15 replies to this topic

[Karl Mitchell-Shead]

Hi all,

Have been asked to create a large fireball effect (ground based) for an organised pyro meet.

Have at my disposal quantities of powerful flash powder, was considering using this as the burst perhaps underneath a large container of fuel.

Thoughts?

Chief

[Mortartube]

You can use a flash based plastic bottle ground maroon under a plastic bucket (mayo bucket from the fast food shop, remove the handle) that has been sunk into a hole in the ground IF YOU HAVE ROOM).

But you need a small gerb (even a Titanium based garden fountain will do the trick.) to light above it to be sure that it lights the fuel, otherwise sometimes it lights and sometimes it doesn't. I have done this a few times. Also if the ground is stony, you best pick out all the stones you can in and around the hole the bucket sits in for safetys sake.

Petrol is VERY hot. Is has a high calorific value (which makes it good for it's proper job)so be a good distance away. Try mixing petrol with about 20% diesel to get a rolling mushroom cloud type effect with black smoke (assuming this is a daylight firing).

You will want to be at least 70 metres (minimum)away for safety including the heat given off for about 5 litres of fuel.

Otherwise as suggested you can use BP. Take a large mortar tube with a small BP maroon in the bottom. Put a double thikness bin liner in the mortar tube and add fuel. Tie the bin bags up and fire.

[Creepin_pyro]

This is a 8" gun with Petrol/Diesel (50/50 IIRC) and a blackpowder maroon:

http://www.flickr.co...57617343147696/

Would that do? : )

Edited by Creepin_pyro, 13 October 2009 - 10:04 AM.

[Karl Mitchell-Shead]

This is for UKFR's annual meet.

Posted my credentials in the 'new members' section, hope this instills some confidence

Yes i like the mortar idea, may be worth a try small scale with a 2" tube first. Although the 'fireball' is very column like and direct.

I think the mayo bucket would give a better rolling mushroom cloud type fireball. Maybe place a few bags of flour ove a FP charge close by for spread.

Chief

[Creepin_pyro]

If you want a stouter, less column-like appearance, you might want to try using a empty beer keg cut in half. Or similar trough type container.

I doubt you'll get a particularly impressive effect from a 2" gun. You may not get quite the same rolling fireball by rupturing a bucket from underneath...

EDIT:

There are a few commercial solutions which might be worth considering. Try HFM pyro for starters if you're interested.

Edited by Creepin_pyro, 13 October 2009 - 04:05 PM.

[Karl Mitchell-Shead]

I did think about trying Mike, the issue here is cost. HFM gear is too easy and there wouldnt be the satisfaction of having created something ourselves

So essentially i need a fairly low order burst to project a bag of fuel upwards and out of confinement for the best fireball?

(2" mortar would be for small scale test)

Chief

[wjames]

LPG may prove to be a better option than petrol/derv.


Other than that, biggest fireball i saw came from a 10 inch air canon, was basically fitted with a heating element at the end, then filled with fuel, and pointed skywards.
Worked quite well, huge mushroom clouds, and depending on the fuel used, you can either have a fast, hot fireball, or a slower burning (dirty) fireball.

[Mortartube]

This is for UKFR's annual meet.

Posted my credentials in the 'new members' section, hope this instills some confidence

Yes i like the mortar idea, may be worth a try small scale with a 2" tube first. Although the 'fireball' is very column like and direct.

I think the mayo bucket would give a better rolling mushroom cloud type fireball. Maybe place a few bags of flour ove a FP charge close by for spread.

Chief

The problem with flour is that is not very bright as a fireball compared to the diesel/petrol mix and doesn't always light. If you can get some Bakelite resin powder, Naphthalene or red gum that is much better but I would still recommend using BP rather than FP to lift and light it. The problem with FP is that is sometimes causes the fuel (liquid or powder) to travel so fast that the drops or particles move away from each other too quickly to allow the flame front to propogate through the fuel and you end up with it not lighting.

You might consider firing the powdered fuel through the petrol fireball from each side so that the petrol fireball lights it. If you were using 3 mortar tubes it might look like this ( /I\ )with the central tube having the liquid fuel and the outer ones the powdered fuel. If you have a flashy firing system I would suggest firing the powder fractionally before the liquid to ensure that it is passing through the liquid fireball as it begins.

[Karl Mitchell-Shead]

Yes flour would only be a 'booster' not the primary fuel.

This will hopefully be ran through FireByWire, so what do you think, 0.5s delay between powder booster and liquid fuel?

Have had a lenghty conversation with another 'forum top trump' who is going to attend and assist, think we pretty much have it worked out.

Hopefully have video and photo's in just over a week

Chief

[Karl Mitchell-Shead]

Wall of fire with flour boosters here



They are right at the end of the video

[dave]

another powdered fuel you can use (using blackpowder )
for relatively small fireballs is powdered tar.....very orange and smokey and quickly consumed.
the traditional napthalene obviously works but is a bit smelly.

i have also come across, blends of hexamine and acroides resin, again with blackpowder lift.

propane gas canons give good firebursts but are expensive

dave321

[icarus]

the best fire burst repeatable effect is obtained by filling a pressure vessel with propane gas via a variable regulator /good regulators go up to 4 bar.The gas is then vented via a solenoid as quickly as possible and ignited via a spark or hot surface igniter giving flame plumes that can be syncronised to a drum beat or music.Another approach is to use alcohol with strontium salts is sprayed through an atomising nozzle for a vivid red flame. spray bars in the ground can make massive flame walls of differing colours i am presently making a flame vortex machine to emit a coloured whirlwind of fire.hopefully 10 m high

[Creepin_pyro]

Nice... seen a few videos of whirlwind pyro devices... never coloured though. Have you thought about trying to inject metal powders in there?

This makes me think of El Diablo : )

[Mortartube]

Fine aluminium puffed through a propane flame is used in the film industry to light up large areas to simulate lightning illumination. It tends to produce a bright flash rather than a fireball. Metal powders don't tend to produce the desired fireball effect.