WARNING: THIS IS A STUPID AND DANGEROUS THING TO BUILD AND OPERATE. NOT ONLY CAN THIS KILL YOU, BUT IT WILL HURT THE ENTIRE TIME YOU ARE DYING.
I TAKE NO RESPONSIBILITY FOR ANY INJURY OR DAMAGE CAUSED BY ATTEMPTING TO BUILD OR OPERATE THIS OR ANY DERIVATIVE OF THIS CONTRAPTION.
Last Halloween, to impress my 5 year old son, I cobbled together an automotive lock solenoid and some scrap wood and made a flamethrower using cans of aerosol air freshener from the dollar store. Installed inside my jack-o-lantern and paired to a keyless entry remote, I could make the pumpkin burp a large flame from across the lawn. It was quite popular with the neighborhood kids. This year I bought a 3D printer and when I saw the very rough construction of the original, I thought I could 3D print a sleeker and easier to install version.
I am not a designer. I threw this together in Tinkercad using only the most basic tools. I have no doubt there are many things which could be done better by a more experienced designer using more powerful tools but this is what I could do and it works for me.
In addition to a 3D printer you'll need:
• A generic automotive lock solenoid and the two mounting screws which are generally included (two #8 x 3/4" sheet metal screws)
• A 12V DC power supply and trigger for the solenoid**
• A stubby can of aerosol air freshener***
• A tea light candle
• Three M4 15mm machine screws -or- 8-32 x 5/8" machine screws
• Three M4 lock nuts -or- 8-32 lock nuts
♦ The "base" piece needs supports when printing but the rest of the parts can be printed without supports.
♦ The propellant and carrier burn off but the scent does linger. It dissipates quickly outdoors but you can actually smell it so choose your scent wisely.
** I used a standard wall plug 12V transformer and a generic keyless entry remote as the trigger. You could use 12V worth of batteries and a momentary button if you you do not need remote functionality. This tutorial covers the printing and assembly, if you need detailed instructions on 12V DC wiring and triggering mechanisms there are better sources available on the internet. Edit: I did add a comment with links to some stuff which will work.
*** The type used in automatic air fresheners in commercial settings. I found cans of several different scents at my local Dollar Tree. These stubby cans are both easier to manage due to size but also only fire a single burst of flammable substance rather than a constant stream making the entire operation slightly safer. Rumor has it that some brands are water based and not flammable however every brand I could find in these stubby cans designed for automatic dispensers are based on volatile ingredients which will burn.
I tried to avoid supports but THE BASE DOES REQUIRE SUPPORTS for the pin which holds the vertical arm. None of the other parts require supports.
1.) Print one of each part. The base needs supports, the rest of the pieces do not.
2.) Remove the supports from under the pin and in the screw holes on the base piece. Don't worry about getting the pin "clean" just knock the big chunk of support off. Tighter is better on this fit so a little extra plastic is fine.
3.) Collect your candle, solenoid, can of air freshener, and hardware.
4.) Install the solenoid on the vertical piece of the base and snap the other long skinny arm onto the pin on the opposite side of the base.
5.) Attach the small piece in the center hole of the top rod then with the can of spray in place, install the top bar to the solenoid and the other vertical arm.
6.) Press the two pieces of the candle holder together then insert them into the X of the candle column. Insert candle column into the smaller O on the base plate.
7.) Wire the power and trigger mechanism and carefully light the candle.
8.) When triggered, the solenoid should pull the arm down depressing the plunger and shooting a burst of freshener across the candle. The candle ignites the spray making a burst of flame.
9.) Seriously- Please be safe with this! The candle should not be lit until you are ready to make fire. I have no idea what the freshener is made from but you probably don't want it spraying in your eyes either.