Here it is, almost the Fourth of July already. For anyone who doesn’t know, the Fourth of July is when the United States celebrates the signing of the Declaration of Independence, and whatever remains of the tradition of individual liberty the country was founded on. The Fourth is generally considered the birthday of the United States.
Thomas Jefferson was the author of the Declaration, although it was edited (for the worse, in his opinion) by the Continental Congress. His good friend during the early revolutionary years, John Adams, was instrumental in convincing the Congress to adopt the Declaration rather than continue to negotiate with England’s King George.
The two became estraged in the early years of the country because of Adams’s move away from Republicanism towards a strong central government. However after both retired from public life they rediscovered their friendship which lasted until the end of their lives. Both of them died, coincidentally, on the same day, July 4th 1826, the 50th anniversary of the signing of the Declaration of Independence.
What does all of that have to do with gadgets? Well the gadgets usually used to celebrate the Fourth are fireworks, and recently in Instructables I saw an article on building your own aerial shell fireworks.
Aerial shell fireworks are surprisingly complicated, if you’re not familiar with them. They start off like most fireworks by lighting a fuse. The fuse ignites a black powder lifting charge in the bottom of the shell which blasts it out of the mortar and into the sky. As the lifting charge burns it lights both another internal fuse which goes into the main body of the shell and a “rising comet” attached to the outside of the shell.
The internal fuse is timed to reach the center of the shell when the shell itself has reached it’s zenith. At that point the shell, which is packed with both a black powder bursting charge and a cluster of stars, explodes due to the bursting charge, which also lights the stars. The stars, in turn are the glowing balls of fire that makes everyone ooh and aah.
The rising comet is a star that is attached to the outside of the shell which ignites as the lifting charge ignites, and which allows you to see the shell as it rises into the sky.
There are different recipes for the stars that cause them to burn in the different colors and patterns seen during a fireworks display. The comments contain an excellent suggestion to visit Pyrotechnics Guild International to find a local pyrotechnics club to work with if you actually plan to build your own fireworks.
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