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ManyInterests
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I actually don't know if NHN can be dead pressed (yet) because I have yet to construct my ETN/NHN detonator. But now I know that is a thing. I also
realize that making a det cap with ETN/NHN is quite safe because there's no way I am going to press hard enough to trigger an accidental detonation. A
simple gentle press to hold everything in place and we're all good.
And the matches I use are similar to the design in this video: https://youtu.be/zjAABCRhm8c
I bought my nichrome wire from Aliexpress. I have a ton of good electrical wire from 22 ga to 28 ga (all work fine). I had to practice to make sure I
built e-matches that can be inserted into a tight pen body and still not have any of the electrical or nichrome wire move around. I find that the
thicker nichrome (0.25mm) is easier to work with, but the thinner (0.1 and 0.08) also works, but you'll need to use more of because it likes to bounce
around a lot, so I cut a longer bit of the nichrome and wrap the match head around a few times to make sure the nichrome doesn't bounce around. When I
used short wires even 2 AA batteries light up a match with 0.25mm wire on it.
I don't use any lacquer like in the video or put additional ignition powder on it. The match head alone should be sufficient to set off the NHN,
especially if the match head is pressing directly against the NHN. If I do need more flame, I have a cotton ball worth of NC left, so I can use a
small bit of that.
[Edited on 23-12-2021 by ManyInterests]
[Edited on 23-12-2021 by ManyInterests]
[Edited on 23-12-2021 by ManyInterests]
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Microtek
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If you make a few adjustments to that, you can make a much more reliable system:
Personally, I have moved on from bridgewire ignition but before I did, I used 0.08 mm bridgewires made of kanthal or nichrome (the material doesn't
matter that much - the finished assembly just needs to have a resistance of around 2 ohms). I used multistrand wires, which makes it easier to solder
the nichrome and a small piece of heat shrink tubing to keep it tidy. Then I ground some match heads up and mixed the powder into a paste with NC
lacquer. Then I dipped the end of the wire assembly into this mix. Then after drying, I dipped it one more time.
These e-matches can be set off with three AA-batteries through at least 50 meters of wire and the bridge wire can't become displaced from the pyrogen
which is a known flaw of the system with winding the wire around the match head.
@Brighthermite:
The cap is nothing special, but I've attached an stl so you can see for yourself. The box is just a large lidded box of reinforced polystyrene foam
that I had lying around. You could just as well use any other kind of box, but there should be some sort of lid or covering on top; otherwise the
explosion will scatter your sound absorbing medium everywhere.
Attachment: ArcInsert7_mk2.stl (137kB)
This file has been downloaded 317 times
The putty for the cap is not a great invention either, just my solution for making a simple and reliable means of separating the primary from the base
charge. You just dissolve a little NC in acetone and add your primary of choice. It should be flame sensitive and should have a very short DDT,
otherwise you may just get a flash. Over the years I have used many different primaries from HMTD and acetone peroxide over lead azide and Roscos
azochlathrates to many nitrotetrazole compounds (and NHN). None of them are as effective, safe and reliable as aminoguanidine nickel perchlorate - an
ideal primary in my opinion (some of the others are better in some parameters. AgNT is more effective in truly microscopic devices).
[Edited on 23-12-2021 by Microtek]
[Edited on 23-12-2021 by Microtek]
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ManyInterests
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Yeah it's close to what the person is doing in the video. I had to experiment with finding a way of wrapping the wire around the match head to make
sure it doesn't move. Then I inserted it and removed it from a detonator body multiple times before proofing it (I.E. applying some current) to set it
off and make sure it still works. A dozen times of doing that successfully and I got a working system on my hands.
The main thing is that I don't have NC lacquer and I don't want to get any. I'd rather work with what I have now instead of buying more stuff.
On a side note. When building another test cap (with black powder) I had an premature pop when when I accidentally inserted one of the wires into the
NC terminal of my RF module instead of NO. I did check, but I guess the font was small and I was tired. I decided to apply some electrical tape on the
NC to block it off and make sure I only insert it into the NO (normally open) terminal. That way I can safely set it all up and detonate with the
button when I am ready.
It didn't cause any damage because the cap was already in the bucket. But I should have put it in deeper since I really heard the pop and it did throw
sawdust around. On a plus note. It is my first successful pop with my black powder. The amount of pressing required is non-existent and even loosening
it up worked. Also hot glue works well to seal a detonator.
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Microtek
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You are not supposed to buy NC lacquer. Just dissolve a little of your NC in acetone. Even if you want to stick with the match, at least apply a coat
to keep the wire in place.
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ManyInterests
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That sounds fine. I can do that for sure.
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