aquataur Posted February 11, 2009 Share Posted February 11, 2009 Hi Folks, this is for you chemistry experts. I have heared stage pyros make a stage flash effect by blowing out fine aluminium grit (grinding dust) from a mortar with a small BP charge to disperse and ignite it. No oxidizer has been added otherwise, but substantial amounts of AL powder were used. A classical dust explosion similar to Cremora or sawdust etc. I ask myself if this does produce just a flash (if at all...), which should essentially go without bang, or if there exists the danger of producing a gigantic flash cracker - unwanted and dangerous. There is very little literature available on the behavior of fine metal dust, so if one of you is knowledgable, please tell us. Thanks, -helmut Link to comment Share on other sites More sharing options...
Miech Posted February 11, 2009 Share Posted February 11, 2009 Grindings won't work as they are too coarse. I know of people attempting to create a 'thermobaric' firecracker by dispersing extremely fine aluminium powders (3 micron uncoated flake) in the air, but it takes lots of fine tuning to even get it ignited. It is possible to get a giant 'BADOEMB' with just aluminium powder and BP, I've seen/felt some of these things in real life. Things of importance are the saturation of the air with fuel, the speed of the reaction and the ignitability of the fuel. When you got these things right you're almost there. Link to comment Share on other sites More sharing options...
FrankRizzo Posted February 11, 2009 Share Posted February 11, 2009 If the metal is fine enough, yes, you can get a rather large report. However, baring use of 2micron magnesium, you will get just an extremely large flash and "thump". Since the reaction passes through the cloud due to radiative heating, and air only contains ~20% oxygen, the energy release is slowed. Watch this video. Near the end Tentacles and I lift just over 2tbsp of fine magnalium with a short mortar: http://pyrobin.com/files/creamoras2.avi Link to comment Share on other sites More sharing options...
tentacles Posted February 12, 2009 Share Posted February 12, 2009 Frank: We should try doing a ball shell version of that on top of a rocket, could be really neat.. Lightning in the sky! Link to comment Share on other sites More sharing options...
psyco_1322 Posted April 6, 2009 Share Posted April 6, 2009 Bob and I were going to make a few lampares like that at the convention but materials fell through. I was supposed to be getting about 5lb of 200 mesh Mg from UB for a really nice price and some of that 1000 mesh Ti from Dan. We were going to make two different FAE lampares from the metals. I ended up only getting a pound of the Mg since he somehow found time to break it down and the amount of Ti we got wouldn't have left us with much to play with, and it was kind of clumped up. We were thinking it was going to be like dust. I would still like to give it a try with some other metals if possible. Link to comment Share on other sites More sharing options...
al93535 Posted April 6, 2009 Share Posted April 6, 2009 We make those at work, they do make quite a report! You can feel the heat for quite a distance, and they are very loud. Link to comment Share on other sites More sharing options...
Fluorescein Posted April 20, 2009 Share Posted April 20, 2009 I heard a few stories about pyrotechnic thermobaric salutes. Instead of black powder, flash powder is used to sputter the metal powder.(dark Al is reputed to be the best)If I remember corectly light metal powders in thermobaric bombs are much more powerfull than every flamable liquid. (etylene oxide in the latest russian bomb) 1 Link to comment Share on other sites More sharing options...
Boomer Posted April 20, 2009 Share Posted April 20, 2009 There's a patent including test results of a new type of flashbang grenade. It uses (commercial) FFF BP to blow fine Al out of the opening of a cast metal grenade body. At some distance, both light and pressure output are higher than for normal (flash powder) flashbangs, and last much longer. In the very near field, pressures are much lower so the danger to people (hostages) in the room is reduced. It's been posted here, on SciMad, RS ... and just about anywhere else, so look around. Link to comment Share on other sites More sharing options...
mdawson Posted April 25, 2009 Share Posted April 25, 2009 There's a patent including test results of a new type of flashbang grenade. It uses (commercial) FFF BP to blow fine Al out of the opening of a cast metal grenade body. At some distance, both light and pressure output are higher than for normal (flash powder) flashbangs, and last much longer. In the very near field, pressures are much lower so the danger to people (hostages) in the room is reduced. It's been posted here, on SciMad, RS ... and just about anywhere else, so look around. I used a can to try and make a cremora fireball but with not the results I was looking for. I used BP for the lift charge and covered it with a piece of napkin cut to size. Cremora on top and well like I said it was what you would call lackluster. Link to comment Share on other sites More sharing options...
FrankRizzo Posted April 25, 2009 Share Posted April 25, 2009 This is off-topic, but you need the creamer to be very fine. The generic stuff sold at Sam's and the like doesn't have the right particle size to be used successfully. However, with a bit of airfloat charcoal added, even the crappy stuff will get going without any trouble. Fine magnesium, aluminum, or magnalium makes a *VERY* impressive fireball...definitely not lackluster. Link to comment Share on other sites More sharing options...
mdawson Posted April 26, 2009 Share Posted April 26, 2009 This is off-topic, but you need the creamer to be very fine. The generic stuff sold at Sam's and the like doesn't have the right particle size to be used successfully. However, with a bit of airfloat charcoal added, even the crappy stuff will get going without any trouble. Fine magnesium, aluminum, or magnalium makes a *VERY* impressive fireball...definitely not lackluster. Hey thanks Rizzo. I did use coffee mate brand. Link to comment Share on other sites More sharing options...
FrankRizzo Posted April 26, 2009 Share Posted April 26, 2009 Coffee Mate is no good. You need to use the Borden-brand Creamora. Link to comment Share on other sites More sharing options...
mdawson Posted April 26, 2009 Share Posted April 26, 2009 I haven't thought about trying that kind. I will check it out. Thanks Link to comment Share on other sites More sharing options...
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