Quote:
Originally Posted by Smoke Marijuana
My friend is making a film, and for one of the scenes he wants sand to fly everywhere. The idea is to put some kind of small explosive device under the sand (possibly many small devices), to create a sand storm on demand.
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"Sand storms" are usually made with a couple of BIG fans blowing more or less straight across the camera's LOS from either side, one in front of the actors, one blowing dirctly at them, and one behind the actors.
Lets say Fan 1 blows from left to right, but not at the actors.
Fan 2 blows from left to right,
at the actors.
Fan 3 blows from right to left.
In front of fan 1+3, you'll pour in a load of saw dust, and behind the fans, you'll have a couple of smoke machines.
Behind fan 2, you might put a smoke machine, just make sure the actors are still at least partly visible.
You'll add smoke to "blur" out the image a bit, because if you just threw in saw dust everywhere, the actors would be fucked.
So, "sand storms" in movies, are actually more "dust/smoke storms", and a bit of trickery.
Quote:
Originally Posted by Smoke Marijuana
Can this be done? I am a complete noob to explosives so I apologize for the un-researched question.
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That's ok, if you're starting from scratch, no one expects you to know what's possible, and what's not.
Quote:
Originally Posted by Smoke Marijuana
To make the problem more difficult, we have access to only house hold chemicals, and things that normal people can buy.
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I'm sure there's people here that can tell you how to make whatever compounds you'll need,
once it has been established exactly what you need.
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Originally Posted by Smoke Marijuana
I have no good hook ups for chemicals, and there is a budget on how much this can cost.
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In my experience, spending
a lot of time, can save you a
bit of money, so you should be prepared to do just that.
Quote:
Originally Posted by Smoke Marijuana
I don't think this can be done easily or possibly at all, but still I told my friend I would get some advice.
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I think you're right, something like this, when you have no previous experience with it, isn't easy.
Possible?
Yes, of course it's possible...
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Originally Posted by Smoke Marijuana
Advice is greatly appreciated, thanks.
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We're not done yet.
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Originally Posted by Smoke Marijuana
Just looking to make a small poof of sand fly out
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This, I can only interpret as "I want to make a bullet hit", as when a bullet hits the ground, or something similar.
Just use a squib, that's what they're for...
Quote:
Originally Posted by Smoke Marijuana
like in the movies when you see "mines" explode
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Mines, kick up a fuckload of dust, so it's not just a "small poof of sand", it's something that requires "a little" more, sorry.
Quote:
Originally Posted by Smoke Marijuana
would sticking a roman candle in the ground with sand ontop or pouring powder from a roman candle under sand do the trick?
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Nope...
Quote:
Originally Posted by Smoke Marijuana
sorry for all the questions, i just wanna blow shit up for a battle scene
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Ok, now we're getting there.
So
what exactly, do you want?
Do you need something that looks like a hand grenade going off?
Artillery shell impact?
A full scale artillery bombardment?
Carpet bombing?
Do you need any houses or anything destoyed?
It'd be a lot easier to help you, if you specified
exactly what you want.
And, where's this battle taking place?
It's a whole lot easier to make something that looks good, in a swampy area, than in a desert or on a beach.
You keep mentioning sand, does it
have to be sand?
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Originally Posted by Smoke Marijuana
they dont even have to be real explosions
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Ok, then you can use a whoofer...
It's basically just a big tank with pressurized air, that'll dump it all at once through a short length of pipe, into a fat bellied mortar full of debris, when you hit the switch.
They're usually used in ground explosions, where actors are close to the explosion.
The only problem here, is that you'll need a tank you can rely on not to suddenly crack open from the pressure, and a valve that has a big enough opening, and a fast enough response time.
That cocsts money...
Quote:
Originally Posted by Smoke Marijuana
just sand needs to "squirt/fly" up, sound effects can be added later
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Again, bullet hit or artillery?
And, is it very important it's sand?
Quote:
Originally Posted by Smoke Marijuana
is it possible to ignite it from a distance with some kind of cord or anything that can make a spark by clicking something
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Yes, the cheapest way is to use the good old nail board.
Practically, it's just a plank of wood, with a load of nails driven half way in, down along the center line.
Below each nail is written a number, 1-20 for example.
Nail 1 is connected to charge 1, nail 2 to charge 2, and so on.
The common return lead (that connects all the charges on one wire each), is then connected to your power supply, and from your power supply, to a length of wire with an uninsulated end.
When you want charge 1 to go off, connect the wire to nail 1, when you want charge 2 to go off, connect to nail 2.
If you want a burst of gunfire, place your charges (charges used for this effect are pretty small, and called "squibs"), and then wipe the wire down the board, across all the nails...
Quote:
Originally Posted by Smoke Marijuana
i kinda want to have lots in the ground, igniting at different times without close ups, just a wide view of the chaos with people fighting around
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And that you can get, by using the method I just described.
There is one thing though, you shouldn't put the actors
anywhere near the explosions.
For safety, it's better to keep you "big ones" between the camera and the actors, and smaller smoke charges that only deliver a poof of smoke, amongst the actors.
I wouldn't reccomend you connect your ignitors to a fuse on the charge, but to the main compound itself, that way there's less chance something goes wrong because a charge went off a second too late.
But, then again, this is just technical stuff, of course you
could use quickmatch on your charges and that would solve the problem.
It's not something I want to get into a big argument with anyone over...
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Originally Posted by Smoke Marijuana
I was looking up compressed air tanks, saw a portable simple one, if i say hook up small plastic tubes to one tank that branch off to small tubes filled with dirt, have a pinch on the middle of the tube before it branches off, let air out of the tank, then undo the pinch... would enough air pressure reach each of the tubes to create an outburst of sand...? just bouncin' ideas here
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That would depend on your pressure, the volume of the tank, the distance from the tank to your tubes, and the number of tubes.
Personally, I've only used this set up to "shoot holes in people", because using squibs to get the desired effect weren't parctical or safe.
As a last word, anything you blow out of tubes, or lift off the ground using pyrotechnics, should be light, and prefferably relatively soft.
Any holes in the ground, in which you plan on putting explosives, should be lined with a steel pan or something simmilar -you might only intent to blow out a load of granulated cork and coarse saw dust, but that one little pebble that went airborne too, can really ruin your, or someone else's day.
And,
stay away from high explosives, unless you're an expert in the field.
So...
How to make many small, controlled explosions?
Re: How to make many small, controlled explosions?
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