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Cylindrical Shells


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#31 Creepin_pyro

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Posted 20 July 2004 - 11:13 AM

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

Interesting comet composition.

The blue comp was an oldie from rec.pyro:

60 parts of ammonium perchlorate
10 parts of sulfur
10 parts of dextrin
12 parts of polyvinyl chloride (if you use Parlon, add further 2 parts of
dextrin)
20 parts of copper(II)oxide

I followed the formula exactly. They were very easy to pump - nice and sicky. I was having trouble priming these (any suggestions), so decided to attack some with scissors. Just cut them up until they were small enouth to fit through the nozzle. Perhaps <6mm? They seem quite self-propelled (hard to see in this vid) I think replacing a little of the copper Oxide with Strontium Carbonate/Oxalate would be a good idea - should give a nice purple.

I'm very pleased with those comets. Think they would be good for crossettes. Super-fast burning, though. I wish I had a crossette pump.....

#32 sasman

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Posted 20 July 2004 - 11:46 AM

Creepin Pyro Did you use vermiculite burst charge for the shell break?? ..I was impressed with the Comet what formula did you use and what type of alumnium was it?..

Also how big were the stars in the shell?..Im not to fond of fountains but the nice blue stars poping out of the fountain was a very nice effect ...or as my GF would call it pretty :) ..Have you made other blues without using AP if so does AP give better Blue than other formulas you have tried?...Hope you post some more videos ....

sasman

#33 Creepin_pyro

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Posted 20 July 2004 - 12:18 PM

The burst was indeed BP coated vermiculite. I resisted the temptation to sprinkle whistle in there :D The stars in the shell were about 12mm - too big and slow-burning. They seemed a little over-primed to me aswell. I'm not sure about that comet composition - will see if I can find it. I think it could've been as simple as 60 Perc, 40Alu flake with a binder.

I would normally consider fountains as a waste of my precious meal, but I'm determined to master the blue to purple micro-star charcoal fountain. I have quite a few improvements in mind... not a bad start, though.

I have managed to get a faint, bright blue, and a reasonably colourful purple using Kcl04, Copper Oxide and Strontium Carbonate. Sadly, compared to the AP blues, they were "off-white" I'm sure there are good blues/purples achievable without AP, but trying out all the different formulas would quickly deplete my chemical stock.

I've just tried an AP blue lance, with the simple formula:
Ammonium Perchlorate: 70
Copper Oxide: 30
Red Gum: 15

All I can say is: mmmmmmmmm the blue...... the BLUE!!!!!
Shall post the vid soon.

#34 pyrotechnist

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Posted 21 July 2004 - 12:35 PM

Can someone post how to make spoletes? I do not know how to make them.
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#35 Richard H

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Posted 21 July 2004 - 05:56 PM

See the article on Passfire.com, or the article in Pyrotechnia about canister shell construction.

#36 pyrotechnist

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Posted 21 July 2004 - 06:28 PM

Hmm i don't have them things. I just need an example of how to construct one wich dosn't blow into the shell like someone said in this topic.
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#37 Stuart

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Posted 21 July 2004 - 10:11 PM

Can someone post how to make spoletes? I do not know how to make them.

http://www.ukrocketr...p?showtopic=684

One method B)

#38 Phoenix

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Posted 22 July 2004 - 04:04 PM

This is how I make and use spolettes for my small 1-1/2" shells. This method would probably not work well for larger shells, but I have had 100% success like this for this size:

1. Get a small, strong tube (say, 5mm ID, 7mm OD and 30mm long)
2. Stand it on a smooth surface
3. Put a small amount of meal BP in, and ram it hard.
4. Now put some more meal powder, ram again
5. Continue (like making a fountain) until you have the desired length of hard rammed BP to provide a suitable delay for your shell. You will need to find this out by trial and improvement. The spolette tube will probably be about 1/2 full with rammed powder, and half empty.
6. I now glue the spolette into the hole in the bottom disc of the shell, so that the "empty" end, where it was loaded from, is almost flush with the disc.
7. I then put this disc in the shell casing, against the cardboard liner, but orient it so that the bottom end of the spolette, where the BP core is visible is outside the shell, will sit in the lift charge. The outer layer of kraft is then pleated over the disc.
8. I now place some pulverone in the shell casing, and jostle it so that it fills the empty space in the spolette tube, and creates a thin layer over the bottom of the shell.
9. I now fill she shell with stars, and shake more polverone in to fill all the spaces, until it is level with the cardboard liner, close the top, and spike, paste, affix lift etc.

I have never found it necessary to prime these spolettes with black match, when used like this, as they are sat right in the middle of the lift charge.

If you are making a lot of spolettes, you can save time by ramming all of them with a longer charge than is needed, then using a drill press with a depth stop to drill a hole into the BP, from the "empty" side that will be inside the shell, so that they will all be exactly the same length.

