I had to build a potato canon for a science project and needed one where I could get a consistent launch force. The typical hairspray cannon would not be appropriate for this purpose so I constructed this air powered launcher as a modified version of Pnewton's Petard from the excellent book "Backyard Ballistics". Typical results were a range of over 300ft using a weight, nonsealing projectile, I am sure a potato would go much farther.
Step 1: Materials
The materials needed for constructing the air cannon are as follows:
Â·22-inch length of 1Â½-inch diameter schedule-40 PVC pipe
Â·1.5-inch diameter male-threaded PVC pipe adapter
Â·Teflon pipe tape
Â·1Â½-inch diameter female-threaded PVC pipe adapter
Â·1Â½-inch diameter to 3/4-inch threaded PVC reducing bushing
Â·Electric drill with various sized drill bits
Â·1 rubber-coated, narrow-diameter, replacement-tire air valve
Â·2 3-inch-diameter PVC end caps
Â·2 9-inch-long pieces of 3-inch diameter Schedule-40 PVC pipe
Â·3-inch x 3-inch x 1Â½-inch PVC tee connector
Â·3/4-inch diameter short iron pipe nipple
Â·3/4-inch ball valve (It has also been suggested that a pneumatically modded sprinkler valve would allow for a faster and there for more powerful launch. I have no experience with this so for the sake of this article we will use the ball valve.)
Â·3-foot length of 1-inch diameter wooden dowel or broom handle
Â·Foot-stabilized air pump
Below is the diagram and the assembled materials.
SAFETY NOTE: I have received several comments regarding the use of Cellular Extruded Piping. In short - don't use it. It is not meant to deal with air pressure and could explode violently producing hundreds of deadly shards. I have not had this occur yet but if at all possible please use a better piping.