endotherm
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Posts: 164
From: dunno
Registered: JAN 2001
posted 06-11-2001 04:10 PM
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This never really happened, it is pure fiction but i will write about it like it's true just for ease of reading
I had like 2 gallons of Lye Drain unclogger lying around so i was bored and decided to do an old favorie trick, filled up a balloon, hooray great, little bitch bang. Then i realize it seems like it would be really hard but in actuality it is real easy to fill up a garbage bag, so i rigged it up, with a super huge display wine bottle with like 2 gallons of lye and a pound of aluminum, i ran this through a hose into a little beer bottle where it was filtered through water, in about a 2 minutes the garbage bag was clearly inflted, so i hooked up an air compressor, and filled the other 30% up with air, i attached about 4 min worth of Visco to a pack of matches and taped it on, i lit it in a field behind my house where i could see it from my window, it was about 500-600 yards away, i could just make it out from my window, then it dissapeared, just dissapeaded, no noise, no flash nothing, like a popped ballon, Well that was preety fucking gay i thought and BOOOOOOOOOOM, it startled me so much i was like shaking, it sounded like thunder, like if you were just hangin' out in your house watching TV you wouldnt just be like, what was that, you would jump out of your chair,BY far the loudest thing ive ever heard, for under like 6 bucks you could make something that would litterally shake your neighborhood... I have a new toy.....


J
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Posts: 635
From: United Kingdom
Registered: SEP 2000
posted 06-11-2001 05:32 PM
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Watch out for static! If I were you, I'd make sure the bag is firmly grounded before filling with either gas, but even with these precautions there is still a danger.
How much damage did it do (if any)?

J

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endotherm
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From: dunno
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posted 06-11-2001 06:16 PM
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J- well i wouldn't really know, because i didn' really do it but if i had to make something up i would say it did no structurual damage to the ground or any surrounduings (no crater) , the biggest piece i found of garbage bag was about the size of a sheet of paper, other than some garbage bag shreds around, you wouldnt even know there was just a large explsoion, this doesn't mean that you could light them off in your room...to all those KeWLs out there,they definitley have a lot of pushing power, it doesnt have much power by VOD most likely, but definitely creates a lot of pushing pressure judging by thge sound,this thing could push and compress a large volume of gas.
i want to emphasize the sound was just really tremendous, it was like too loud, like it wasn't like some people might not notice,believe,i got my point across (whatever point that was)
and also J, I went over the inside with Supercats antistatic spray, it's funny considering i use this in my "Fake" piezo electric combustion cannon, its a paradox of some sort, using something to prevent an explosion, that i use to cause an explosion, things like that are real deep and...wait, what did i jut say, are hydrogen fumes toxic? Just Foolin'

[This message has been edited by endotherm (edited June 11, 2001).]



blackadder
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Posts: 315
From: London
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posted 06-12-2001 12:18 PM
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Yeah, I've experimented with these things tons of times. They rule!
I used to place two wires hooked up to model rocket ignitor inside the bag. Then, I would chuck in an aerosol can with tape over the button, so aerosol can will be spraying constantly. Then the bag would be sealed, by pulling on the string things, and tying the top bit so that you get a knot in the actual bag. Then, I would wait till bag inflated to the maximum capacity, and then put the two wires to the batteries, and BANG!!!

Eventually I progressed to using propane, butane, and eventually hydrogen. I never bothered putting the air compressor in, I just left a bit of air in to start with.

Remember to tape bricks to the hydrogen binbag to prevent it from flying away, that nearly happened once.



Mr Cool
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posted 06-12-2001 01:09 PM
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Why did you progress to hydrogen? Both butane AND propane are more powerful!


Anthony
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From: England
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posted 06-12-2001 02:02 PM
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I once filled a bin/garbage bag with hydrogen, as a step up from hydogen filled ballons which give a fairly impressive bang.
After attaching it ot the cat for a while, I release it and it didn't go bang, it just gave a gentle fireball and crashed burning in someone's garden. I think it's the pressure of hydogen in a ballon that gives the bang.

A bag full of just propane or butane can take several seconds to burn.



endotherm
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From: dunno
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posted 06-12-2001 02:34 PM
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quote:
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Originally posted by Mr Cool:
Why did you progress to hydrogen? Both butane AND propane are more powerful!
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Ummmm, where did you come up with this?



