small crossettes with great timing and burst

[lloyd]

Usually, I'm strong on opinions, but try (try!) to quiet my desire to brag. But here, I must succumb to my more base nature.

I have had the honor of working with and for some master pyros. Recently, Evolution Pyrotechnics of Billings, MT asked me to design a mold, cavity pin geometry, and burst package for some small (3/4") crossettes. (54-cavity mold)

Theirs is the way (when I made them) that all my hundreds of thousands of crossettes worked every single time, and I believe it's the goal to strive for. Note the timing and the regular geometry of the bursts.

(and Yeah... I'm BRAGGING! <G>)

This is the result: http://www.pyrobin.com/files/Well-timed%20crossettes.mp4

Lloyd

Edited February 13, 2016 by lloyd

[Aspirina]

I cant see the video, just audio, am I the only one?

[lloyd]

I've had over a dozen people view and comment on it this evening. It's just an MP4. Not all instantiations of QuickTime will play it, but a host of other players (like VLC) play it just fine.

 

One thing... it's only 10 seconds long, so some players won't get the video portion through their codec even ready to view before the whole thing is over.

 

L

[dusty56]

From the stuff I have read from and about you, you have every reason and right to brag. But it ain't bragging if you can do it. Tell me how. Thanks

[Mumbles]

I had to download it to make it work. Whatever embedded codec or video player my browser has couldn't handle it.

 

Very impressive Lloyd.

[Fulmen]

WOW!

[lloyd]

Dusty,

Of course I cannot give out the design or formula, since both are proprietary to this client. But I can tell you in a single phrase all you need to know to make crossettes (or any fireworks) behave that uniformly --

 

"Precision in everything". It's not so much what is in those as how accurately (and repeatably) they are manufactured.

 

I know that client well enough to know that if they make a thousand or a million of them, every last one of them will perform exactly like its predecessors.

 

LLoyd

[dynomike1]

Yea Windows 7 and MP4 codec doesn't get along very well.

[Fulmen]

Stop being such a bore, Lloyd

[lloyd]

Heh! Fulmen, you were just kidding, but you hit the nail right on the head. The way to consistency, especially with small products, is the truly boring task of making sure every step is done identically every single time.

 

In a production environment, with employees doing the work (anyone but you), it's the hardest thing of all to hit that consistency level, um, consistently!

 

More than anything, it involves designing processes and documentation that make it possible for even someone who doesn't care how the product performs to do as good a job as you would do, if doing it yourself.

 

Of course I'm proud of the mold/cavity/burst designs, but if all those were perfect and the process suffered, they'd still be bad crossettes.

 

If all that physical infrastructure is good but not perfect, and if the manufacturer knows his/her job, they can be made to perform well, anyway.

 

Of course, as a designer, I like to see a confluence of both those 'rightness' conditions!

 

LLoyd

[pyrokid]

Hey Lloyd, you have more experience and expertise than me. Could you please speak on the viability of crossettes smaller than 3/4"? Is it possible to make crossettes that consistently break into 4 pieces with a round cavity, or is some variation on a cruciform shape the only way?

[lloyd]

Kid,

In all cases, from about 10mm diameter up to 50mm (or so), a square cavity works as well as a cruciform cavity, with a great deal less trouble machining the cavity formers.

 

I have an associate (who's no longer in the business - retired) who routinely made 6mm crossettes for shooting directly at an actor in a stage presentation, and who never had 1) one of them hit the actor, or 2) fail to burst properly. His used square cavities, also.

 

The presentation was a Wizard shooting his 'magic wand' at a miscreant, and the goal was to have the crossette burst in front of the bad guy -- which it did reliably. (That sort of potential liability isn't for me; no!)

 

Lloyd

[Aspirina]

I got to see the video. That is incredibly perfect

[Mike]

Loyd you got a video ofthat magic show?

[lloyd]

No, I don't. It was a show in Las Vegas. I won't say the supplier, because I don't know if he wishes that to be published.

 

But 'magic', 'Las Vegas', and 'wizard with a fire-shooting wand' might be enough clues to find one!

 

LLoyd

[Fulmen]

The way to consistency, especially with small products, is the truly boring task of making sure every step is done identically every single time

This cannot be repeated often enough. Consistency breeds consistency. A slight case of OCD really helps.

[MrB]

In all cases, from about 10mm diameter up to 50mm (or so), a square cavity works as well as a cruciform cavity, with a great deal less trouble machining the cavity formers.

 

Squares work great, but in reality, the more difficult to machine shapes used aren't dreamt up to "make it work", it's an attempt to make the crossette effect "last" longer. With a square the midsection of the split-parts is thinner and so burns out faster. For a given size you get more out of the effect with the X shapes. In fact, the smaller you can make the central cavity, the better. Sadly, we need to be able to deposit the flash, and such a volume that it will actually split the darn thing.

If someone is machining them on their own, with a lack och the "right" tools, squares, and triangles work, and are easy to machine.

