giod Posted September 5, 2013 Posted September 5, 2013 So working on some 2" canister shells for my first shell, and the first thing I realize, is that there isn't a whole lot of room inside there to pack in the goodies... Especially when using MCHR as the burst.. they take up a lot of room (as they are designed to do.) But I'm wondering if in a smaller shell (where space is limited) I'd be better off with a flash bag. Is there a calculation of quantity of FP to weight of shell for burst? I'm afraid with the limited amount of MCRH I can put in there it won't burst properly.. I made a prototype with MCRH and some loose FP. Haven't tested it yet.. BUt I'm wondering if confining the FP in a baggy will help it burst rather than burn. Any insights are helpful, and yes I DID search fisrt, but I get waaay tooo many threads that do not answer this question...
Shadowcat1969 Posted September 5, 2013 Posted September 5, 2013 Actually, the literature says to use neither, it calls for straight BP granules, usually in the 2 Fa range. I usually sprinkle in some 3-4 Fa as well to help fill the interstices between the 2 Fa, especially in the 2" canisters and have had good results. Be sure to use a canule when filling your inserts/stars, then fill the canule with the BP, pull it out slowly, backfilling with more BP until the canule is out, and top off with BP to fill the shell to capacity. You can add a little flash as boost for the break, but I haven't had to, as long as my spiking is done nice and firm. Check out Fulcanelli's article in Pyrotechnica IX and Pyrotechnica XI for great info on Cylinder shell construction. 1
Carbon796 Posted September 5, 2013 Posted September 5, 2013 If your making 2" plastic cans this is a good/simple effective method. http://www.skylighter.com/fireworks/how-to-make/2-inch-canister-shells.asp#new 1
Mumbles Posted September 5, 2013 Posted September 5, 2013 You might want to take a look at this thread: http://www.amateurpyro.com/forums/topic/8456-first-2-canister-style-shell/ If you can't tell, cylinder shells are one of my favorite topics. I don't bother with a cannule on this size of shell. I just fill the entire thing with stars, and then fill in all the gaps with 4FA and they break pretty well. A little flash can get them breaking big and symmetrically. Fulcanelli has recommendations for flash bags, but not for shells this small. There really isn't a good rule. Bigger shells need proportionally less flash powder, so going by weight isn't going to work well. You really will need to read up on how to properly use flash bags, but for a shell of this size you'd be in the 1-3g range. Flash bags also normally depend on using good flash powder, not the MgAl based stuff you've been using.
psyco_1322 Posted September 7, 2013 Posted September 7, 2013 I'd bet that even a gram of good flash would have the shell bursting pretty wild. You could simple dump it into the burst, and let it migrate around inside the shell. Making actual flash bags in this size would be tedious and more work than it's worth. Usually flash bags are only seen with spider type shells, most everything else (larger shells) will use a cannule with 2Fa. You could try a cannule, I've used them in smaller shells. I'd try about a 1/2" one, fill it with your MCRH, maybe dust them with some flash. Fill the stars in around the cannule, and use some fine granulated bp between the stars. This is building like cylinder shells are typically made, not like the Chinese make the class C ones. With that being said, don't expect your shells to compare equally to consumer ones, they probably won't be as loud, big, or hard breaking.
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