Air cannons are an iconic DIY project. You can find a lot of great examples online. There are cannons that are powered by combustion and cannons that are powered by compressed air. They can be used to fire anything from golf balls, to water bottles, to candy.
But in this project, we are doing something a little different. We are going to make a baking soda and vinegar cannon. This is very similar to the baking soda and vinegar volcanoes that we made as kids. I have just scaled up the reaction so that it can be used to send a potato flying through the air.
Step 1: Safety Warning
This should really go without saying, but POTATO CANNONS ARE NOT SAFE! If you do not handle them properly, they can seriously injure or kill you. They can also cause great damage to property. Mixing chemicals in a closed container can create high pressures that can cause the container to explode. Build this project at your own risk. Please be safe. Have responsible adults nearby at all times. Don't do anything stupid.
Also, it may not be legal to fire a potato cannon in your area. Be aware of your local laws.
Step 2: Materials
Here are the materials and tools that you will need for this project.
4 inch diameter PVC pipe
2 inch diameter PVC pipe
Two 2 inch to 4 inch PVC pipe adapter
Two 2 inch PVC pipe ball valve (solvent weld)