everything’s better with fireballs
Friday, 2 October 2009
I never intended for the Selleck Striker to include fireballs. But this time last year we started thinking about fireballs for something else and got all the pieces together, so they were really just waiting around for something awesome like this. Here’s how it’ll work.
The fire itself is created by igniting “flash paper”, which is a nitrocellulose paper used by magicians to create relatively safe indoor fire effects in their act. Basically the stuff flares up and it’s gone… no burning embers, hardly any ash at all. It is fire, but you can basically hold it in your hand, it’s there and gone that fast.
The flash paper is ignited by a model rocket engine ignitor, which is essentially a tiny incandescent filament with some flammable paste packed around it. You apply 6-12 volts with enough current and it flares up breifly, but plenty long enough to light the flash paper. The Arduino can’t supply nearly enough current to light it, so I’ll end up using a transistor to switch a higher-current (and slightly higher voltage) power supply to the ignitor.
For now I’m just concerned with the hardware. I’d like to have a replaceable “charge” that can be unplugged once it goes off, and replaced with a fresh one. So the sketch below shows a small metal tube with a 1/4″ phono plug on one end that plugs into a matching jack behind the Tom Selleck head.
The tube is copper and the end fitting just slips on snugly, but everything else turned out just like the sketch:
For now I’m using a 9V battery touched across the plug’s contacts. The trick, it turns out, is packing the right amount of flash paper in the right way. It took a few tries, but I think the third attempt got it right: