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Motherload
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[*] posted on 21-12-2012 at 22:44
Blasting Caps/Detonators


I searched this forum with multiple keywords and their combinations but can't find any relevant info.
What I am after is first hand practical .... Not theoretical ... Input.
Has anyone successfully made commercial/military grade detonators ? With consistent, reliable and repeatable results.
I mean everything from the casing material to pressing of charges, combination of charges and quantity to crimping etc ...
I am having a hell of a time with it.
I am not referring to a straw pressed with ETN and TATP or HMTD with tape on it.
I am not after Mickey Mouse improvisations but quality detonators .... Call me chicken shit .... but if there is one thing that I absolutely hate about the energetics field is when the fuse fizzles out or nothing happens when the switch is pressed to the detonator which is stuck in a 2-5 Oz charge inside a rock.. I treat that rock like it was plutonium ... I really don't want to approach it for a few days at least to try again.
So having said that ... Anyone have anything they have tried ?
Thanks




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Oscilllator
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[*] posted on 22-12-2012 at 00:35


I don't think its possible for a home chemist to make EXACTLY the same type of detonators the military use given their detonators are mass produced with machines, and probably made from far higher grade chemicals than it's possible to produce at home.

Also there is a reason people use a straw rather than a bullet casing, the reason being I never saw a straw produce shrapnel.




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[*] posted on 22-12-2012 at 01:05


If "the straw" is used in a secondary charge ... I won't be worried about thin brass fragments ... I'd be worried about the charge and the "fragments" it causes vs the casing.
I am not trying to get my detonators certified ... But reliability is good.




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CaliusOptimus
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[*] posted on 22-12-2012 at 01:10


http://www.youtube.com/watch?v=aOriXCYRKkE

There is a lot involved, mostly in tooling from what I understand.

PS: I wouldn't recommend asking for practical advise here.
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[*] posted on 22-12-2012 at 02:13


How can a thing such as a homemade blast cap misfire? I don't see the problem. Also we can add more secondary at will, not just the 1g or less PETN.
Oscillator, how may times the industry recrystalizes their RDX? What's wrong with us making even purer product? There are many good things to make case of-plastic and paper for high sensitivity large volume secondary. Arrow aluminium tubing and glass for high reliability and RDX-azide in foil for micro charges. Designing the perfect low tech blast cap with only AP and low tech stuff like that is extremely interesting for me.
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[*] posted on 27-12-2012 at 21:06


Caps have fizzled out on me. That's wyi I prime them with flash powder now.
Although the reason I was asking about experiences .... Is cause some of my cap tests have left a white powder residue. Which is most likely PETN which I use as the base charge in my caps.
My PETN is needle shape and seems very insensitive to even hammer blows as well as priming powder out of cartridge primers.
I am gonna try it with some pure lead azide. But the needles sure are insensitive.
Experiences ??




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[*] posted on 28-12-2012 at 12:49


Any detonator may misfire for any number of reasons; it is not possible for either amateurs or professionals to make one that will always work when required, and never otherwise.

Having said that, I must second the sentiment that energetic materials made in the (home) lab are often of a higher grade than those made in larger volumes at an ordinance factory. Just look at the colour of the TNT or NG produced commercially, and compare it to what you can achieve in the lab with a little care.

With regards to the design of a reliable detonator my recommendations are these:

Case: Al rod, about 7 mm, bored in a lathe to a wall thickness of about 0.5 mm. Length about 50-60 mm.

Base charge: PETN or RDX, about 1 g total. The first fraction (ca. 0.7 g) should be pressed to a high density (~5000 psi), with the rest just hand pressed.

Primary: High performance material with good chemical stability and low sensitivity. For instance nitrotetrazoles or azides (eg. Roscoe's "azo-chlathrate").

Priming: A flame sensitive composition that is relatively insensitive otherwise, such as blackpowder or other pyrotechnical compound.

