Cavity pump and stars, how make ?

[Jordan123]

Hi guys,

 

I have see lot of cavity bombs and i find this beautifull, so i have buy a cavity pump..

But i will know how make this stars, i pump the star and after ?

 

And i know we can make a various effect with this, can you know me about this ?

 

If you have any pictures or movie please add in the topic

[nater]

Cavity bomb?

 

Cavity comets are intended to be long lasting color changing effects. Traditionally they are first pressed with a charcoal comp and filled with a bright white or color. According to one experienced pyro, a dim charcoal to bright "luce forte" would be most traditional.

 

To make this effect, the cavity comet is pressed and dried. Once completely dried, the cavity is filled with a color comp by buttering the comp in to the cavity. It should be moist like you were going to cut it. The comet is again allowed to dry. Once dry, the sides are pasted with a band of kraft and the color end is closed with a triangle fold.

 

We just got a run , more posted later

[Jordan123]

Ok thank's, but which side must be wrapped ? the side with the hole or the another side .?

 

The cavity stars can make an effect "changing direction of the stars" (not line drawn) ?

[Mumbles]

Can you maybe find some videos of what you're talking about? It's not entirely clear what you mean. It's probably a language barrier. When wrapping them, the sides of the comet, as well as the end with the hole in it are covered with paper. Only the flat end is left exposed.

 

It sounds like you're talking about wanting to make crossettes. Crossettes and cavity comets are two different things, and require two different tools to make. You might also be talking about go-getters, which are yet again a different device entirely.

[pyroman2498]

You could just buy one cheap from my friend at FireworkTools.com, He is also super nice and very helpful And He also has VERY high quality tooling. He Ships world wide , and his shipping is really reasonable.

Hope you take a look at least.

 

If you have any questions message me or him, His Account name on here is Californiapyro

 

Thanks,

 

Steven

[nater]

Now that I am off work, I'm expanding from my first reply.

 

First, pump the stars with the cavity pump. In this case, the comp is D1 Glitter and I was using the 1/2" pump from Californiapyro. For timing and stacking the comets in the shell, it is very important that length of each comet is identical. If you order from Californiapyro, get the option with the pin. It makes sizing much easier. Use the cavity pump like any star pump, plunging into dampened comp, pressing the comet, using the pin as a gauge to shave the excess off and extracting the completed comet onto your drying surface. Allow the comet to fully dry.

 

 

Next comes time to fill the comet. My favorite combination is blue and gold, so I mixed up Hardt #6 blue and dampened the comp with enough water it feels like clay, just as if you were cutting stars. To fill the cavity, just scrape some of the dampened comp into the cavity like you are spreading butter on a roll. Fill the cavity, scrape off the excess back into the bowl and work on the next comet.

 

 

Allow it to dry again. Remember the color comp is fairly wet, so give it plenty of time to fully dry. Next comes the tedious part, pasting each comet. Prepare strips of kraft long enough to wrap around the star 3 times and wide enough to make a triangle fold over one end. Paste the strips of kraft, folding the ends down around end that is filled as you go. (Note I did not do this in the picture, and the build up of paper causes those pointy ends. They'll look nicer and stack better if you fold the end down as you go.) Also, try keep the paste wrap the same distance from the solid end of the comet. If you leave 1/8" of space before the pasted band on the first comet, make the rest identical. The timing will be better. Now let the pasted comets dry. Prime the exposed end. D1 does not need much if any prime, I just brushed some NC lacquer on the end and pressed it into some fine BP and set aside to dry.

 

 

Finally, build your cylinder shell as you normally would with stacked comets. For bonus points, stick it on a rocket.

 

 

Here is the shell. Blues are harder to film and the effect does not show up well. I was trying to prove the concept to myself and need to dial these in. The effect should be the glitter tail slowly transitioning to blue tips. This shell was on the last rocket, I used too much delay on this batch of motors. Some larger comets have demonstrated the effect better, but I'm not ready to show any more just yet.

