fake explosions

[bob]

I just wanted to share my latest project with you guys.

I have been trying to make a fake explosion for a while now and thanks to some very good advice from some people on pyroguideforum I have gotten a pretty good effect.

First I have a picture of my first effect which uses a three inch mortar full of dirt.

The second effect is a five gallon bucket full of peat moss and 200 grams of black powder.

Tell me what you think

Edited May 9, 2013 by bob

[Bobosan]

The 5gal looks like a mortar round or cannon ball hit. Maybe by cutting the sides down a bit you would get a better spread and acceptable height.

[psyco_1322]

I can't tell what's going on in the first pic, just looks like a bit of smoke. The second one doesn't look too bad though.

[AirCowPeacock]

Second one looks great. Deffinetly needs better spread though. Dirt sounds a little dangerous, I'd worry about little pebbles raining down. Could we see videos, preferably with some sort of scale.

[Mumbles]

Typically one will screen the dirt to remove stuff like sticks and small rocks that could become projectiles.

[bob]

Second one looks great. Deffinetly needs better spread though. Dirt sounds a little dangerous, I'd worry about little pebbles raining down. Could we see videos, preferably with some sort of scale.

. Yes like mumbles said I did screen out the rocks and sticks.

All though I really think that peat moss is a lot better then plain dirt for several other reasons. Did you see the marker on top of the dirt? Would say 10 pictures of it going off work? Cause I don't think I can get a video on here.

It is a fairly large effect (31 feet in the second picture) and I think if I shot off say 3 side by side at once it would look pretty good.

Bob

[Pretty green flame]

I've seen explosion simulation been done with cement and gasoline. Now the ones i saw used a length of HE cord, you c(sh)ould switch this to straight flash or BP (probably reccomended). Anyway, the whole thing was done in an inverted hollowed out pyramid (welded from steel plate), the explosive charge was put on the bottom, a bag of gasoline put over it and the whole thing "burried" under some cement (Atleast several kilos, more is better actually)

 

The effect is pretty badass, usually looks like this (depends on the size though). Much more realistic than standard hollywood gasoline explosions. A smaller version can still look pretty awesome as the cement gives a much better cloud when finely dispersed.

 

http://www.fxguide.com/wp-content/uploads/2010/10/10Mar/ocula/press1.jpg

[Arthur]

Enjoy - It was a totally compliant SFX day for the UK forum

 

Towards the end is the big dirt blast About 3 feet high pile of a mixed compost and non oxidising soil fertiliser -at least half a ton!

This was lifted with a slurry HE but could be done with a large BP charge.

 

Cement is bad form in the UK because it can consolidate into shrapnel and it can cause cement burns.

[bob]

ok so just to clarify they would take three pieces of triangle shaped steel and weld them together to form a hollow pyramid. Then they put that up side down in the ground (the point pointing down into the ground) and put in the propellant then put a bag of gas on top (love that part) and then put the cement powder in until the hollow pyramid is full? The cement they use is simple cement powder like the stuff you would buy to make small amounts of cement right?

I fail to see how cement powder would form shrapnel, mind explaining that.

I'm thinking of trying this as it sounds like it would work pretty good but if cement will not work then I might try it with peat moss.

here are ten pictures of my five gallon pail going off.

thanks for the movie next time I'm in town and can use the library's wifi I'll watch it.

bob

[psyco_1322]

bob,

 

I was talking about the photo on the left, then one with the 12ft mark. Sorry to get those mixed up.

 

 

Arthur, that video was pretty cool, looks like you guys had a lot of fun that day. Blowing up that Honda got pretty intense. The line of fireballs was also pretty cool. But I'm not sure I would want to be that guy that walked back through that cloud of compost and fertilizer dust... hope he had a dust mask!

Edited May 10, 2013 by psyco_1322

[bob]

Shot another one off earlier.

I made a pyramid shaped mortar put it in the ground put 452 grams of four mesh black powder and two 500 mls bags of gasoline on top of the black powder and about 13 gallons of damp peat moss on top.

It looked pretty good, here is a photo the only think i would change is the two bags of gas I would change to three or four.

bob

[Pretty green flame]

Nicely done. Congrats.

[AirCowPeacock]

These are cool. I'm thinking about making a few.

[flying fish]

Nice work.

 

My brother and I used to make silly short films. One of our techniques for creating explosions involved putting a very small charge (say, M-80 sized but filled with black powder). under a small layer of dirt. We draped a green screen over the background and videotaped it at close range. Later it can be keyed into a film and scaled to what ever size is needed. These were great for grenade explosions.

[dave321]

the hurt locker explosion may even have been done with air cannons

 

a lot of explosions in band of brothers used air cannons

 

dave

[psyco_1322]

Looks great, love those flaming dirt explosions!

[bob]

Any ideas on how to get a bigger base?

if you want to make one your self PM me for details.

bob

[busspuppy]

Not sure how it would work, but what about a cremora that is covered in peat moss. Of course you would keep the peat moss and creamer seperate. Anybody ever tried it, and knows if it would work?

[bob]

I got those pictures of the three inch mortar going off.

bob

[Bobosan]

Mortar pics it shoots more upwards and doesn't seem to spread like a ground burst would.

[kpknd]

I made miniature explosions that looked really good on film. All I did was to take a 3/4"I.D. rocket tube about 1" long and ram a plug in one end and drill a hole for visco in it. Then put a little black powder in it and close it off with wadding.

 

It works best by putting it in a shallow hole in the ground, fuse end up, cover with a pile of very dry fine clay or ash or any thing fine and dusty.

 

Light fuse and watch the fun. It dispurses the cloud in a very realistic manner. You can use the tube over and over again.

 

Tryi it, you'll like it.

[busspuppy]

I agree with Bobosan, I think the bucket looked better and had a better spread. The mortar blast looked too tall and skinny, unless that is the kind of blast you are looking for.

[50AE]

For movie explosions, we are using HE cord, cement bags, like previously mentioned and pieces of peat and cork wood to make lightweight, much less dangerous debris simulations. It depends of the effect. The cement bag usually deafens the HE cord sound and gives a nice grayish cloud like in the previous picture.

 

http://www.youtube.com/watch?v=JV51bDyObpw

 

At 4:08 , also 4:20 you can see an explosion (used to be a BP nade in the scenario). We do this in a very thick steel metal pot shoven in the ground, HE cord, peat, cork and a bit of cement.

Edited May 14, 2013 by 50AE

[bob]

Yeah I know the three inch one isn't as good as the other ones but one thing you have to remember is that was one of my first tries and a three inch mortar is way smaller which seems to make things harder.

bob.

[bob]

Any one know how to get a larger base as it seems to me that would make it look more realaistic.

PS I was cutting some steel pipe and got some of the shavings, any one know off hand of a bp comp with steel?

bob