bottom shot ?

[mudmanc5]

Im constructing an 8" plastic hemi and would like to have a 4" plastic hemi fused though the top as a bottom shot. My question is how safe is it to put 100 + grams of 70/30 in a plastic hemi or should I throw in 10 grams of rice hulls and

roll it down my drive way a few times to mix ? This amount of flash scares the shit out of me. Also Perc with cab should I add for the amount of cab in the perc or just mix 70/30 . If I diaper the flash should I go with 100G at once or 10 /20G increments that I am more comfortable with mixing ?

[Miech]

Good to see such an amount scares the crap out of you. It tells me you know what you're dealing with.

 

If I had to make such an amount, I would make it in small batches I think. I limit myself to 20 grams per batch, which I consider a large amount. By working in batches you reduce your injury in case of an accident from being death to severe injury but still alive.

 

I would recommend to use cardboard tubes for salutes and bottom shots however. That might be because I like stuff the traditional way, but I think it is safer too in terms of static electricity building up.

 

When using dark or black flake aluminium adding Cab-O-Sil isn't needed when making 70/30. The aluminium will act as a 'fluffysizer', so adding another thing making it fluffy isn't really needed.

[Mumbles]

It sounds more like the cab-o-sil is as an anti-cake agent in the perc, which I feel IS needed. You don't want clumpy perc when you're trying to diaper it all together, or mix it inside of a shell. It tends to be as a very small amount, so you don't need to take it into account. Flash isn't very sensitive to ratios, +/- 10% is good enough. I would also tend to stay away from plastic for static reasons. I use no plastic, and no sparking metals with flash.

 

There are two schools of thought on the mixing amount. Mixing is by far the most dangerous part. One is to limit the total quantity while mixing to minimize damage in the event of an accident. The other is to limit the time you spend mixing. IE make one bigger batch. I tend to go with the latter. With bigger bottom shots, I'd feel much safter mixing one batch that would kill me if it went off, than I would mixing 15 smaller batches that would only maim me.

 

Now, I hate to burst your bubble, but 100g is not nearly enough. 100g is more appropriate for a 3" shell. You'd be looking more on the order of 300-400g for a 4" ball shell. Having that much empty space around 100g of flash just seems like an accident waiting to happen to me. No amount of filler or fluff would make 100g safe in a 4" ball shell in my opinion.

[tentacles]

I agree with mumbles here, make one larger batch and dole it out to your devices, don't make a bunch of small ones. If you're making a number of devices that take flash, have all the parts ready first, then mix the flash and assemble quickly, get the stuff contained and I suggest wrapping in foil if you're in a dry climate. Don't even think about making flash in the winter if you don't properly prepare your work area first - bare minimum a can of static guard and spray EVERYTHING. I'd recommend boiling some water in your work area to bring the humidity up if it's feasable... just be sure to turn off the heating element or burner before you begin.

 

100g will easily fit in a 3" shell - if 100g is your target, save the 4" hemi and use a 3. The easiest way to fit loose comp like flash into a plastic shell is to put the comp in a plastic baggie and stick that in the shell.. Just be sure to nose your timefuse with good blackmatch or a bit of BP prime.

[mudmanc5]

All safety precautions will be adhered to !!! The static and the plastic thing were My main concerns but is it safer to diaper or mix in hemi with rice hulls or other wise as bulking/mixing agent ?

[tentacles]

When binary mixing you don't actually need anything else in there, though if you're going to store it a long time (better not without a magazine!) I'd suggest a bulking agent to keep it from packing down. I don't think the plastic hemi would be a problem either - salutes are commonly shipped and used in plastic hemis and there don't seem to be many accidents, certainly not ones derived from the shell itself. Diapering, or binary mixing in the shell, depends on how much vitamin F you want to put in there. If you want a full shell, then diapering is required as it won't mix in the shell without some airspace.

[mudmanc5]

So binary mixing would be the safest way ? Say 75g of 70/30 and about 10g of rice hulls in tissue paper in 3" plastic Hemi

[tentacles]

If you're going to mix binary, you can't put something like tissue paper in the shell, that would possibly prevent the components from mixing, giving at the least, a potentially subpar product.. Just put the aluminum in one hemi, the screened perc in the other, and put em together.. If you don't have the trick of doing it quickly without spilling, then put a piece of saran wrap or waxed paper/parchment over one half, and pull it out when the hemis are together. I suppose you could use regular paper too but waxed paper would carry less off with it.

[Mumbles]

I'd still worry that 75g would again be too little. I know you want to play it safe, but underfilled is more dangerous than it seems. I do wish you'd look toward a paper product. Anything plastic scares me with regard to flash. I also hope you have a healthy supply of static-guard.

[tentacles]

Can you give details on how you plan to attach the bottom shot (or is it an insert?) to the 8" shell? I'd think that putting it on the outside of the shell might end you up with a big boom and lots of shattered stars. Plastic hemis are fairly forgiving but that's asking a lot to survive the brunt of an 8 bursting in it's face. Have you considered just rolling up a paper bottom shot? Roll up a tube, or get a piece of carpet tube or similar, and just make a small canister shell to attach. Just fuse it seperately from the 8, and attach to the top with rope or pasting in, whatever.

