Comparing bursts for small shells

[PhoenixRising]

Wanted to do a little test comparing different boosters that I was interested in for bursting small shells. Here's the first 3:

 

5-3-2

 

KNO₃ - 5 parts

S - 3 parts

Al - 2 parts

 

3-3-4

 

KNO₃ - 3 parts

KClO₄ - 3 parts

Al - 4 parts

 

Chinese burst

 

KClO₄ - 40

S - 20

Mg/Al - 25 (200 mesh)

Al - 15 (325)

 

 

For both the '5-3-2' and '3-3-4', Eckart 5413 was used and the Nitrate was only blade milled.

 

For Chinese burst, Mg/Al used was 80-200 mesh and Al was Eckart 120 (200-325)

 

These were used as boosters in small 1.4" canisters. The outer measurements were 1.4" diameter and 3" long. From what I understand this is not optimal, as you do not a canister to be much longer than it is wide. IMO this is immaterial for this test as we are only comparing bursts, not shell design.

 

Each canister was filled with:

10 grams BP

5 grams Burst powder

35 grams stars

7 grams lift

3 gram spolette

 

These were essentially bulk-filled except for around the spolette where some symmetry is inevitable in the design. The burst powder was mixed with the diaper method, and then the BP was added and diapered with it. The process of making all 3 canisters was followed to as close as possible, resulting in 3 shells within 1 gram of each other. The Chinese burst shell weighed 1 gram less than the other 2 after adding stars, which IMO is almost inevitable using a bulk fill method.

 

Main body is made from 3 turns of 60#, then 8 strands of spiking, then 1 more turn of 60#, then 1 turn of 20# computer paper.

 

 

Titanium was added to each spolette for easy tracking. BP used was a slow ERC that I made; I messed up and got ash in my charcoal but I still decided to use it. Result was a much longer spolette time, almost double the norm. Lift (and burst) powder was douglas fir with 1% dextrin. The first mortar was destroyed but luckily I brought a backup for the last 2 shots. That's what happens when you use a salvaged spiral tube for over a dozen shots. I love masking tape.

 

 

The video for the 5-3-2 canister was taken from a different camera as my normal one failed for that shot. Sorry about the obnoxiously loud wildlife.

 

My personal thoughts here are that the 5-3-2 should be milled first (the Al being left out of course) and also I used slightly coarser metals than suggested for the Chinese Burst, resulting in a slightly slower reaction.

 

It should be noted that more confinement will have resulted in better results for the 5-3-2 and the Chinese Burst, but the point of this test was only comparing the power of each, not necessarily to get the best results from each.

 

Also, the 3-3-4 can be adjusted a number of ways to dial in what you want, let alone just simply using less of it. For instance, going 2-4-4 (2 KClO₄, 4 KNO₃, 4 Al) would give you almost all the oxygen with a little less speed. Getting the biggest burst isn't always the goal, so I do realize you should tune each burst according to the effect. I hope to be doing some more testing soon. Any input is welcome!

Edited June 4, 2016 by PhoenixRising

[Maxim]

Weren't you afraid of pressing a Ti-containing spollet?

[lloyd]

????

Max... we press Ti-containing spolettes and gerbs all the time! In fact, Ti-gerbs are one of our most popular commercial products!

 

"Pressing" is not dangerous with BP containing metals. "Ramming" is, perhaps, but not pressing.

 

LLoyd

[OldMarine]

I've hand rammed plenty of 3 lb gerbs using spherical titanium after using plain BP to above the nubbin of a spindle.

[lloyd]

Patrick, note carefully that I said, "perhaps". A few ignitions HAVE occurred during ramming. Virtually none have during pressing, if the tools didn't scrub on each-other.

 

Lloyd

[BlueComet24]

I would be interested in seeing 70/30 compared against the others. I'm pretty sure it'll outdo them by a fair amount. I've also heard that dusting the BP in 5% Eckart 5413 gives a good boost.

 

Is ramming metals ever safe? I've heard some mixed things about it, so I just don't. However, I'd like to make some N1 Glitter comets with a wood and PVC pump, and I'd like to know if ramming dampened N1 (made with Alcoa 120) would be safe.

[OldMarine]

I go by what I've read from Ned's article on Skylighter and Fireworking.com. His thinking is that the spherical shape minimizes possible friction or pinch. He's also emphatic that sponge type metals should never be hand rammed.

I wear my face shield and a welding glove on my holder hands just in case!

I would think a dampened material would be unlikely to spark or to ignite if it somehow did. Try to light the damp comp and see!

Edited June 4, 2016 by OldMarine

[OldMarine]

I don't like pushing the envelope but I love to ponder what lies beyond!

[PhoenixRising]

I only hand press the spolette and work with only as much composition as I need at the time. The biggest pile of comp was when loading the canisters.

 

Not sure that I'll try 7/3 as I've already had the 3-3-4 smash a bunch of willow stars. Not only that, you will have trouble getting enough of it to go around evenly and spread the force out, possibly resulting in a blowout of one side. The goal in bursts, IMO, is to break the shell to allow for the BP to do its job. In small shells, however, BP by nature is not going to do as well in smaller spaces and amounts, making the booster a more important factor. I do believe people use 7/3 in a bag sometimes, but again, not sure how I'd fit one inside of this tiny little canister. Would be neat to try though and I may do it, I love working with things on a small precise scale.

