Halloween Pyro Costume

Written by: NetworkError, on 03-11-2008 22:48
Last update: 10-04-2009 10:12
Published in: Public, Technical Wootness
Views: 15393

For Halloween this year, I was a Pyro.  I based my costume on the Pyro from X-Men.  Naturally, I needed to be able to throw fire from the palm of my hand.

I wasn't able to engineer as advanced of an effect as I wanted, so I stuck to basics.  Initially, I had a remote cable to activate my system, but I wasn't able to work the kinks out in time.

In the end, I settled for a basic fuel delivery system and a very stone-aged ignition method.

Fuel Source:
For my fuel source, I used an aerosol can of starter fluid.  It's highly flammable and comes conveniently packaged with a simple valve and propellant built in.

For the flow-control valve, I ended up using the little plastic deal that comes with the can.  I bored the nozzle out a little to accommodate my hose.

Fuel Line:
The fuel line was a little more complex. The smallest hose I could find was 1/4 inch which proved to be far to large. (The fuel would "glop" out of the end and form big, burning pools on the ground.) Instead, I used wire insulation from some small gauge, 2 pair wire. I pulled the wire out and fed the insulation through the 1/4 inch hose (which acted as a protective layer to prevent kinks and leaks). The small hose kept the fuel pressure high. This ensured it would fly further, stay airborne longer, and burn a bit quicker. Last, I put a piece of straw from a spray can of motorcycle chain lube in the end of the wire insulation. This keeps the stream of fuel focused and helps it fly even further and burn even quicker.

It's vital that your fuel disperses cleanly and is propelled quickly. If this stuff pools at all, it burns for a long time. You want it all to burn while it's flying through the air.

Remote Valve:
In my original design, I had a remote valve. This was basically a brake cable and squeeze assembly that I held in my off-hand. When I squeezed the assembly, it would move the brake cable and press down on the aerosol can's valve. It worked great! Some of the time... I didn't have enough time to work the kinks out. (The piece that fitted over the aerosol can's valve wasn't really finished and tended to get gummed up.)

Remote Valve EPIC FAIL:
The first time I fired off my costume on Halloween, I had the valve attached. It didn't fully depress the aerosol valve, so it was throwing globs of fire onto the ground. I reached into my coat and manually depressed the valve the rest of the way. After a good burn, I released the valve and nothing happened. I had to quickly rip the over-the-valve assembly off and extinguish my hand. I got a little singed during all this. After that, I removed the remote valve and just activated the unit by reaching into my coat with my off-hand and pressing down on the aerosol can's valve.

Strapping on the Flame Thrower:
One of the challenges was figuring out how to wear this thing. In the end, my wife and I sewed several straps (like the ones used to hold a sleeping bag on a backpack) and a belt pouch for the aerosol can of lighter fluid. I put 3 straps on my arm and ran the hose through each one. Once everything was strapped on and tightened up, it stayed in place pretty well.

If I had it to do over, I would have added a loop to the arm straps and run the hose through the loop. This would have secured the hose more effectively.

Testing the System & Safety Notes:
I tested the assembly in my gravel driveway with the flame thrower assembly sitting on the ground in front of me. (Don't try to wear it until you have all the kinks worked out of it.) I found quickly that I needed a good 15 - 20 feet of clear space to ensure I didn't accidentally light things like cars or trash cans on fire. If you do happen to light something on fire (including yourself), remember that this stuff is really easy to snuff out with a few claps of the hand.

Another thing to keep in mind is sanitizing after each test. If your test run fails to ignite, be sure to allow the fuel from that run to completely evaporate (from the test area and yourself) before proceeding with the next test. This is doubly true if you're wearing the costume and accidentally spray unburned fuel.

Don't do this without gloves. This stuff burns really really hot. You'll probably need to take your glove off right after a longer burn, because it will be smoldering.

Keep your fire-arm extended away from your body. I have my arm too close in some of these pictures, and that's not good. It's easy to get comfortable with the flame thrower and not hold it away from your body enough. Keeping it at arms length will help prevent burns, keep you sleeve from getting singed, and in the event of a fuel leek, reduce the odds of you lighting yourself on fire.

Start slow. Don't go for a long burn right off. Do a half second burn and see how that goes. Do a full second burn and see how that goes. Work up to longer burns. If you burn yourself, you will not feel it right away. By the time you feel it, you'll already be blistered.

Also, ensure all fuel line connections are seated firmly and do not leak. If your fuel line comes undone when you're throwing flame, the fire may flash to the fumes and light you up like a roman candle. If you do go up like a roman candle, bat yourself with your arms and hands to clap the flames out. It will take a moment for the flames to do damage and if you act quickly you can snuff the fire out almost instantly.

Do not use this indoors. The quantity of fire produced is far too mighty for most indoor areas.

Above: 1 can of starter fluid with a slightly modified white, spray nozzle. (Its hole has been enlarged so the fuel line can fit inside snugly.) 1 small-gauge fuel line inside of a 1/4 inch protective hose.

Note the red bit on the end of the fuel line in the picture above and below. This is a piece of straw from a can of motorcycle chain lube. Coffee stir straws would probably work too.

For the ignition, I sprayed a few drops of fuel onto my gloved fingers, lit them with a lighter, then pressed the valve with my off hand and sprayed fuel over my hand at full blast.  Once the initial fire started, I pulled my hand out of the way to prevent burns.  (That last part is very important.)

This turned out to be pretty convenient. I would just stick my fingers in front of the flame thrower's hose and tap the valve on the aerosol can to spritz my fingers. Then I would dramatically present the lighter, light my fingers on fire, stick my fire-arm out and subtly reach into my coat to activate the flame thrower's valve with my off-hand.

Props to Chris B. for this picture.

Props to Chris B. for this picture.

Props to Jessica P. for this picture.

Props to Adam S. for this picture.

Final notes:
The next version will have a better valve that will prevent the fuel hose from coming loose.  I'll also find a more durable hose. (One that doesn't slowly dissolve when exposed to starter fluid.) I may also opt for a remote-control for the nozzle.  It would also be nice to build an ignition system in, though there is some flair to the lighter method. Hmmm...

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