 

http://www.youtube.com/watch?v=VKrzsIMGBFI

 

The nozzle eroded on this one, so don't pick on me too much for the round trip. The stars looked nice though.

 

http://www.youtube.com/watch?v=SrPSW8dOoxs

Edited August 4, 2013 by nater

[dangerousamateur]

 

 

 

Once you have acieved this - cant you just put the star back in the pump and just add another few mm of the outside composition to close it?

Then you wont have to do the paper work around.

[Jordan123]

Can you maybe find some videos of what you're talking about? It's not entirely clear what you mean. It's probably a language barrier. When wrapping them, the sides of the comet, as well as the end with the hole in it are covered with paper. Only the flat end is left exposed.

 

It sounds like you're talking about wanting to make crossettes. Crossettes and cavity comets are two different things, and require two different tools to make. You might also be talking about go-getters, which are yet again a different device entirely.

 

Thank you for the wrapping helping, no i speak cavity stars, i know make crossettes, is not problem.

But i have ever seen a movie of cavity stars and the stars changes direction Instead of a normaly line of the stars in the sky

I'm sorry for my english...

 

You could just buy one cheap from my friend at FireworkTools.com, He is also super nice and very helpful And He also has VERY high quality tooling. He Ships world wide , and his shipping is really reasonable.

Hope you take a look at least.

 

If you have any questions message me or him, His Account name on here is Californiapyro

 

Thanks,

 

Steven

 

Hi, my cavity tools, comet pump and time fuse cutter is from firework tools he make very good tools, and he has ake for me a BP puck press !

 

 

 

nater, thank you for this pictures, movie and nice tutorial, i go make my cavity stars now !

[nater]

If you are wanting to make stars that change direction, cavity stars won't be what you are after. Cavity stars are a way to make pumped color changing stars. I suppose it is possible for cavity stars jet and change direction, but that is not their intended effect.

 

Stars that move around use different techniques. Go getters are a common way but there are others too.

[Mumbles]

You'll have to wrap each comet, even if you did "cap" the color section.

 

Very strong burning color compositions might have some propulsion, and might give a swimming effect. Using some of the high magnalium content compositions or parlon bound stars might be worth a shot.

[Jordan123]

If you are wanting to make stars that change direction, cavity stars won't be what you are after. Cavity stars are a way to make pumped color changing stars. I suppose it is possible for cavity stars jet and change direction, but that is not their intended effect.

 

Stars that move around use different techniques. Go getters are a common way but there are others too.

 

Okay, beacause, in a movie i've watch stars changing direction and the title of the movie is "cavity stars" but i have not recover the movie...

 

 

Very strong burning color compositions might have some propulsion, and might give a swimming effect. Using some of the high magnalium content compositions or parlon bound stars might be worth a shot.

 

Sorry, i've not understand, you will say if i find a composition with strong burning i can make the effect "changing direction" ?

[Mumbles]

What I mean is that if you have a composition that burns very fast, you might be able to get the stars to change direction or move some. I can't really say how much though. The effect is normally called "swimming" and is usually undesirable. It comes from fast burning compositions not being lit all the way around. When they only light on one side, they self-propel.

[Jordan123]

What I mean is that if you have a composition that burns very fast, you might be able to get the stars to change direction or move some. I can't really say how much though. The effect is normally called "swimming" and is usually undesirable. It comes from fast burning compositions not being lit all the way around. When they only light on one side, they self-propel.

 

Ok, and you can help me for make the 'swimming' effect ?

[schroedinger]

One different question, if you would not cap the Cavity star, and use something like TT in the cavity, would that give e.g. a bright colored star, with leaves a nice tail of sparks, like diadem stars?

[nater]

According to Mike Swisher, if you do not paste the star in hopes of creating a tailed color star, the cavity tends to fall out and spoil the effect. I have not tried this myself, I have only been experimenting with them the traditional way.

[Jordan123]

SOrry nater i not understand, i'm french and i have bad english ...