Spudguns: Potato Cannon Guide

I used to think these were really cool and harmless fun as a teenager. Then at college, some guys I knew made one (and they weren’t dumb at all, pretty competent people). They were firing it near where people were sitting on the lawn and it suddenly shattered, sending sharp jagged pieces of PVC flying. One of the pieces hit a girl sitting nearby and gave her a nasty cut near her eye. Her face was covered in blood and it was totally horrific for her and everyone else. It made me realize that the fun of the activity was just significantly outweighed by the possible safety downside. It could have been so much worse, too— she could have been blinded instead of just gotten a nasty scar on her face.

I was doing ecological work in a lake when we came under spudgun fire. Someone (kids?) began slowly firing from a distant treeline on the side of one of the hills that surrounded the lake. I knew the distinctive thump, so I was looking out for the first splash, which ended up being much closer than I expected it to be! I had assumed they would be aiming somewhere else. I informed my shipmates that we were under attack and we rowed to shore as fast as possible. They got in about three or four shots, but we escaped injury and no one was ever caught.

PSI rating on your spudgun, shouldnot be overlooked

e.g. https://www.klkntv.com/one-man-injured-after-potato-gun-expl... [2017]

[ALSO] dont exceed rated pressure, and know that constant pressure is different than repeated shocks

https://www.engineersedge.com/fluid_flow/steel-pipe-pressure...

https://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-...

I remember the first time we fired one of these. It was dusk and my brothers and I had rigged a remote igniter, and I was elected to hold the cannon itself. We loaded it up, sprayed hairspray in and my brother pushed the igniter.

None of us had any idea of how powerful one of these was! The flame that came out the front was over a foot long. We thought maybe the potato would reach the back fence of our yard, but it was launched into oblivion. Luckily our house backed up onto a nature preserve, so at least no-one had a surprise potato land on them.

We had much fun that summer iterating on designs and trying every type of various projectile we could find.

I made few of these when I was a kid. My pièce de résistance was a 10' 'coaxial piston launcher'. It scared the bejeezus out of most people... I usually shot ice slugs, which would throw a hole in a piece of plywood at 50 psi.

A golf ball with a chipped off shell fits perfectly in a 2" PVC barrel. The problem with chipping off the shell (along with an unrifled barrel) is that it makes it like a knuckleball - you have no idea where it's going to go. They would curve violently in any direction. One of the few times I shot one of these, it curved directly upwards, and I'm guessing landed a half a mile or so away. Hopefully it didn't hit anyone or anything. That was the last time I shot it.

The links on the 404 page bought me to some very nostalgic feeling pages. Very late-90s aesthetic. An MP3 directory index. A webcam with a frame that hasn't refreshed since 2009. I miss the old internet.

These are so fun and easy to get started, but quite challenging to tune and make optimal. The differences between "i just glued a tube together and hair sprayed it a bunch" and having optimal chamber/barrel ratios with a proper air/fuel mix are incredible to see!

In the summer of 2004 I was enjoying the mountainous view and ample sun of Kandahar, Afghanistan. It was there, eating one of my allotted MREs, that I noticed the MRE heater was printed in large letters "Do not expose to flame." Being a bored jarhead, I couldn't help but try and figure out why. Being able to rub a few brain cells together, I thought about how the heaters are activated by the addition of water. Since water is hydrogen and oxygen, I was willing to bet that those were some of the reaction products. I never bothered to look it up, but I did find that whatever was coming out with the steam was also quite flammable.

Once that was proven, I recalled that recently a contractor had dug a well near our work site. I ambled over and found a 3 foot long, ~3 inch diameter steel pipe that had a 90 degree elbow with a quick release cap. All that was required after that was a touch hole, added with a drill, some MRE heaters, and projectiles.

Potatoes were not available there, but fruit like oranges and pears were. I started with an orange and just jammed it into the very end of the barrel, it was too big to go all the way in, and went for it. The distance was laughable, 1 or 2 feet, but the sound? Everyone came running out of the work center tents because they thought I had just loosed a round from my weapon.

After being called an idiot by the local Lieutenant, I switch to only pears, which were easy to jam in hard enough to cut the excess off. At this point, I was lobbing pears across the perimeter road, into the scrub / minefield outside the wire. Never found a mine with it though.

All my fun ended one faithful day when I accidentally dropped a pear in front of a Romanian MP truck on patrol around the perimeter. The 50 cal on top turned to point at me, I dropped the pear cannon and walked away, never to return.

I had an amazing science teacher in high school who brought a potato cannon he had built into to class to show us. Except he called it a "sock cannon" and had loaded it with a large tube sock that he had rolled up. He explained how it worked, how he built it from a few basic plumbing parts anyone could get at the hardware store, how the fuel was just hairspray and how we definitely shouldn't build one ourselves.

Naturally, I went home and decided to construct a much bigger version of the one he showed us. After convincing my parents to drive me to the hardware store, I picked out what I needed -- including 7 feet of PVC. The clerk immediately figured out what I was building and that was the first time I heard the term potato cannon. They seemed concerned that my mom was on board with the whole thing, but I stuck to my guns and said it was a science project and was for shooting socks. I had figured I could wrap the sock around a smaller projectile, but that clerk made me realize I didn't even need the sock.

