ExPLoSiOns!

NieblerProductions · Post by **NieblerProductions** » Thu Dec 18, 2003 10:44 pm

I'm looking to start filming a war movie in the next couple months...I've got a question tho.. Does anyone know what I could use to make large explosions? They do not have to be loaded with flames.. I'd personally like to make it look like the ones in the first scene of Saving Private Ryan where you don't see any flame but just a load of dirt, however I would like them to be bigger than the ones talked about earlier using the lever sequence.. So if anyone knows of any materials I can use to accomplish this that would be great... I don't have to worry about taking any power liines out or starting a forest fire it's in an empty field. Thanks for your help!

Grant · Post by **Grant** » Thu Dec 18, 2003 11:27 pm

many threads throughout this forum on such effects. Maybe not as large as you want though. Depends on what materials you can get your hands on also

El Brenty · Post by **El Brenty** » Thu Dec 18, 2003 11:59 pm

Seeing that it's an amateur production, If you can get your local fire-brigade involved it would be great. They look for opportunities like this for training, so if you could help each other, then bonus! They would probably provide low-explosives suitable for what you need as well.

Otherwise, you'll need to set up specific points along your field (Map and number them if necessary), hooked up to a control panel, and make yer own low explosives. I'll post a thread soon about stuff you can legally buy from the chemist that you can make low explosives with.

NieblerProductions · Post by **NieblerProductions** » Fri Dec 19, 2003 12:25 am

that would be great thanks

Epsilon · Post by **Epsilon** » Fri Dec 19, 2003 12:50 am

An open field has its advantages. If there is no one in the scene, you could easily make it appear a lot bigger than it is with a low camera angle. You could even use a high zoom or long lens to get the appearance of a much larger explosion behind a character. Experiment with your camera anlges. You could probably even get a level sequence to look huge. Something to think about!

Most mortar and artillery explosions do not have any fire at all, so SPR was actually quite accurate.

NieblerProductions · Post by **NieblerProductions** » Fri Dec 19, 2003 2:25 am

Although you guys were helpful You didn't really give an answer to my question...I'm asking if anyone knows how to any of this stuff

Grant · Post by **Grant** » Fri Dec 19, 2003 2:54 am

well it could be seen as a topic, especially with effects as big as you want, that we cannot really comment on? You could be a terrorist, how could we know

Epsilon · Post by **Epsilon** » Fri Dec 19, 2003 6:35 am

How? Buy some explosive, bury it in the ground, detonate it, see what happens.

Unfortunately, getting explosives is nearly impossible now, especially since 9-11. I'd go with the dirt/lever action and use some tricky camera work to make it look big. But it would have to be a fairly large guy hopping on that board!

U.S.Amateurfilmaker · Post by **U.S.Amateurfilmaker** » Fri Dec 19, 2003 6:56 am

Just go down to your local McDonald's and recruit someone, preferably a daily patron!

Epsilon · Post by **Epsilon** » Fri Dec 19, 2003 8:41 am

Whoa... I was thinking fairly large, not someone to break my board in two!

Everyone should be able to find a Mc. Donalds too, they are everywhere! And I know that you aussies make your big macs with kangaroo meat! It don't taste at all like beef!

Grant · Post by **Grant** » Fri Dec 19, 2003 10:57 pm

Who told you that!!!! The fact is the Maccas makes burgers over here from 100% Aussie beef and that the company that sells them the burger meat is called "100% Aussie Beef". So they are not lying to us but there is no guarantee that we are not eating Roo. Roo is actually very nice and so is snake

Epsilon · Post by **Epsilon** » Sat Dec 20, 2003 5:50 pm

I've never had snake. In fact, I don't know of any resturants that sell snake.

Is it everything they say it is?

Grant · Post by **Grant** » Sun Dec 21, 2003 12:26 am

we normally kill the snake ourselves and cut and skin under the poison sack

DAZMAN · Post by **DAZMAN** » Wed Dec 31, 2003 3:55 am

This method never fails. Get a Nearly full deoderant can or wd40 or somthing put it on the ground, put news paper near it and set it on fire. then when you want the explotion shoot the can with an air rifle. ow an happy new year for tommorow every 1

I3lade203 · Post by **I3lade203** » Wed Dec 31, 2003 3:59 am

yeah what they said up ^^ lol

Epsilon · Post by **Epsilon** » Wed Dec 31, 2003 7:12 am

DAZMAN, why not just use a can of lighter fluid??? Those methods are actually quite dangerous and personally I would not attempt to create such an unpredictable contracption. But hey, it is your film and your life!

rankz · Post by **rankz** » Fri Jan 02, 2004 9:20 pm

The deodrant can method, how big is the explosion?

Grant · Post by **Grant** » Fri Jan 02, 2004 11:21 pm

it would be just a small fireball yeah?

