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51K
September 30th, 2003, 07:00 PM
I have searched this site but have yet to find a string on using airbags as blasting caps. I found a couple strings that mention airbags but no good discussion of their use so I figured I would start one here. I bought a couple airbags to experiment on and was able to disassemble them to the large round aluminum machined assembly that houses the initiator. I am a little apprehensive about prying this sub assembly apart. Does anyone here have any experience pulling this large aluminum machined assembly apart? In the two I have pulled apart, this assembly is identical and is about 6 inches in diameter, about 2 inches thick and has flanges that allow this sub unit to bolt into the larger airbag unit. The initiator wires run out of the center of the unit.

Also, has anyone here had good or bad results in using these initiators to get off HE?


Any opinions appreciated.

pic one is http://www.hot51.com/one.JPG
pic two is http://www.hot51.com/two.JPG

I was pretty sure I posted this in the HE forum but it is in the pyrotechnics forum now. Maybe I mis posted it to the wrong forum(?) Maybe someone moved it. I am not sure.

TreverSlyFox
October 1st, 2003, 03:34 AM
I seem to remember reading a .pdf document during the 2 week wait before posting about using an Airbag for a det. As I remember the cost, size and power of the Airbag dets made them a bust as a source. It was quite extensive in it's investigation and included pics of the entire procedure and disassembly.

51K
October 1st, 2003, 03:43 AM
Do you have a link to this document? I would be very interested. I have not found it by using the search function.

grendel23
October 1st, 2003, 07:12 AM
Airbags are a good source of NaN<sub>3</sub>, but the assembly itself and the pellets inside are not useable as is for a detonator, as the pellets will deflagrate, but not detonate. There is an electric squib inside, but it won't detonate either.
The one I cut apart contained 93 grams of pellets, which yielded 43 grams of azide after extracting with water.
These are a bitch to cut open, very heavily constructed. Also be very careful of the dust of the pellets, NaN<sub>3</sub> is very toxic, when I cut mine open, I became very light headed and my heart rate shot up. I finished the job the next day with gloves and a gas mask.
Also be aware that NaN<sub>3</sub> in an acidic solution will evolve HN<sub>3</sub>, a deadly gas.
The product of all this trouble is worth the effort, as lead azide or silver azide are both good primaries. I use mine to make a lead azide, lead picrate, lead nitrate clathrate, which has the performance of undextrinated lead azide with better stability and flame sensitivity, and less static sensitivity.

Mr Cool
October 1st, 2003, 07:46 AM
Anthony made that document about hacking them open, and I have also done it using exactly the same airbags. It's simple enough, it just requires a bit of sawing. I got ~100g of pellets.

blindreeper
October 1st, 2003, 09:13 AM
This may be a stupid question but where does one get replacement airbags? I assume your not just ripping them out of your cars :rolleyes: Got any ideas on the price of these thing because lead azide would be very nice indeed...

Cricket
October 1st, 2003, 12:22 PM
I think it would be very very expensive to obtain it by buying them new. Maybe if you visit the local junkyard or hicksyard and find a car with one in it. I don't know if you should hide your intentions to obtain this certain componet because it may be known for use in clandestine labs. Good luck.

51K
October 1st, 2003, 02:55 PM
On a very well known online auction service airbags routinely sell in the range of 1 to 5 bucks each plus shipping. That's where the two I am experimenting on came from. Sellers don't care who you are or why you want it. It seemed like a cheap way of getting caps but after all the hacking on the casing I have done and all the hacking I have left I am not sure it was / will be worth it. The urban legend of the airbag I heard was that there was a blasting cap at the heart of it. If it turns out all it has is a ematch surrounded by some comp then I think all the cutting / hacking / prying will not have been worth it. I am into these two fifteen bucks each which I was happy to pay if I ended up with a couple factory made blasting caps. I have a couple hundred factory made ematches we use for commercial display pyro and they only cost a buck apiece.


hack - pry - :eek: - hack - pry - :eek: is no fun when ripping the housing apart. I think I have lost 5 pounds of sweat tearing this casing apart from worrying if it will pop during disassembly. I have hit the whole area well with antistatic spray and am careful not to mangle or pry on the wire but I can't help sweating it.

