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chemstu
#1
Nov4-06, 03:33 PM
P: n/a
Does anyone know why commercial detonators have small gage solid
conductor leg wires? And why only solid conductor wire is recommended
in a blast circuit?

I have an idea, but I cannot be sure. I have some electrical/physics
knowledge, and I understand that both solid wire and stranded wire have
advantages, but I do not understand the details as to the why solid
wires are chosen in commercial caps. There is so much unreliable info
on the web about comparisons between solid and stranded wire -
especially as it pertains to the home audio and data communication
industries. Some of the info is contradictory. It is hard to sift
through it all.

Here is what I know on the subject: The DC current carrying capacity
between solid and stranded wire is negligible in most cases.

I understand that skin effect allows higher frequency AC to travel
easier through stranded wire than it does through solid wire because of
the increased surface area due to multiple strands. Although, at least
a high frequencies, I believe that the benefit gained from skin effect
is in turn lessened by the slight inductances that can set up between
individual strands. Then there is the matter of corrosion throughout a
stranded wire on the surface the strands or between strands that grows
with time. No doubt these inductances etc. degrade signals - I am
assuming that that is the main reason that CAT5/6 is solid conductor.
It seems that stranded wire is only advised for CAT 5/6 when patching
and where physical stress is expected on the wire.

I am aware that DC voltage is used to fire a detonator. However, at
least in case of an EBW, foil, etc., the current pulse rise times are
so fast that, the waveform appears as critical as the current and
voltage delivered. High frequency? at least for one pulse?

Then there is the notion of physical durability of wire. In cases of
physical usage, stranded wire outperforms solid sire due to its
flexibility. However a detonator is not a repeated use item.

I am sure that stranded wire will work in a blast circuit in the real
world. There are plenty of sites for homebrew detonators that instruct
the maker to use stranded wire. But, I am specifically speaking of the
sole use solid wire in commercial caps. I have read that article about
the failure of the IED that Ted K made and tried to use. Apparently an
EOD investigator concluded that had he used solid wire the IED would
have detonated. So, solid wire appears critical doesn't it.

Theories -

Stranded wire - reasons to use:
1. flexibility?
2. skin effect allows for faster rise time in detonation pulse?

Solid conductor wire - reasons to use
1. inflexible, possibly wires assist in physically holding the
detonator in place?
2. inflexible, leg wires are not expected to be bent many times
3. lack of skin effect not benefit not a problem - likely true with
slower caps
4. lack of skin effect not benefit not a problem - waveform not
critical affected for EBW etc..
5. broken wire can be discovered easier than with stranded before use
6. less possibility of corrosion buildup as between strands in stranded
wire
7. less possibility of inducing current into stranded wire broken
strands from ext RF source
8. more reliable connection when wires are twisted?

I hope I am not to far off in my theories. Please feel free to comment
on my theories and to any specific relevance to an explanation as to
why solid wire is chosen in commercial detonators. Any other info is
appreciated.

THX, EC

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