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Re: L/D ratio and gauges



In a message dated 4/25/00 12:33:24 AM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:

> Original Poster: "m0neyfromyuba" <m0neyfromyuba-at-netzero-dot-net> 
>  
>  greeting
>  i was wondering about if my coil had the right lenth to diameter aspect
>  ratio. Which ratio works the best? my program says the L/D ratio shouldn't
>  be anymore than 4.5. but i've seen many long thin coils put out long
>  streamers. Does the wire gauge have to do anything with the L/D ratio? Why
>  is 22 awg wire preferred over other types. Some prefer thin wire such as 26
>  gauge. WHY?
>  thanks for reading
>  ---------manjinder bains------------
>  

manjinder,

The details of the secondary are generally unimportant in regards
to the ultimate spark length as least when compared to other
factors of TC design.  Yes, the wire thickness, and secondary
size will make some difference.  Such things as power input,
break rate, bang size, gap losses, will make the most difference.

There is nothing special about #22 wire.  I prefer to use # 28 wire
for a small coil that gives 42" to 60" streamers.  Narrow secondaries
will give about the same output as wider ones.  If the secondary is
narrower, than the wire can be thinner to keep the inductance high.
High inductance in the secondary is good because it permits the
use of high inductance in the primary, which reduces gap losses,
and therefore gives longer streamers.  There may also be effects
that relate to impedance effects in the streamers, this is being
explored by some list members.   For example when I tried
replacing my # 28 wire with # 20 wire, I lost 4" of spark length in
my coil.

Yes, the wire diameter and coil height is related because it's a
good idea to have enough turns to give a good amount of inductance
in the secondary.  I like to use about 1500 turns in my secondaries.
It is possible that a larger coil can tolerate fewer turns, but I'm not
sure.

It is possible that some folks who use # 22 wire on a small coil
do so because they do not realize that they would obtain longer 
streamers by using a thinner wire.  It is possible too that they
used # 22 because it happened to be readily available.

You can see my latest coil at:

   http://members.aol-dot-com/FutureT/TT-42index.html

Cheers,
John Freau