Air Powered Potato Cannon

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:

·shaping file
·22-inch length of 1½-inch diameter schedule-40 PVC pipe
·1.5-inch diameter male-threaded PVC pipe adapter
·PVC primer
·PVC cement
·Teflon pipe tape
·1½-inch diameter female-threaded PVC pipe adapter
·1½-inch diameter to 3/4-inch threaded PVC reducing bushing
·Electric drill with various sized drill bits
·1 rubber-coated, narrow-diameter, replacement-tire air valve
·2 3-inch-diameter PVC end caps
·Wrench
·2 9-inch-long pieces of 3-inch diameter Schedule-40 PVC pipe
·3-inch x 3-inch x 1½-inch PVC tee connector
·3/4-inch diameter short iron pipe nipple
·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.)
·3-foot length of 1-inch diameter wooden dowel or broom handle
·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.

Comments

[blazer101]

where is the cap you put the tire valve on?

[blazer101]

also, wont you need a PSI measurer

[dog digger]

All on the bike pump, air compressor etc

[jj.inc]

I always feel bad when people have to pump it up by hand, and not just hook it to an air compressor and have a fill time of 1 second +/- 0.5

[omnibot]

Don't, that's good exercise :D

[jj.inc]

Lol, at least get a foot pump, I have one of them and it works much better.

[nutsandbolts_64]

I still remember when I made my first one. The valve was so tight it took me 1 second to fully open it, therefore, much energy was wasted. The valve used must be airtight and smooth-opening for efficient operation. The faster the valve opens, more air can and will come out in a given amount of time. Just a reminder. And please do use ABS piping, it's safer due to its reaction to a catastrophic failure (i.e. it turns into strips and not bits and pieces similar but not exactly like a grenade, plus PVC will be hard to show up on x-ray)

[soggymushrooms]

Hard to show up on x- ray... Way to stop people from building it

[tulavatalo]

Help i pumped upp the barrel with a projectail to over 80psi and it din't move att all 

[beehard44]

did you close the valve? was there air flowing out? if the valve is open, close it while pumping. IF the air wasn't flowing out, either ur barrel is glued shut by the glue or your projectile is so tight it chokes the barrel

[extra-flyer]

 First i made it with a pvc valve for way more flow because it was 1 1/2 inch and You probably sealed the valve by letting the glue drip down. Check that and I think you will be okay.

[muchachos]

stupid questions - Do you have to pump it after every shot? how long would it take to pump it up to about 30PSI?

[Pizzapie500]

With a bike pump, maybe 3-5 pumps should be enough. If you have a compressor then 2 seconds. If you have an electric pump, 13 seconds. And yes you have to pump it after every shot unless you have a reservoir and a blow gun valve.

[LX_COCOS]

nice job but ive asked my dad for permission to do this but he says it could blow up in my face is this safe? if so how can i prove it to him any help apreciated

[pasha.mostaghim]

Tell your dad that the teapot in the kitchen could also blow up, the oven could explode, and etc. Nothing will happen to you if you don't set yourself up for it. Example? Looking down the barrel, even when its not pressurized, is stupid. I said the same thing to my mother, back when I made my first combustion (...explosion...) launcher, and she let me do it. I've switched over to pneumatic due to school regulations.

Cheers.

[pufferfish9108]

im going to quote you on that first line. somehow somewhere someday ill quote you

[owwio]

i have fired something alot like this at 120 psi with no problems.

[Hermes]

If you use pressure rated pipe (generally about 150 PSI) and accurately glue your joints, this is a very safe design, far safer than the hairspray cannons. The recommended max of 30PSI that I have included is a fifth of what the cannon can take ensuring that it is very safe. As long as you follow the instructions, use pressure rated pipe, glue well, and don't over pressurize, this is far safer than a conventional lawnmower... ~Hermes

[pufferfish9108]

30PSI??? REALLY IS THAT SAFETY PRECAUTION REALLY NECESSARY?? MY 1ST PETARD IS PVC AND MY SECOND IS STEEL. THE PVC GOES UP TO 145 PSI AND STEEL 450. MAKE A STEEL CANNON. PLUS USE A COMPRESSOR.