For the record, the total comp in each of these was right at 60 grams, making them "consumer legal!" MAXIMUM LOAD... 500g bla bla Hey buy this 1.75" inside a 3" casing for $70 bla bla bla.

[OldMarine]

What is the sfera burst I keep reading about? Is that a mixture or an employment method?

[lloyd]

"I would think a dampened material would be unlikely to spark or to ignite if it somehow did"

--------------

I don't believe that's the case. I DO believe that dampened comp would be less explosive, and thus less harmful to the practitioner... but not much if any less liable to actually ignite.

 

I've seen a lot of impact-induced ignitions. Not fun, really...

 

LLoyd

Sfera is an effect.

 

Lloyd

[OldMarine]

Thanks Lloyd for saving my limbs and eyes! Don't know if I don't ask.

[lloyd]

Patrick,

Whatever bad I've had, you're welcome to know. I could hide my accidents (I guess) and pretend I'm 'better' at it than all that (and a bag of chips), but the truth is that everyone does bone-headed things, and learns from them -- or dies because of them.

 

I'd rather, If I survived a mistake, to help you avoid that same mistake.

 

LLoyd

[OldMarine]

What you said! I blasted a rock as big as a truck onto a truck. I made damned sure the other guys learned from it. It could've just as easily landed on someone rather than a vehicle. That's why I'm not scared or ashamed to ask questions or pose scenarios. How else will I learn other than flattening another truck or worse?

[Mike]

What is the sfera burst I keep reading about? Is that a mixture or an employment method?

Thats a method of building a cylinder shell.

It is close to the spiderweb shell, but gives a better pattern a d shout be used for this effect at 6" and bigger (where spiderweb isn't recommended, but for smaller sizes it is fine too).

Start with a flash bag tied to your spolette.

Pump your stars out of an easy ignited comp, like c6, c8, spiderweb and stack 'em around the perimeter. The central cavity is filled with polverone. The voids beetween the wall and your stars are filled by your favorite method (sawdust, polverone, tubes). Then spike and paste like a regular shell.

The flash bag contains a quite big ammount of flash and thus provides the break power. Ammounts are written down in fulcanelli.

[OldMarine]

Thanks Mike, I kept seeing it referenced but never explained. I reckon the fact it's mentioned in Fulcanelli would be why it's taken as a granted as far as the definition.

[Maxim]

Funny, Sfera is just what the word sphere sound in russian!

[lloyd]

And for good reason, Max! <G>

LLoyd

[OldMarine]

Thanks for suddenly being cryptic..or should I say cyrillic there Lloyd.

[lloyd]

Heh! I love it, Patrick! You are one of the few people I've ever met who actually understand language! (and I LOVE language!)

 

In this case... it's Maltese. Sfera means exactly what it imports... "spherical".

 

Lloyd

[OldMarine]

Thanks for explaining and laughing. Both are good things.

Especially since you've figured by now that I am The Inquisitor!

Edited June 5, 2016 by OldMarine

[OldMarine]

[Guest]

Hi Gang. I'm a somewhat experienced noob.

I don't necessarily follow convention in everything I do, but I usually follow principles.

I've been making varied canisters using prefab #4 tubes with good success.

 

My other shell I'm making rather unconventionally, but successfully using reinforced packing tape, cardboard, hot glue, and in some applications a little earth. The shell comes out at 2"diameter and 2.8" tall, and they usually weigh about 100 to 130 grams.

I've had great luck using tiger tail stars with various burst charges, or just use them as a hefty salute.

 

I've been experimenting using #2 tubes as inserts with varying internal components.

 

I can fit 5 of them in one of my cases, leaving a fillable core that a 5/16 x1/2 spolette tube fits in perfectly.

 

My issue is that of my break for these inserts.

 

I either get a wimpy break, and the inserts pretty much just fall and ignite, or the burst sets off or destroys the inserts.

 

I recently read in Fulcanelli using 70/30 mixed with sawdust at either a 3:1 or 4:1 ratio.

 

Has anyone here tried this method for a canister shell break?

 

(sorry if I'm kinda hijacking this thread, while at least staying on topic, but apparently I can't posy my own thread yet, only replies)

[Richtee]

You may now post your own thread.

 

Tried the BP coated rice hulls? I know..it’s a PITA, but they fall between a BP break and a flash break. Slow (nitrate) flash might also be an option.

 

Never head of the sawdust thing. Might be worth a shot... heh...

 

BBQ Joe eh? we could prolly trade some stories

[Guest]

You may now post your own thread.

 

Tried the BP coated rice hulls? I know..it’s a PITA, but they fall between a BP break and a flash break. Slow (nitrate) flash might also be an option.

 

Never head of the sawdust thing. Might be worth a shot... heh...

 

BBQ Joe eh? we could prolly trade some stories

We probably could. I owned a bbq joint for almost 10 years.

Maybe sometime I could tell you the story about the guy from Texas who’d never seen a smoke ring before.

He thought his smoked brisket was raw on the outside.

 

I haven’t tried the rice hulls yet, but I’ve tried my lift powder, 70/30, mill dust, pulverone, fine bp, and an potassium nitrate burst/flash that I can’t locate the source of again, but it was 50/30/20 kno3, charcoal, sulfur.

I’ve also tried many combinations of the above, getting real close, but still missing the mark.

 

I might just try the 70/30 sawdust tonight and see.