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Potatoes Of Doom

  1. Jun 29, 2004 #1
    Hopefully this is the right topic, but I am soliciting advice on the wonderous invention of a potato cannon.

    A prototype was created which was powered by a 150psi Porter Cable pancake compresser. We chose to use air power as the traditional hairspray or butane method did not seem trustworthy seeing as how we were working with black PVC piping and did not know the kind of strain it would take. The main air chamber is a y-joint section of pipe with a ball valve "trigger". the cannon is loaded directly from the compressor hose with a quick connect fitting and pressure gauge to see chamber pressure.

    The problems experienced so far are:
    1) Lack of portability
    2) A new release trigger to facilitate quicker expulsion of compressed air.
    3) Need of new sealing compound (any suggestions which provides best seal???)

    Another idea is to rifle the barrel to spin stabilize rounds upon exit. Any ideas regarding this cannon or anyone who is interested please contribute your opinions or ideas. Help is greatly appreciated. :)

  2. jcsd
  3. Jun 30, 2004 #2
    Before we can offer suggestions to improve performance, can you give us any idea of the current performance level?

    A solenoid valve may provide a quicker release. Perhaps one that is semi pressure assisted (the line pressure helps open the valve against high inlet pressure).

    As for portability, perhaps a hand compressor model could be developed.

    The sealing that you are talking about goes where on the apparatus? Silicon sealing caulk might work.
  4. Jun 30, 2004 #3


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    Thats pretty sweet. I had never considered using compressed air for a potgun before.

    On the portability issue, perhaps you could take a lesson from paintball guns? You can use c02, or perhaps even the compressed oxygen to fill the tank. Also, taking another lesson from paintball guns (you might even consider getting a 30 dollar walmart gun for parts) you could probably use the solenoid valve as artman suggested.

    I know my gun is capable of pumping out 13 rounds/seconds. You of course would not need such a firing rate, but it will certainly fill the chamber quickly.

    But that is the problem I'm running into trying to visualize this gun. How exactly are you compressing the chamber which holds the potato? Are you using the potato to seal it off until the pressure reaches a certain point? This is similar to the way paintball guns work. The ball actually seals off the back portion of the gun, providing area for the pressure to build up.

    And actually, while I'm thinking about it, I'm not so certain that compressed air is any safer then a combustable. Shrapnel is shrapnel, fire just makes it sting.

    Another thought on the portability would be getting a mini compressor, like the ones walmart sells for $10-15 with a light. Dismantle it, take the motor/compressor and hose. If you can, I've always wanted to get a small oxygen tank and splice the output of the compressor into the tank. This way you could have a rather small compressor system, however it might be slow going to fill.

    Another thing, if you've got an old beater car with AC, you can manipulate the compressor system to actually fill a tank instead of produce cold air. People do this trick for off road vehicles. Then you would have a pretty strong compressor built into the vehicle. Probably not feasible for your project though.

    Good luck, and let us know what kinda distances your getting, I might attempt a project similar to this.
  5. Jul 1, 2004 #4
    We reached ranges of 100-150m with the prototype. This was something that was thrown together for fun. We learned alot from the original. We started off using potatos but then began to use wooden craft balls about 2in in diameter. We were achieving the most distance with those. I have been toying with the idea of creating fit ammo so as not to waste any of the pressure escaping with projectiles that are too small.
    The chamber is kept sealed by a ball valve while it is being pressurized. The ball valve is not easy to operate and this thing is big. we are talking 4 ft. I need to calculate the interior volumes and other technical aspects to fine tune it for the next project.

    We used a silicone caulk for the main pressure chamber and all the joints after we had epoxied the pieces together. But it still leaks, small ones but nonetheless.
    The mini compressor is a good idea. I can maybe weld a small frame together and use it as a backpack like on a flamethrower....

    Any ideas on rifling the barrel? If i start to make custom projectiles, spin stabilization will really assist in getting more range. Maybe putting something that goes boom in the tip for fun ;) i'll try and get some pictures to put up so you guys can see what Im talking about.
  6. Jul 2, 2004 #5
  7. Jul 2, 2004 #6
    How about rifling the shell instead of the barrel? You said you want to create a fitted projectile, that would be a possible place to start. Dimples in a golf ball make it fly better than an undimpled ball, just putting surface irregularities on your wooden craft balls should improve their distance and accuracy.
  8. Jul 2, 2004 #7


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    Golf balls sound like a fabulous projectile! Have you tried that yet, Optimus?
  9. Jul 2, 2004 #8
    The golf balls work extremely well. We just didn't have a ready supply sitting around. The idea of a fitted projectile was to carry some sort of incindiary warhead. Let's face it, we all like seeing things go boom, right? Go into a field in the middle of the night and let a shot rip and just see a wicked fire ball upon impact :) I wonder if I can fit my sniper scope on........
  10. Jul 6, 2004 #9


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    Why even bother fitting the rounds, find a method to fashion a simple sabot like the guys on "Mythbusters" did for their tree-gun and you could fire regular fireworks from the gun. Low-tech way to get to the boom quick!

