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Hey-- You can make a very high quality toroid using mandrel bent
elbows. You get four of them and carefully cut off the straight
sections, then weld them into a torus. Clean up the welds and polish
the whole thing. If you leave some of the straight sections, you can
get a square toroid of any size. My coil has one using 4" tubing, with
the outside dimension 32" square. The cost for four elbows was $70.00.
Do a Google search on "global engineering mandrel" or any other supplier.
You could be really cool and make a pentagonal, hex, octagonal or
irregular topload. Or even make something like that weird Soviet
apparatus--
If you want my opinion, it looks like it was built by someone with more
budget than ability.
--- Carl
On 12/11/2017 6:07 AM, Antonio Queiroz wrote:
Em 10/12/2017 08:22, phil escreveu:
All,
I'm currently assisting in the construction of a ring type toroid
(60" x 12") consisting of six tubes (
https://www.flickr.com/photos/33962508@N03/ ). Using Dr. Antônio
Carlos M. de Queiroz's 'Inca' program (
http://www.coe.ufrj.br/~acmq/programs/ ) and, along with some help in
its actual use from Bert Hickman, I now have a good idea of the
expected toroid's capacitance.
Now the six rings or hoops obviously need supporting in free space,
and the conventional toroid method is a solid central disc in the
horizontal plane supporting the outside minor diameter tube.
I wondered just how much this solid central disc contributes to the
shielding of the secondary, and if its replacement with support arms
(like wheel spokes - but only four of them at 12, 3, 6, 9 o'clock)
would leave the secondary more exposed to strikes, than if a solid
disc had been used?
(The effect on the capacitance value is believed to be small, so left
out of the decision.)
You can use the Inca program to compare the electric field at the top
of the secondary with a solid disk closing the toroid hole and without
it. The difference is very small, unless the hole is very large. You
can add one or two rings (that the program can simulate) along with
the radial arms (that it can´t simulate) to improve the shielding,
but the effect would be mostly mechanical.