Faking explosions

USNFilms

USNFilms

Hey all,

This weekend I'm filming a 3-4 minute vfx sequence, which needs to have a few explosions. I have acquired a replica grenade launcher and I want to have some juicy explosions. I've been doing the entire explosions in AE in the past, but I kind of want to do some with practical effects on set.

Live explosives are out of the question. I want to do something like this:
https://www.youtube.com/watch?v=JZDIKU7OW2E

That is the general idea of how i want to portray an explosion, but I don't feel as if the exact device the person used in that video is too effective. Do you guys have any suggestions or ideas for me to pull this off?

Thanks
 
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I'm doing that in post with a rocket attack on cyborgs who use their own bodies as shields to protect the Humans they were sent to rescue. I discovered now, I'm going about it the right way--in layers of video. You can get primitives of smoke, fire, and explosions from a place like Pond5.com and minipulate them with Vegas and add lighing effects to blend in better. I'm even adding in ash effects that are important in an explosion.

Another way of doing it is like in my last production with off-camera explosions and just add sound effects and camera shake and show the aftermath.
 
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That box launcher in the video seems unnecessarily clunky... you could just make the same thing out of large PVC pipe that you could bury in the ground, then using fishing line, a nail and a couple of eye screws, you could fashion a remote release mechanism.

2 eyehooks on the bottom of the PVC with enough room between for the 1 that is on the end of the funnel - eyehooks to redirect the fishing line on the nail that holds the 3 eyes together out to your launching board, then you can bury several of them and operate them all from one off camera location.
 
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If the explosion happens offscreen, and you want to see the efect on the character(s), just have someone throw dirt and debris around them.
Watch a ton of explosion footage. The explosion on the video you posted, looks like a landmine explosion. A granade launcher explodes on impact so it does not bury enough to lift that kind of dirt.
 
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I built something similar to the "Thunderpipe"...
TFX-1.jpg


Its a compressed air mortar. You fill the tank with compressed air, fill the tube with fullers earth (dirt hits), styrofoam, water, etc and hit the button. It uses an electric sprinkler valve to release quickly. You can use the powder coffee creamer for explosions.

I built mine from thick wall PVC, and I only run a maximum 100psi in it and I dont do pyro with it. Mostly I've shot blood and bits of shredded sponge and latex from mine (google "gore cannon"). Its waterproof so you can fire it off underwater, which I highly recommend!

Even though I have been on a few shoots where the coffee creamer gag worked perfectly, its still fire... and alot of it.

Dont be stupid.
 
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Special Effects Unlimited (in Hollywood) will rent you an "air mortar" (including compressor, funnel system and trigger mechanism) for about $100, although if you're dealing with insurance companies for your shoot they'll freak out and charge you more or not insure your shoot at all.
 
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