Cooking up a little something...

Harness the power of precision mixtures of pressurized flammable vapor. Safety first! These are advanced potato guns - not for the beginner.
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mark.f
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Mon Jul 01, 2019 10:19 am

Hey, nice fucking work Moonbogg! I don't think I've seen a cannon from you since your photobucket/tinypic/whatever it was stopped working. :D How much easier was this build without using only hand tools like for the Striker?
Moonbogg wrote:I'm going back to try out my new bike pump, so I'll find an old board or something and shoot the thing with a can of soda. Also, I had to set my iphone in a coffee mug to hold it up since I don't have a tripod and don't make videos normally, so I suck balls at the whole youtube thing.
Those tiny ones with the flexible legs made out of lubricant hose for machine tools are nice enough to throw on the outside of a backpack, plus there are a number of things you can mount on them like antennas/mirrors/etc.

Good to hear from you again, I'll be free in less than a month to start building stuff again, hopefully I'll still be sticking around.
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Moonbogg
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Tue Jul 02, 2019 12:46 am

Thanks Mark! This cannon would obviously be pretty impossible to make with a drill press and hand tools, which is also the reason why the Striker looked cool but totally sucked in terms of function. Even so, this cannon took a ton of hard work and effort. It took a lot of aggressive sanding, buffing and honing because not everything was machined.
I left the ID’s of the brackets in the water jet condition and the barrels weren’t machined. Machining all those surfaces would have made the fit and finish easier and nicer, but could have also nearly doubled the cost of the cannon, so some sacrifices had to be made and then compensated for with ball busting grunt work in the form of sanding and honing. Maybe my next cannon I’ll be able to implement the lessons learned and machine everything for a super nice fit and finish with anodize and everything. In fact that’s how the next cannon is likely to be: an accumulation of all lessons learned from all my previous cannons in a no compromise implementation. There’s always room for improvement.
I’m already thinking of ways to improve the next one and have ideas for what to do. All in all this last one ended up being pretty special.
I hope you get around to making something to share with us. This is a great hobby for many reasons and sharing our work counts for a great deal of those reasons.
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Moonbogg
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Tue Jun 02, 2020 10:00 pm

Final update. After putting hundreds of shots through this cannon I can declare it a complete success, for now. There are no compromises to speak of. I'll report again in some number of years on its long-term reliability. The piston works reliably and as intended. The performance of the cannon is better than expected. This is a solid 4X cannon. Best recorded velocities:

12oz can of soda: 379fps
Lime: 849fps
Golf ball: 1067fps
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mrfoo
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Sat Aug 08, 2020 1:07 am

Wow, missed that update, came back here from the link you posted elsewhere. 100% success indeed.

1067fps for a golf ball means you're basically being maxed out by the shock wave, i.e you're hitting the sound barrier. This makes me wonder what could be done with a streamlined projectile of the same caliber.
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Sat Aug 08, 2020 1:59 pm

A streamlined projectile could be interesting. I think the mass would have to be relatively low and use a sabot, like a dart or something. Could possibly go supersonic with some effort. It would be interesting to see how much pressure is needed to push past the sound barrier with a golf ball. I know the 10X hybrids are supersonic. I wonder if 5 or 6x would get there. I'd want an alloy steel cannon for any more pressure, even though the aluminum should be fine for 5 or 6x. It's beyond my comfort zone given my face is directly behind the backplate when firing. Gotta keep that safety factor high enough for my balls to drop so I can have the nerve to actually use the thing and have fun with it.
In my opinion, such a power class as anything around 10x starts to pull away from what a spudgun is in nature. You can't reliably fire fruits, vegetables and soda cans from something that powerful. They just vaporize or break apart. Something like that starts to bridge the gap between the spudgun and the black-powder cannon. If I wanted that much power I'd likely just start researching black-powder cannons. They can be made and used legally if done right. It would be more powerful than any spudgun, easier to make, much easier to use, and probably cheaper as well, lol.
I saw a youtube video of a guy who made one out of nothing more than an ugly piece of pipe and remote fired it. He got 1700fps from a goofball, lol. Probably cost him $20.00 haha. That's too easy and not for me though. Hell, I got a 12ga shotgun that I can go shoot slugs from any time I want. I'm all about the spudgun.
I feel that based on my experience shooting between 2 to 4x with different sized cannons, that 2 to 4x is the place to be for maximal power from a spudgun at any given size without destroying the potato. The design I'm toying with for a future build is a larger cannon but still operates up to 4X max. The greater chamber volume and longer barrel is needed to get the spud going at a greater speed without destroying it. It's the same principle behind why pumpkin cannons are very low pressure with MASSIVELY long barels and gigantic air chambers. Maximize the pressure the projectile can withstand and the performance is then governed simply by the size of the cannon.

For instance, with my larger hybrid, potatoes go 730fps at 2x, but at 3x they come apart, even with a very conservative burst disc. Sometimes even at 2X they break apart in that cannon. With my new, medium-sized cannon using the tennis ball barrel, giant potatoes stay together at 3x but break up at 4x. Using the small barrel potatoes stay together pretty well at 3x although I haven't tried a small spud at 4x. So it depends on the specific design characteristics of the cannon, such as port and barrel size, opening pressure etc. But the general limit seems to be around 4X for spudgunning based on my experience.
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