You’d be amazed at the sort of thing that pyros talk about over lunch. We discussed making a really big shell, and dropping it from a cargo airplane.
A blimp wouldn’t work very well, because big shells weigh a lot and blimps have limited cargo capacity.
The largest shell I’ve ever seen launched had a diameter of 36", three feet. The problem with that sort of thing is that you have to be at least seventy feet away from the crowd for each inch of shell size – so the closest that the public could be to a 36" shell is 2520 feet, close to half a mile. Of course, this was at a non-public convention, so we were usually inside the radius.
You can be much closer to a twelve inch shell, which makes it seem much larger. They’re also a lot less expensive, but still really expensive. 12" is near the common upper limit for many reasons:
1: Shells get really heavy. It takes two people to drop a 12" shell into a mortar, using ropes and stuff.
2: The concussion from the lift charge of a shell that large is very unpleasant. Anything larger tends to knock unconscious if it’s being fired by hand, which many shows still are.
3: The mortar has to be buried about three quarters of it’s length, which is about four or five feet for a 12" mortar. Digging that hole is a bitch, and you have to but a big rock or wide board at the bottom of the hole to keep the shell from driving the mortar deeper. It’s also a pain to pull that mortar afterward.
4: When something goes wrong with a big shell, it goes really wrong, and the sheer size means that you need more lift charge, which means the probability of something to go wrong goes up. These are called mines when they’re intentional, flowerpots when they aren’t, and OH SHIT!!! when you’re the one hand lighting that shell.
Most small town shows don’t go above sixes or eights, for good reason. By ‘small town’, I mean that the short, once a year show that dosen’t cost more than $20000.
rjung: depending when it was, my dad might have been one of the ones setting up and shooting it.
handy: a shell and a star are two totally different things. I’ve never heard of radio ignition in single stars, and I hope I never do.
lieu: Those are usually called salutes. If it’s just a flash of white and a boom, it’s a regular flash powder salute. The best are made with potassium perchlorate and German black aluminum. If it’s a white flash with a sphere of white sparks, it’s called a snowball, or more accurately a titanium salute, because chips of titanium are added and burn to make the white sparks. Hopefully some of you will eventually see the coolest type of salute, the lampare. It’s a standard salute with a bottle of a flamable liquid, so you get the boom and a big orange fireball from which you can feel the heat. Very cool, very dangerous, and mostly seen at pyro conventions. Recently a company finally got government approval to ship them; they’re a bit tame and use naptha.
Finally, as munch points out at the end, one of the other rising types are shape shells. I’ve seen circles, spirals, letters, hearts, triangles, saturn (a sphere and a circle), and so on. I’m currently working on a patent on a new kind, which will hopefully get more of them in public shows.
Maybe I should have started a thread for ‘Ask the Fireworks Guy’…