Mr Cool
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From: None of your bloody business!
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posted 06-12-2001 03:51 PM
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Hydrogen:
Equation = 2H2 + O2 --> 2H2O
You must break 2 H-H bonds and 1 O=O bond to cause a reaction. This requires a total of (397+(2*436)) = 1269 kJ
This is the amount of energy that is used up when 72 litres of hydrogen and oxygen explode (there are 3 moles of gas, each taking up 24 litres at rtp).
The reaction gives out energy by making 4 H-O bonds, each releasing 464 kJ, thus releasing a total of 1856 kJ. Subtract the energy needed to break the original bonds, and you find that: 1856 - 1269 = 587 kJ/72 L
1 litre of hydrogen and oxygen burning in an optimal ratio therefore produces 8.153 kJ of energy.

Propane:
Equation = C3H8 + 5O2 --> 3CO2 + 4H2O
You must break 2 C-C bonds, 8 C-H bonds, and 5 O=O bonds to cause a reaction. This requires a total of ((2*347)+(8*435)+(5*397)) = 6159 kJ.
This is the amount of energy needed for 144 litres of propane and oxygen.
The reaction gives out energy by making 6 C=O bonds and 8 H-O bonds. This releases a total of ((6*803)+(8*464)) = 8530 kJ. Subtracting the 6159 kJ required to break the bonds leaves 2371 kJ produced by 144 litres.

1 litre of propane and oxygen burning in an optimal ratio therefore produces 16.465 kJ of energy.

You can see that a bag full of propane and oxygen will release more than twice as much energy as an identical bag of hydogen and oxygen. Do you want me to do it for butane as well? Check them if you like, just look up the bond energies in any chemistry text book.



ANTI-SYSTEM
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From: FL. USA
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posted 06-12-2001 05:15 PM
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Your both right in a way. Hydrogen is better for this due to its higher speed of burn. butane and propane are more powerful if the way of creating more gas volume but it takes a lot longer to catchup to hydrogen. by the time it does the bag is torn or burt open allowing all the gasses to escape.


endotherm
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From: dunno
Registered: JAN 2001
posted 06-12-2001 06:17 PM
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quote:
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Originally posted by ANTI-SYSTEM:
butane and propane are more powerful if the way of creating more gas volume but it takes a lot longer to catchup to hydrogen. by the time it does the bag is torn or burnt open allowing all the gasses to escape.
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That was not what Kj means antisystem, it is not a measure of volume, but a measure of energy, Kilojoules
Mr. Cool, interesting formulations, but are we discussing theoretical (though true if the numbers are correct), or the practical power as an explosive, gasoline has 20-37 times the stored energy than TNT but does it show it? Propane and Butane may greate more joules but hydrogen is a much more violent and explosive combustion, although the overall energy is lower




PYRO500
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Posts: 1513
From: somewhere in florida
Registered: SEP 2000
posted 06-12-2001 07:07 PM
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I have an idea on how to make a garbage bag setup that will ignite and not require inflation with air amd will be simple to setup, just to check, Al + NaOH, HCL, or H2SO4 makes H2 right, just to make sure.
anyways, what if you had a jar of H2O2 in the bag too and small bucket, like the pool chlorine buckets and you weighted it down and filled the bucket with water to the top of the jar (to cool the jar so it dosent crack or the water turn to steam) and put the reactant+AL in the jar and place a jar of h2o2 30% next to it, then take a garbage bag and place it over the assembly and put bricks on either side. now take two jars, one of dilluted bleach and the other of water, or if your usning a liquid pour that in, the bleach should decompose the H2O2 and the acid/metal should make H2 and just ignite it with steel wool and a camera flash ignitor (+2 caps extra ) I might try this tonight when I get the extra cap added to my camera flash detonator




endotherm
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From: dunno
Registered: JAN 2001
posted 06-12-2001 07:49 PM
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yes they all make H2, but i find the most efficient to be Hcl and nect to that sulfuric, then Lye, be careful though, us the antistaticspray and try it with something small like a shopping bag first


mark
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From:
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posted 06-12-2001 08:03 PM
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And I thought one gallon paint cans were loud.....


