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Hennig Brand
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I agree with Microtek, also even small increases in case thickness significantly reduces the effective transfer of impulse from the explosive in the
cap to the secondary to be initiated. Metal casings can have very high strength even when relatively thin.
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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DetaDude
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Detonator Materials
When I had my consulting co. we used to make up "look alike bombs to imitate real letter bombs and other types of explosive package's" and when it
came to producing the detonators we used hobby shop K&N aluminum tubes with a dowel inside to keep it from bending etc. We were training police
and fire first responders
how to handle bomb threats et. al. The point here is that the finished product looked
like the real McCoy. and the tubes were soft enough to roll them on a hard surface
until we got the end to look like a factory made working detonator.
Genius creates many a great works............Labor alone finishes them!
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kecskesajt
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Paper is better than any metal blasting caps.On another pyro-site I heard that somebody used iron blasting caps and after det. he heard iron pieces
flying and whistling.Quite unsafe.
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ecos
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I use syringe.
syringe would be better than paper.
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hissingnoise
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Soft aluminium tubing (silvery confetti) from an old freezer; good for most primaries except mercury fulminate . . .
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Bert
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Threads Merged
14-12-2014 at 13:41 |
NeonPulse
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Most hobby shops stock Al tubing in various diameters. Cheaply. Seal the end with a little epoxy putty, insert a straw or paint with nail polish for
extra safety and your good to go. The only problem is if the base charge is pressed too hard you will deform the end.
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Hennig Brand
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I was doing that for a while; gluing a slice of hardwood dowel or using an epoxy plug in the end of a detonator casing. It does work, but it is not
ideal. The bottom end of the detonator, opposite the ignition end, is where the velocity and pressure are at their greatest and therefore it is also
where the cap has the greatest initiating ability. Separating the bottom of the explosive charge in the cap from the secondary to be initiated with a
thick plug of glue or wood, or whatever, significantly reduces the transfer of the strongest impulse the cap has to offer for initiation. The sides of
the cap are still effective, but a lot is lost by putting a thick layer of material at the end IMO.
[Edited on 15-12-2014 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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NeonPulse
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I agree there. I guess perhaps drawing the end over a small steel bar with a tiny disk of metal to fit the hole may work well to stop the large plug
being needed if you know what I mean. You would place the tube over the steel leaving a few mm over the top of the bar, put the disk in place and heat
gently as not to melt the Al and draw the edge over the disk. Seems like a lot of fiddley bits but if you could get a system giong.... it sure would
help with micro testing as the length wou would need to insert the cap is reduced. In fact I attribute this end contact problem to a recent failure I
had with a 15g blob of plastic that did not fire and have considered trying the method I just outlined. that video on YouTube of the guy who made that
real professional cap on detonators anonymous channel had an end made this way. Not enough free hours up my sleeve lately though.
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Microtek
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This is why caseless or semi caseless detonators are nice. If you use a cast energetic or a PBX for the base charge you can leave the end open, and
therefore getting the most intimate contact possible between donor and receptor explosives.
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markx
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Quote: Originally posted by Microtek  | | This is why caseless or semi caseless detonators are nice. If you use a cast energetic or a PBX for the base charge you can leave the end open, and
therefore getting the most intimate contact possible between donor and receptor explosives. |
True that, but cast base or pbx might be relatively hard to initiate, at least in the classical dimensions of an initiator charge. Depends of course
what composition is used.
But perhaps the easiest way would be to leave the end of the base exposed....as in pressing the base charge into an open ended tube type containment.
That way one can still retain structural integrity of the unit and have the added value of the exposed base charge tip. Just my 2 cents... 
Exact science is a figment of imagination.......
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Microtek
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You just have to have the lower part of the base charge cast (or bound). If you simply press the charge, you will lose too much structural stability.
If you are worried about initiability, use something like nipolit (RDX bound in NC or NC/NG in a solvent casting process), a PETN analogue, PTX-II or
you can use a small percentage of an inert binder such as a PU based epoxy. In a base charge there is no need for mouldability (indeed, in a
semi-caseless or caseless design it would be counter-productive), so an appropriate glue can be used in amounts of just 2-5 % to make a hard PBX,
which is easily initiated.
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markx
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| Quote: Originally posted by Microtek | You just have to have the lower part of the base charge cast (or bound). If you simply press the charge, you will lose too much structural stability.
If you are worried about initiability, use something like nipolit (RDX bound in NC or NC/NG in a solvent casting process), a PETN analogue, PTX-II or
you can use a small percentage of an inert binder such as a PU based epoxy. In a base charge there is no need for mouldability (indeed, in a
semi-caseless or caseless design it would be counter-productive), so an appropriate glue can be used in amounts of just 2-5 % to make a hard PBX,
which is easily initiated. |
Yes, options are plentyful and limited mostly by the reach of our own imagination or lack of knowledge
Though I'm a bit worried about the critical diameter of PBX or melt cast bases with "classical" initiator dimensions (6-8mm). Depending on formulation
this might become a limitation to success. Not saying that it will happen, just another aspect that must be accounted for when designing such a
device. I've often ran into trouble when trying to initiate charges with limited dimensions and high density, either due to pressing, phlegmatisation
additives or inert binders.
Exact science is a figment of imagination.......
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Turner
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I have found the best option to be using basic plastic pen cases, the tubes can be cut to length, easily loaded and fused.
I have never had a failure in initiating a charge with these caps I made. People like to try and get clever and creative with detonators when I see
no need to do so. There isn't much sense in using cast melt explosives or PBX's in the detonator itself. 500-1000mg of Pressed RDX, PETN etc. with
30-150mg of primary is all that's needed.
