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Re: what makes a good torrid

Original poster: FutureT@xxxxxxx In a message dated 5/6/06 10:07:12 PM Eastern Daylight Time, tesla@xxxxxxxxxx writes:

What makes a good torrid for a coil.




The best toroid for a particular coil depends on a number of factors.

1)  The size and power of the coil.  A large powerful coil will work
best with a suitably large toroid.  A small wimpy coil will work
best with a small toroid.  Generally, if one expects 3 foot sparks,
then use a 1 foot diameter toroid.  In some cases the sparks
can reach 4 times the major toroid diameter.  For example a
13" toroid may support a 52" spark length.  It seems that
higher breakrates can give longer streamers from a given
toroid diameter (assuming adequate input power).  Usually
to support a given spark length, a smooth toroid can be somewhat
smaller than a rough or corregated one.  Usually there should
be a 1:3 to 1:4 ratio of the minor and major toroid diameters.

2)  The desired look of the streamers.  A smaller toroid will
produce a greater number of simultaneous streamers but they'll
be shorter.  The largest useable size will produce a single streamer
of greater length.  The use of a smooth toroid will permit the
spark roots to glide around on the toroid surface.  On a rough
toroid, the spark roots will remain fixed at various rough edges.

3)  The coilers pocketbook.  If the coiler has sufficient cash that
he's willing to spend, then he may opt for an excellent spun
aluminum toroid.  If the coiler is working on a shoestring budget,
then he may make a toroid using dryer duct or something similar.

4)  The desired appearance of the coil.  For a professional looking
coil, a spun toroid is the gold standard.  Usually the toroid is
spun from aluminum but can be spun from copper, brass, or other
metals.  The price will usually be lowest for the aluminum.

5)  The toroid should be electrically conductive.  Usually they
are made of metal or are plated or coated with metal.  Some
folks have tried applying conductive paints over plastic toroids.
This works somewhat for small coils, but the paint tends to
burn away.  For very large coils, an open mesh chicken wire
is sometimes uses over a foam skeleton to keep the toroid
light in weight and low in cost.  Other folks have made toroids
from slinky toys, welded metal tubes, tire tubes coated with
aluminum foil, fan shrouds, or any number of toroidally-shaped