ALENGOSVIG1
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From: Canada
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posted 06-12-2001 09:34 PM
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i like pressurizing the bottles better becuase they are transportable. Hydrogen and oxygen will make MUCH more sound that hydrogen and air. Propane is more powerfull than hydrogen but hydrogen is more violet and fast burning.
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nbk2000
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From: Satans asshole!
Registered: SEP 2000
posted 06-13-2001 12:26 AM
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I wonder what would happen if someone were to place several large bags full of hydrogen and oxygen (seperate bags) inside a big garbage bin (like behind a store), close and lock the lids, and ignite it?
Hiroshima II?

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ALENGOSVIG1
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From: Canada
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posted 06-13-2001 01:09 AM
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or fill the bin with baloons full. that way it would be under a little pressure. might take a LONG time to fill up the baloons but it would be more effective


Mr Cool
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posted 06-13-2001 07:09 AM
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Strange, I once saw a video comparing the two fuels. 2L plastic bottles were filled, one with each fuel and oxygen in the correct proportions. They were sunk to the bottom of two large plastic bins, and set off electrically. The hydrogen/oxygen sloshed all the water around quite violently, but the propane/oxygen did this AND smashed the bin!
I suppose this is because they were in bottles though, so the pressure could build up more and more of the propane could burn before the bottle burst. I forgot that you were only doing it in bags, so yes for that purpose hydrogen might be a lot better.


PHILOU Zrealone
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From: Brussels,Belgium,Europe
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posted 06-13-2001 08:39 AM
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A three gallons trash bag full of acetylen and air (1Vol/9Vol) can destroy a brick wall!
VOD is arround 3000m/s!
As you know:
KMnO4 + H2O2 --> O2 + H2O + KMnO4+ heat
CaC2 + H2O --> CaO + C2H2 + heat

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endotherm
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From: dunno
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posted 06-13-2001 02:44 PM
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You could shoot people out of it if they didn't mine being deaf and have disfiguring burns all over their body.
And it will have sucky compression if all the bins were the same size, i doubt it would even make a bang, just flame up. It has to be from a larger chamber into a smaller chamber
For an experiment to try if you dont believe me, get two soda bottles, one with the top cut off so it's like a cup, and one that is regular, try hairspray in both of them, the cup one will just flame up , but the regular soda bottle will go ROAR and have a 6" Blue jet come from the mouth



[This message has been edited by endotherm (edited June 13, 2001).]



Anthony
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From: England
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posted 06-13-2001 06:18 PM
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Obviously if you leave the end open it'll just flame since there's no pressure build up. If you push a circle of card down to make a "projectile" or tape a sheet of paper overt he muzzle you'll get a hell of a bang. I don't know whether the bins will take the force though because it's going ot be a hell of a lot. I considered making a spudgun out of a steel 45 (55) gallon drum with like a foot diamter barrel to fire footballs. But I worked out it'd need about 2 gallons of propane and also I remembered a story about a guy who was cutting one of these drums, but it had petrol vapour in it and the blew the top off the drum and sliced his head off. So I figured they wouldn't take the pressure...


blackadder
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From: London
Registered: DEC 2000
posted 06-14-2001 05:51 AM
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I don't need compression, I'm just going to shoot massive flames into the air, It's gonna be real loud, that's all I'm looking for.
Also, how about hot glueing the lid to a plastic (or even metal) bin and filling with propane, butane, acetylene, etc. and igniting it the same way as with spudguns? (The two screws connected to the barbecue ignitor thing). That would ensure a big bang!!!



mark
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From:
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posted 06-14-2001 07:03 PM
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http://www.ipass.net/~shschem/C2H2experiment.htm


cutefix
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From: california
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posted 06-15-2001 03:02 AM
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When I was a small boy I used to play with my friends a carbide cannon.We use the empty casing of a 105mm howitzer shell or a sturdy metal pipe about 2-3 inches in diameter and 3-4 feetlong with a welded metal seal at the other end.We put in some calcium carbide granules then pour enough water to submerged the grains.There was ahole made at the side near the sealed end.Somebody blows enough air into the hole,then lit it with a taper(candle).We can make loud explosion from this effort. And continue doing so until a white stuff(lime) forms from the carbide reaction with water and no more acetylene forms.We also place an empty tin can as projectileWe were able to send the can tumbling 50 � 100 meters away depending on the quality and quantity of the explosive mixture of air and acetylene. .Another friend of mind use the acetylene tank for welding to create the same effect.It sent the can at a farther distance and created louder noise., He attached a small hose through the cannon with a sort of metal coupling.but it was very dangerous with the pure acetylene;because one of my pals almost suffocated from it while blowing the lighting hole.It was an unforgettable way to celebrate the fourth of July!
[This message has been edited by cutefix (edited June 15, 2001).]



