KaBoom

One of the advantages of being a member of a pyrotechnic organization is that you get to legally make things that go boom. At a recent meeting I attended a class on making 4 inch canister shells. Each person in the class got to make and fire their own shell.

Building shell

Loading burst charge

Here I am loading the burst charge into the shell I am building. Around the outside of the inner tube are the stars. The burst charge, black powder, will be put into the center of the shell so that it can blow the stars out in a uniform pattern. Stars are little balls of material that burn to provide the colored streaks seen when the shell bursts. After the black powder is poured into the inner tube the tube is removed.

Packing shell

After the tube is removed the remaining space in the shell is packed with rice hulls coated with black powder. This keeps the stars from rearranging themselves and ensures a strong burst. After this the shell is closed with a lid and taped shut.

Spiking the shell

Then the shell is spiked. Which is wrapping the shell tightly with strong string.  Here is my wife, Sharon, spiking her shell. This if done properly will cause the shell to build up pressure when the burst charge is ignited and explode uniformly sending the stars out in a nice symmetrical pattern. You don’t want just the lid to come off or blow out a hole in the side.

Gluing on paper

After the shell is spiked it is wrapped with a layer of brown paper coated with paste and softened by wadding it up a couple of times. This needs virgin paper not recycle paper which disintegrates instead of getting soft. In the center of the shell you can see the end of the time fuse which is ignited by the fuse that fires the lift charge. This fuse delays the bursting of the shell until it is up in the air.

Drying

The shells needed to dry overnight before they were ready for the next steps.

Completed shell

The final assembly of the shell consists of attaching the fuse to the time fuse, adding the lift charge, more black powder, and wrapping the whole thing in more brown paper. Here is Sharon’s completed shell.

All loaded and ready to fire

That evening all the shells were taken to the firing site and wired up to the remote firing system. Each shell is loaded into one of the black plastic mortar tubes and the fuse attached to an electric firing device called an Ematch. For safety you really don’t want to light the fuses by hand. In fact the fuse we used burns in a fraction of a second. No getting away from that.

Jim's shell

Everyone got to push the button firing their own shell. Here is mine.

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