DBSP
October 1st, 2003, 03:16 PM
Let me tell you something. You are fucking stupid, your dissapointed about getting 200g of NaN3:eek: Have you got any idea of what you can make with that?? well let me tell you, Lead/Silver Azide and that is not something to be dissapointed about:mad:

And seriously, did you really expect to find a blasting cap in the airbag:confused: I mean how the hell can you belive that? If the airbag had contained a blasting cap you would get your face sprayed with metal fragment penetrating your skull when the car smashes into something triggering the airbag, not very protective now is it?:mad:

Use your fucking brain, if you can't even figure that out then you really shouldn't be playing around with explosives!!!

51K
October 1st, 2003, 03:46 PM
Well thank you for your well thought out, informative and thought provoking response. I feel I am a better pyro for it. :rolleyes:

For years prior to actually getting my hands on an airbag I was under the impression that there was a cap at the heart of the device. I really had my hopes up that I could come up with a factory produced finished item detonator. I just recently decided to put a couple bucks into exploring this idea. I am just an experimenter. I work with commercial display pyro and the occasional le/he for entertainment. I don't need to whip up some he to blow a train off the tracks or an armored car open.

I know the 200g of NaN3 has value. You act like I wanted a toyota and ended up with a ferarri and don't want it. I am into each of the airbags 15 bucks including shipping. Big deal. In my mind that is cheap fun.

And for the argument that if it contained a blasting cap it would blow apart when it went off, have you seen how the insides of the airbag module is made? I think you could have a blasting cap in there and it would not blow apart into chunks when it went off. They are built like the proverbial brick shithouse.

And I did finally find the post by Anthony on tearing these apart but the page link he posted was no longer good.

Mr Cool
October 1st, 2003, 04:38 PM
I've seen how airbags are made, because I have also ripped one open, and I can tell you that DBSP is right. A blasting cap inside one would shred it to pieces. It may be thick, but it's only Al.

"I really had my hopes up that I could come up with a factory produced finished item detonator."

So, you had expected to get one detonator per airbag. Now you find out that instead, each airbag will allow you to make enough primary for a few THOUSAND detonators, and your DISAPPOINTED?! :confused::confused::confused::confused::confused:

51K
October 1st, 2003, 04:59 PM
:)

I am not disappointed.

I would say more like previously confused and now straightened out.

I am happy with the results - it was just not as I was expecting.

Anthony
October 5th, 2003, 09:38 AM
If anyone has a copy of that .pdf or knows of a link to it, I'd appreaciate it, seeing as I've lost the original :(

51K
October 8th, 2003, 08:21 PM
Finally grew a pair and finished cutting open the airbag initiator - only to make it safe for disposal of course :D Another gallon of nervous sweat and it is apart.

here is a link to a picture page. Page loads slow due to large pic sizes.


http://www.hot51.com/rendersafe.htm


Warning sticker on the initiator housing says it contains potassium nitrate and sodium azide. Are the pressed pellets are a composition made from the two (?) or is the potassium nitrate in the squib housing? Cause I stopped cutting after releasing all the little pellets. Of course I will research the earlier postings as well in case this was covered earlier.

It seems like there should be a way to make a drilling or cutting template so that you would not have to hack the whole housing apart but rather cut a large circular hole in the bottom and shake out the pellets. Maybe a hand turned hole saw style drillbit at the right place.

0EZ0
October 9th, 2003, 03:00 AM
To my knowledge, the main formulation of the pellets in airbags contain NaN3, KNO3 and SiO2. The newer systems these days may use quite a different formulation due to advances in technology.

