It all started in a hotel bathroom. My reluctance to shower meant I would wear body spray. If you smell good you're clean right? I sprayed a large amount of the propelled spray and did a quick spin to ensure full coverage. I then left the bathroom. My dad, clearly more into personal hygiene than me, had already taken a shower and came into the bathroom to dry his hair. He grabs the hairdryer and turns it on... BOOM! Just kidding, nothing happened. But in that moment I realized what could have happened and the inherent dangers of body care.
As a teenage boy a little too fascinated by fire, I know that a fire requires three things: fuel, heat, and an oxygen source. The body spray, which is propelled by propane is fuel, the red hot wire inside the hairdryer acts as heat, I knew the air inside the room acted as a source of oxygen. I quickly pulled out my phone and began searching for stories of hairdryers igniting hair spray and body spray. And I found one: Link. After reading this, I decided the idea was possible and began sketches and research.
DISCLAIMER: Fire, Pressurized Containers, and Hot Wires are all dangerous. Keep in mind common sense while performing this project. By building this project, you assume all risk associated.
Step 1: The Science
You're on the run from some bad criminals. You run down the street as they shoot their guns at you. You dodge and quickly take cover in your house. You find refuge in your bathroom and lock the door. You know there is no escape. You have to fight, or die trying. You look around the room for supplies. A hairdryer and hairspray are the only things in sight. Most people would sit and cry, waiting for death. But not you. You're smart, you're cunning. You hack the hairdryer, quickly pulling out the nichrome wire. The criminals begin kicking on the door. You know it's only a matter of seconds before they enter the room. You plug in the now hacked up hairdryer, the wire goes red hot. You grab the hairspray, coconut dream, cute. The criminals bust open the door. You spray the hairspray at the nichrome wire, aiming at the first of the bad guys. The hairspray ignites and goes up in flames. The criminals get scared, run away and call their moms. You just avoided death, and made a rad flamethrower!
Through my research I found that the heating element inside most hairdryers is nichrome wire. Nichrome is an alloy of nickel, chromium, and iron. It is a popular heating element due to its high resistance and lack of oxidation at high temperatures. Due to the high resistance of nichrome wire, it takes electricity a long time to flow across it. This dissipated power is turned into heat energy, allowing the nichrome wire to reach temperatures of up to 2000 degrees Fahrenheit (1093 Celsius).
Propelled sprays contain propane. Propane is the gas used in barbecue grills to cook your hamburgers, veggie burgers, kale, you name it. Reading a data sheet, I found that propane needs to be heated to a temperature of 920-1020 degrees Fahrenheit (493-549 Celsius) to ignite without a spark. While our nichrome wire does not produce sparks it gets extremely hot.
From this data, I found it is possible to ignite propane with nichrome wire because nichrome wire can get above 920 degrees Fahrenheit. The question is can WE? Let's find out.
Step 2: Things to Find
This flamethrower can come in many different sizes. I built a bluetooth controlled flamethrower. This flamethrower sits on an immobile stand and is activated by a button on an Android phone. I've come up with two other applications for the flamethrower but I'm sure there's many more. Attached is the parts list for the bluetooth controlled version. While more dangerous, holding and spraying the body spray bottle at a hot piece of nichrome wire is a quicker and more affordable option.
Nichrome Wire - I salvaged mine from a hairdryer, the thinner the gauge, the less current required. You can also buy it online.
Propelled Spray - I'm sure you have this at home. Found in the form of butter spray, hairspray, body spray, WD-40, etc...
Power Supply - I'm using a 12 volt, 2 amp power supply. I think a stronger one would be better.
Bluetooth Controlled --- Going Further
Microcontroller / Development Board - Any works, I used an Arduino Uno variant. Bonus points if your board has an ESP module built in.
Bluetooth or Wifi Module - I used my trusty HC-05 module. The attached code supports only bluetooth. Wifi could be used instead which would be really cool. The bluetooth module I use has a range of 30 feet. A wifi module can be controlled from almost anywhere in the world!
Micro Servo - SG90 Micro Servo. I hot glued a popsicle stick to the horn to add reach. The popsicle stick pushes down the button on the top of the spray, allowing body spray to flow out.
Power for electronics - I used one of the power banks meant to recharge phones. These are my go to portable power supply.
Wood - I used scrap pieces for the stand.
(x2) Large Screws - These were decking screws. They act as electrodes, allowing a stable connection between power and the nichrome wire. I used these because the nichrome wire was melting the plastic surrounding the alligator clips of my power supply.
Screws - These were leftover from the chicken coop I built. Used to attach the pieces of wood together.
Popsicle Stick - To be attached to the servo horn. Any lightweight, stable rod/stick could be used instead.
Weight - I used two cement blocks to add bottom weight to the stand. This ensured the flamethrower would stay in place.
Alligator Clips (Optional) - I used these as a switch, power supply connected to them and then connected to large screws.
Saw - I used my trusty handsaw. No electric saw required!
Drill - To drive the screws into place.
Hot Glue Gun - Used to attach servo to body spray can and the can to wood.
Rotary Tool (Optional) - I put a small indent on each of the large screws. This helped secure the nichrome wire in place.
Staple Gun (Optional) - To secure wires in place.
