This cannon is the most simple launcher you will ever find. Assuming you have a Home Depot or Lowe's nearby, you should be able to quickly build this cannon for under $10. Feel free to use it, but do so safely! Only use outside and never shoot at a person or animal! I'm not responsible for any injury or damage!
Step 1: Materials
one 2 foot long piece of 2" diameter PVC $3.81
one 2" PVC end cap $1.26
one lighter of your choice $2.79
one bottle of isopropyl alcohol (rubbing alcohol, 91%) $1.79 at Hannaford
hot glue gun with glue
drill with drill bit that is the same diameter as the barrel of your lighter mine was just over 3/8"
Step 2: Drill!! Then Glue!!!
Drill a hole in the back of the end cap. To do this, attach the appropriate drill bit to the drill and then lay the end cap on the floor so that the round end is up. Now drill vertically down in the center of the cap. Go all the way until it slips through and hits the floor. (Try to avoid banging the drill bit on the ground as it will damage the bit.) Try to push the barrel of the lighter through this hole as best you can; it should be a tight fit. If it is impossible to push through, try widening the hole by depressing the trigger fully and putting it in the hole. Then angle the drill in circles... its tough to describe, but do your best. Once the hole is wide enough, push the lighter into the hole until it is fully in. Now use a large amount of hot glue to secure the lighter.
Step 3: Finish It Up!
Push the end cap onto the pipe so that it is tight, but still allows you to pull it off by hand when enough strength is applied.
Step 4: Testing, AKA, the Fun Part!
This cannon shot a small foam football about 50'. In order to shoot something (it could probably do lemons, or potatoes, or something, as long as it fits tightly in the barrel) you must pour about a teaspoon or two into the back of the barrel, after you remove the lighter/end cap device. Try to turn the barrel so that the isopropyl can spread across as much surface area inside the pipe as possible. Once you feel this is spread enough, replace the end cap and put the projectile in the other end of the pipe as seen in the picture. Click the lighter until it fires and enjoy! To refire, add a little more ispropyl and blow oxygen into the barrel. Thats it! Be safe and enjoy!