I also often use meal with added charcoal, to slow it down a bit, so that I can use a shorter charge (saves time ramming) and have not had problems. However, spolettes made like this, with a shorter charge, are more likely to blow through. It's probably best to start off with a long charge meal.

Edited by Phoenix, 22 July 2004 - 04:08 PM.


#39 pyrotechnist

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Posted 22 July 2004 - 09:40 PM

Thanku but few questions.

Do you keep the empty end open with no gunpowder in it or something?

Do you put the blast charge over the empty end of the spollete?

Does the full end of the spollete go in the lift charge lololol :D . Stupid question but just wondering lol.

What is blow thru in a spollete?
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#40 Stuart

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Posted 23 July 2004 - 06:31 AM

You put your pulverone or what ever your break is loosely into the empty end and this goes into the shell. A blow through is when instead of burning through like its meant to, your spollette flashes through and ignites your lift charge straight away.

#41 Phoenix

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Posted 23 July 2004 - 12:12 PM

The empty end points into the shell, and is filled loosely with granulate pulverune, so that when the solid, rammed gunpowder charge is all consumed (and the correct delay time has elapsed) the flame will flash through to the shell contents. Other people use a few sticks of black match to ensire the flame reaches the shell contents, but personally I just prefer to use pulverone.

The filled end, that is the end where there is a smooth, flat surface of rammed BP, is the end that sits in the lift charge.

One other thing that I perhaps didn't make clear is that the open end is almost flush with the shell end disc, so that if you were to look at it from side on, it would look like a "T" rather than a "+". This means that you can glue the soplette in the disc, fix the disc in the shell, and then put say a teaspoonful of pulverone in the bottom of the shell, and shake it to fill the spolette, and leave a layer covering the bottom of the shell.

#42 pyrotechnist

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Posted 23 July 2004 - 04:14 PM

Ok thanks but the fuse in a canaster shell is at the top isn't it its been ages since i seen a canister shell picture. But does the fuse from the top bit of the shellgo down into the lift bag and then ignites the lift bage, then the bage blows off and lifts the shell into the air and then the spollete is ignited by the hot gasses generated and burns strait into the shell is that right? lololol thanks.

Edited by pyrotechnist, 23 July 2004 - 04:15 PM.

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#43 Richard H

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Posted 23 July 2004 - 05:00 PM

That is more or less correct.

#44 Phoenix

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Posted 23 July 2004 - 05:46 PM

Small shells like mine are often bottom fused, as it is a little simpler than top fusing, and in small shells the likelyhood of a blow through is also smaller, so the extra integrity gained by top fusing is not so necessary.

Furthermore, in this size I almost always breech fuse my mortars (basically set them up like a big star gun) rather than use a leader down the tube, so top fusing would be very inpractical.

Here is the basic sequence of events in a bottom fused shell:

1. You light the safety fuse (which lights the leader, if the shell has one).
2. The leader, or just the fuse, lights the BP lift charge.
3. The lift charge burns up, lighting the spolette, which is right in the middle of it.
4. The shell leaves the mortar

And for a top fused shell:

1. You light the safety fuse
2. The safety fuse lights the leader
3. The leader is bared and wrapped around the spolette, which pokes out the top of the shell. As the fire passes this point of the leader, it ignites the spolette.
4. The fire continues down the leader, past the shell, and into the lift charge.
5. The lift ignites and lauches the shell out of the mortar.

As you see, in the top fuse method, the spolette is lit just before the lift charge. However, the time it takes the fire to continue along the leader down the side of the shell is so tiny that the same length spolette can be used as if it was bottom fused.

#45 sasman

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Posted 26 July 2004 - 05:17 PM

I'm in the early stage of plastic ball shell construction i can find lots of information on shell construction but very little on Mortar tube size ...?? The plastic shells are as follows
1... 3" shell actual size 2 5/8" (65mm) What size stars to use in this shell?
2... 4" shell actual size 3 3/4" (93 mm) What size stars to use in this shell?
3....6" shell actual size erRRRRRR?? what size stars to use in this shell?
I have searched on this forum but cant find an answer to what i want to know.

What Length mortar should i use for the above shells?.Given the same amount of Lift powder what effect would a longer or shorter mortar have?

Also i have looked for HDPE mortars and as yet struggling to find any & the tubes i have been able to find are Metric not imperial .
. So Even though i know a 4" shell will fire from a 4" mortar what effect would it have from being fired from a 102mm Mortar which is the nearest metric equivalant? .. it will probably be ok but wont i be wasting lift due to the over size tube?.. I'm intrested in buying/building a rack of mortars? say 5 or six tubes per rack Please PM if you know were to obtain commercial mortar racks?

cheers




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