As seen here:
Here is a 17g TNT cast with the hole molded:
45g Picric Acid booster w/ same detonator:
A 60g ETN cast here detonated with the same detonator:
Decomposition of said ETN cast:
I've done quiet a few detonations but always stuck with the same style detonator, 700mg ETN and 200mg roughly SADS
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markx
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| Quote: |
People like to try and get clever and creative with detonators when I see no need to do so. There isn't much sense in using cast melt explosives or
PBX's in the detonator itself. 500-1000mg of Pressed RDX, PETN etc. with 30-150mg of primary is all that's needed.
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Well, it depends on what your goal is....if you need a simple and working solution that does nothing more than fulfilling its function, then there is
no need to get more clever about it
On the other hand one might feel the need to explore the effects of a more complicated and untried system. Who knows, perhaps we might stumble on
something interesting in the process.....
Exact science is a figment of imagination.......
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Microtek
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I'm sure that your (Turner) detonators perform just fine with the type of demands that you place on them, but it seems that your charges are rather
large, so it is not out of place to use a large detonator, possibly along with a booster. But if you're experimenting on the sub gram scale (main
charge) then these solutions don't work well.
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Hennig Brand
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I have seen that cast TNT picture before. I think it was from a YouTube video. Seems to me the charge didn't detonate IIRC.
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Turner
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Yes, that one failed because I over pressed the ETN base charge in the cap and was insensitive to the SADS. I corrected this and they worked fine ever
since.
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Hennig Brand
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Did you get the cast TNT to detonate? If so, what did you use for an initiator?
From what I have learned, having a good understanding of initiation is very important and it can be much harder to learn (less intuitive) than a lot
of the other energetic materials topics.
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Turner
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No, the TNT was scattered around in small bits/pieces. I didn't really bother to pick the pieces up. When experiencing with the detonation of an
explosive as insensitive as TNT I think you need to use larger amounts. Probably 30 grams at least for a cast charge just to meet critical
diameter/critical mass. I had the intention of trying to detonate TNT again, but it is by far the most time consuming and tedious process to make the
material and I never got around to it, might be a neat little project some time down the line. 17 grams was all the yield I got out of my synthesis
because of a few mistakes I made.
By the way for anyone who is curious, here is the video of the AN/Al and picric acid booster detonating:
<iframe sandbox width="560" height="315" src="//www.youtube.com/embed/Orp9gb_uE3U" frameborder="0" allowfullscreen></iframe>
[Edited on 19-12-2014 by Turner]
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Hennig Brand
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Good to see you staying heart healthy by getting some cardio. 
I don't want to get too far off topic, but I thought I would include the following jpg of a table taken from an old defense document (Powder and
Explosives by A. G. Gorst). It provides some minimum mercury fulminate initiator charge weights for cast and pressed TNT and Picric Acid. As you know,
granular TNT and picric acid are much easier to initiate than their cast forms. Very commonly, granular or crystalline TNT or picric acid was used as
a booster to initiate cast TNT and cast picric acid.
BTW, did you check the melting point of your TNT? TNT even when of high purity is relatively insensitive to initiation.
TNT does take a bit of time to make, but after doing it a couple of times I find it fairly straightforward and with the right equipment (large flasks,
etc) it could be made in large quantities relatively safely. It wouldn't take much longer to make a pound batch than it would to make a 15g batch.
[Edited on 20-12-2014 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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ecos
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What is wrong about syringe casing?
I found some pics for this but it doesn't look nice
i personally shape it in a better way
is there anything attractive about metal casing?
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NeonPulse
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They look pretty large. What is in them? The rubber plunge could be replaced making them a little more compact. And the confinement isn't going to be
as strong as if they were made of Al.
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markx
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| Quote: Originally posted by ecos | What is wrong about syringe casing?
I found some pics for this but it doesn't look nice
i personally shape it in a better way
is there anything attractive about metal casing?
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There is nothing intrinsically wrong with syringe casings...just one has to pick a suitable size and work out a neat and clean assembly and a "safe"
process for it. For example insulin syringes would be of more appropriate dimesions.
The ones on the picture are quite horrible and I would stay well away from using or handling such devices. If one can not spare the time and effort to
perform clean and reproducible work, then researching the field of energetics is not a suitable passtime.
Apart from unrivaled mechanical integrity in construction and handling there is not much more attractive in a metal confinement. In fact I would avoid
it in amateur practice at all cost. The danger of shrapnel outweighs any possible advantages of metal casings for me. That's my personal opinion on
the matter, but one has to make up its own mind about these choices.
Exact science is a figment of imagination.......
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magneet
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An old photo:
4 mm dia Transparent straw casing, with direct contact HE plug, handpressed.
12% inert PETN PBX ribbon on 3 mm Al, covered in sand.
Hi,
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ecos
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| Quote: Originally posted by markx | | Quote: Originally posted by ecos | What is wrong about syringe casing?
I found some pics for this but it doesn't look nice
i personally shape it in a better way
is there anything attractive about metal casing?
|
There is nothing intrinsically wrong with syringe casings...just one has to pick a suitable size and work out a neat and clean assembly and a "safe"
process for it. For example insulin syringes would be of more appropriate dimesions.
The ones on the picture are quite horrible and I would stay well away from using or handling such devices. If one can not spare the time and effort to
perform clean and reproducible work, then researching the field of energetics is not a suitable passtime.
Apart from unrivaled mechanical integrity in construction and handling there is not much more attractive in a metal confinement. In fact I would avoid
it in amateur practice at all cost. The danger of shrapnel outweighs any possible advantages of metal casings for me. That's my personal opinion on
the matter, but one has to make up its own mind about these choices. |
I agree the picture is horrible. I just got it from internet.
i also use insulin syringes 1mL. I close the narrow part using small fire then fill from other part.
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