Potato Guns
So Merlin calls me up one night and is like, "Dude, let's build some potato guns." Being the persuasive person that I am, I drove over to his house and we began work on the toys. The first night of testing we ran into some complications so we expect this to be another ongoing project to improve upon the design.


Materials
2" ABS pipe (10ft)$4
3" ABS pipe (10ft)$8
3" ABS cap$2
3" female adapter$3
3" to 2" reducer$4
ABS cement$2
carburetor cleaner$1
lantern lighter$3
total$27

Construction
  1. Cut the 3" ABS pipe to whatever length you want. We cut ours somewhere around 2-3 feet long. This will be your chamber. We were going to use a 4" chamber but the only 4" to 2" reducer we saw was rubber. We weren't sure if it would handle the heat.
  2. Cut the 2" ABS pipe to whatever length you want. Ours were cut around 3-4 feet long. This is going to be the barrel. We were thinking about a 1" barrel but..
  3. Glue the female adapter to one end of the chamber. On the other end, glue the reducer and to the other end of the reducer glue the barrel. Obviously, the cap will go into the female adapter.
  4. Drill a hole as far into the chamber as your arm can reach. A good idea would actually be to drill it more towards the top of the chamber before you glue it to the reducer. This is where the lighter goes, that's why it's better to have it placed towards the top. The flint on Merlin's lighter ran out so he used a push-button ignitor from a gas grill in place of the lantern lighter. These ignitors are rather tough to use, but if you can do it they work very well
  5. The last thing you need to do is place a screw or bolt at the base of the barrel, just above the reducer so that the potato doesn't fall into the chamber. Also use a dremel tool or some kind of sander to sharpen the mouth of the barrel. This makes it easy to give your potato a tight fit.
  6. Now, with the cap off the chamber, take a potato (or an orange, apple, or tomato..) that is bigger than the barrel in diameter, and shove it into the barrel. Use a long stick to jam it down the barrel.
  7. Aim the gun up towards the sky as you do a quick spray of the carburetor cleaner (or other flammable spray) into the chamber of the gun. Cap off the chamber and give the lighter a quick flick. If all was done correctly you'll get a big boom and a flying potato capable of destroying windows.
We have many ideas for our guns, such as launch stands, triggers, and laser sighting.

Photos