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Author: Subject: Spark Gap Detonators for ETN
Aurium
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[*] posted on 13-11-2015 at 06:19


Grant

Nice detonations there! The detonators I made used only 0.1g which could only impact plastic. Still I have the remains of a 60g ETN impression on a steel plate. I'll post it when possible.
What cable length have you used? Have you tried 0.1uF yet?

Lipatkov

Once again, thank you for your recognition!

Bert

Well I still haven't given up on finding interest for these detonators but I don't know were to look for people in the business.
If I go to the guys that make movie detonators already they'll just protect their business and say the SGD is useless.
I'll have to talk to the guys buying and using the detonators.


For me these detonators are a way to move into secondary and tertiary explosives regardless of my success with primaries.
I won't be making peroxides anymore but many primaries are perfectly safe.
I'll give a go at making better primaries for chemical interest if I can gather the ingredients.
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Grantr
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[*] posted on 13-11-2015 at 19:04


Aurium thanks! No i have not tried the small caps. They just came today. I am using 6 feet of RG 6 coax with about 2 feet of speaker wire. I have thin wire test leads connecting the cap to the rg 6.
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Grantr
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[*] posted on 17-11-2015 at 19:31


SGD is working well with the MOC cap at 4kv. I have two MOTs running parallel to give me 4kv. These feed one MOC with the internal bleeder resistor still in tack. I have a crude switch with a string on it for me to pull to fire the gap. So far it works every time. I tested it on a dense charge today.

I was able to press 1.35 grams into a 1/4 inch vinyl tube down to .9 inches which gives me .72cc so a density of 1.87 grams cm3. I used a 2x4 wood block with a 3/8 inch hole drilled in it then cut in half through the hole.

This was clamped around the vinyl tube and I used my drill press and a 1/4 inch steel rod to press the ETN. The tube is not strong enough without the board as it will bulge out and not press the ETN after a certain amount of pressure is applied.

.14 grams was poured loosely on top. The charge was tape to the top of the mild steel tube. Detonation was very loud and the steel had a 1/4 inch hole blown through it with a dent on the other side.
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Aurium
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[*] posted on 18-11-2015 at 07:15


I see you'r having fun making Swiss cheese out of metal!
Have you taken the time to experiment with different voltages, capacitances and cable lengths so far?
1uF at 4kV is very much like what one would use for an EBW. The SGD is only interesting because it works with just 0.1uF.
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Grantr
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[*] posted on 20-11-2015 at 10:32


Yea I am having fun! LOL

I have tried using the ebay hv power supply to attempt to set it off. It does not work at all. I set a large spark gap about 1 inch near the HV supply to get the max voltage out of it. I ran 6 feet of speaker wire to the charge with the small 2mm gap. Loud spark but no burn or bang of the ETN.

i also tried the 4kv direct from the MOTs feeding through the MOC. The tube of ETN blew off of the electrode but no bang. The arc melted the tips of the electrodes in the ETN.
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ecos
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[*] posted on 20-11-2015 at 11:27


MOT can supply more than 400A at low voltages :)
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Aurium
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[*] posted on 20-11-2015 at 16:43


Grant.
The hv module is meant to charge the capacitors, not firing the SGD directly. By your description you didn't use any capacitor?
If you want to use the MOC with the hv module you'll have to remove the internal resistor.
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Hey Buddy
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[*] posted on 30-1-2021 at 11:55


Quote: Originally posted by Aurium  
SGD


I'm quite sure that it is the spark discharge that initiates the ETN.
I do not yet know, however, how this happens exactly. High pressure, high temperature, shock wave, maybe a direct electrostatic phenomena?



This is an old thread, but just to shine some light on this, these are known as dielectric breakdown initiators. They are used in missiles mostly, but are also used in some ordnance main charges. What you made is very similar, probably the same way engineers discovered it. In the production DBIs, one leg is the actual case which holds the detonating compound. Typically in a threaded coax configuration, the other leg is a central wire, typically nichrome 36 or 40 ga. The primary wire is insulated by materials like zirconia which have known resistance. By controlling the primary wire diameter, and the distance between poles, the output joules are controlled. Usually they input from a circuit that fires at only around 500v to 4000v then the dimensions between the dielectric material and conductive detonator body are fixed in place such that when the dielectric threshold is met, the circuit is shorted creating instant plasma through the detonating compound in the space around the core wire. That compound is usually pressed to 1500-2000 psi and cured to form a homogenous, hardened fill. The standard initiator compound is BKNO3, for igniting missile grain. For detonation, typically a train of BKNO3 or MTV or BKNO3AP/LP, then a compacted nitrocellulose and if needed a secondary like HNS. I'm not great at math but when DBI occurs it amplifies the source of high V low I, and turns it into high I and V in a very short instant. Resulting voltages and amps depending on configuration can be very high, like 48kV-100kV at surface of center electrode. The distance between legs and the resistance of components in the detonator make it so that small input voltages and very small currents cause plasma detonation, as the plasma is formed within the initiating fill between the detonator body and the center pole. The thinner the wire, the less voltage required and the distance between poles is very close. Sometimes around .03". Resultant energy delivery can be on the order of 1,000mJ per mil at electrode surface with input of 4000V.

For more information on these types of devices a very useful patent which I've referenced in this description is a very good detonator which I personally prefer.
US9329011 B1 "High Voltage Arm/Fire Device and Method"
Smith, Orbital ATK, Inc. 2016

Hopefully you will enjoy these. They are very nice and relatively inexpensive if cheap components are used. Very versatile. Thead in. And quick detach if you use BNC/SMA.

20210130_134320.jpg - 2.1MB

I'd imagine Minemans comp would be peachy keen with these. I've been working on some other OTC det comps but its so cold and wet out its put me behind for a while. Really interested in using other forms of boron other than elemental because reducing it or dissolving magnets in hcl is a PITA. Will be trying some Mineman comp variants though soon. I will report anything useful.

[Edited on 30-1-2021 by Hey Buddy]
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MineMan
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[*] posted on 30-1-2021 at 13:15


Haha. Yah I was actually going to use a spark gap for the industry applications because the mixture is so insensitive to flame. It will work extremely and will not be as sensitive to particle size, except the Al must still be nano. The spark gap gives a wide margin of error correction. It should turn the nAl to plasma, speeding up ddt.
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Pyro_cat
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[*] posted on 9-2-2021 at 18:15


I wonder if I could just use grid power, back in the tesla coil days messing around exploding foil with the 200 amp main, it was quite energetic.
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Pyro_cat
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[*] posted on 23-2-2021 at 19:53


I guess I have to try it I thought I could put the idea out and someone else would.

Small pile of ETN on grounded Al foil and pop it with an arc by touching the foil - etn pile with a grid power 120 v hot wire so the plasma ball spark blast hits it.

alright, I will get this experiment done and report back.



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