mark
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From:
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posted 06-15-2001 10:09 PM
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Be warry of acetelyne devices. I filled a balloon a little bit with mapp gas and atempted to light it. I ignited my lighte 3 inches away from the fuse and the device went off! My arm is missing all of its hair now.


ANTI-SYSTEM
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From: FL. USA
Registered: JUN 2001
posted 06-16-2001 10:59 PM
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I got the supplys so i wanted to see if i got this right. i got the acid and the al foil to make some hydrogen gas. so all i got to do is put this gas in a trash bag tie er off and get some delying fuse and let it go with it lit and it should give a decent report after it has sailed off for about a minute or so. should the bag be tightly tied?
SO thats all right?


CragHack
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From:
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posted 06-17-2001 11:02 AM
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well the person who spoke of the static electricity problem was not talking out of there ass. You could be one hurting boy if the device when off next to your face.I would suggest, just like the others have, and done, to line the bag with an anti-static spray so as to CUT DOWN on the potential for static electricity. Mind you this won't reduce the risk 100%, you still migth have a mishap, but it will reduce it ALOT. I would suggest staying away from filling plastic bags with flamable gases. To dangerous if you ask me. Use paper bags, or cloth bags woven tight enough to hold gas.
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mark
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From:
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posted 06-18-2001 01:10 PM
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Isnt rubber grounded?


blackadder
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From: London
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posted 06-18-2001 01:26 PM
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mark, you're a bit confused here. Look inside a physics textbook for "static electricity", or if it's a good book, "grounding appliances".
I might be confused as well, so, um, yeah.



PYRO500
Moderator
Posts: 1513
From: somewhere in florida
Registered: SEP 2000
posted 06-18-2001 07:37 PM
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I'm thinking that you could make your own anti static spray for your purposes with a super saturated solution of salt and water in a spray bottle, any ideas?


mark
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From:
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posted 06-18-2001 10:10 PM
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Does anyone know a good homemade wick for hydrogen balloons?


c0deblue
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From:
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posted 06-19-2001 12:24 AM
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Some of the anti-cling/anti-wrinkle products made for use in home laundry dryers (like "Cling-Free" spray) have excellent anti-static properties and are fairly inexpensive .


Mr Cool
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posted 06-19-2001 12:49 PM
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Give the inside a quick dusting with very fine metal powder.


nbk2000
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From: Satans asshole!
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posted 06-20-2001 04:02 PM
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Shavings from a pencil lead will also work (graphite).
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goiterjoe
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posted 06-29-2001 03:16 PM
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http://www.h2go.co.uk/hydrogen.html


Ctrl_C
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posted 07-03-2001 02:17 PM
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in general, H2 and acetylene explosions dont really have all that much power, they just give the illusion of having power with such a loud sound.
and btw, i dont think graphite would work well for anti-static because grapite is very conductive. i would think that it would aid in the static arcing across the latex to the graphite.

A quick note on static, also handy if you're trying to avoid it in any other endeavours, which we generally are. Static charge can build up easily on most insulators as a result of friction. You can get it on (amongst other things) plastic bags, balloons, glass and fabrics. the problem is that the objects are not conductive, so if a charge gets onto the material, it lingers until it can travel to ground. (either positive or negative charges will cancel out when grounded) If you rub a balloon, it can build up enough static charge that if you touch it, it can make a spark as it discharges through you to ground. If you have a balloon full of an explosive mix, this is clearly a bad thing. Anti static sprays, graphite dust, and even the idea of a brine spray will render a surface conductive rather than insulating. As long as you're holding the object when spraying, you'll have grounded it and avoided any net charge. This, of course, assumed you're grounded to start off with, and haven't just spent your afternoon shuffling back and forth on a polyester carpet. Check you're grounded by touching any grounded object, for example, most household appliences with a metal casing have the case connected to their ground wire for safety.
If you're working with explosives, and you think static shock might be a danger (and I can't think of many cases when it mightn't be) you can use an anti static wrist band connected to any ground point. They're cheap and regularly used when fixing PC's, so you don't accidentally give your DRAM a massive shock and wipe it out. I'd heartily advise them when working with anything remotely sensitive. I use them when I'm working on my computer, and I value my fingers more than my PC (just).