 

edit: having re-read the OP, I agree with mumbles here, 75g is NOT enough for a bottom shot for an 8, unless you're dropping it on the crowd. I'd say proper bottom shots for 8's start at 400g...

Edited December 31, 2008 by tentacles

[mudmanc5]

Time fused threw the top of a 6" hemi change of plans on the size glued and pasted 3" hemi to the top

[Mumbles]

If I understand this, the fuse from the 3" will protrude into the interior of the 6". Thus making it look kind of like a snowman?

 

something like the biggest and smallest circles here, on on top of the other:

http://www.mfdabbs.pwp.blueyonder.co.uk/Ma...fs/Script14.gif

 

If so, it's an interesting idea. Make sure to reinforce that joint with a lot of glue/paper/string, and let us know how it works. It doesn't carry all the functional purposes as in a canister shell, but it sure would be interesting. I know there have been a few ball shells I've dreamed up that would look great with a bottom shot.

[asilentbob]

On the anti-cake note:

A very small amount of fine dark flake aluminum will act as an anti-cake agent. A guy I know who builds very large ground salutes for use at PGI recommended this to me. Measure out how much of each chemical your going to need, then screen the oxidizer(s) alone, then re-screen it/them adding in a small fraction of the aluminum powder... Not enough to make a mix that would burn appreciably but enough to take advantage of the aluminums anti-cake effect... Then mix the rest via diapering or in the shell.

 

I couldn't give you a ratio.

[Mumbles]

I've heard that too. Something on the order of 2% was recomended to me. I don't know if that was 2% by mass of the perchlorate, or 2 parts out of the 30 parts of the Al used. Eh, probably doesn't matter. It's 2% by total mass vs 3% by total mass. Either way it's not exploding. Said person did so and screened it well together before diapering.

[mormanman]

Reading this kind of makes me worry now. I remember reading about how salute shells are made and how they use fillers but I made a 3 inch for the 1st of Jan with a 2 in can bottom shot. I think it will work and I know I didn't use 100 grams of flash. I used maybe twenty of flash some saw dust and some Ti powder for the effect.

If it doesn't work so be it but if it does then it shows that a little flash can go a long way. I would use a wood shaving filler but thats just me.

Good luck.

[Richtee]

Reading this kind of makes me worry now. I remember reading about how salute shells are made and how they use fillers but I made a 3 inch for the 1st of Jan with a 2 in can bottom shot. I think it will work and I know I didn't use 100 grams of flash. I used maybe twenty of flash some saw dust and some Ti powder for the effect.

If it doesn't work so be it but if it does then it shows that a little flash can go a long way. I would use a wood shaving filler but thats just me.

Good luck.

 

I'm sure yer fine... get a vid if ya can. But as I said in another thread..I think I'm just gonna enjoy my small setup :{)

[Mumbles]

Reading this kind of makes me worry now. I remember reading about how salute shells are made and how they use fillers but I made a 3 inch for the 1st of Jan with a 2 in can bottom shot. I think it will work and I know I didn't use 100 grams of flash. I used maybe twenty of flash some saw dust and some Ti powder for the effect.

If it doesn't work so be it but if it does then it shows that a little flash can go a long way. I would use a wood shaving filler but thats just me.

Good luck.

 

What we meant is that a 3" shell full will hold around 100g. A full 3" ball I think is around 125g I think. I've heard something similar for canisters actually. A 2" canister will obviously hold much less. I've used 15g in them before, and they worked fine out of mines. Lots of spiking and pasting, and a heavy walled tube I do believe though.

[psyco_1322]

I think some are misunderstanding what Mumbles was saying about under filled salutes. I think he was trying to state that a salute that has a large airspace is quite prone to being ruptured open. It would need to be full to have structural integrity. If I perceived this wrong myself, correct me.

 

I managed to get 130g of CuO/Al, thermite/flash/whatever you want to call it, in a 3" ball shell. It was plastic with both hemis quite full, about the max amount that would fit.

 

Snow man shell FTW !

Edited January 1, 2009 by psyco_1322

[mormanman]

I'm sorry I do this a lot I know but I meant that the my salute shell is the three inch on top.

[Richtee]

Snow man shell FTW !

 

Heh cute! I would think you have to lift the fug outta that to get a good height given the drag on that shape eh? Or?

[Swede]

using 1 or 2% Al as an anti-cake makes sense in the Perc, and does not create a dangerous mix. I do something similar when handling airfloat for BP, except instead of anti-cake, it's an anti-float substance... a small % of Sulfur goes a long way towards keeping the charcoal from floating.

 

Now we're "floating" off topic - sorry - but I do like the idea of compatible chemicals making their handling characteristics better.

[psyco_1322]

I later came back and pasted over the entire shell. It was lifted with 1/12th? of 2fg or 3fg Goex? Cant remember. From the distance I seen it at, it looked like it got planty high. The top break failed to light. The other two looked pretty lame from how far away I was.