  11. Jul 8, 2004 #10
    What if you forced one potato in one end and had another pipe fitted to sleeve inside the main pipe with lots of grease so as to be a plunger, with handles and rammed into it manually? Do you think that would work? Probably not as powerful but more portable for those covert missions, making a smaller miniature would probably be a better way to test it. With a tappered pipe the potato might get lodged in the business end resulting in the need for greater force, could even be set up so as the leg muscles would force the plunger and shot from a sitting position.
    Last edited by a moderator: Jul 8, 2004
  12. Jul 12, 2004 #11
    Happened across this solution today in a General Discussion PF thread:

    Thread: In the name of science

    This sounds very portable, but dangerous
  13. Jul 12, 2004 #12


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    That was the way a buddy of mine did it, except he used a spark plug to light them off.

    They are very dangerous. His detonated after a few uses. If he'd have been lighting it with a bbq lighter, he could have been killed or maimed.
  14. Sep 27, 2004 #13
    Just so you guys know a company called spudtech sells rifled barrels for use in potato cannons. They have a machine they bought from someone that rifles them so its not quite that easy to do it by hand but they have them if thats what you need. I have had great success in making both combustion and Compressed air powered cannons if anyone has any questions feel free to ask me at bebartlo@eagle.fgcu.edu. Also in regards to using CO2 its a great idea but you need to use a regulator that can handle the CO2 pressures 700+PSI or 3500-4500psi for HPA/nitrous. You can get inline regulators from Paintball supply places but they arent cheap 60-100 min. but not sure about qaulity or actual functionality in regards to potato cannons. Also just because a paintball guns regulator and bolt system can provide enough co2 quickly enough to fire 13+ rounds per minute doesnt mean it will work with potato cannons. Depending on the design of the regulator, and other parts of the paintball gun I highly doubt they will provide the airflow/co2 flow needed to fill a potato cannon quickly enough for that rapid fire but may still work. I havent endeavored to try that yet due to lack of funds. Also a little tip for igniting combustion cannons, instead of using a fixed sparkplug/ set of nails attached to grill igniter there is a better way. The problem with the fixed types other than lack of reliability(in my experience anyway) is that they get gummed up with hairspray residue. I have been using a lantern igniter from walmart with wonderful success. It fires the first try everytime after you get used to the amount of hairspray needed for comubstion in relation to the air. I find that approx. a 3 second spray works well.in my guns I use a Y shaped 3"X3"X1.5" for the comubstion chamber, i tried an extended model for larger comubstion chamber but it didnt seem to require much if any more hairspray and didnt give me a huge increase in performance. The only consideration with the lantern igniters is that they are L shaped, they utilize a piece of flint much like a lighter and at the end where the striker wheel is a metal tube that extends 1-2"'s(cant remeber how long exactly). this means that it cant be used in small cannons. I mount mine in the end cap on the combustion chamber(threaded cap). That way it is removed everytime I fill the chamber with HS and is less likely to get gummed up. Also when drilling the end cap you have to create an indentation to allow for the fastening nut on the lantern igniter. If you dont you cant really tighten it in place since the exposed portion othe the igniter with the threads is too short. that depends on the size of the endcap though since the smaller ones are not as thick. Sorry for the long post just thought id share some info and if anyone has any questions feel free to ask, I just ran into this post though and may not check replies which is why I included my email. Ben
  15. Oct 12, 2004 #14
    Instead of a release valve, use toy balloons for the purpose. The barrel would have a threaded fitting with the balloon stretched across the male end and the female end screwed over the balloon to entrap it, one balloon for low pressure and more for higher pressures. The threads may have to be sanded down to accommodate many balloons.

    I did make a potato cannon with a Bar-b-que spark ignition and tried propane. It was exiting but I would not recommend it. The potato didn’t like it either, emerging as mashed rather than baked. I switched to cold engine starter fluid and a modified perfume atomizer to inject it, keeping the bar-b-que igniter. I also wrapped the whole firing end, and a short part of the barrel with duct-tape and kept the grand kids behind me.

    Great fun
  16. Oct 15, 2004 #15
    Make a rocket..

    Well, I have been toying with the idea of making a rocket for some time. How about using a CO2 cannister as your projectile? Fit fins, find a way to puncture accurately and test. :devil: Another option may be to simply put a fireworks rocket inside your pipe, aim & ignite. It would be nice if you could fire it with a delayed ignition so as to protect yourself from the flame.. Hehe..
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