One of two times I have needed medical intervention for pyro related injury
was from Acetylene/Oxygen in a garbage bag. Don't disrepect this, it is
very dangerous and very touchy. Acetylene explosions regularly kill welders,
you can do yourself too. A couple of kids made some acetylene balloons
4th of July before last here in the US. They blew from static inside the
car they tried to transport them in. Broken ear drums all around, plus
the legal problems they had afterward.

Shock waves from fuel air explosives are coupled to the surrounding air on
a very large surface area relative to the "point source" of an HE or deflagration
explosion. They do a great deal of damage to "soft structures"... Buildings,
the human thorax, etc. Don't mistake the lack of shrapnel holes and torn
up ground for a lack of danger.

I was surprised to find out that during the displays at the PGI convention this year there were oxyacetlyene garbage bags used to produce a few of the bangs. During the show one of them went off accidentally, most likely from static. Everyone thought it was a big bottom shot that hit the ground, except it looked a bit funny since it wasn't as bright as a flash explosion. I only found out what it was afterwards. My dad was talking to the people who filled the garbage bags, and they described to him a test they conducted.

First, let me say that I found it a bit hard to believe and certainly nobody should rely on this (now third hand but supposedly true) story. They told my dad that they filled up a garbage bag with oxyacelylene mix and actually blew it up while a volunteer was holding it over their head. I suppose they had lots of hearing protection. The point is that since he was holding it above his head the shockwave passed over him instead of hitting him square on. This resulted in him coming out uscathed. Now, when filling the garbage bags, they always hold the bag above their head. It reminded (though it's really not the same) me of the whole lightning thing where if you are standing with your feet parrellel to the strike you can get shocked badly, but if your feet are perpendicular then the current does not go up one leg and down the other, greatly reducing the shock.

So, I don't suppose anyone can confirm or deny this story?

I was at the PGII convention and if anybody used aceylene/Oxygen
garbage bags in that environment, they were insane. Constant sparks
falling, it would be CERTAIN to go off accidentaly unless it was the
first item fired. Which group was supposed to have done this?
I know most of them...

The axis of body orientation in respect to the source of the explosion makes a difference in the bodies resistance to overpressure.

If you're oriented so that your body length is pointed towards the source of the explosion, then you can survive 10x the overpressure as if your body wasn't. That's because the body is exposed to the same amount of blast energy over a longer period of time, resulting in a lower pressure over any one part of the body. At least, that's how I understand it to work.

Oh, and the gas mix would tend to rise because the gases are lighter than air, and because they'd be burning (albiet at a highly accelerated rate) they'd be rising from convection/heat bouyancy, so it can't hurt to have the ballon over your head, rather than under your feet.

Sorry Bert, my dad could not remember the name of the group who did it otherwise I would have said who it was.

Do you remnember which night it was? I've got the
schedule, and I watched the shows every night.
(Maybe we should take this discussion to pm or e-mail.)

The business of hitting the blast wave with the smallest surface area
pointed at it makes sense. When I got hit by mine, I was squarely
facing it and less than 4' away. Ouch. Much bruising. Plus 2 broken ear
drums.

Continuing by email would probably be good; I would have responded by email, but I notice you don't have your adress showing in your profile.

I have decided that the incident almost deffinetly happened on either Monday, Tuesday, or Wednesday by eliminating the other days as possibilities. I'm not sure that the garbage bags were only used during one show. If you're really curious about who made them, why not post on rec.pyrotechnics? Someone there is likely to know.
I got the impression that there was more than one used, but only one went off accidentally. After all, who would bother to bring all the stuff to make them, then only make one.

Sorry to hear about the accident :eek: . Was that a whole garbage bag of the mix going off, or a smaller amount? And I suppose static determined to be the cause?