The first reaction:

2NaN3 ----> 2Na + 3N2

Molten Na then reacts further with the KNO3:

10Na + 2KNO3 ----> K2O + 5Na2O + N2

The N2 produced from both reactions inflate the airbag. The Na and K oxides further react with the SiO2 in the pellets to form a glassy solid. Only an electrical squib is used to initiate the combustion process. As it's obviously been stated, a detonator in an airbag system would be quite hazardous from a safety standpoint.

sauvin
October 10th, 2003, 03:51 AM
I believe more recently manufactured airbag assemblies use a different combination of substances to effect explosive gas generation because of ecological concerns of leaving so much sodium azide languishing in junkyards all around the country. Sodium azide is said to be every bit as deadly as KCN but infinitely more unstable and can break down to worse poisons, like hydrazoic acid (sp?) which could conceivable be used as a war gas in confined volumes.

I believe sodium azide is now also a Controlled Substance in the US; possession of it, if noticed by the authorities, may conceivably result in lifelong internship in the grey bar hotel industry.

grendel23
October 10th, 2003, 06:30 AM
The other main airbag system in use is pressurized argon, used in some passenger side systems.
The pellets used in most airbags have Fe<sub>2</sub>O<sub>3</sub> along with the azide. The Na liberated when the NaN<sub>3</sub> decomposes reacts with the Fe<sub>2</sub>O<sub>3</sub> in a thermite reaction, which provides the heat to drive the reaction, as well as preventing the presence of elemental Na.
Sauvin, I am not sure I agree with your statement that NaN<sub>3</sub> is unstable, It doesn't like acidic conditions, but is otherwise very stable, toxic as hell, but stable.

Bert
January 7th, 2004, 09:31 PM
Looking at the MSDS for Sodium Azide:
Solubility in water: good (41.7 g/100 ml water at 17°C)

From previous experience, I know that Potassium nitrate varies with temperature widely- From 13.3 grams of KNO3 in 100 ml of 0 degree C water up to 246 grams at 100 degrees C. It's 31.6 g at 20 degrees C- Close enough to the 17 degree figue above.

I have no idea what the solubility curve for Sodium Azide is, and a couple of different searches on google hasn't shown me.

From grendel23-
93 grams of pellets, which yielded 43 grams of azide after extracting with water.Pardon me if I'm being a bit thick, but how would you carry out a water extraction of a mixture where the two constituents are this close in solubility? Is there something I'm missing here? Could you explain your procedure in a bit more detail?

grendel23
January 8th, 2004, 05:52 AM
The main components of the pellets are NaN<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub>. I do not belive KNO<sub>3</sub> is a major component in the pellets in most airbags.
I have read reports that the squib used to fire the airbag contains black powder, that would explain the label on some airbags saying they contain KNO<sub>3</sub>. The azide should be the only water soluble component in the pellets.

I had hoped that the pellets would more or less fall apart in water as the NaN<sub>3</sub> dissolved, it was less rather than more, I had to crush them with a stirring rod against the bottom of the beaker. I probably could have had a higher yield if I had powdered them first. I filtered the solids out, then gently boiled off the water, leaving reasonably pure NaN<sub>3</sub>.
I wore a gas mask during the entire procedure as a precaution against HN<sub>3</sub> gas.

Mr Cool
January 8th, 2004, 07:50 AM
The ones I had contained potassium nitrate and boron in the ignitor, and sodium azide, iron oxide and silica in the pellets, so the sodium azide is easy to extract. Not that you'd need to. Just crush the pellets under warm water, let it all settle, decant off the solution through a good filter paper, and add the metal nitrate of your choice (silver/lead)...

Mr Cool
January 8th, 2004, 08:04 AM
By the way, gas masks might not protect against HN3, they're not designed to.

Bert
January 8th, 2004, 10:59 AM
Thanks for the information- Some of the earlier posts had the pellet components wrong, apparently. (OEZO in particular). Could someone post the correct Nitrogen producing reaction? Enquiring minds want to know... The actual percent composition of Azide in the pellet mix would be interesting information.

Boron/Potassium Nitrate igniters? Those are what's used for military applications where high flame temp. and instant ignition are required, as in rocket weapons. I'd save those igniters... Pure Boron is expensive and hard to come by.

Jacks Complete
January 8th, 2004, 02:08 PM
http://auto.howstuffworks.com/airbag1.htm has a good little bit about airbags, and they say they use Sodium Azide and KNO3 mix.

