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Cylindrical Shells


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#16 BigG

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Posted 06 July 2004 - 12:17 PM

I guess that the mix in terminology is down to the fact that the people on this threads are from different countries.

So, Here we go:

First, regarding Mesh. As Richard mentioned ? 10 mesh will give you roughly 2FA. The idea is to get your granulates to around the 10 mesh. One way of doing this is to use every granulate that passes through a 10 mesh screen but stays on a 20 mesh screen.

Still, even so, there is no exact formula to how much you need to use. The rule of the thumb says 1 ounce of 2FA for every 1 pound of shell, but I must say that I hardly ever seen this work for home made black powder. Depend on the amount of dextrin, the density of the granulates and milling quality, you might require three time that amount of home made BP. The idea is to develop repeatable work procedures that produce the same home made BP quality and granulation, try a few shells with different lift, and find the amount of lift most suitable using your home made BP.

As for the delay post - a bit of confusion there. The fuse connecting your delay fuse and lift charge MUST be a quick match so delay and lift ignite together. Any other way in not reliable. Again, the length of the delay fuse is a matter of trail and error. Three inch might require two seconds, while a brothers 1-3/4 shell uses only about 0.75sec for delay. Make procedures that fit your workshop best.

#17 pyrotechnist

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Posted 10 July 2004 - 06:47 PM

So you saying the fuse igniting the lift charge connects to the time fuse leading into the shell? Or can the time fuse inside the lift bag be seperate from the fuse leading into the lift charge bag? I am confused here i thought the shells lifting charge bag had one fuse leading into it to ignite the lift charge, then you had your time fuse comming out from shell into lift charge bag seperate from main fuse am i right or wrong? Thanks.
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#18 Richard H

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Posted 10 July 2004 - 07:09 PM

That is correct. The leader ignites the lift charge, the lift charge ignites the time fuse.

In cylindrical shells, the leader ignites the time fuse, and then blackmatch passes fire to the lift charge. (Unless the shell is bottom fused, which is unlikely for larger can shells.)

#19 pyrotechnist

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Posted 11 July 2004 - 04:37 PM

:D Thanks i was just cheking to see if i was right i didn't understand bigG on what he was saying lol. I don't have any shell cases to make shells yet to dam hard and time consuming to make ;) .
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#20 neo

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Posted 12 July 2004 - 07:12 AM

For smaller shells like 1-2" can I use normal black match as time fuse?
In case not, dose any one know where I can buy them, where they ship inside Europe?
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#21 Creepin_pyro

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Posted 12 July 2004 - 08:48 AM

For smaller shells like 1-2" can I use normal black match as time fuse?
In case not, dose any one know where I can buy them, where they ship inside Europe?

Erm, you can't use blackmatch as a time fuse, however - you can use it to cross-match time fuse. For smaller shells, Visco or similair safety fuse can be used, or just make a spolette.

When you say "them" do you mean plastic shell hemispheres? They are possibly the easiest pyrotechnic supply to ship. I don't think any company would refuse to ship them to Europe. If you are asking for a fuse supplier, do a search.

#22 alany

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Posted 12 July 2004 - 08:56 AM

If you can't buy timefuse you can make your own spoulette, or roman fuse.

A spoulette is basically a narrow but thick walled tube rammed solidly with meal powder to a depth sufficient to implement the required delay. Other compositions are sometimes used for effects like comet composition or even whistle.

Blackmatch is normally tied across the outside end of the spoulette and/or the powder scratched with a cross to make it take fire more easily. On the inside sticks of blackmatch are often tied into some kraft nosing to increase the spurt of fire when it burns through.

As spoulettes are large in area they blow into shells quite easily causing flower pots or muzzle breaks when bottom fused. Sealing around them and the disk is critical. The powder column itself can blow through as well and tricks like clay plugs and ramming excess length of powder then drilling down to achieve the timing is used to prevent blow through.

It may also be possible to make timefuse in a cigarette roller as I posted about a while back, but I don't fully trust it yet.

#23 Stuart

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Posted 12 July 2004 - 04:37 PM

Spollette's made in a cigarette roller are excellent. Always use them and I have never had one flower pot or anything like that, always worked perfect and very reliable as far as time goes. Just roll the tube and then ram.

#24 neo

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Posted 15 July 2004 - 05:54 AM

okay, so if I put a comet or something on the shell then I don't need the time fuse, right?
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#25 Creepin_pyro

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Posted 15 July 2004 - 08:18 AM

Don't know where you got that idea! You need something to pass fire to the inside of a shell, which the time fuse/spoulette does perfectly. A comet merely sits on the outside of the shell and burns itself up, and should only pass fire to the burst charge due to some error in construction.

#26 The_Djinn

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Posted 15 July 2004 - 08:23 AM

Neo,

Take the commet out of the equasion. The commet is an optional extra and has no relevance to the construction of the initial shell. It is added to the finished shell to add an additional effect during the firing / lift stage of the shell.

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#27 Creepin_pyro

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Posted 18 July 2004 - 10:46 PM

I finally finished my shell. Made the time fuse lots shorter, added some extra tape around the middle, and changed the lift charge: 5.5g - sieved to 10mesh.

I buried the mortar good and deep, and used a fountain and two single shot candles for delay. Both the candles blew blind, but still passed fire to the shell leader. I think the shell could've gone a bit higher, and the stars were definately too big, but apart from that, I'm quite pleased :D

Here's the shell

and the fountain

Edited by Creepin_pyro, 18 July 2004 - 10:56 PM.


#28 alany

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Posted 19 July 2004 - 08:24 AM

What comp and binder did you use for the microstars in the fountian? Also how big were they?

Interesting comet composition.

#29 neo

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Posted 19 July 2004 - 04:10 PM

The idea by using a comet instead of a time fuse is to put a comet that will burn for let?s say 3 sec, then when the comet is all burned up it will ignite an black mach which goes into the shell and ignite the shells bust charge, that?s my idea and I only wonder if it will work?
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#30 paul

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Posted 19 July 2004 - 04:41 PM

Of course it will work, if you do it correctly :P
Larger shells use that kind of fuse too. But you have to press the composition into a very robust tube. Then you can glue this "fuse" into the shell. (Don?t use hot melt glue, woodglue works way better and is more stable)

You certainly will have more success with a normal fuse.....

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