Explosives advice (never minds)

[thegayhare]

First off I want to stress I am not doing anything bad,  I'm not building a bomb or the like...

What I want to do is detonate a pumpkin for a film

Now websites I've stumbled across previously had mentioned using pvc piping around a black powder charge.  that seems stupid to me the plastic shrapnel alone would be to dangerous.

my plan is a small black powder charge in a baggie,  you then wrap the baggy tightly in duct tape,  this gets you the compression you need for the explosion with out the shrapnel.  Its something I saw long ago on a documentary on practical fx.  my problem is I don't have any thing for a fuse.   If I could get to one of the new fire works stores in the state I'm sure they would have something but then again I could simply use M80s if I could do that.   My Idea is to use a sparkler.  I run the sparkler into the charge so that the bottom would touch on the powder charge.   the duct tape should be resistant enough to with stand the random sparks and prevent premature detonation,  but I am worried that it might smoother the sparkler before that...  

what do you folks think

PS I can under stand if this sort of thing is deemed out of place on this board,  and I wouldn't want to cause trouble so if anyone feels its inappropriate I will yank it.   sorry

[llearch n'n'daCorna]

It's something you want to be very careful with - too much is as dangerous as too little.

What I would suggest is a test firing somewhere. Find a nice empty space with nobody and no pets in range, set up a sparkler with a pile of gunpowder around the base, and see if the sparkler will ignite it.

Then set up a duct tape cover as you would in the real thing, with a test charge at the bottom - and by test charge, I mean "big enough you can see it go bang, but no bigger" - and set that off. If it works, then you know your method will work in the real thing, and you can set up a full-scale size explosive.


Be aware that you don't need too much explosive to blow up the pumpkin - you're breaking it from the inside, after all - but you do need enough to not just come back out the hole you make to put the charge in there. Also consider that the inside of the pumpkin is going to leak juice into your system, so don't keep the charge inside for a long period of time - be prepared to insert it just before you need it to go bang, I mean.

Does that help?

[thegayhare]

I know I have to be careful I don't want to lose any fingers here... I like my fingers

the test charge is a good idea I don't have a lot of powder but I should have enough for that  

I've even got a good spot to set it off out fire pit is stone on three sides with a stone base below .  A test charge will also give me a timing test to see how long it will take for the charge to go off

[Brunhidden]

my expertiese is typically associated with people who really shouldnt do this, either due to motive or compitence

lets focus on the latter, no offense



articles to address include do you have a reliable source of black powder, is it properly stored, measured, and sealed? black powder is a temperamental beast if not handled properly (even if the improper handling was by someone other then you), and the chance of being on 'smoking gun presents worlds dumbest produce tricks' should be enough deterrent to make 100% sure you know what you are doing- losing a finger is private but having danny bonnaduchie laugh at your eyebrows on fire over cable is another

duct tape i am questionable about, ideally you would have your explosive in a paper casing that will burn up uppon ignition. true duct tape is better then pvc shrapnel, but due to the ways it tears you may have a problem with erratic pattern of combustion. if you feel bold and creative try some test charges in thin cardboard if you have ideas for a shaped charge, perhaps you want a specific part of the pumpkin to be the epicenter of the explosion

i will go on record as saying do NOT trust the sparkler. ideally a remote electronic detonation would be the best, but that's likely outside of your skillset. a better solution would be a simple fuse, which you can purchase probably wherever you are getting your initial explosive, or even tying fuses from many smaller fireworks together, which would be likely if you are in fact re-purposing firework filling for your explosive. if you dont find fuse lying around you can make your own, but be sure to test out what you create before attaching it to anything, finding out your foot of homeade internet recipe fuse burns in nine seconds instead of thirty is good to know

decide what balance of explosive force vs flaming burst you want, perhaps for a pyrotechnic flair you use less high explosive and more energetic combustibles- a cereal box filled with crumpled paper towel / bathroom tissue soaked in cheap rubbing alcohol goes up like the mofo deathstar but is less likely to impale you with gourd

[thegayhare]

The powder was storred properly but it's what's left of my father's muzzle loading hunting supplies

And all I want is to have the pumpkin shatter on camera,  the bare minimum I can digitally add in any other effects wich is much safer.   In fact before I thought of this I spent several days looking for exploding pumpkin footage I could add in.

[Brunhidden]

keep two things in mind

1- virtually all explosive supplies suitable for use will be monitored, black powder you already have asside anything else will be tracked so dont look crazy

2- this is the internet if you hadnt noticed, whatever footage you get will spread. make sure if any other parties footage it you can trust them. many is the idiot college kid who lights their own crotch on fire and their five 'friends' post the video, or just took pictures of them having peed their pants drunk and left it as a googleable doccument for all future employers. i speak from experience, as a video of myself wearing a owl costume to promote a store inside of my highschool was shot the same day as another person in the same costume was shot flipping the bird to the principal; also a commercial where i wore a dress. but if you find either of them i will pay you fifty dollars and probably not punch you - the internet knows all -

[thegayhare]

no worries actualy 

your comments got me thinking and I have a stun gun I think if I run wires from the electrodes I should be able to create a spark gap on the other end testing will need to be done first but that might make a decent electrical detonator giving me more control and allowing me to better time the explosion

and what I ment by footage is I was looking for exploding pumpkin footage I could digitally add to my existing footage doing away with the need for me to film a pumpkin at all

I have plenty of explosions I can referance but no pumpkins....  ohh well

I'll test the stun gun first before proceeding

[Tuyu]

You can buy a package of Estes model rocket igniters for $5.50 online. A local hobby shop that sells model rocketry supplies should have them. That might be more reliable than a spark gap.

[thegayhare]

Tested the spark gap and your right it rolls right over the powder with no effect

I could try a fuel air mix.   A spark gap would definitely set that off

I figure a small hole spray in wd40 then follow with the wires

[thegayhare]

well I couldn't find a way to blow up a pumpkin safely with what I had on hand.

so I went with digital effects

http://youtu.be/_EYn2iX1_mA

[Alondro]

I suggest lots of plutonium surrounded by high explosives!