A small note would also be to get older airbags for taking apart, as these tend to have more power to them. They might even be cheaper. Apparently, new, they cost $150 or so. Secondhand they can be almost free!

Mr Cool
January 8th, 2004, 04:58 PM
I don't doubt that there are different compositions used in airbags.
Bert, yes I wanted to get the ignitor out, but after sawing for a few hours I gave up! Maybe I'll have another go at it some time!

The reaction in the iron oxide containing ones is

6 NaN3 + Fe2O3 + 3 SiO2 --> 3 Na2SiO3 + 2 Fe + 9 N2

Strange, I'm sure I tested my pellets to be more than 53% sodium azide... I must have screwed up my test somewhere! How embarrasing..!

I suppose the iron oxide is to get rid of the sodium, and the silica is to get rid of the sodium oxide. Maybe it's also useful for forming slag droplets, otherwise the combustion might make lots of nasty particulates...

Mr Cool
January 8th, 2004, 05:03 PM
Although 53% does fit in quite nicely with grendel23's experimental yield of 46% azide...

(why can't I see an edit button??)

hpy2bhre
January 20th, 2004, 12:38 AM
The air bag I got off of a well known auction site isn't housed in aluminum but rather steel is used as a containment. The bag was easy to take apart with common hand tools and the cartridge shaped unit even has a patent #.Its made by the Bendix Alantic Inflator Company and has patent #5076607 and 4981534 on the outside. This inflator unit looks to be easy to disasemble all the way to the azide pellets by simply unscrewing a plug on one end. As soon as I can get a spanner type wrench that fits I will take it further apart. A patent search revealed a good diagram of the internals of this design. This seems to be a good bag to hunt down. It fits dodge vans on the passenger side. The patent, I think mentions that sodium azide is a main ingredient.

Bert
January 21st, 2004, 11:33 PM
SWIM recently dissected an airbag. The reports of a blasting cap being the actuator ARE NOT far wrong, at least for the item examined. Actuator was an HE squib. An additional small cylinder of Boron/nitrate was placed over the squib to assure ignition of the gas generator mix. The gas generator was loaded with thin, doughnut shaped DISCS rather than pellets, inside a completely sealed Aluminum can. The squib served both to actuate the high temperature igniter mix and to puncture the can, allowing the hot gasses to reach and ignite the main gas generating charge. The squib contained in this device initiated a piece of PETN det cord when tested.

Bert
March 23rd, 2004, 12:59 AM
How stable is Sodium azide when heated in a solution of distilled water? Could a solution extracted from airbag inflator composition be dried completely by gently heating in a large flat pyrex pan in an oven, or would the azide decompose?

grendel23
March 23rd, 2004, 05:21 AM
That's what I did, I did it over a hot plate and gently heated it until it was almost dry.
I had read that it can decompose and give off HN<sub>3</sub>, so I did it in a well ventilated garage and used a gas mask. I don't know if there wasn't any HN<sub>3</sub> produced or the mask did its job, but I didn't notice any ill effects.

Bert
March 23rd, 2004, 12:02 PM
That's what I did, I did it over a hot plate and gently heated it until it was almost dry.

Did the solution before drying and resulting slightly slushy mass after "almost" drying have a slightly yellowish color? Did you attempt a final drying by a non heated method, such as drying over Sulfuric acid in a dessicator, as the retained water would make measurement for use somewhat problematic...

grendel23
March 24th, 2004, 06:51 AM
My NaN<sub>3</sub> is a very light gray due to a small amount of Fe<sub>2</sub>O<sub>3</sub> passing through my filter paper. I didn't notice any yellow tint, but a very light cast could have been masked by the gray.
After I was finished drying my NaN<sub>3</sub>, I put it into an improvised desiccator with CaCl<sub>2</sub> for about 24 hours. I usually do that with anything I make. I had left it out for several hours after turning off the heat, it did not change appearance after being in the desiccator, but I didn't check the mass before and after it was fully dry.

FrankRizzo
September 28th, 2004, 02:07 AM
Was anyone able to resurrect a copy of Anthony's airbag dissection PDF?