First I cut the copper tubes to length, drilled each end cap and JB-Welded 1/4″ phono plugs into each one. Then I soldered model rocket ignitors to the phono plugs’ contacts inside the caps. The gray boxes are aluminum project boxes with phono jacks installed in one side. These will be mounted to the back of the Selleck head, but for now they were a good way to hold each cap as I was soldering. I then assembled the tubes to the caps and used a little electrical tape to hold them together.

I cut each 8″ x 9″ sheet of flash paper into strips (across the short length),

folded all the strips in half together and twisted them loosely,

then stuffed the whole thing into the end of the tube.

Done!

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:

So Crushtoberfest is approaching again, and the party plans are in full swing. In case you missed it, Crushtoberfest ’08 was the house party that capped off a six week mustache growing contest among BDC employees and their friends and families. Last year’s feat-of-strength competition featuring the Captains of Crush grippers was a huge success, so we decided to step it up this year.

We liked the idea of a Hi-Striker, the classic carnival game where you swing an oversized hammer and try to ring the bell. But renting a Hi-Striker is not cheap, and we saw the opportunity to build something awesome. So going with the vague carnival theme (and the overt mustache theme) I generated this concept sketch for an electronic Hi-Striker, featuring a larger-than-life Tom Selleck head with light up eyes and fireballs shooting from his ears.

Here’s the plan: The contestant will strike the rubber pad with the hammer, compressing the sealed rubber hose under it. An air pressure sensor attached to one end of the hose will generate an analog voltage (up to 5v), the Arduino Mega will read the voltage and light up the LEDs according to a predefined scale. If the hit is a “ringer” then the LEDs will light all the way to the top, Tom Selleck’s eyes will light up, and fireballs will shoot from his ears. BTW the fireball effect is a flash paper/model rocket ignitor thing we worked out for last year’s party but never used. We also plan to have sound effects go with the LEDs, using the Adafruit Wave Shield for Arduino.

Stay tuned for more.