Stating the obvious, perhaps, but anyways, the X shape ones are "optimized" to give a longer lasting the split. Nothing wrong with squares if you want a shorter effect.

B!

[lloyd]

Stating the obvious, perhaps, but anyways, the X shape ones are "optimized" to give a longer lasting the split. Nothing wrong with squares if you want a shorter effect.

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

 

To that, I could write volumes, but I can fairly and simply reduce those many lines to -- "Oh, fluff and nonsense!"

 

First, the difference might be 5%, if everything else were equal. That's because no matter what, that central cavity must still be a certain minimum cross-section in order to contain (and centralize) enough burst to explode well without too much light output.

 

And second, in exchange for 'cavity-to-wall thickness', you give up volume radially in the individual particles. This also often results in a FASTER BURN, because three faces (plus bottom) of each branch are burning, instead of its igniting from only one face!

 

One controls the length of burn of the branches by varying the speed of burn of the composition and the diameter of the crossette. One controls the time and distance of the rise with the thickness of composition between the face and the shot tit. It's as simple as that.

 

If someone needs to use a cruciform cavity to preserve the length of branch burn, then it tells me that the practitioner has inadequate skills at adjusting formulae to meet requirements (or it just never occurred to him/her to try). I don't wish this to sound disparaging, because I know nothing of your skills, but this whole 'pyro thing' is a multi-disciplined endeavor. Just having part of the skill set or insufficient willingness to 'try other things' won't always get you where you want to be.

 

Sorry. This isn't personal. Like I said, I know nothing of your skills, and I told ya' in advance I was "strong on opinions"!

 

It does help that I have an in-house machine shop in which we can prototype such things in order to experiment. I've made hundreds of thousands of crossettes. I've made them from all sorts of cavity shapes, including color-changers, crossettes with multiple-color branches, and crossettes where the branches again crossetted (and in one experiment, even a third time).

 

Except in a few 'special cases', cruciform molds are a waste of time, energy, and materials. They wear out much faster than simpler geometries, and they do not give the results for which they're touted to give (and most-especially, they almost never give longer-burning branches).

 

Lloyd

[MrB]

If someone needs to use a cruciform cavity to preserve the length of branch burn, then it tells me that the practitioner has inadequate skills at adjusting formulae to meet requirements (or it just never occurred to him/her to try). I don't wish this to sound disparaging, because I know nothing of your skills, but this whole 'pyro thing' is a multi-disciplined endeavor. Just having part of the skill set or insufficient willingness to 'try other things' won't always get you where you want to be.

It's simple physics. The burn will be just as much longer as the crossette is thicker. I'm the first one to admit that i wouldn't even start to be able to alter a color-formula without also ruining it, and my personal preference would be to simply switch to the next bigger size if i wanted a longer second phase. But if your already pressed for size, and you are trying to do as much as you can with what you got, even if your able to alter your formula, or simply use a different one, your still going to get slightly thicker bits when they break of, leaving you with slightly longer burns. If it's an increase in burn that is worth the invested extra processing time when making it, or the price premium it costs buying it? That is a question everyone has to answer for them self. For "everyday" fireworks, i wouldn't bother, for competition, or at least comparative work, perhaps.

 

 

Sorry. This isn't personal. Like I said, I know nothing of your skills, and I told ya' in advance I was "strong on opinions"!

Rofl, don't worry about it. Your opinion is valued. Opinions are like asses, everyone has one. Some even have a few. This is the Internet, if one gets (that) easily offended, i'm not convinced the Internet is a safe place to roam. I like you, and about the opinions... i like that you share them. Sometimes i might not agree. I this case i think we do. The x shapes are there to try and enhance the effect. If it does so to a significant degree... well, that probably depends on the maker. This maker isn't much of a chemist. i can tweak my charcoal comps, well, most the time, but colors? Nope. So if i needed a bit more, and i absolutely couldn't go up a size, would i try a X cavity over a square? Quite possibly.

B!

[Fulmen]

It's simple physics.

 

Experience trumps theory every time.

[MrB]

Experience trumps theory every time.

 

Yes, it does. I have tested it. Have you?

B!

[lloyd]

I have... (don't know about Fulmen)

 

<G>

L

[Fulmen]

I haven't (yet), but it was not clear from your post if you had either. And I've learned that sometimes "simple physics" is anything but simple.

 

I have a couple of crossette tools in the making, and I chose a cruciform insert as it seemed like the best solution at the time. And while I'm sure a square insert works just fine I still have a feeling that a cruciform is a slightly safer bet. If one is to argue from simple physics it seems likely that it would be easier to get a clean break without shattering the comet. I don't expect wear to be a major issue for my limited work, and besides I like making complicated tools.

[lloyd]

Fulmen,

It IS easier to get a uniform break with a cruciform cavity former, and that is their singular advantage.

 

Once 'dialed in', a square cavity will break with the same uniformity, but it takes a more precise balance of explosive strength to comet strength to get that just right.

 

LLoyd

[Fulmen]

Glad to hear, guess "simple physics" has some merits after all :-)