UK Pyrotechnics Society Forums: seymour - Viewing Profile - UK Pyrotechnics Society Forums

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I've heard what you're saying and similar things about the role of NC in crackle quite a lot, and I'm quite unconvinced. While I cannot say what the role of NC in crackle is, largely as an extension of the fact that we have very little information on what happens in the reaction at all, I do know that whatever NC does do, other than it's binding properties, is quite unimportant.

I have made dragon eggs with a range of formulas using Nitrocellulose, Double Base and Dextrin as binders, and know of many more binders being used successfully, Red gum, Sparky using Parlon, and so on. I have not noticed any change in performance based on binder (unless you increase the % of NC to higher levels).

For some reason almost everyone uses, or recommends the use of NC. Perhaps some people have decided it is slightly louder. I cannot deny that it is my preference too, but other than the fact that NC is a rather nice binder, the reason why I have yet to discover, though I suspect tradition is a large part of this.

What we do know about crackle, is that after ignition a primary reaction occurs that is revealed by a red or gold 'wave' which sweeps the star, shortly followed by another reaction, the explosion.

I think that the primary reaction partially burns the MgAl (or perhaps just one of the two metals in it), generating an unstable chemical that in the semi liquid phase intimately mixes with the remaining reactive metal, and once the thermal buildup is sufficient an entirely different reaction is triggered, a detonation, or an explosion powerful enough to appear to be one.

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Possibly if it's not sufficiently washed the acidity could have reacted with the MgAl, but other than that possibility I doubt it.

Of all the crackle mixes I've made, by favorite by far, Created by David Trimmel, is 37.5% each of Bismuth trioxide and Copper oxide (black), 25% MgAl, and 4% binder (usually NC, as noted previously). With 60-100 mesh Mgal (50/50) I can cut them at up to a quarter inch cube and if ignited evenly, they appear to be entirely consumed in the blast. They punch fearsome holes in corrugated cardboard, but appear to be prone to only partially explode when primed (as in Dragon flowers).

With -100 mesh my experience is that they multipop fiercely, burning quickly to form a cloud of multitudes of pops, like crackle would sound in a hollywood movie. I know though that others have succeeded in getting this formula, or variants of it to go off in a single bang using even finer MgAl, so tune-ability seems extensive.

While many published formulas have very high Bismuth or Lead oxide contents, more closely matching the conventional stoichiometric balance of all components reacting in a straightforward process, I consider them less effective than those with an "excess" of MgAl (and often CuO).

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I've heard what you're saying and similar things about the role of NC in crackle quite a lot, and I'm quite unconvinced. While I cannot say what the role of NC in crackle is, largely as an extension of the fact that we have very little information on what happens in the reaction at all, I do know that whatever NC does do, other than it's binding properties, is quite unimportant.

I have made dragon eggs with a range of formulas using Nitrocellulose, Double Base and Dextrin as binders, and know of many more binders being used successfully, Red gum, Sparky using Parlon, and so on. I have not noticed any change in performance based on binder (unless you increase the % of NC to higher levels).

For some reason almost everyone uses, or recommends the use of NC. Perhaps some people have decided it is slightly louder. I cannot deny that it is my preference too, but other than the fact that NC is a rather nice binder, the reason why I have yet to discover, though I suspect tradition is a large part of this.

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Possibly if it's not sufficiently washed the acidity could have reacted with the MgAl, but other than that possibility I doubt it.

Of all the crackle mixes I've made, by favorite by far is 37.5% each of Bismuth trioxide and Copper oxide (black), 25% MgAl, and 4% binder (usually NC, as noted previously). With 60-100 mesh Mgal (50/50) I can cut them at up to a quarter inch cube and if ignited evenly, they appear to be entirely consumed in the blast. They punch fearsome holes in corrugated cardboard, but appear to be prone to only partially explode when primed (as in Dragon flowers).

With -100 mesh my experience is that they multipop fiercely, burning q

I do have some experience with this composition, and while I've never used it as fireball lift, I can definitely see how it'd work.

With fine Zn it goes "thump" and you get a voluminous, thick smoke cloud. This is how I expect they are doing it. I used about ten micron Zinc flake for this.

With much coarser Zinc, a pile on the ground erupts in to a pretty greenish fireball on it's own. Not lift suitable.

I expect they're using it primarily as a smoke generator, since you need to use so much more material to lift it, and you get more smoke out of it per gram than BP I would hazard to guess.

The Zinc may add some effect to the flame too, but considering the dirtiness of the classic fuel fireball, I doubt it'd be anything but negligible.

I have some experience with horsetail shells which I can share. Obviously everyone has their way, and other people do it differently, but this has worked for me.

I cut the time fuse about two thirds the length I normally would for this size shell. This is because I want to shell to burst BEFORE apogee, to give it the... well "horse tail" form.

The timefuse is then sealed to the shell using the normal strong and glue method.

I load the shells hemmies COMPLETELY with stars. Obviously the stars used depend on the effect desired, but as a point of reference, the shell in the video I'll show used brocade stars sized for a 6" Brocade Crown. Formula was SIMILAR to Slow Gold.

In a 4" shell I add ten grams of "grater grain" - BP granulated similar to the screen method, but using a kitchen grater instead. This just sits between the stars. It's not much, but not much is needed.

After closing, I paste the shell minimally. Two or three layers, depending on the paper, sounds about right. In fact, so long as the timefuse-hemisphere join is well sealed by the glued string, you only need a strip around the equator, as long as your hemispheres are the ordinary chinese chipboard or stronger.

All the construction of the case of this shell is purely to make sure the shell withstands lift. Strength does not need to be nearly as high as it does when your burst symmetry and size is affected by it, so sealing the shell from leaks that can cause a premature explosion are by far your primary concern.

Finally, I over lift it.

Instead of playing with inert weights, and fancy pasting, I fill her right up (I'm not keen on shells having anything inert in them unless it's really necessary). The form of the effect is created utilizing the fact that as the shell is weakly burst at significant speed, the momentum of the contents is the most significant factor in determining the trajectory.

Angling the mortars and firing salvos looks fantastic, as anyone who's seen this effect can confirm I'm sure.



Skip to 26 secs.

This was lifted with 100g of relatively low quality BP.

I like to have a paint tin of wood cooking in the fire at home at much as possible. While a paint tin of a size that fits in the domestic fire only has enough volume to make a few hundred grams, doing it daily adds up! I now estimate that I've got charcoal for a few hundred kilos of BP

What wood are you cooking up there Vic?