Jellyfish Shell

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This is the shell built in the tutorial.

Shell casing

Casing

WORK IN PROGRESS. I HAVE TO GO AND MELT METALS NOW (mmmmmmm MgAl).

This article should give readers a good understanding of how to make ball shells which burst in patterns. As an example, I will be describing the manufacture of a Jellyfish shape shell, using plenty of pictures to aid in explaining how it works. Since a 6" jellyfish pattern shell is hardly a beginners project, this tutorial will not be written for the complete beginner. However I hope that it can be informative even for those with no experience in manufacturing fireworks. Compositions used

Since this tutorial is based on describing the unique aspects of the shell, namely the pattern production, I do not consider the compositions used to be of any great importance. I will however list them, and make sure that they are all added to the composition database, so that if anyone wants to check they can. It could be helpful to many to see videos of compositions in action, even if they are only on video where they do not look quite like they do in reality.

Rising tail: The rising tail was made by attaching three 20mm pumped tigertail stars (though here they are being comets. Stars/comets, at this size, both)and one 20mm pumped Pakeha Aqua star.

The 'head' of the jellyfish (the bit with colour) was made with rolled stars. The cores were Pakeha Pink, with Emerald Green (MgAl) rolled over the top.

The 'tentacles' were made with 20mm Tigertail comets, and some Pakeha Brocade using pretty large titanium particles. There was also a rather ordinary D1 pistil for that we bit of glittering in the centre.

Burst charge
The bust charge, like most aspects of the shell are not strictly important. To get this effect you must be able to burst a round shell and get a sphere. Whatever methods you use, if it bursts in to a good, symmetrical ball, all it takes is a slight rearrangement of the contents to get it to burst in, well, almost any shape you want. I will however be ding it my way, which seemed to work fairly well. Just be aware that other methods work too.

I burst this shell with meal coated rice crispies (the breakfast cereal) and a 2g 70% Potassium perchlorate, 30% Dark flake Aluminium flash booster.

I often burst my shells harder than this, but I decided to be conservatively careful on this one, to try and resist my normal urge to over do things, which often results in things going wrong. Blind stars for example.

Time fuse
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Glue
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Other
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Shell Construction

The first two construction pictures show the timefuse and passfire set-up that I have here. The tubes filled with black match are used to transfer fire from the timefuse to a central location in the shell, so the fire spreads uniformly out towards the stars as the burst burns. This can improve the burst symmetry noticeably. It is a number of simple processed such as this that can make all the difference between reliably performing, good shells and ones that do not quite fit that description.

The second image shows the tape covering the ends of the timefuses (there are two for reliability) to protect the powder core from getting wet during pasting and causing problems later on. The paste soaked twine wrapped around the base of the timefuse plays two roles. Once dry this will bond quite will to the timefuse and resist it being blown through, and it also forms a perfect seal around this join, which is probably the location of most casing failures that cause mussel bursts and other 'unintended starmines'.

I have fairly neatly lined the bottom of the hemisphere with coloured stars, and have meal coated rice crispies (Pyro cocopops) on a sheet of tissue.

The tissue containing the busts is placed on top of the stars as shown. Having the tissue layer seperating the burst from the stars is an important step for getting a good shape from your stars, since it prevents the burst and stars mixing, and with your shell packed tightly with contents, nothing should move at all. The tissue layer does not affect the transfer of fire, which gets through it with ease.

Star Construction

You can now add more burst in to the tissue, and place more stars around it. The 'bag of burst' helps prevent the stars from falling down in to the shell when you are adding ones on the steep edge of the hemisphere.

Hemisphere loaded! It is probably not at all neccisary to cut away the excess tissue, but it looks pretty!

Here is a trick I use to make it much easier to put the hemispheres together without things leaking out. Even if you manage to get the hemispheres together without the entire contents going on the floor, a good shell is slightly over-filled and needs to be compressed shut to lock the contents tightly in to place. So in between the time you put the hemispheres together and the time that you have forced them shut, the contents can shift out of place, or even fall out of the gap if it is too wide. So I cap it with tissue.

Burst Charge

First some paste is applied around the edge of the hemisphere, and then the sheet of tissue is applied, pulled tight, and folded down on to the glue to secure it.

Here are the tentacles, made up of pumped tigertail and rolled brocade. To help fill this hemisphere (the one with timefuses) I use a round container to place it in, since the timefuses prevent you from placing it on a flat surface without it falling over.

Those were all the stars for this hemisphere. Now two holes are poked in some tissue for the passfires to fit through, and the hemisphere is filled with burst. Don't forget to over fill slightly so you can lock the contents together later.

The white ball is the 2g flash wrapped in tissue and placed in the centre of the shell.

The hemispheres are now loaded and tissue capped. It is time to 'mate them'.

See how they are over filled?

The Author inspects the timefuse before using the wooden stick to tap the shell while pushing the hemispheres together. This is an effective way of settling the contents in to a denser arrangement, and compressing everything. Once this is done, you should be able to shake the shell without it rattling. No stars should come loose.

After tapping, they are mated.

Pasting starts. I will not cover 'how to paste shells' in this article, but you will see that I do it with wide strips of paper soaked in wheat paste until they are soft and pliable. This shell was fairly well pasted, even though I used low-grade recycled kraft (rubbish bags).

Fortunately a jellyfish is a shape that looks fine from any angle so long as you rotate it along the line of symmetry. This means that all you need to do to get it to burst the right way up, every time, is to add a 'tail' to make sure that it flies with the head facing the sky and the tentacles facing the ground, and make sure that you burst it while it still has some speed, since this tail only works while it is moving. I used a hemp cord pasted on well, to secure it, and make it stiff.

I'm using low grade lift here. It was not ball milled all that much, and as you see, it is granulated to form any size granules, big and small. I borrow a trick from the Maltese to get low quality BP working very well indeed, even if admittedly, 100g was more than enough to send this shell up.

The lift is spiked like a canister shell to give it plenty of confinement.

And pasted.

The shell is complete. The comets are under the paper cap, where the timefuses are also. It is unusual to top-fuse ball shells I know, but I slit the QM there so the fire will light them all, and decided to put all the things that needed to light in one place.

It can be watched on my youtube at http://www.youtube.com/watch?v=C8TO2NR_rqk

it is the second to last shell.