a little knowledge is dangerous".You can get any system to work
somewhat if you stick with it.I am now building a low power (bylund)
transistor switcher (192 watt) to test small tesla coils,close wound,space
wound, lorentz.Keep coiling.
Any comments constructive/destructive welcome.