Raptor · Post by **Raptor** » Sat Jan 03, 2004 12:05 am

The deodorant can will probably not be a longlasting fireball, but the problem with using aerosol can is the fact that you can't control the results. Having seen aerosol cans rocket 100 feet + in structire fires is enough to convince me that is NOT a safe controllable explosion. Also you are using a metal container which conceivably could rupture producing shrapnel, not real likely, but again have seen aerosol cans in the aftermath of fires where there was definitely portions of the metal of the can missing... it had to go somewhere!

DAZMAN · Post by **DAZMAN** » Sat Jan 03, 2004 2:17 am

"it would be just a small fireball yeah?"

about 10 feet in all directions.

"DAZMAN, why not just use a can of lighter fluid??? Those methods are actually quite dangerous and personally I would not attempt to create such an unpredictable contracption. But hey, it is your film and your life!"

all im saying is that i use this method often, it works every time, all of my actors prefer tis method as well because its just 1 big explotion of flames that are gone in 1 second and so there is no scraptnel or shards of glass hitting you. The can does not explode. it gets a hole straight through and lets the gas out which is then set on fire. if you dont like the method, dont try it, if you do then go for it, im just givin my opinion. and you cant call me for being dangerous when we are talking about explosives because lighter fluid does exactley the same thing.

Syras · Post by **Syras** » Sat Jan 03, 2004 2:57 am

dazman is right about the hole in the can - its the hole that stops the pressure from getting to great and sending shrapnel flying. Having said that i've seen the round bottom plate from a deo can go through a 3mm thick steel garage door (this was after it went through the cookie tin it was in)

Epsilon · Post by **Epsilon** » Sat Jan 03, 2004 3:34 am

Got it once... twice! Double post! Ahh!

Raptor · Post by **Raptor** » Sat Jan 03, 2004 3:35 am

Yep, and we're assuming that an air gun is going to punctire both sides of the can and ventilate the pressure fast enough, any pressure vessel that 'rockets' has got to have a rupture..... Have you ever heard the term "BLEVE"? If not ask some fire fighters who have been killed or seriously injured...
BTW BLEVE is boiling liquid expanding vapor explosion here's a brief description of it
BLEVE

Under rapid heating (for example, from a pool fire engulfing the tank), a tank containing pressurized liquid may fail suddenly producing an explosive effect. The liquid in the tank absorbs energy from the surrounding fire and heats up rapidly. The resulting increased rate of vaporization produced increases the ullage pressure. When this pressure exceeds a certain limit (characteristic of the material properties of the tank wall, wall thickness and temperature), the tank fails. The liquid released from the tank boils rapidly and expands. The resulting explosion may fragment the tank into pieces and propel them over large distances. If the hazmat is flammable, it may ignite and form a fireball posing additional hazard. This phenomenon is called a BLEVE or Boiling Liquid Expanding Vapor Explosion.

BLEVE accounts for the following key coupled processes:

heat transfer:
from flame to tank
from tank walls to the liquid and vapor phases
between liquid and vapor phases
thermodynamic transformations within the tank and pressure buildup
activation of pressure relief valve (or PRV) and venting
wall stresses and material property degradation
tank failure
depressurization of liquid upon tank failure with concomitant thermodynamic transformations

Now keep in mind that a deoodorant can is a relatively lght weight material. Not designed to contain much more pressure than it normally has. As soon as you have flame impingment on the can, the pressure starts to increase. A dent in the can on a seam could be enough to cause a failure. Hey, I'm all for some good pyro, but pyro can be done safely, and this definitely is NOT the way to do it. I hdon't wanna sound like I'm lecturing here, but guys, take the word of a pyro who has probably been walking this ole planet as long ( and maybe longer than some) as your parents ( 47 years and I'm still relatively in one piece). I spent 10 years in my younger days as a volunteer firefighter/paramedic and have seen most of the stupid things people can do.. ( like checking the water level in a car battery with a BIC lighter.. hello.. boom...) Any pressure vessel has the potential to rocket when exposed to flame or when punctured... that's why they all say do not puncture or incinerate.
And I think the lighter fluid line was meant in sarcasm......
If you are going to do pyro, use something that is relatively safe and controllable, cause aerosol cans definitely are not...

Raptor · Post by **Raptor** » Sat Jan 03, 2004 3:50 am

Here's a bleve link specifically about aerosols....
http://www.usmra.com/BLEVE/AerosolJM.pdf
Also check some of these links here..
http://www.chemaxx.com/aerosol3.htm
The stuf ain't toys guys....

rankz · Post by **rankz** » Sat Jan 03, 2004 1:34 pm

Ok then, you used a couple of cigarette lighters, how nig would that be? Ive seen 1/2 a full lighter on a fire b4........