My friend and I put it all together pretty quickly the next day and set it up in my backyard for testing. I think we probably started with socks, but I honestly can't recall. What I do remember is taking a hacky-sack I had lying around that fit perfectly into the barrel to try and fire it at our back fence. We were using a piezo igniter from a lighter I had disassembled, and it took some trial and error to get the fuel to air mixture just right. It took both of us to operate: one person aimed the barrel, the other operated the trigger. This time, I was aiming and he was lighting. But it just wasn't lighting... so I turned around to try and help and BOOM the cannon went off like, well, a cannon. Except I wasn't pointing at the fence anymore, but well above it. The hacky-sack tore through the branches of several trees before exploding on the metal siding of the house on the opposite side of our block. The sound could probably be heard for blocks.

We both just looked at each other with a mixture of delight and panic before immediately running back into my house. We saw someone come out of the house we hit looking utterly confused, trying to figure out what just happened. We started laughing uncontrollably, realizing how close we were to causing a lot of damage, or possibly injuring someone.

Luckily, nothing every came of that incident, and we made sure later tests were done in a nearby park. We never did attempt to put an actual potato in the thing. Perhaps 7 feet was a little overkill...

PS - Dr. Vince, if you're out there, thank you for being one of the best teachers I've ever had. I'll never forget that class, or that "sock cannon"!

I built the fauxtato a while back; a small capsule to simulate a potato but with a 32g accelerometer (8g is wildly insufficient) and WiFi to be able to log data and make basic analyses about different cannon & fuel usage.

Really interested run some tests based on things in this thread, like different propellants.

Here are some good tips for a spud gun: - Schedule 80 PVC where possible - Use anti-static spray instead of hair spray, it's cheaper and doesn't leave a tacky combustion chamber - Put a small PC fan into the combustion chamber to mix the fuel and air, this will ensure you get a fuller combustion.

If you're an adult, you can make one out of metal pipe and use an oxy acetylene torch to fuel it. Perfect stoichometric ratio, very very energetic!

Made many spud guns as a kid. Spud mortars. It all ended when we fired a rotten crab apple, missed our target, but struck the door of a passing car. The drive chased us through the woods of our property for a while before giving up. Now my buddy works in defense lol.

Surprised to see people talking about spudguns firing whole potatoes! I didn't even know that was a thing. The spudgun I had when I was young just fired small parts of a potato, with a whole potato enough to last for ages. I think it was the Lone Star Spudmatic. Not only safer but less wasteful.

FWIW, it looks like Wikipedia differentiates the smaller spudgun from the larger potato cannon: https://en.wikipedia.org/wiki/Spud_gun vs https://en.wikipedia.org/wiki/Potato_cannon

If this is of interest, be sure to check out https://www.spudfiles.com/ - multiple types and versions of cannons, including very clever single inlet piston style ones that shoot incredibly far. Here's an example: https://nighthawkinlight.wonderhowto.com/how-to/make-powerfu...

Iv been interested in this on and off for a few years.

My most sunkworks idea was based of atechnology connections video, to use a stocheometric ratio of liquid hydrogen and liquid oxygen, dump it into a steel pressure chamber....then let the liquids convert into a gas, then detonate the mixed gas using a high voltage arc. The detonation force blows a burst disk open and blasts the projectile slug forward at what I hoped to be hypersonic speeds.

Never really got to into it though cuz I'd need some machining equipment and a budget for the materials

I wish Supah Valves [1] were still available so I could recommend them. They use a smaller sprinkler valve as a pilot to move a much larger piston based valve _very_ quickly. That lets a lot more of your reservoir pressure get to the barrel before your projectile has shot out the end. The result? More range. More grins.

[1] https://www.spudtech.com/store/index.php?main_page=product_i...

Potato cannons first inspired my love of physics. In high school I was amazed when I discovered that I could fire one vertically, time how long it took for the potato to hit the ground, and then mathematically reconstruct both the potato's exit velocity and the maximum height it reached. It felt like magic.

I ended up performing a science fair project on the effect of the potato cannon barrel length on the potato's max speed and height. (My experiments also led to a short encounter with the police, but that's a different story.)

IANAL :

Potato cannon legality https://en.wikipedia.org/wiki/Potato_cannon_legality

in US: bare minimum it is a dangerous device as in pelletgun or archery equipment.

how/why its used, as well as ballistic features may cross a threshold.

if you construct a firearm, you must not have legal restrictions on ownership.

if the projectile of a firearm,is an actual .50calibre or greater,that is a destructive device and you must be rigorously vetted to construct or own that

A fond memory I had as a teenager was making a potato cannon with my brother and dad.

The cannon was in a J shape, where the end of the J had a cap for spraying in fuel - like propane or hairspray. Near the end of the J shape we cut a hole to put in an elongated lighter.