You can make an ozone enriched H+O mix by electrolysing very dilute H2SO4 with a lead anode and a copper cathode at a high current density and at a low temperature. I have actually used this for blasting! (Just for fun; I dug a hole, inserted the bag and fuse, covered hole with earth, patted earth down, lit fuse... Bang. No real mining here as I dug all the earth the explosion moved later.) I use "small food bags" filled to ~300ml for this and the largest layer of earth I have blasted with is was about 10cm of compacted mud with an air gap and a wooden board on top. My friend (who decided to stand on the board) said he felt the board jump underneath him and when we took the board away, all the soil we put had on top was at the opposite end of the hole in a loose heap. However, the casing (greaseproof paper) of the fuse had survived almost intact and the bag was still in one piece (full of holes, but still in one piece). My next plan (if I decide it is safe enough) is to use a pressurised container full of this ozone, oxygen, hydrogen mix, as I heard (off Sam Barros' old site) that if the pressure of H2 + O2 goes above 500PSI it can achieve detonation. I suspect this pressure would be lower for H2 + O2 + O3.

Is it possible to induce DDT in hydrogen/oxygen mixtures at stoichiometric ratio (produced by electrolysis) at atmospheric temperature and pressure? I ask after noticing a considerable increase in volume of a H2/O2 filled 25cm balloon over open air volume when suspended inside a section of cement tube ~ 2ft in diameter [found by the side of the road - I think used for stormwater drainage].
Am I wrong in thinking this may be due to reflection of waves by the tube back into the region of combustion? Would the addition of a relatively small blasting cap result in a complete detonation - how would the transition be recognised? I'm not exaggerating when I say "considerable" - nearly twice the previous volume - followed by very nice echoes from the surrounding neighbourhood. And all from a balloon only 20 - 25cm in diameter! I haven't repeated the experiment since - my neighbours found the volume of that explosion a tad unbearable.

Just a simple question: what do you guys use to destatic your balloons, garbage bags etc. I found about 10 20L propane cylinders (full) near my house, and tomorrow is halloween :D nothing illegal though (cept a few balloons and maybe a garbage bag worth). Its almost all wooded so there will be plenty of places to hide from the pigs. I have this stuff (well my mom uses it) called Endust, its used to dust furniture, I'm not sure if it contains an anti-static formula for dust or not.

The brand I use when making flash is "Static Guard",if you live in the US it should be available. I would make sure you have an effective product before making something as static sensitive as a fuel-air device, although propane will not be as bad in that regard as acetylene or hydrogen.

I'm still not quite sure that hydrogen+oxygen mixtures can detonate under normal conditions but I am fairly sure that they can if under high pressure (the shockwave from the first few CCs is enough to detonate the rest) and this high pressure could be momentarily created by a shockwave from a blasting cap - in this way it is no different from any other explosive. The blasting cap would do more work than the hydrogen though :D.
I think that a stoichiometric ratio would not be best in the way of ease of detonation to deflagration transition, but, instead, a low hydrogen/high oxygen mix. It's the way it is with FAEs.
I'm absolutely sure that ozone would make the DDT easier as well, if not spontaneous in high concentrations...
I'm thinking about a curiosity explosive of a hydride with a solid oxidiser, after all, hydrogen/oxygen is just a curiosity as far as we are concerned (unless anyone is thinking of making a spaceship :D).

Hydrogen is lighter then air. hmmmm
I wonder if you could ground a hydrogen ballon by attaching a static wire to it. The idea is that any static would go straight to the ground via the wire.

Well I had a thought. If you wanted to awaken the neighborhood or its the 4th july etc. Igniting a bag of hydrogen in the atmosphere will certainly get peoples.

IIRC 1 cubic foot of hydrogen gas can carry about 0.09 pounds of weight. since you can get 50L garbage bags, a large inflated bag should be able to carry a small payload such as a small thermite charge etc.

So my idea; inflate serveral bags of hydrogen and attach them to a small timed incendary device. then simply let the "balloon" float off with the delay set. When the delay goes off so does the balloon. Setting them off at night may have a better effect since anyone seeing the ballon going off will only see a fireball. Garenteed to make people theres aliens landing/terrorist attack/ plane crash/ nuclear war going on.