[kharosh1691]

Hey there...I'm pretty new here, heh. However, I'm planning on building a potato gun this year for my science project. I couldn't come up with anything, however, one of my close friends suggested a potato gun. Consider me stupid, because I think I am many times, however...wot does a potato gun have to do with science? Am not a science person at all. Matter of fact, 'tis the subject I hate viciously. And I was going through a few sites, came accross this one and noticed that you knew wot you were talkin' about. I need some help. Am desperate, I'd say. Science fair is on May 14th, I'm sure I'd get it done before that, but I need all the help I can get... I've settled down to doing a potato gun as my science fair project. If you can help me, then talk with me here...But, I'm a new comer, and I'm very ignorant of technology and this...er..site(?)/chatplace thinger...Ahem. So, I'd not know how/when to sign online. If you can help, I'd be much too thankful and you may email me at [e-mail] Your help would be very much appreciated and some weight off my shoulders. :sigh: - Kharosh

[pasha.mostaghim]

 2 years late, but nevertheless... -- Physics entails the study of motion, force, gravity, etc. A "potato gun" is a less formal way of saying a "Projectile Launcher". In physics, you study a topic specifically named Projectile Motion. See the correlation? Air pressure is built up (in this model), and you're monitoring the various forces exerted on the object leaving the barrel.

Cheers.

[tulavatalo]

will this work with bigger pipe and bigger valve?

[Lance Mt.]

 Maybe. You'd need a bigger Air Chamber though. I'd suggest bigger than the scale your increasing it at (ie, if you double the barrel diameter, 2.5x the Air Chamber.)

[dietpoop]

aaahhhh, backyard ballistics such a great book

[cdwrestler18]

i made on of my own and it works great its for a school project for tenis balls i moved the pipe sise up to 2 and a half

[Zem]

Could you launch those tiny pumpkins if you have the correct diameter barrel?

[Zerogw]

this is a nice back yard toy, i built a potato gun myself heres where i posted it, it runs 20-120 psi and is a lot more powerful than this http://www.spudfiles.com/forums/viewtopic,p,260826.html#260826

[KNEX BUILDING IS FUN]

how much does this cost on average? also wat would i need to do to make the barrel bigger, would i have to chance anthing else besides the size of the barrel? also if i use this thing with about 15 psi could i hold it whiile i fire it?

[KNEX BUILDING IS FUN]

by bigger i mean diameter

[v2rocketboy]

A great build to make, I adapted your design to one made from stainless steel both the air chamber and the barrel for extra strength, added a pressure gaugle and a bike pump input. Same sort of release design but much higher pressures which resulted in a further distance, Just wanted to say thanks for your great documentation inspiring me to build this.

[Hermes]

No problem. I'm sure everyone would love to see some photographs!

[H20]

I was wondering if there was a way to add something to check the pressure.

[zgr95]

Yes all u have to do is get a psi gauge which u can either install on the cannon or use one of those automotive gauges tht u just press up agains the tire valve

[QwertyuioLP]

good idea but with the second idea you would have to take the nozzle from the tyre pump off the valve.

[Leomage]

I built this by the directions and it works great, but just a couple things. The ball valve definitely works better, especially if you extend the handle with something and in the directions it says you need only 1 reducer bushing but you need two.

[zgr95]

I think using a push button valve is more effective but i havent tried the valve

[waycoobeens]

Where can you find that tire valve...honestly thats the only part i cannot find...the rest i just got from home depot

[zgr95]

I actually found a gauge and tire valve in one i use at a plumbing supply house

[bob the builder #1]

at advanced auto or other autoparts store.

[codongolev]

a tire seriously, I got an old tire and ripped it out