73 replies to this topic

[acoop101]

Cannonfuse.com has a page dedicated to making fireballs, they recomend priming the Nepathaline with a25% by weight of black powder or pyrodex(a black powder substitute) to help with ignition. I haven't tried this since I can't find moth balls made from nepathalien.

[Kevin J]

Would it work (I don't see why not but i just thought I'd ask), to make a miniature version of the petrol/diesel fireball?
Something like: Bury a 1inch diameter cardboard tube all the way in the ground, pour about1/2 inch granulated black powder in the bottem, fit an electrical ignighter in the black powder, place a bag in the mortar, pour 4 inches of petrol/diesel into the bag.

thoughts?
(I always like to try small versions of things before the full version.)

[Steelrat]

Hi im a SFX pyro designer.
thought you would be intrested in a Propane gas explosion i created for the met police training video,
i used 3 propane gas cannons at 30 - 40 psi with one 4 inch and 2 two inch electric solonoid ball valve outlets, into this i mixed napha flakes to give it a more rich orange flame with black smoke, this was repeated 5 times , without even smoke damage to the building, and could gurentee the safety of the actor who was 20ft away from the action who on cue fell onto a crash mat out of frame, no petrol mix was used, the flame in the doorwas was from a gas flame bar windows treated with a IPA spray and gell for instant burn, all could be reset in 2 mins for further takes and angles.
gas can be made to look like petrol

[adamw]

Very nice. Good to have another pro on here.

Yes, propane can be used to very good effect, and is one of the only safe ways an effect like this can be used in / around buildings and people.

And to be honest, petrol fireballs are probably my least favourite effects, but for some godforsaken reason directors prefer them. I'm all in for realism over 'stylisticness'.

[BrightStar]

I'm slightly in awe of the professionals here... So much to learn! I discovered a few months ago how NOT to do a fireball so I thought it might be helpful to share it with others.

I started by mixing 15g of 70/30 perc/benzoate whistle with approx 5g BP meal and used it to fill a small plastic vitamin pot. An e-match was placed inside, it was spiked with string and duct tape and placed in the bottom of a 60mm id cardboard Pringles tube. About 300ml of unleaded petrol in a sandwich bag was then lowered on top, and the whole thing partially buried in a field.

On pressing the button at about 30 metres range (having anounced to family and friends that this would be a 'Hollywood Fireball') there was something close to a detonation. An enormous bang but with no flash and no fireball at all. The petrol was atomised and just vanished without ignition. The Pringles tube was shredded into a 6-point star. It was so loud that I had to apologise to my audience...

I'm told that some titanium in the maroon would have guaranteed ignition. Does anyone have a source for this in the UK?

Edited by BrightStar, 13 August 2006 - 11:01 PM.

[Steelrat]

I'm slightly in awe of the professionals here... So much to learn! I discovered a few months ago how NOT to do a fireball so I thought it might be helpful to share it with others here.

I started by mixing 15g of 70/30 perc/benzoate whistle with approx 5g BP meal and used it to fill a small plastic vitamin pot. An e-match was placed inside, it was spiked with string and duct tape and placed in the bottom of a 60mm id cardboard Pringles tube. About 300ml of unleaded petrol in a sandwich bag was then lowered on top, and the whole thing partially buried in a field.

On pressing the button at about 30 metres range (having anounced to family and friends that this would be a 'Hollywood Fireball') there was something close to a detonation. An enormous bang but with no flash and no fireball at all. The petrol was atomised and just vanished without ignition. The Pringles tube was shredded into a 6-point star. It was so loud that I had to apologise to my audience...

I'm told that some titanium in the maroon would have guaranteed ignition. Does anyone have a source for this in the UK?

you should use a mortor pan 2ftx 2ft V-type 1/4 to 1/2 thick welded steel - 20 - 50 grm maroon or hard wrapped black powder maroon is placed in the bottom, i normaly use det cord 8grm to 12grm per mtr and a no 8 det, but maroons work as well, place this in the pan , then fill 2 ltr- 4 ltr of petrol/ diesel 60/40 in to a bin liner bag tie off with tape, and cut and remove the rest of the bag or this will burn when falling, tie off the bag to
the mortor pan for the same reason. then fix a small plastic bag with about 3 teaspoons full of lose black powder 4 inches above or away from the main maroon, make sure your wires lead back to your firing point about 70 ft away and check that no wires are over the main charge or the blast could cut the black powder charge wires and also check wind direction if it fails you could get covered in petrol .. not good! , then hook up to the battery, and fire this will make a fireball about 30- 50 ft high, also think of the problems that can go wrong before you even try it .. whos about, radio transmitters, and anything that may catchfire and have a back up to put anything out... hope this is of use to you pyros out there

Edited by Steelrat, 13 August 2006 - 11:04 PM.

[Kevin J]

"And to be honest, petrol fireballs are probably my least favourite effects, but for some godforsaken reason directors prefer them. I'm all in for realism over 'stylisticness'."

I'm with you there, it irratates me to no end when I see a movie where there is an exp*****n and it is all fire and so obviosly done with gas or oil..

[adamw]

For the best 'real' explosions, see modern war productions (Saving Private Ryan, Band of Brothers etc). The older (50s - 80s) war films still had the tendency to user petrol mixes.

I think now that people have seen a lot of televised action from both Iraq wars, eastern Europe and Afghanistan, they know what a real HE blast looks like so directors and SFX guys will start to turn the realism up.

[Kevin J]

I recently tried a napathelene fireball. It was small, 1 inch diameter. I did it based on what I have read in a few places. I had a very strong tube, put some granulated and some meal in the bottom, put some 50/50 meal/crushed mothball (napthelene) and then filled up the rest with crushed moth balls. When it went off, there was an astounding bang, but no fire other that normal "black powder fire". Do you know what I did wrong? I did pretty much the same thing twice with the same results.

[Creepin_pyro]

How long is the tube? I have a feeling that you're using too long a tube and confining the BP too much...

[rocket]

I?ve tried these many a time and only one has a slit flame from the naphthalene, I was using 1? tubes as well. So I?ve come to the conclusion that this type of fire ball work well in larger tube because the vids I?ve seen have had large mortars.

[pymp]

With permission from the admins, I'll post a couple of videos of my ones. There's a 1" ID tube video, a 2.5" ID tube and a bucket. My avatar shows a still from the latter.

Also..

When it went off, there was an astounding bang

I had this problem at first, and I assumed it was the powder on top of the BP being sufficient to confine it. So I changed my BP by adding more charcoal/milling it for less time. Works perfectly now.

Edited by pymp, 14 October 2006 - 11:11 AM.

[adamw]

Go for it...

[pymp]

Here we go
I didn't see any reason to add flashy editting, so I didn't.
Kevin J- Was the problem with your one similar to the problem in the first video?

[Kevin J]

Thanks guys, Mine was similar to the first clip, but there was less fire.
Will try the slower powder.