This went against the design of the video we watched - the video suggested taking the ignition stuff out of the lighter and making it part of the canon. Cutting a hole and just gluing a lighter was the easiest option... but also caused a lot of problems - namely with ignition.

During the building of this, right as my mom came home, I looked down the PVC pipe (there was nothing in it thankfully) and asked my brother to click the lighter so that I could check to see if it was lighting or not. My father was not in the room.

This ignited the residual fuel in the pipe and burned ALL of the eyelashes off of my left eye. My father came running in and started to scold us, and then my mom came in the room asking what happened. We all hid everything, because my dad didn't want to get into trouble either.

We shot many potatoes that summer, and the whole experience made me realize how useful eyelashes are.

Fun Fact: There are Countries where Spudguns are illegal and treated like a weapons charge. Germany being one of them.

This website was my dad’s second bible when I was a kid. He went down the rabbit hole and ended up building a massive steel spud gun that had a 10 foot copper barrel. That thing could throw a potato close to a quarter mile. Some great childhood memories right there.

Back in the late 80s in college a guy in my dorm made a combustion gun. We were watching him shooting spuds from the dorm lawn into the air not caring where it landed. Later that evening he was arrested because one spud gave the parent of a visiting student and orbital fracture 300 yards away and her eyeball literally fell out. Since he was doing it in front of the whole dorm the police had no trouble finding him. He lasted only two weeks in college no idea what happened after he was arrested. Be smart if you make one of these things they are super dangerous.

This takes me back. Dad was a plumber so I had ready access to all the gear for this growing up. I was introduced to it when he turned up at home one day with one, we launched a few spuds into the neighbouring paddock using Mum's hairspray.

I was about 13 at the time so I spent hours on this site planning different launchers. Managed to blow my friend's Dad's air compressor up while firing a smaller one. I don't know how the hell I still have all my fingers / eyes but I had some fun :)

> Took a bit of doing to code the design by hand in Notepad with all the nested tables originally, however with Dreamweaver it's only taken a few hours, not weeks.

So many memories...

I made something like this in HS out of coffee cans with the bottoms cut out in half moon shapes. Then I duct taped them all together and would put rubbing alcohol in the top, shake it up and let it evaporate, and ignite from a nail hole in the bottom can. I could launch Gatorade bottles filled with water about 100 yards. It blew up once and I never bothered to put it back together. Plus my mom was hysterical.

Ahh good memories. Over the summer in college, I made a pretty advanced propane-powered one with an integral mixing fan for the chamber and an cheap taser for electronic ignition. Fired every time. Had great fun with my roommates shooting them out into the ocean off our balcony (UCSB — how lucky we were!).

Sadly it was confiscated by the police shortly after. They drove by me loading it into my car at night. The 8ft barrel was fairly obvious...

My username comes from the fact that I built and sold potato guns back when I was in high school.

I should really write up a thread on some of the stories from those days.

Good book on this and similar subjects - Backyard Ballistics: Build Potato Cannons, Paper Match Rockets, Cincinnati Fire Kites, Tennis Ball Mortars, and More Dynamite Devices

https://www.amazon.com/Backyard-Ballistics-Cannons-Cincinnat...

This is going to be the last week someone in this thread has all ten of their fingers, working ears, or both.

Built a bunch of these - both combustion and “compressed air” based as a teenager, with varying results.

I had been inspired by a “science demonstration” at a science fair where “Doctor Bunhead” (of “Brainiac” TV fame) shot one through a tennis racquet to make “instant chips”.

Relevant: this video with some info about dangers/safety especially related to non-pressure-rated PVC: https://www.youtube.com/watch?v=KqstP9ics2A

William Gurstelle's Backyard Ballistics and The Art of the Catapult were two extremely influential books in my development as a young engineering minded person. Countless hours of fun were had experimenting with spud guns of varying designs.

Adam Savage made something similar, with compressed air, for the Slow Mo Guys - https://youtu.be/w9i9rwg1L_A?feature=shared

A buddy of mine had a compressed-air spud gun that he made from an air compressor tank, a ball valve, and a length of 3" copper pipe. That thing could put dents in a 1/4" thick scrap steel plate.

Related vegetable ballistics:

Punkin' Chunkin' Championship https://www.punkinchunkin.com/

I have NEVER EVER used one of these to fire across a US Interstate at night (successfully).

Mind your PSI and test your ballistics prior to using it for more, artful, purposes.

My best friend in grade school was a bit of a deviant and we definitely experimented with these things. Very powerful!

wow this is a fancy one. the one friends & I built in high school was more simple

1) a narrow tube to put potato in 2) a larger tube for firing chamber with a screw cap 3) a sealed hole cut into firing chamber for a lighter

put potato in one end, unscrew the cap, spray hairspray liberally inside, screw cap back on, aim, and fire

>> sees link to slashdot in the header

Can we add (2008) to the title please?

Can parts of these be 3d printed?

Silicon Valley, the show, is a documentary. https://youtu.be/Q1QPXyebhiY?si=5YWYlCuI2aJ2fu-l&t=474

ted kaczynski alternate timeline