Step 3: Hacking the Hairdryer
I bought my hairdryer for $3.99 at Goodwill. Broken hairdryers will probably work too. The hairdryer I bought was easy to dismantle. I unscrewed the two screws and was able to effortlessly pry the two halves apart. Hairdryers are pretty simple devices.
The 120 volt wall power enters the hairdryer and goes through the nichrome wire. The high resistance drops the voltage to 12 volts. Attached to the nichrome wire is a temperature fuse. If the hairdryer becomes too hot, the fuse blows, opening the circuit. The 12 volts ac then enters a diode bridge. A diode bridge is made of four or more diodes and switches the ac voltage to dc voltage. The electricity finally reaches the motor, which runs on 12 volts dc, before returning to the wall.
I salvaged a lot of nichrome wire from the hairdryer of varying gauges. I also salvaged the motor. The nichrome wire can be found wrapped around the cone at the end of the hairdryer. The nichrome wire can easily be unhinged from the cone, and snipped at its connection points. You will find different gauges and lengths of wire! I found the thinnest gauge was easiest to heat up.
Don't have a hairdryer? Nichrome wire can also be found in toasters, some vape pens, electric furnaces, and for purchase online.
Step 4: Nichrome Wire Circuit
The nichrome wire circuit is very easy. Take your power supply, I used a 12 volt 2 amp supply, and connect it to a piece of nichrome wire. That's it! The wire should glow red hot if sufficient current is provided. I've seen videos of people use 9 volt batteries as a power source. The thicker the wire gauge you use, the more current you will need to provide. My supply is able to heat about an inch of nichrome wire to a glowing white hot. Slide alligator clips up and down a piece of nichrome wire to determine the amount you will need to use. The attached link has a chart at the bottom that provides amp requirements for different gauges of nichrome wire Link.
At first, I started attaching my power supply directly to the nichrome wire when in use. However, this would result in the plastic casing around the alligator clips melting. With the bluetooth flamethrower, I attach the nichrome wire to two long screws. These provide a secure and strong connection. Next, I attached alligator clips (with the plastic casings removed) to the bottoms of the two screws. These are attached to two screws halfway down the flamethrower stand. The power supply also connects to these two screws. The purpose of the middle screws is to provide an improvised on/off switch and to prevent the power supply wires from touching and shorting.
Step 5: Spraying the Spray
To spray the propelled spray we use a micro servo. This micro servo is controlled with an Arduino board. Also connected to the Arduino board is a bluetooth module, I use the HC-05 module. Bluetooth works within about 30 feet of the module. This provides distance and protection from the flamethrower.
The servo is mounted with hot glue. A piece of a popsicle stick is mounted to the servo horn. When glueing the servo, ensure the popsicle stick can make contact and press down on the top of the canister.
Regarding powering the Arduino, use whatever power supply you want. I used one of those portable phone chargers. They supply 5 volts and enough current to get the job done. Batteries, ac adapters, they all work. Originally, I tried using the same power source as the nichrome wire but I was unsuccessful.
Attached is the code, you may have to change the servo values to fit your can and servo configuration.
I use the Android app "Arduino bluetooth controller". Connect your bluetooth module in the settings of your phone. The password should be 1234 or 0000. I use the switch mode on the app. This mode switches off sending 0 and 1 to Serial each time the button is pressed.
In the Home Alone movie series, the boy who is home alone must set up tricks and gadgets to protect his house from burglars. This gadget would be a great candidate as it is remotely controlled. You can flamethrower burglars while watching your favorite television show!
Arduino - Servo
Arduino - HC-05
Step 6: Building a Stand
The stand is made of scrap wood and some screws. I found this main piece of wood in the alley and figured it was a good start. The piece of wood on the bottom provides a place for some weight to be added. This ensures no flipping of the stand. A falling flamethrower is a little dangerous.
The stand is entirely up to your needs. I built it for the specific body spray I had at home. I mounted the screws with the nichrome wire attached in the top of the vertical piece of wood. I then attached the piece of wood for the body spray to sit on. I measured the height of the nozzle so that it would line up with the nichrome wire. I left this piece of wood long so that I could experiment with different distances between the spray and nichrome wire. An adjustable base for the body spray would be a nice touch.
Below is a stand for the electronics. I measured this out to be just large enough to hold the Arduino and mini breadboard. I used the breadboard because I was out of male to female wires to connect the HC-05. You'll notice the width of both shelves as smaller than of the main board. This is to allow the alligator clip wires to wrap around.
I secured the alligator clip wires to the main wooden board using staples. This is to make sure the wires don't fly around and catch on fire. Safety first!
I also attached two screws near the bottom of the vertical wooden board to act as both an on/off switch and to ensure the wires don't touch and short.
Step 7: Remote Flamethrower
The remote flamethrower is a success. Give it power and hit that button! An impressive flame is let out. My flame is a beautiful mix of yellows, greens, reds, and blues. It also makes a pretty awesome roar as it burns!
Please remember to be safe and practice common sense while building and using this project.
Check out the videos below of my flamethrower in action. It's a pretty cool thing. The basic idea of this project; turning a hairdryer into a flamethrower can be adapted in different ways as shown here.
Additional ideas I have for the flamethrower include:
Flamethrower mounted on rc car
Flamethrower battle bot
Motion activated flamethrower
Thank you for getting through this Instructable! If you enjoyed, please consider liking and voting for this project!! I love to hear from the community, so leave questions and comments down below!