73 replies to this topic

[pymp]

Petrol/flammeable liquids above a BP comp have been mentioned as a possibility earlier in the thread, just to clarify, does it need to be confined BP to "blast/heat" the liquid into a flammeable vapour, or can it simply be anything that lights the liquid? Also, with what ratio? Should it the BP/liquid be mixed? or have say the BP underneath the liquid- which is kept in a bag of some sort to stop spillage?
(Excuse any ignorance shown, relieve yourselves with the knowledge that i'm not going to be attempting to make this, i'm just intrigued as to how someone might do it)

[Frozentech]

Petrol/flammeable liquids above a BP comp have been mentioned as a possibility earlier in the thread, just to clarify, does it need to be confined BP to "blast/heat" the liquid into a flammeable vapour, or can it simply be anything that lights the liquid? Also, with what ratio? Should it the BP/liquid be mixed? or have say the BP underneath the liquid- which is kept in a bag of some sort to stop spillage?
(Excuse any ignorance shown, relieve yourselves with the knowledge that i'm not going to be attempting to make this, i'm just intrigued as to how someone might do it)

The best example I've seen was in a video from the Winter Western Blast of the WPA in the US. The used a 6 inch steel mortar, with about 2 gallons of gasoline. The dropped a resin sealed bag with 75 grams of BP electrically matched down to the bottom. It looked like a miniature Hiroshima.

[adamw]

Should it the BP/liquid be mixed?

No

It needs to be confined on the sides, such as in a sturdy tube, or even a hole in the ground, place the BP underneath (50g in a plastic bag, wrapped with electrical tape to confine the package... or if you are feeling fancy, heavily spiked like Maltese cylinder shells) and then on top, several litres of 'gasoline', (mixed 50/50 with diesel if you want a long lasting, black smoky fireball) - which should cost you a good few ? over here in the UK.

For the record, I am not a fan of petrol fireball effects (unless the effect is intended, such as a fuel dump explosion). For munition effects, I always prefer napthalene, which gives a rolling, sooty black fireball if used in quite large amounts... and most importantly, it doesn't last too long and goes out quickly. Even better is to use only 100g or so of napthalene, and use cement, lampblack (or a mix of the two) or fullers earth. This way you get only a wisp of flame in the plume of dust.

Some examples attached:

[pymp]

So, if one needed a row of fireballs going off at once, for a series of containers or somethin exploding in a film- or for whatever reason. Could one do what is badly explained in the picture below? A row of them are connected by quickmatch, which is connected to an e-match, and when the e-match is activated the quickmatch lights all the mortars simultaneously. Also, is the diagram correct in other ways? Also, if it's underground, does it matter what the mortar is made from as it has the support from the soil walls? Ie. could it be made of plastic instead of steel?
Cheers

[adamw]

I wouldn't trust quickmatch to ignite all of them, especially if buried underground. It would be best to fire all from seperate ignitors.

If it is buried in the ground, if it is dry, hard soil then you can probably get away without a mortar, but if you were to use one, metal is best because paper and plastic will burn

There are different types or mortar too. The type you have shown is a 'straight up' "shotgun" mortar. There are also 'pan' type (sometimes called 'boiler end') (like a wok) and V-pan (like \___/ ie angled sides but straight front and back, like a trough). My favourite (sad eh) is the V-pan because you get good projection to make the explosion look big because the effect follows the outline of the mortar, but at the same time it is safer than the normal pan because the effect cant spread out as much in the forward direction.

The diagram is OK in every other respect. I see you omitted the wooden disk

[pymp]

Hehe yes, I see no reason to introduce another hazard (the board) to create an effect that can be achieved via safer methods.

With the V-Pan mortar you described, would you have to make that from scratch? Or can you buy metal in that shape?

As far as ignition goes, you suggest omitting the quickmatch and using, for instance, 5 e-matches which can all be activated simultaneously?

Is this, crappy diagram V2, a v-pan? (I assume it wouldnt be this squat, and be a more acute trapezium, if you see what i mean)

Edited by pymp, 03 May 2006 - 07:50 AM.

[adamw]

Wow.. in 3D-o-vision

That's pretty much correct. Of course, you can have different angles, more pointy at the base etc etc, but the important thing is that it's bigger in the L-dimension.

The black powder won't perform as well if it isn't wrapped up in a container, such as a cardboard tube, or even a plastic bag, and then bound up a couple of turns with string. With enough confinement from, for example, earth on top, you might get away without doing this at a pinch, but you are guaranteed a better chance of success if you purposely confine the BP in a container.

