Step 1: The Materials
-5 feet of 1.5" ABS (DWV) pipe
-2 feet of 3" ABS pipe
-A 3" to 1.5" reducer
-A 3" threaded adapter
-A 3" end cap
-A BBQ ignitor (+1 Screw)
-Cheap aerosol hairspray
-Potatoes or similar legumes
Step 2: Assembly
-Make sure the reducer fits over the pipe
-Spread some ABS cement on the inside of the reducer and outside of one end of the pipe, slide the reducer onto the pipe with a twisting method
-Repeat this for the threaded adapter
-Repeat this for the barrel (5' of 1.5" pipe)
Make sure your gluing is done properly, you dont want it to explode.
Step 3: Install the Ignitor
Drill a hole in the 3" pipe for the metal lead from the ignitor to fit, mount the ignitor using screws provided, you can slop some glue around the hole to make sure there wont be a gap where the flames will shoot out and burn your arm......
In order to create the arc (spark) to ignite the gas, there needs to be a metal contact between the lead from the ignitor and the metal chasis of the ignitor.
If you mounted the ignitor with bolts into the pipe, bend the metal lead to be within 1/4" of the bolt to make a spark,
I however put another screw in from the other side, but had to run a piece of wire from it to the metal chasis.
Both methods will work.
Step 4: You Are Finished; Firing
-Unscrew the end cap
-Force a potato into the barrel (this is easier if you sharpen the end of the barrel with a file)
-Pack it down with a broom, make sure its still inside the barrel, and not the combustion chamber
-Spray some hair spray into the 3" pipe for 2-3seconds
-Quickly screw the end cap back on
-Point it at a 45 degree angle to maximize range and push the ignitor