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BEWARE: ABS IS NOT PRESSURE RATED. It can and eventually will fail over time. stick with pressure rated PVC!

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BEWARE: ABS IS NOT PRESSURE RATED. It can and eventually will fail over time. stick with pressure rated PVC!

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hint: sand the end of pipe before glueing. also, isnt a tazer a bit overkill?

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hint: sand the end of pipe before glueing. also, isnt a tazer a bit overkill? Also, thats just a lil' tater tosser.

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Just wanted to point out that these might not be legal in all countries, like in Sweden where I live for example. :( Apparently someone got arrested a while ago for firing one from his balcony (maybe not the best idea anyway). Well, it does look fun though, just make sure you wont get arrested for making one :)

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ABS can be certified for to hold a pressure (which is the stuff I use). I guess there's a debate over which is better - PVC or ABS?

On one hand - PVC is readily available and its rating is stamped on the side (so easy to classify). It has a high tensile strength and is hard (aka: brittle).

On the other hand - ABS is slightly more expensive and will fail by stretching (I don't think ductile is the right word here). The rating is usually within a certification number stamped on the side rather than the pressure rating explicitly stated.

Why I prefer ABS: ABS is resistant to the elements. Over time, ABS does not become brittle like PVC from exposure (and degeneration). I have yet to see anything about ABS or PVC fatigue curves - so I'm personally not worried about failure in that manner for either plastic.

All that said, I've never had a PVC OR an ABS cannon fail on me from firing. However, I did have a PVC failure from an impact - it cracked. It was a pain in the butt, but it was repaired. In the end, you must ask yourself.... When this "thing" fails, how do I want it to do so?

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Oh, I've seen a plastic called ABSi. And from what I've been told at the local plastics co. It is available in a semi transparent color (or lack of color :P) but is pretty expensive.

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Good point o-tang, always make sure to check local laws before making projectile hobby apparatus!

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USE ABS, even if it isn't pressure rated. When pvc bursts it shatters and sends chunks of Plastic all over the place, when abs bursts (highly unlikely) it just sorta rips, no shrapnel. Also use old apples, they go about twice as far as any potatoe will (any not rotten potatoe)

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I wanted to see it with clear PVC. Its cool to see how it works on the inside.

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I wanted to see it with clear PVC. Its cool to see how it works on the inside.

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I'd recommend against ABS. A description of the production of ABS versus PVC is that ABS is a "whipped" version of PVC (though they are different: styrene versus vinyl, respectively), which turned me off when building my first spun cannon. This whipping thins out the material making it weaker (which is why it is often not pressure-rated while PVC is). You can actually look at the end of a cut ABS pipe and see the small "pockets" of air formed by the thinning process.

Anyway, PVC can be found to be pressure rated very high (I used 430+ psi [sch120] material, while i remember some forum posting that standard combustion potato launchers do not exceed ~60psi), and is (in my experience) cheaper. Besides, in a high pressure system like a combustion cannon, the first thing thats gonna blow is your endcap (i've had this happen many a time... too much hair spray! nailed my brother right in the kneecap. it didn't do him any damage, though. okay, maybe psychological, considering he didnt stand directly behind me while launching anymore!). Spudtech has some more relevant pros and cons to PVC vs ABS:

http://www.spudtech.com/content.asp?id=14

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Excellent project! Nice presentation too ;) Thanks.

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As far as the pvc vs. abs debate, i'm uninformed, but i do know this. This project was made waaaaay more complicated by the use of a taser. A much easier (and cheaper) alternative is an igniter for a gas grill. They usually cost around $15 or less. This does require a slight modification to the overall design though.
Instead of using a simple barrel for the combustion chamber, the piece which should be used has a small side inlet. Depending on the size of the inlet, the igniter can either be glued directly onto this inlet or a hole big enough to fit the igniter must be drilled into the endcap which the igniter would then be glued in to. Attaching the igniter on the side in this manner prevents potato debris from mucking up the workings. If anyone has any questions about this, let me know.

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My problem with this page: http://www.spudtech.com/content.asp?id=14 is this:
"If it [ABS] fails, it will fail. When it goes, it will turn into many little shards of sharp plastic that will invariably find you in some way."

That is exactly how PVC fails - ABS will stretch - PVC will crack into little shards. Here are two samples of PVC vs. ABS -- notice the lack of sharp edges on the ABS sample.
http://www.monarchplastic.com/QualityControl/qualitycontrol.htm

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"A description of the production of ABS versus PVC is that ABS is a "whipped" version of PVC..."

ABS is a resin, just like PVC - I've never heard of it being whipped (say like cream to make whipped cream :P). I have also never seen pockets of air in my ABS (nor did I see anything in this video) - perhaps you got a bad batch? I have seen ABS extruded using power screws and molds (just like PVC :P). Processing is a big deal - but you really can't compare how something looks to its strength properties. Margarine and plastic may be 1 molecule off (not sure - just an example) -- but 1 molecule makes a huge difference :P

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Good job Bre, after all these material-bashing comments, you're obliged to make one from aluminum.

Have fun with that :]

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meth-elated spirits (100% alcohol) works much better and burns cleaner (no more sticky combsution chamber)

put in a cap full and swirl it around to let it vaporize then BOOM!

if the weather is too cold to vaporize, tip in a half cap, swirl it around and light it. this will burn for a few seconds and slightly heat the chamber ready for the first round.

everyone uses CRC and spay can propellants, they are useless and messy.

enjoy! and spread this info, I hate good spud cannons going to waste ;)

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It turns out that you want 1.5x the volume for the firing chamber as you have in the barrell, so ya, it's a tiny tosser... and it could have gotten more speed by having a longer barrell, but as it is there is a ton of muzzel flash and I like that!

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i just drew you, bre.

http://strange.commongate.com/post/make_your_own_potato_gun/photos/24901

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I was inspired by the article in the magazine as well as your post, so I made one for my Thanksgiving project. I used a spare barbecue grill lighter for the igniter. Here's a video of it:

http://www.youtube.com/watch?v=B6906Be55Yo

Here are few of my photos of it:

http://www.flickr.com/photos/57023238@N00/

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Bit late on commenting on this, but we made one of these out of ABS in boy scouts a few years back, but it had a couple main differences. For one thing it was designed to launch tennis balls instead of vegetables, the biggest advantage of which is making the ammunition reusable. Also being tennis balls are rather flexible they can be loaded from the back hatch instead of needing to be stuffed down the barrel. Second like others we used an igniter from an old BBQ rather than a tazer and fashioned the button into a nice trigger to make it easy to fire. Our favorite propellant was starting fluid (ether), its a bit more expensive than hair spray, but it works really really well.

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