Instructables

Handheld Fireball Launcher Magic Trick

This is a magic trick I learned about by watching the TV series "How I Met Your Mother." In it, the character Barney Stinson (Neil Patrick Harris) performs a magic trick where he shoots a fireball from his (apparently) empty hands. Neil Patrick Harris is actually an accomplished magician; he is the current president of the Magic Castle, an organization for magicians. To recreate the trick, I researched how the tricks work that you can buy off-the-shelf. The basic theory is fairly simple: a short (3-4") metal tube is sealed on one end. The sealed end has a glow plug screwed into it. A glow plug is a component of gas engines designed for RC vehicles. It contains a coil that heats up when 1.5V is applied across it. To load the launcher, you lightly tamp down some crumpled flash paper into the open end.  To fire the launcher, you hit a button applying voltage to the glow plug, which then lights the flash paper. The burning of the flash paper propels it out of the tube, where it completely burns in the open air. Flash paper is tissue paper that has been specially treated to burn cleanly and rapidly, making it a material perfectly suited to this project.


 
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Step 1: Materials Required

Picture of Materials Required
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Needed for Fireball Launcher:
Flash paper
Aluminum Tubing 1/2" ID (OnlineMetals.com)
Aluminum Rod 1/2" (OnlineMetals.com)
Epoxy or other strong adhesive
28 gauge stranded wire
2 glow plugs (eBay)
1/4-32 Tap (eBay)
Tap wrench
Copper pipe strap
Slide switch (DigiKey)
Tactile switches (DigiKey)
AAA battery holder (DigiKey)
Calipers


Needed for Coloring Flash Paper:
Colorant chemical powder (UnitedNuclear.com):
Copper Chloride for blue/green
Potassium Nitrate for Violet
Sodium Nitrate for Yellow
Strontium Nitrate for Red
Strontium Chloride for Crimson
There are many other chemicals United Nuclear sells for pyrotechnics that can be used here, as long as it's water soluble it can probably be used.
Glass jars
Distilled water
Plastic spoons
Wax paper
Nice work! I AM a pyrotechnician so I can reassure you (as I'm sure you suspected) that this is an inherently UNSAFE device! This instructable shows an admirable amount of knowledge and respect for the materials you are using, but I'm always concerned when I see instructions for "messing about with fireworks". the actual legal situation varies from country to country and state to state, so it's obviously your responsibility to ensure that you are complying with all relevant laws and other requirements.

Things that WORRY me;

Your breach blocks are merely pieces of rod, glued into the back of the tube. This may be adequate so long as nothing goes wrong, but I'd like to see something more robust. At least a properly machined surface and a more secure joint, if something DOES go wrong, that thing will be shooting flames, sparks, corrosive chemicals and shrapnel, up the inside of your arm. That kind of failure is rare, (especially if you are taking care to ensure that your shooter is properly cleaned and maintained) but it's not impossible and should be considered.

Consider putting the battery on a separate harness, (further up you'r arm) not only will it reduce the profile of your shooter, but it will reduce the risk of an accidental short circuit where you REALLY don't want an exploding thing in your hand. It also means that you can completely disconnect the firing circuit from the shooter (a requirement for some professional venues).

You might want to check the bimetallic/electrolytic corrosion for copper and aluminium too.

Store your materials carefully, (clean, dry, safe, non-sparking container) and never keep more than you need.

On the subject of colours? This will vary from supplier to supplier and to some extent from batch to batch. The chemistry is complicated, (and fascinating,) so you should always test each batch to be sure that it does what you expect.

Other than that, do take care, but enjoy your project.