3" insert shell

[Chris]

Edit note: there seems to be some sort of limitation is how many pictures a post can contain. Thereby, some of the pictures are linked to insted of showing directly

 

I decided to photograph the construction of a 'sun and planets' insert -type shell and write a tutorial of the approach. Canister is the prefered type of confinement for this type of shell. The basic idea is to get small simultaneous bursts in the the middle of a star spread. This shell is slightly different from the original 'sun and planets' -shell since it contains less 'sun' stars and the spread should be somewhat different. Thereby I shall call it the 'planet and stars' -shell.

 

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The basic requirements for this shell:

 

3" canister casing with end disks + extra disk

Time fuse

>60 grams 2FA BP

5 insert shells ( 1-1/4" dia, 2-1/2" long) (see first picture)

Glassfiber tape

Kraft paper for pasting. 70 lbs is prefered.

Wheat paste and wood glue

Black match

A handfull of 1/4" stars

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http://www.pyrosource.com/Tutorials/4inch/tube.jpg

This drawing shows the content of an insert shell. The hot glue together with 1/8" fuse gives a delay of approx. a half second. Half of my inserts contain zinc stars with charcoal tail and the other half has iron streamer stars in them. The burst is 2FA BP. The inserts should be about half stars, half burst. Glassfiber tape is applied on the inserts as the drawing shows. I don't have any detailed pics of my inserts but what I can tall you, the walls are about 1/16" thick and they are closed with triangle fold method.

 

Components laid on surface

 

The case is rolled of 3 layers 50 lbs kraft and the bottom disk is ready attached.

 

Insert alignment

The inserts are inserted in in the shell with fuses facing the middle

 

http://www.pyrosource.com/Tutorials/4inch/2.jpg

In this picture, the center cavity has been filled with burst and the outher cavities are filled with 1/4" stars. I'm using red KP stars.

The stars should reach to the top of the inserts.

 

[no picture]

The next thing to do is to stuff the shell with as much burst as possible. All componenets should be totally covered by 2 FA. Shake and tap the shell to get the burst settled. I don't know the burst weight but I can say with confindence that you can NOT have too much of it.

 

http://www.pyrosource.com/Tutorials/4inch/3.jpg

After adding enough burst, the fused end disk is carefully inserted without crushign the fuse. It would have been wiser to install the fuse in the 'bottom' disk. The excess paper is cut like in the picture.

 

http://www.pyrosource.com/Tutorials/4inch/6.jpg

Glue is applied to every flap and the flaps are then pressed down one by one. This one gets to dry for a day.

 

http://www.pyrosource.com/Tutorials/4inch/5.jpg

Next step is to insert the top disk with fuse hole punched. I put some glue under the disk but it might not be necessary.

 

http://www.pyrosource.com/Tutorials/4inch/7.jpghttp://www.pyrosource.com/Tutorials/4inch/7.jpg[/url]

The next phase is to spike the shell. Lazy as I am, I decided to use glassfiber reinforced tape instead of string. I really don't know how much confinement this kind of spiking will give, but I wanted to try out this method. The shell has 3 layers of gf tape in the order of onevertically aligned layer, one horisontaly aligned layer, and then again one vertical layer.

 

http://www.pyrosource.com/Tutorials/4inch/8.jpg

The next step is to cut a 28" x 5-1/4" piece of 70 lbs kraft. Wheat paste is applied to the whole stripsheet and the shell aligned for rolling. This sheet should last for 4 layers around the shell. While 4 layers of 70 lbs kraft should be enough for this shell, I used 30-40 lbs kraft, which forced me to perform the same pasting twice.

 

Sheet rolled around shell

 

http://www.pyrosource.com/Tutorials/4inch/4.jpg

The excess is again torn and the flaps are glued with paste. Goes without saying, this is done in both ends.

 

http://www.pyrosource.com/Tutorials/4inch/10.jpg

The result should look like this

 

http://www.pyrosource.com/Tutorials/4inch/11.jpg

To prevent the fuse blowing out or other malfunctions, I decided to fuse the shell from the top. A small hole was puched in the black match at appropriate length and the fuse was insesrted through the hole. The match was taped well to the shell to prevent a pulled leader.

I cut the fuse a bit shorter for a potential shorter delay.

 

The lift for this shell is 35 grams 2FA-3FA mixed BP put in a plastic bag.

 

http://www.pyrosource.com/Tutorials/4inch/12.jpg

The last step is to finish the shell in spanish style. This involves rolling the shell in a sheet of paper and then closing the package with string. The lift charge should also be tightened with string.

 

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Building this shell was an experimental project that I hope to get feedback on. I'm sorry I don't have any better documentation on the insert shells, but generally any working solution can be used.

[Mephistos Minion]

That is a very nice looking shell there. Smaller shells (Sub 4") really interest me as I prefer to make many of them rather than a few big ones. I am very interested to hear the results of the glass fiber tape spiking. I really should try something like this soon. I am always deterred by the paper availiable to me (all in gsm not the # rating) It is confusing. But I have the mortar to launch so I shall get cracking (going to lab tommorow)

[TheSidewinder]

Yes, I'm also curious how the fiber tape works for spiking. Keep us posted on how well it confined.

 

I use traditional flax twine but that's cause I got a good deal on some rolls at the PGI. Hemp twine is another one I'm going to try.

 

M

[Chris]

It is going to be a while before I can shoot this shell. However, recent tests with 3" ball shells pasted with gf tape have given good results with the brake. It is to see how it works with can shells.

[Painter]

I can understand the "Lazy" part!

After making all the stars, BP, and such, anything that makes construction go faster helps!

I've had very good luck with GF Tape on clear plastic display shells from craft stores, as well as fiberglass sheet rock tape with Aluminum duct tape, both plain and fiber reinforced.

These were on round shells as well as cans.

[JamesH]

Hi Chris, I'm realy looking forward to seeing the video of the shell in action. Any updates on when it will be tested?

[Chris]

As I live in an urban area, shooting shells here is very much out of question. I really don't know when I can shoot the sheel, but I'm doing it as soon as possible.

[PyroPicasso]

Its been about 3 months... have you shot it yet?

[Chris]

Nope. I can't just go out shooting shells whenever. Especially during the summer. Locals are very strict when forest fire warnings have been given. I'm going to ask if I can use the testing site of the display company I work for to test my own shells, but I'm expecting a negative answer.

 

 

 

EDIT: Right now I'm serving in the army, so it will be a few months before I can shoot anything

[moonshot]

Looks like a great dispay shell. Good clean construction and concise instruction. I'm looking forward to building some larger shells and this has been a big help. Like you I'm in a state that, how can I put it politely, FROWNS on amateur pyrotechs. It's really frustrating when you put time and quality into building a nice shell or other piece and can't shoot it without being branded a felon or terrorist. Anyway great tutorial and thanks for the info.

[Skycastlefish]

Its been 4 years. Have you shot that shell yet?

 

 

[guntoteninfadel]

Ummmmm, five years and counting..........