I recommend investing in a lathe, since it is an invaluable tool in this hobby (and great fun in its own right).
I feel that you should always use priming on top of the primary, since pressed primaries can be surprisingly unresponsive to flame and spark.

Finally, you should always employ two separate firing trains if at all practical. This squares the probability of failure taking it to the 1 in a million level (with well made firing trains).
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[*] posted on 28-12-2012 at 16:56


Sarstedt 55.526.006 are very useful test tubes.

The following page may provide some helpful information

http://www.sciencemadness.org/talk/viewthread.php?tid=389&am...
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[*] posted on 30-12-2012 at 09:35


Thank you guys..
Microtek, Rosco .... Very helpful.

Rosco ... Those centrifuge tubes are cool. I have only ever used epindorf type. I can press the PETN/Azide in the tube and install a e-match or fuse with a flash powder prime in the cap end.
Assemble it just prior to firing.
I do need some pure primary.
For testing I don't foresee any issues but for say setting of a plasticized charge ... Would the non brittle-ness of PolyPropylene tube ... balloon and cause problems with proper detonation in a plasticized charge ?

Microtek ... How do I measure press density/compression of a solid ?
Can it be calculated by the amount of force I am applying ?
I can make reversible modifications to my reloading press to help press charges in a tube but I don't know of any force gauges made for a press type setup.

Ral123 ... I will try some 1516 arrow shaft tube as well.


[Edited on 30-12-2012 by Motherload]




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[*] posted on 30-12-2012 at 13:57


Quote: Originally posted by Motherload  
How do I measure press density/compression of a solid ?[Edited on 30-12-2012 by Motherload]


Use an arbor press with a torque wrench. This is common for pressing model rocket engines. The amount of pressure exerted can easily be calculated from the torque applied to the pinion gear.
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[*] posted on 1-1-2013 at 15:15


Yes, you can calculate the pressure you exert by dividing the force by the area (in proper units). It doesn't have to be very accurate just press the bottom part of the base charge with somewhat more force than you can do by hand, and the top portion corresponding to very firm manual pressure.

If you have an accurate scale (priceless tool in chemistry) you could also measure the inside dimensions of a cap and then press a certain amount (eg. one gram) of PETN or RDX into it. Then by measuring the height of the coloumn in the cap you can determine the loading density of the charge.

Aim for a pressure that will give you above 90 % TMD for the bottom portion of the base charge.
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[*] posted on 1-1-2013 at 15:33


What does TMD stand for?
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[*] posted on 1-1-2013 at 16:44


I believe TMD stands for Theoritical Max Density.
Since PETN is 1.77g/cm3 .... One should load 3/4 of the PETN base charge to around 1.6g/cm3. And IIRC .... the top 1/4 charge should be loaded around 80%.
Correct me if I am wrong




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[*] posted on 1-1-2013 at 18:43


Quote: Originally posted by Motherload  
Thank you guys..
Rosco ... Those centrifuge tubes are cool. I have only ever used epindorf type. I can press the PETN/Azide in the tube and install a e-match or fuse with a flash powder prime in the cap end.

In addition to the Sarstedt 55.526.006 which has more usefulness with a 3/8" diameter press pin, and a slip fit for bushings made from common 3/8" OD thickwall polyethylene tubing, a more materials efficient capsule can be made using Sarstedt 60.546.002 but the sizing there will be metric or odd fractional inch sizing for the diameters involved with tooling and tubing. Depending on where you are in the world and whether metric or english sizes are more common, or what increments are available, this second tube can be a good choice also.
Quote:

Assemble it just prior to firing.

Yeah there are different configurations which you may use, field assembled with either a firing squib or a fuseholder bushing, which may be made watertight using a gasket cement.
Quote:

I do need some pure primary.