A fun idea for a salute, perhaps. Of course I don't need to tell you it's dangerous, but you will markedly reduce the risk (a bit) if you only work with one balloon at a time.

Two points though, if you want to try this:

1/ Attaching a wire to an ordinary balloon, bin bag or other non-conductive container will not ground it. If the balloon was conductive, the static charge could flow across the surface to the wire, then to earth. As the balloons are made from insulators, they just build up the charges in local areas. This is why static guard sparys are used. They make the surface conductive, so charge can flow along it, and can discharge at any point connected to earth. Spray it before you inflate it, and keep it grounded when you do so. You may need to spray it repeatedly, if it takes considerable amount of time to put these together before they're set off.

2/ An incendiary device would probably not be neccessary. I'd go for a circuit to create a spark in the balloon. Whatever you use will probably be used only once, so I'd make it from stripboard, and try to keep the components as cheap as possible. The incendiary charge sounds heavier than I think a one use circuit would be, especially as you'd need some electronics anyway. I'd use a 555 timer in a monostable configuration [i] to introduce a delay before it activated a transformer to set off a small multivibrator/rectifier circuit [ii] across a small spark gap. Hmmm, perhaps a 556 [iii] chip (of which I fortunately happen to have about a hundred lying around) could be used to generate the multivibrator signal, as well as the delay. Alternatively, a simple filament wire may also set off the fuel/air mix.

If you want to be suitably perverse, strap the electronics underneath the balloons, and make the whole thing up to look like a blimp. Instead of July 4th, set it off on May 6th and celebrate the annivesary of the hindenburg disaster. [iv] Be warned that you really don't want these going astray. If one of these catches an unfortunate air current, it could cause a lot of damage, and not just to you. I'd carry along an air rifle so you can take them out if the ignition fails or the wind changes. That said, I think a fleet of model blimps exploding in sequence or together would look awfully impressive.

Oh, and weight supported by balloon = weight of air displaced - weight of gas in balloon.
Which varies a lot as the density of air can vary considerably, but for a rough estimate...
Weight of 24l of air at approximately 80% N2, 20% O2 [v] is 28 X 0.8 + 32 X 0.2 = 28.8g
Weight of 24l of H2 = 2g
Weight of 24l of H2/O2 mix = 2 X 2/3 + 32 X 1/3 = 12g in stochiometric ratios 2:1
Weight of 24l of H2/air mix = 2 X 2/7 + 28.8 X 5/7 = 21.1g in stochiometric ratio 2:5
So a H2 balloon can lift about 1g per litre, while a H2/O2 balloon can lift 1/2g per litre and a H2/air balloon can lift 1/3g per litre, very approximately.
I think that's more or less right. I've no doubt someone'll correct me if it isn't.
As you can see, you'll need much more gas if you're trying to lift with H2/air as you need far more air to provide enough oxygen for the explosion. Acelylene would be even harder to get off the ground, being far closer to the weight of air, and propane is heavier, and will just sink. I wouldn't bother with anything less than H2/air, but I'd be tempted to try the more dangerous H2/O2 mix.

[i] http://www.mitedu.freeserve.co.uk/Circuits/Timing/555mono.htm

[ii] Similar design to a stun gun. Very handy circuits can be found on J's site.

[iii] A chip with two 555 circuits on it.

[iv] for those who will, undoubtebly correct me on this, yes I know the Hindenberg was not felled by ignition of its hydrogen fuel, but by the flammable paint used on the outside. There's an alternate idea. Filled with pure H2, and painted with aluminum flakes. Won't go up as dramatically, but would be a fun model to make.

[v] http://education.jlab.org/glossary/abund_atmos.html

[edit: added following]

For getting hold of Hydrogen, I'd just go out and buy it, as there's loads of legitimate uses for it. You could be using it for welding, glassblowing, nameless chemistry experiments, etc. If you're over 18, it should be no problem.

The H+O2 in a rubbish bag has long been an ambition of a friend of mine & with guy fawkes coming up on the 5th of november it might just happen.

What would be the cheapest & safest way to fill the bag with H?
AL foil Mixed in a jar with HCL then the gas bubbled through water then into the anti-static bag sound's ok but would like to get other people's opinion on what the best way to go about it is.


