Turbo Pyro

[DaMounty]

Hi,

 

In chapter 15 the festival ball shells. Would anyone have some advice on using can shells instead?

 

Mortar = HDPE pipe ID = 1.65"

 

Shell = 1.5" OD - 2.25" height - .25" clay plug (or paper???) - NC laquer dipped visco fuse

 

As you can see I am just in the design phase of the shell.

 

 

Any suggestions advice help is greatly appreciated.

 

Thanks,

 

Da

[mikeee]

Small cylinder shells can be quickly and easily made using a wood dowel as a case former.

You might want to read the Fulcanelli articles on traditional shell building, they are on the internet if you look for them.

Start with the outside diameter of the shell you need to build and work your way in for the design.

Smaller shells of that size usually have thinner sidewalls because you don't need much lift for that size of shell.

You could also use some thin wall tubes and end plugs for a basic shell, a smaller short tube on the bottom can

be used to hold your lift charge with paper glued over the tube and a fuse inserted thru a hole in the side wall.of the tube.

The shell needs to withstand the lift charge so make sure you design the bottom of the shell to handle the lift charge

without having fire make it inside the shell before it leaves the mortar.

[Mumbles]

I used to make shells approximately this size all the time. Plan on your former being approximately 1/4" smaller than the mortar you intend to fire from. 1.40" in this case. One possibility is 1" schedule 40 PVC as a former. It is approximately 1.375" OD, which should be close enough. You can also place an equal length piece of dowel inside to make a solid former.

 

I tend to use a chipboard liner in this size of shell, since most of my applications are height dependent.

 

2" wide x 9" piece of posterboard or manilla file folder paper

4.75" wide x 9" piece of 70lb paper (think grocery bag thickness)

4.25" wide x 9.5" piece of 30lb paper (think paper lunch bag thickness)

Some twine. I like 20lb hemp from walmart, or butchers twine. It'll be around 1/16" or thinner in either case.

Wheat paste - sometimes sold as wall paper paste, or can be made from boiled flour

 

Roll one turn of the chipboard around your former, and then center the 70lb paper in and roll it all up together. You can tape the outside flap down if it makes you feel better, but not entirely necessary. Fold down one side of the paper over the end of the shell. Make two more folds to lay everything else down flat. This is called a tongue fold. Smash the end against a table or give it a few raps with a mallet to set the folds. I tend to place a piece of masking tape over the end now to hold everything together. It also helps with this next part. With the dowel inside the pipe, punch a hole the size of your fuse. I normally use time fuse, but visco and spolettes also work. Insert your fuse and glue it in place if you want. Fill half with stars, and fill in the spaces with granular BP burst shaking to settle. Repeat again to fill the shell. Pleat down the other side the same way you did the top. Again, you can tape if you want. From here tie off spiking twine to the fuse. Spike a vertical around the shell, and turn the shell 90 degrees, turning the twine around the fuse. Spike another vertical. Repeat twice more going in between the two verticals earlier for 8 total. I normally don't use any horizontals, but you may want to experiment to see what works best for you. Tie off the twine around the fuse. I normally use dry hemp to spike, but cotton soaked in wheat paste works well too.

 

From here I let my twine dry if it's soaked with paste. You'll want to take your 30lb and soak it with the wheat paste. Depending on what paper source you have, it might be fairly fragile at this point. Virgin paper will be great, recycled may be easy to tear. It will be wet at first, but with some crumpling and squeezing and resting will turn darker brown. This is called breaking the paper in, and gets paste inside the paper fibers. Once it's uniformly dark, roll the spiked shell in it. I place the shell so that the bottom will get 1 full diameter of extra paper. The top will seem like it has extra paper, but I assure you this is normal. I generally fold down the paper over both ends of the shell about 1/4 roll at a time. After it's totally rolled rub the sides with more paste to squeeze out any air. The spiking should be very visible. Afterwards rub the bottom end of the shell to seat all the paper down. On the top, I twist the paper around the fuse in the direction I rolled it. This will twist the paper around the fuse and make a fireproof seal.

 

Once done let it dry. From here you will need to prime the fuse, and prepare for firing however you plan. The mortar can be side fused, or you can use quickmatch to top fire it.

[DaMounty]

Thank you both Grandmaster and Pyrotechnician,

 

I will post pictures soon.

 

Safety first, last, always

Da