Not necessarily for use as such directly but perhaps useful as part of a composition. Most initiators are blends of different materials. A pure primary is generally only used as a laboratory standard for comparison with other mixtures designed to be improvements WRT certain properties which may not be quite what is wanted for the pure material alone.
Quote:

For testing I don't foresee any issues but for say setting of a plasticized charge ... Would the non brittle-ness of PolyPropylene tube ... balloon and cause problems with proper detonation in a plasticized charge ?

No.

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[*] posted on 23-1-2014 at 15:11


I wonder, is it worth it to add aluminium to the base charge? They diluted the MF in caps with chlorate, but adding aluminium will really increase the energy and may be will be quite efficient for materials like AN mixtures. I'm not too competent with Al and mostly it's safety, but I was wondering what you guys think?
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[*] posted on 23-1-2014 at 16:19


Why??

With a detonator you want a sharp and fast crack detonation that causes a high amount of instantaneous pressure (impact) Al would only decrease the crack or sharp impact (slowing down the explosive)


AN mixtures I would just use a brisant and dense booster depending on the comp.
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[*] posted on 23-1-2014 at 16:21


BTW,

Who is this Detonator's Anonymous on YT and why did he stop making vids? He has the most professional set-ups of any amateur, if that is even what he was.
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[*] posted on 23-1-2014 at 18:41


Maybe he blew himself up.

I second Turner, I don't want a primer that is pushing out a cavity because of power but one that is cracking sharply.
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[*] posted on 23-1-2014 at 21:54


The KClO3 is not used to dilute the fulminate but to enhance its brisance by better OB.



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[*] posted on 23-1-2014 at 23:52


Quote: Originally posted by Turner  
BTW,

Who is this Detonator's Anonymous on YT and why did he stop making vids? He has the most professional set-ups of any amateur, if that is even what he was.

A cool guy who wanted to share a his methods. Nothing wrong with him.
I cant see how KClO3 will increase the brisance of anything rather then sugar or coal.
Anfo suffers from large critical diameter, rather then sensitivity. The significant energy increase may be a benefit. With the chlorate they say crap about "the hot flame ignites or something". Aluminium will give good density increase and make the base charge highly sensitive, even when heavily pressed I feel like.
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[*] posted on 24-1-2014 at 00:56


This thread has attracted the cautious attention of some users who have expressed their concern with it's legality. I can't see a violation of the site rules (whereas previously I might have closed this thread), but please remain scientific in the pursuit of this topic :)



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[*] posted on 24-1-2014 at 13:28


simple.. get thin alumininium tube
TIG weld bottom (quality, youknow?)
obviously let it cool down more than enough, then add in a 3mm fuse, you might want a decent width tube
thereafter add in HMTD or other primary of desire, then push cotton wool down along the fuse to keep it in place and for faster DDT
thereafter put a 2g PETN in a larger aluminium tube sorrounding the first aluminium tube, this tube is also TIG welded (quality.. yeah?)
the tube is longer than the smaller primary tube, so you can be crimped above the primary tube
this entire thing can be sealed in plasti dip or a PVC tube to be made waterproof

anyhow a cheaper solution would be sensitive secondary 90% then 10% by weight MF, LAz etc, fuse inserted and secured with cotton wool, straw coated with a decent layer of thick aluminium tape to avoid bending etc




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[*] posted on 25-1-2014 at 14:40


Antiswat, don't take his warning lightly, that is getting too much like spoonfeeding and isn't really serving the intent of the OP, nor is it scientific. We should be discussing getting ways to a better density of the booster while offsetting the loss of sensitivity with a sensitizer or things along those lines.
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[*] posted on 25-1-2014 at 15:36


Yes Ral, and if you saw his blasting cap videos, you would say there is VERY little difference in those and industry detonators. Also his tooling, and methods for making them was very clever, effective and safe. If there is someone to copy, it would be that guy, what those videos.

[Edited on 25-1-2014 by Turner]
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[*] posted on 25-1-2014 at 16:46


Wondering if he made his own tooling or repurposed existing items for the job.

Interesting either way.
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