The Automatic Silenced Potato Cannon

Alright, here are the supplies you are going to need.

2 segments of 4" PVC pipe. One of the segments will be used as your combustion chamber and it will be 4" thick x16" long The other segment will be used as the silencer and it will be 4" thick x10" long.

You will also need a 2" thick by 45" long piece of PVC pipe. This is going to be the barrel for your gun.

Three 4" thick to 2" thick pipe reducers, these will reduce the size of your pipes down by half. You will use 2 of them for your silencer. and 1 of them for your combustion chamber/barrel attachment.

You need to find a 4" thick end cap with a screw in cover. This is just in case you need to load up the chamber by hand.

Two 2" thick 90 degree elbows. these will be used to connect your chamber to your barrel.

A spark generator, or a grill starter, we got the spark generator from an old lighter we had laying around the house. Worked just as fine as a grill starter.

1/4" by 6" piece of copper pipe, you will use this to inject the fuel into the cannon using the automatic sprayer.

a 1/4" compression coupling, these are used to attach a copper pipe onto an area. We'll show you how to use them. The package comes with instructions on how to use them and what they are for. Just in case you need additional help check the back of the bag :)

lastly you will need an automatic air freshener. You can use a glade air freshener or any other type of automatic release freshener. 

Of course you will need tools too. A drill bit with a 1/4 of an inch drill bit, sand paper, potatoes, and PVC cement.

Anyways, that's enough supplies lets get to building this thing!

Alright first things first in the building of the chamber.

Grab the 4"x16" piece of PVC Pipe and measure out about 6 inches from the end of the pipe down to the other side and place an X.... or a Dot... . whichever you feel more comfortable with.

Then using your 1/4" drill bit begin to drill a hole to fit your compression coupling in.

When you finish the hole you will notice that although the coupling fits in the hole, the screw part of the coupling is to short, so you need to sand out the edges of your newly made hole to fit the coupling inside.

Once you get it to fit, place the primary coupling from the inside of the pipe, then place the small piece of brass pipe inside the first part of the coupling and lastly place the second part of the coupling on top of that. You will be able to screw in the first and second part of the coupling together.

Get your copper pipe and place that inside the coupling and then tighten the first and second parts are tight as possible, this will create a seal between the coupling and the copper pipe.

Alright now that you have your pipe in the coupling you need to place the end cap on the end of your chamber, pick the side that is closes to the copper pipe.

You need to add primer to both the inside of the end cap and to the end of the chamber. Once you do so you will be able to permanently attach the end cap to the end of the chamber.

Next you need to place several layers of duck tape around your copper pipe, this will make sure that you have a permanent seal and there is no leak coming out of the chamber.

At the opposing end of your chamber you need to attach one of the 4" to 2" pipe reducers. Place glue on the 4" side and attach that to the combustion chamber.

Your 2 - 90* Degree elbows will be glued together, make sure that they elbows make a horseshoe pattern and not an S pattern :) 

Lastly attach the Elbows to the end of the 2" reducing pipe.

Now you have to go and fix your automatic loader, you need to first bend the copper pipe in a form of an "S" in order to fit your automatic gas loader.

This is where your ingenuity comes in hand. Using a small coffee straw you need to hot glue/supper glue the straw to the very top of the air freshener exit hole. Your primary purpose is to be able to direct the gas into the chamber to the best of your ability. The straw will work as a sort of connection to send the gas into the copper pipe. See video for a demonstration.

Alright so by now you have the chamber ready and you're ready to get to the fun stuff.


Get your remaining two pipe reducers the ones that reduce the pipe from 4" to 2" 
On the inside part of the reducers you will see that they have a lip to prevent a pipe to fully go through the entire reducer. You need to file that down or sand paper that lip down. When you are done you should be able to fit that into the barrel all the way down to the 18" mark from the tip of the barrel.

Once you have the fitting down your barrel about 18" from the exit part, you need to start drilling several holes on the side of your cannon. A total of 46 holes with a 1/8 of an inch drill bit.

next place the 4" thick x 10" long pipe and attach it to the pipe reducer. Your barrel should be in between of the 4" pipe. and you need to start drilling holes into the pipe as well, make sure that you have the same number of holes (give or take a few if you want) lastly the cavity that you have left over in between your 2" pipe and the 4" pipe will have to be filled with some sort of muffling material, cotton works best but if you have none in hand use toilet paper, not as effective but still kinda gets the job done.

To finish up your silencer place the last 4" to 2" reducer in the other end of the pipe and you will have a sealed silencer! by now you should start to see the cannon take shape.

Grab the barrel and silencer assembly and attach it to the other end of the 90" elbow.

Okay now to the last part of the construction :)

In the screw in end cap, you need to drill two screws onto the side of the cap next to the square box that is bulging out at the end. place one screw on the top side of the square and another one on the left side of the square.

Then attach the spark generator, the generator has 2 cables, a positive and a negative, attach one cable to one screw and the other to the other screw. Make sure that if you are using a lighter spark generator you place a lot of hot glue around the terminals if you don't want to get shocked.

Then test out to see if you get a spark across both screws. if that works then test out if you have a good flow of gas going into the chamber.

place a small birthday candle on the inside of the chamber and light it. Then press the gas release on the automatic sprayer and you should see the flame get big and bright. This means you have done everything right and you are ready to test this thing!

Like I said on the intro to this instructable, make sure you know your laws before firing this thing. We don't want you or your friends to get in trouble over something that may be considered a toy by many.

Watch the video on the introduction slide and at the very end you will get to "hear" how loud this cannon fires. without the silencer, when we fired our cannon several neighbors were observed coming out to their front lawns to check what had gone of in their "hood" after we placed the silencer, we could even shoot it from the inside of the house because it was about 1/4 of the actual sound than before.

The silencer muffles about 75% of the sound created by this monster :)

We hope yall enjoyed this instructable and have fun and be safe :)