Compression in firecrackers?

[Pyroboy]

Hi guys, it's been a while since I've posted, but I've still been checking out what's going on every now and again... Anyway, I'm going to be making some big flash bangs for new years eve with KCLO4/Al flash and I wasn't sure if I should compress the flash or not. I've always filled my crackers up about 3/4 full, but it's a bitch to fill them 3/4 full and then try and get an end plug to set in the end with out compressing the flash powder. Does anyone know how I can solve this problem? Maybe some tissue befor the end plug? I'm only asking this because I think I remember reading somewhere that the powder for a cracker should not be pressed in. Anyway, any help would be nice. Thanks, Pyroboy....

[RTC]

If you press it hard enough (serveral tons PSI) chances are you'll have a very fast burning rocket if not a cracker. But I doubt anyone by just brute force can compress something to even a ton PSI.

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We have assembled here today to teach you all a little lesson. One cannot remain on top for years while closing one's mind to the influence of others. I will demonstrate the true meaning of inovation for all you to see.

[Madog555]

you want to have roomfor expansion in the caseing, it will make a bigger bang. so i would sugest filling it 1/2 full.

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"To live is to suffer, to survive... well thats to find meaning into suffering." -DMX

[Anthony]

Yes, definitely half full and loose allows the deflageration front to spread through the composition faster. You could try gluing in a solid end plug (dowel etc), or using a solid glue endplug (hot glue is good for this), or if you want to use a setting filler of some kind, tack in a disk of card to the correct depth in the casing with glue and spread the filler on top of the disk.

Or maybe cut the end of the tube into several tabs, fold them and apply glue. A lenghways binding of tape helps them hold more pressure.

[Pyroboy]

Ok thanks a lot guys and thanks a lot Anthony your suggestions are good http://theforum.virtualave.net/ubb/smilies/smile.gif

Thanks Pyroboy...

[Kdogg]

Rtc, can I quote you : "If you press it hard enough (serveral tons PSI) chances are you'll have a very fast burning rocket if not a cracker" I dont know if you have any knoweledge of flash powder, but correct me if im wrong, if his flash powder is worth a crap it could self confine very easly causing a pretty bad accident.

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Monkeyman

[Anthony]

I want to know what a "Ton Pounds Square Inch" is... Unless "Ton" is used in its "many" definition.

[Donutty]

Self confine?? That'd be useful!

Do you mean self-combust? I have never heard of anything self-confining, let alone knowing how it would do it.

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...AAGH! It Burns!...

[RTC]

Kdogg, in reply:

I've not toyed with flash as much as many others. But it's to my minority knowledge that if you press the flash to a certain extent it'll form a solid, and just burn allbeit extreamly fast.

An example into what I mean is BP, bursts when confined, burns when solid.

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We have assembled here today to teach you all a little lesson. One cannot remain on top for years while closing one's mind to the influence of others. I will demonstrate the true meaning of inovation for all you to see.

[vulture]

I've cut open several blackpowder firecrackers and found that they are entirely filled like this

|wood dust|blackpowder|wood dust|

(i'm not sure if it's wood dust, could be fine clay also)
and it's all packed together pretty tight.

[the freshmaker]

Ladies & gentlemen let me refresh the meaning of the word "self-confine". Ex: Most flashpowders will self-confine when they are ignited in big amounts.. meaning if they are set off in big amounts they'll explode violently without any confinement at all!! The "critical weight" as it's called varies from flashpowder to flashpowder. Some Chlorate flashpowders with very fine Al fx. German Black aluminium will selfconfine = explode without confinement in amount as low as 5g <

The critical weight for BP is as far as I remember lots of kg's!!!

[nbk2000]

I think he's using PSI to abbreviate "PER Square Inch" and not "POUNDS per Square Inch".

[Agent Blak]

Myself and another one of my crew made something that goes against everything all of you are saying.
We use a 1 1/2" piece of ABS 4" long, Polyester resin was the cap. after it had cured we used News print wadding poured in some Prydex tamed it and fused wadded and capped it on the other end. let it cure. The whole thing was splintered(shards length ways)
just thought you all should know.

[MacCleod]

I also know a guy who makes BP 'crackers that he fills completely,tamps the hell out of,and they are loud!.Buying the chem's for flash is usually more cost-effective,though,as it takes so much less flash to make a good bang with.
Oh,pyroboy-if you use a long eough tube,a bit of tissue in the ends works great(especially if you use a side-fuse).I fill mine about 1/3rd. to 1/2 full (depending on the powder) without tamping,and plug the ends with 5/16th's of an inch of hot glue.

[ January 07, 2002: Message edited by: MacCleod ]</p>