Regarding the construction, you most likely would have to make it yourself. If you can work an angle grinder and a welding torch / MIG / TIG etc then you could make it out of steel plate. If you search around a scrapyard or industrial equipment seller they probably will have something that fits the bill (a 'boiler end' quite often is just that. I've used the ends of propane bottles (EMPTY!!), beer kegs etc). You can also rent mortars from SFX suppliers, but you are better off making one yourself.

[pymp]

Yeah, if the BP isn't confined then the gases it releases just escape, if restricted to a container the pressure builds up and forces it's way out.
As for making your own mortars; I have, as baldrick would say, a cunning plan.
After researching metal pipes, i decided that they were all hideously expensive, so would the following work?
(something i forgot to put in the diagram, all bottoms/tops of cans removed where appropriate!)

(i apologise for yet another paint-job diagram!)

Edited by pymp, 04 May 2006 - 09:48 PM.

[adamw]

I think a tin can would be a bit flimsy, and thus more likely to rupture and potentially spread thin metal shards around if used above ground. In ground, it could be used if the soil was wet, but in dry soil there is no real need for a mortar if you want the blast to go straight up. Dry, baked earth should contain the blast fine.

[Arthur Brown]

The fireballs I used to do for airshows were a theatrical maroon in a hole in the ground with a big (2-5 litre) poly bag of petrol/gasoline/Avtur/diesel/old lube oil placed on top. Dig the hole the shape you want the fireball th grow from, exactly as the drawings above. Naphthalene and coffee whitener also work. Confine the primer do NOT confine the bulk charge.

Only way to find out is to experiment on a safe firing ground. FX to camera are best done remotely with as long a lens as pos to keep all people and property out of harms way.

[Darkstar]

The "Cremora" or "Cremola" fireball is a good effect, much beloved of
PGI conventions. Cremora is a US brand non-dairy creamer, similar to
"Coffee-Mate" here in the UK. "Cremola" is just a b*st*rdisation!

It's too expensive to use creamer for large effects, so most people use
animal feed equivalents such as calf, lamb and piglet "milk replacers"
These can still be around ?1 per kilo, so unless you can find a really
cheap source such as factory floor sweepings, this effect is best used
where the flaming fallout from liquid fuel based effect is an issue.

Some have said that the higher the fat content the better (piggy feed
has the highest), but others dispute this. I've used Volac's "Blossom"
calf feed, with a oil percentage of 18, to good effect. Other flammable
powders, such as wood dust, will also work.

Here's how to do it:

Take a 5 gallon plastic bucket and tape a length of quickmatch down the
side and into the center of the base (bare the end of the match).
Sprinkle 1 pound of BP over the base of the bucket and cover it
with a sheet of newspaper (it helps to cut the paper into a circle, slightly
larger than the bucket's diameter). The trick is to press the paper against
the side of the bucket to stop BP and milk powder mixing. Next, sprinkle
in a layer of milk powder NO DEEPER than the diameter of the bucket.
Try to get as much air as you can into the powder, as you load the
bucket - and DON'T move it once loaded as this compacts the powder
and can cause the bucket to blow, ruining the effect.

Add an e-match or delay fuse and let rip!

Important points to remember:
DO NOT use an e-match taped directly to the base of the bucket. Some
accidents have occurred using this method, probably due to static generated
when the powder is poured into the bucket. DON'T move the bucket once
filled - instal this effect in situ. Don't use a long tube, such as a mortar.

This effect will scale up - and down to a degree. Sometimes the bucket
survives, sometimes not!

Paul

[FrankRizzo]

And you need not use a full pound of BP; 4oz of 2FA works just fine..and your bucket survives

[burningbush]

And you need not use a full pound of BP; 4oz of 2FA works just fine..and your bucket survives

the pro ratio is 1/10 trust me I know!!

[Darkstar]

the pro ratio is 1/10 trust me I know!!

Given that "Blossom" comes in 20kg sacks and knowing how much I use
in my buckets, I'd say my one pound of BP is about right, ratio wise.

I guess there is a lower limit where the quantity of BP would be insufficient
to lift, disperse and adequately light the powder. There probably isn't an
upper limit!

Paul

[burningbush]

Given that "Blossom" comes in 20kg sacks and knowing how much I use
in my buckets, I'd say my one pound of BP is about right, ratio wise.

I guess there is a lower limit where the quantity of BP would be insufficient
to lift, disperse and adequately light the powder. There probably isn't an
upper limit!

Paul

YEAH your right it just depends if you want your bucket and stainless bowl to be found/usable again
Ive only set off 100 or so of these,I use only goex bp for lift. 2fa
Pc