Oh & also ISA or International Standard Atmosphere says desity of air is 1.225kg/m3 under ISA conditions of 15 degree's C At Mean Sea level, same info as the post before i think but not in litre's

I would use Al foil and HCl. HCl is pretty cheap and Al foil you can get from any supermarket.
You could also try electrolysing water to produce H2 + O2. this has the advantage of already coming in the right proportions, though you'd need a good transformer for that to work.
For best results, dissolve some salt into the solution to improve the conductivity and have containers to collect the gasses that evolve. the Hydrogen will be evolved at the catthode IIRC.

This is probably a bit late now but if you use the H2O/Al/NaOH way to make hydrogen it can solve quite a few problems:-
I'm not saying that HCl/Al or H2SO4/Al doesn't do this as well but this reaction gets very hot, especially if you mix the NaOH/Al and then add water slowly. Lots of water vaporizes and, if you don't collect the gas, you will notice the choking smell of NaOH(aq) mist. This has actually prevented the hydrogen going off several times in my experience. If you just let the NaOH(aq) mist into the bag it will solve the static problem.
NaOH/Al/H2O has an advantage over the other mixtures in that the NaOH is not used up. You just add more water and aluminium foil. True, the aluminium hydroxide does tend to clog it up, but you can easily separate them, by adding more water and decanting. I have found that the reaction is quite slow to begin with, but as it heats up, it turns to a runaway.

Also, a small amount of H2SO4 in water makes a very good electrolyte. You need to add quite a lot of salt to water in order to make it very conductive, and, if you do this, you get chlorine as well as hydrogen and oxygen. Judging from the H2+Cl2+Light reaction this would make the mixture a bit (if not a tiny bit) more unstable, and certainly too poisonous for use at parties (we all love to pop balloons :D). I'll shut up about this soon but electrolysis of a dilute non oxidising acid at a low temperature produces ozone and hydrogen (this is poisonous and unstable, just like H2+Cl2, but at least it burns cleanly, and, as I said before, it does actually have some power, not just noise). Perhaps someone could try electrolysing HCl, as I do not have easy access to it. Lead/Copper electrodes will not work though (they will corrode in HCl).

I heard of some guy off Battlebots that experimented with acetlyne gas in his garage, he somehow filled it with gas and there was a tremendous explosion blowing off the garage roof, he lost half his hearing.

If using Al+NaOH/Acid then bubble the H2 through water before into your balloon. This will condense any steam which would otherwise end up in your balloon ruining it's bouancy.

has anyone tried this method?

http://www.unmuseum.org/exhydro.htm

you would use a 12v car battery of course & obviously ignore their warning at the bottom and tape a anti-static bag over the top of the jar hehe

Thats just simple electrolysis, spydamonkee. Its been discussed throughout this thread. As Ollie Snowie said, H2SO4 makes a much better electrolyte than salt or sodium bicarbonate like they suggest. I personally have found electrolysis a very inefficient way to produce hydrogen, well, at least with a small current as all sources suggest. And I sure as hell dont have the balls to do HV electrolysis! However, if anyone was crazy enough, I imagine that putting mains current through water could produce an impressive amount of H2/O2

Back when I knew little about electrolysis, I tried using mains power to produce hydrogen, it works, but only slightly, this is because electrolysis only works properly with DC current, mains power is AC.

Has anyone ever tried rectifying mains power to DC (at the same voltage) and using that?

I've tried putting mains through H2SO4 and got no H2 or O2 - not even a little. I haven't tried rectifying mains to DC and electrolysing water with that, but if you do, I think it would be much more efficient if you use lots of cells in series so as to make the voltage drop as slowly as possible. This also means that if one electrode accidentally touches another, there is no short circuit.
I know I shouldn't mention the "free energy" pages here but one of them said that electrolysing deionised water with high voltage, high frequency, low current AC is a more efficient way to break water into its elements. If anyone tries this, I would recommend using test tubes filled with iron filings or something similar as electrodes, because you don't want any DC arcs when there is lots of hydrogen and oxygen around. I'm not saying that it really is overunity, but, if their principle (water molecules resonating and eventually splitting) is correct, then it probably would be a very efficient way to produce H2 and O2. Sam Barros' page describes something like this so it might not be pure B.S.