Experimental 0.9" shell

[schroedinger]

Do you glue the fuse in or do you press the clay around it? Also are both plugs pressed in and the recess trimmed of or wet bound?

[Maxim]

Well, get ready to call me a moron, the plugs are made from PVA glue. Yes, I know it might fly in your face.

[Merlin]

I would never call you a moron. We all humans.

[schroedinger]

No worries i would never do that. I'm just currios since i started last year to go heavly into cake items.

Do you use a filler, like sawdust, with the pva? I built just press the bottom plug, fill in the stars and burst, insert a fuse and paper disc and press with a notched rammer. The void gets filled with a comp and acts as the delay element and raising effect.

[Maxim]

I used clay as a filler for 1 plug and no filler for the other one. But clay is not a good choice ( it makes the plugs heavier than if you use saw-dust ). I use this for plugs ONLY cause I can't ram stuff in the city appartment and cause I don't think that the 1.5 cm of clay-pressed plug will survive the bursting of 2 mm thick walls.

Edited April 21, 2016 by Maxim

[schroedinger]

Nothing wrong with that. Next time use sawdust as the filler, it very easy to work with and saves a lot of expensive glue.

[EyeForSky]

I am making a multi shot cake using 2in cardboard tubes as shells, what would be a good lift charge to achieve a good height before report?

[Mumbles]

That's a pretty ambitious project for asking such a basic question. You may want to take a step back and get a handle on everything before going forward. I would at the very least suggest firing some testers or dummy shells to ensure everything is working correctly before fusing up a cake and firing live items. You also should leave the salutes and reports for after you're comfortable and confident in your cakes to function correctly. They can turn a bad situation isn't a horrific one in a matter of seconds.

 

The best choice in lift charge is the same for this as it is for basically everything else. Black powder.

[Maxim]

Eye, if this your first shell attempt - don't do it. First try some shell alone. Making a good cake is a hard thing. All the mortars might ingite at once, or the cake might fall to the side. Just try some shells, that you plan for using in the cake, but be sure to run far away and make your mortar stand very firm, to avoid injuries.

About the amount of BP for the shells. I use 15% of very hot BP to shoot the small shells like 0.8". Start with 20% of BP and find your way to the height which you like!

[schroedinger]

Eye, like mumbles and maxim said, start with using normal single fire shells. If your goal are cakes you start with making skngle shots (you can use normal HDPE or fibreglass mortar for this). If they work propper, read up on fusing cakes and start by making a milk crate rack cake. Repeat until you get the firing reliable. After that move over to actual cakes.

If you want to save a lot of work i would recommend that you collect a couple of the pyromould cakes after firing and start with reloading them. This makes the cake construction really easy (but you are limited to diameters they come in). Pink visco is the right timing element for these.

[Mixer]

That was a nice little bombette Maxim. I`m currently doing a lot of work on developing them - but I use a lot less burst charge than you - 1.2g of the same chinese flash for a 19mm unit.

[Maxim]

Mixer, I like biger bursts, thats why I put so much burst in. I was scared that it might tear of the prime, but no, the prime sure is as hard as the star.

[Mixer]

Mixer, I like biger bursts, thats why I put so much burst in. I was scared that it might tear of the prime, but no, the prime sure is as hard as the star.

Yes, that`s the main reason I haven`t gone with more burst, for fear of blind stars.

I`m always curious as to what other pyro`s are using - would you mind detailing your prime and method?

[Maxim]

Sure.

Prime:

KNO3 50% KClO4 20% Charcoal airfloat ( hardwood ) 10% Sulfur 10% Phenolic resin 10% + 5% Dextrin + 5% MgAl ( 200 mesh ) + 5% Fe2O3.

Star composition:

Sr(NO3)2 or Barium nitrate 55% MgAl ( 200 mesh ) 20% PVC 12% Phenolic Resin 8% KClO4 5%.

 

This is how I make them.

First I add enough 70% alcohol into the star mix so that it would be like dough. I place it into a plastic bag for a few hours for all phenolic resin to dissolve in alcohol. After that is done I form a 5 mm thick sheet from the star dough and let it dry a bit, so that it would be comfortable to cut with a sharp knife.

If you don't let it dry a bit the dissolved phenolic resin will start to stretch and stick to the blade. If you over dry the sheet the stars would crack during cutting, because the upper layer is dry. This is how the crack looks like:

 

 

The crack devides the star into two solid, but smaller stars, not gonna spoil everything still.

 

Anyway, this is how they look like after cutting.

 

 

Now, about the way to prime them.

I put the stars into a deep backet. For priming stars from 3x3 to 6x6 mm I use 35% of prime, That's 35 g per 100 g of stars. For priming I use 50% alcohol, this allowes both Dextrin and Phenolic resin to work as binders. I sprinkle a bit of the solvent on the stars and then I shake the backet to evenly wet the stars. Then I sprinle a teaspoon of the prime mix upon the stars and shake them very hard, so that they would fly up and down in the backet. Next I sprinle some more solvent and then the mix again and ect. Until all the prime is on them. After I rolled all the prime on them I shake the backet for 10 min to make all the prime " well-rolled " on the stars, I also like to sprinkle some BP+5% Dextrin on the stars to be sure that the prime will ignite. I roll the BP+5% Dex without adding any solvent. It also helps the stars to be not super smooth on the outside. This is not actually needed when you are using hot bursts like Chinese flash or Slow flash ( the green 1.75" cans in the previos video contained stars without BP+5% Dex ). But just to be sure.

This is how they look in the end.

 

Also got the photo of the tubes like the one that I used for this shell.

 

[Mixer]

That was a great post Maxim.

Thank you for taking the time to put it together - much appreciated

[braddsn]

Excellent shell Maxim!! Very impressive, powerful, and great color! Keep up the good work friend!

[MeowMix]

What's the comp for chinese flash?

[Maxim]

KClO4 - 40%

MgAl 200 mesh - 25%

Sulpfur - 20%

Al 325 mesh bright flake - 15%

[Maxim]

Found the photoes of that 0.9":

 

 

 

 

 

 

 

 

And then I put another wad and filled the PVA plug,

[pyrokid]

Maxim, thank you for the pictures! Is that plug a mixture of PVA and sawdust?

[lloyd]

Man! Apparently, the ONLY thing that kept that plug from blowing through was the liquid glue over the top of it!

 

Did you see the GAPS at the tube walls? That plug would never have survived any serious pressure.

 

(Sorry, that's not a condemnation... just an observation!)

 

Lloyd

[Maxim]

Yeah, it's the mixture of PVA and clay, I would go for a safere clay plug, but I think it would just be blown away.

 

Lloyd, there were no unglued layers of paper, the black line which you call a gap was a pencil drawing. I often make my tubes of paper used for drawing and always it looks like it has a gap in there, but there are actually non.

[lloyd]

No... Max... no. I'm talking about the "shrinkage line" between the plug and the tube. You didn't SEE that? Really?

 

Come on, Max! You're one of the 'smart ones'. Look at the pictures again.

 

Lloyd

[ExplosiveCoek]

That why he uses the glue right.. The plug is only there to prevent the glue from falling down in the tube and holding the fuse in the center. Of course a plug like that will never be able to withstand serious pressure without the glue on top of it, then again that is not the purpose of these kind of plugs.

[Maxim]

ExplosiveGeek is correct, the glue is thick enough not no squize down through these gaps.