So, are potato cannons safe?
In short, Yes. Also, No.
Wait, what? I'm confused.
Confused? Well, here's the skinny: PVC pipe manufacturers do not approve of the use of their product in the construction of potato cannons. Although the pipe is pressure rated, this rating is for water pressure. As water is incompressible, it will not release much energy if a pipe ruptures. Compressed air, which is by comparison highly energetic, will blow sharp shards of PVC everywhere if it manages to rupture the pipe. This is the "no, it is not safe" part of the answer.
Holy Crap! That's scary! Why do you do this?
Despite the perceived scariness, I've built many dozens of cannons and been very active in the potato cannon community for nearly ten years. In that time, I have not seen a single combustion or pneumatic cannon explode when used in any semblance of a safe manner. The only times I've ever heard of a combustion gun exploding involved using insanely powerful fuels like acetylene gas (used in welding) or even gunpowder! Millions of people around the world participate in this hobby safely; the most dangerous aspect of potato cannons is what comes out of the barrel end and is the sole responsibility of the person firing the cannon: the projectile. A potato traveling at 300 feet per second will have enough energy to seriously injure and possibly kill a person. The fastest baseball pitch ever was 107.9 mph, or 158.25 feet per second. Thus, it is not inconceivable that being hit by a potato traveling twice as fast as the world's hardest pitch could be fatal. This is not a hobby for the irresponsible. Do not buy a potato cannon for someone who you wouldn't trust with a loaded shotgun.
So, they don't "blow up"? Ever?
As far as I know, they do not frequently explode. It's possible that you could significantly damage the PVC enough that it could shatter upon firing, but this has not happened as far as I know. If you suspect your cannon is damaged, including any cracking or chipping, do not use it.
What's "significant damage"? What if I just drop it?
Sadly, if you even drop it from a foot high on a hard surface, it's possible to crack the PVC. You may not be able to see the cracks. Don't drop your cannon, EVER. If it's cold outside, take even more special care, as the PVC can become brittle as it cools.
So coldness makes PVC brittle? Should I stop firing my cannon during the winter?
If it's 45 degrees F or less outside, don't leave your cannon out there in the elements for more than a half hour. Go out, shoot it a few times, and bring it back in to warm. This is probably unnecessary, but still a good idea. I live in a relatively mild climate, so for you folks who endure actual snow on the ground, be cautious. If it's snowing, play it safe and don't shoot.
Alright, be careful with the cold weather, got it. Now what fuels can I use that aren't "insane"?
Propane and butane are the best. They, along with denatured alcohol, are used as the propellant in many aerosols, such as hair spray or deodorant. I used to suggest using Right Guard in the brown can, but they've since changed to a different propellant. Right now I use unscented Sure deodorant.
Whoa now! Propane? Isn't that dangerous?
Nope. When you fire a cannon fueled by a propane-containing aerosol, it's the exact same as from a direct propane injection system, except that aerosol contains fragrances, sticky stuff (for hairspray especially), and other additives that can gum up the endcap on your potato cannon's chamber, coat (and effectively ruin) a flint type igniter, and reduce the efficiency of an electric igniter . This is why most high-end spudguns use direct propane; it's all fuel, no other chemicals to mess things up.
But what if I put too much fuel in?
If it's an aerosol, it'll either not fire, or fire with terrible performance. If you use direct propane injection, it simply won't fire. Period.
Why wouldn't it fire?
Simple. Propane's upper flamability limit is 10.1, meaning that if it exceeds roughly ten percent of the chamber volume, it won't ignite. Science is cool!
Is MAPP gas okay?
I do not use MAPP gas. Other people's experience suggests that it is as safe as propane, but I cannot corroborate this. Use at your own risk.
Hey, at Home Depot they sell this cool MAPP and Oxygen rig. Can I put more oxygen into the chamber and "supercharge" it?
NO YOU WILL DIE.
Very likely, yes. At the very least, you WILL blow up your cannon, and it will injure you. Severely.
Can I use gasoline?
Technically yes, but I highly recommend against it. As a liquid, it's messy and easy to get on your clothing by accident. The risk of accidental self-immolation is not worth the cost, especially since safe alternatives are so cheap.
But what do I do if my cannon doesn't fire? I swear I did it all correctly...
Check out my handy troubleshooting guide for help! Also, email me if you need anything clarified.
Okay, so now that's all cleared up, got any important lessons not already mentioned?
I may have touched on this before, but let me reiterate and summarize:
Spudguns are not toys. Treat them with the same care and responsibility as a real firearm. Follow the same rules of safety as you would with a real firearm, such as:
1. Treat the cannon as loaded at all times.
2. Never let the muzzle cover anything you are not willing to destroy.
3. Keep your fingers off the trigger (piezo or flint igniter) until you are ready to fire.
4. Be sure of your target and what is beyond it. You are responsible for where that potato lands, even if you can't see that far.
If you hit a house, car, pet, or person, you will be held responsible.
Got any questions that this mock-dialogue didn't answer? Email me! Please!
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