Potato Cannon

Premise: Create an impressive potato launcher out of PVC parts.
Danger Level (0-5): 5
Fun (0-5): 3.7
Cost Range: $15 to $50
A great simulator for the gun

There are three basic elements that a combustion based potato cannon needs to succeed:
  1. Combustion Chamber: This is the place where the fuel explodes, so it must be made of a sturdy material, like ABS or PVC piping. This chamber should be 4" to 6" in diameter, and no longer than 2'. The chamber must be stout to reduce heat losses. Making a bigger chamber will NOT make a larger explosion. It will dampen the expansion and the launch will not be as powerful. You must make a filling port with a screw-on cap in which you can inject the fuel. The chamber must be well sealed and have a reducer on the front in which to attach the barrel.
  2. Barrel: The barrel is where you ram the potato in to prepare for launch. The longer it is the more accurate it is, but the potato will not go as far due to friction. I recommend a five foot barrel of PVC or ABS. The barrel should be slightly smaller that the potatoes you are using, so about 2" in diameter. The front should be sharpened to cut the potato to size.
  3. Ignition: The ignition system can be simple, like a barbecue igniter from Home Depot, generating a 30,000 volt spark that lasts for a fraction of a millisecond. This ignites the fuel about 40% of the time, so it is not that reliable. But it's what I use because it was cheap and easy. Or, for a more advanced potato cannon, a flyback generator creates a 20,000 volt continuous spark. I have never used this method, but it is supposed to work very well.
You will also need:
Cost Table*
Combustion Chamber Cap$2
Combustion Chamber$8
Reducer $2
Barrel $5
Fuel $3
Barbecue Igniter $13
Total $33
*All of the above prices are estimates, costs may vary.

Some Stats: Muzzle Velocity: 120 mph, 175 fps Launch Distance: 270 yards