Over shoulder potato cannon

[Techexical]

Hey all, I am building a combustion potato cannon for a school project, a 1.5 inch ABS pipe based cannon (yes I know, pretty risky seeing how people see dmw ABS with its pros and cons here, also because I made the mistake of not researching beforehand), posting about it to get feedback and criticism on it, areas where to improve and all that.

Cannon uses a brass "shell", also known as the 1.5 inch brass fitting I found in the home depot plumbing section, covered the lip area with wax and electrical tape to keep in the pressure so the gas doesn't escape, along with heat shrink on the wires to keep it from fraying, 2 points of ignition for more power, and of course, the "bolt" of it, the floating barrel just simply sitting there with Vaseline applied to keep it's movement smooth, handle and the layering I've added onto it required me to apply heat and bending it to shape, thankfully had a p100 mask my dad gave me beforehand incase of fumes, even when I did it outside

Planning to add a fan and possibly a gas injection system for butane, to make it more 'advanced'

Also credits to this man for inspiring me to build this thing, aka Auxiliary on this site, basically built a shoddy version of his

Overview, don't mind my messy worktable, will eventually come around to clean it... maybe

Wires wrapped around 8-32 machine screws

Combustion chamber

Open bolt

Brass shell

Open bolt 2


Shooting tests and seeing if it'll explode on me or not, shown with me hiding beside things, and then finally firing it over shoulder lol


Didn't even notice the bird there

[Techexical]

Well, this is a bit awkward, tried to post this a really long time ago but regardless its on here, much appreciation and thanks PCGUY!

Regardless, the current cannons design,

New stuff: gas metering and injection, the thing is a fairly small but it works well regardless at 20-40 psi worth of butane, found just 1-2 injections makes pretty good launches, crude as hell 'thumb hole grip' that's literally being held by a hose clamp with a L bracket screwed to the grip under the clamp, new trigger that replaces the old big red button one for a 1.5v bbq igniter that automatically sparks when pressed (something I salvaged from my schools auto shop scrap yard from a grill ), and a air pump, purpose of it is to get air inside incase of a misfire because of a lack of oxygen, had to drill out the nozzle of it to make room for the vinyl tubing

Few more stuff is new electros, went from 8-32 machine screws to 10-24 ones, new 18 gauge wires taken from a broken washroom mirror light, extra cut coupling solvent welded onto it to make it more sturdy, and make it... look less flimsy, no fan as of it yet, because I done goofed up and shorted it by getting too curious with batteries, lets just say; don't directly shoot 16 volts into a 12 volt computer fan with a drill battery

Had on it on my bed since I had to get my hot glue gun to attach the air pump onto the cannon, hot glue gun being in my room and couldn't be bother to bring it to my garage (not like there would a nearby outlet anyway lol)

[jimmy101]

Nice job!!!

[jackssmirkingrevenge]

Good stuff, not often you see a breech loading design.

[Techexical]

Thanks for the comments! The cannon performed nicely when I went out back to shoot a large paper cone type of dart and 3 cut russet potatoes, found the optimal mix is filling the cannon 3 times or 30 psi of butane, air pump worked as expected and 'troubleshooted' the misfires

Now to figure out how to get ggdt or whatever the programs name is to get running on my laptop, so I can see the stats of my of cannon, haven't even got it setup yet

[hectmarr]

Good job !

[jackssmirkingrevenge]

Now to figure out how to get ggdt or whatever the programs name is to get running on my laptop, so I can see the stats of my of cannon, haven't even got it setup yet

You can download it here

[Techexical]

Now to figure out how to get ggdt or whatever the programs name is to get running on my laptop, so I can see the stats of my of cannon, haven't even got it setup yet

You can download it here

Got it to work just last night, just had to run the application as a admin to make it work, and found out it was hgdt I was looking for
...also found out quickly why the hgdt/ggdt thread exist, already had my first crash, the program couldn't comprehend the numbers
Hopefully it wont happen much seeing it run pretty nicely for something from the window xp era

[Techexical]

Finally got around to plugging in the supposedly right numbers to hgdt, life being life and just being distracted by stuff
Not entirely sure if the stats are right considering I have disc data on it and just shoot cut potato's from a brass tube in the barrel, despite it clearly just being a regular combustion cannon, hopefully doesn't goof it up

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[mark.f]

Nice cannon! Any plans for using that threaded adapter on the end of the barrel?

[Techexical]

Nah, it just there for more or less show but, the muzzle end is chipped when my dad gave to me from his workplace, so I grabbed a spare piece from a box of parts I have and attached it, maybe not all for show then, even seems like it affected how the sparks left my cannons barrel, giving it a little spin

Possibly though, thinking of doing a 'conversion' mod for it where I can screw a 1/2" pvc barrel in it, not much practicality in it but I have multiple spare nail rounds from my first potato shooter (which I had to repair countless times), plus it seems interesting and fun to do

If I do end up doing the little modification that I can just screw off and put back on, I'll be sure to post it here

[jackssmirkingrevenge]

Not entirely sure if the stats are right considering I have disc data on it and just shoot cut potato's from a brass tube in the barrel, despite it clearly just being a regular combustion cannon, hopefully doesn't goof it up

You need to "trick" HGDT for combustions by putting disk failure at zero and the disk diameter the same as your barrel inner diameter

[Techexical]

As it turns out it goes at 320-ish feet per second or 97 meters per second, still pretty solid for a second build, especially when I load it with a dart round or regular spuds still mauling a rotting tree stump

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However for the incomplete combustion issue, I could just add an extra 6 inches of barrel, going from 28 inches to 34 inches, which would bring it to 350-ish feet per second or 106 meters per second, won't be doing that for a while since my school project (being this potato cannon) is coming pretty soon after winter break and will be presenting it to my classmates, and already blew crap loads of money on a hho generator project in school too, at least I know mc master carr and metal places around my area are pretty good...

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As for the wooden stump claim:

Aimed a bit high and was close (considering how awful my aim is sometimes ) but still tore a good chunk off


And metal dart from a carriage bolt and card paper, with a side of electric tape and hot glue as mentioned:

(my laugh in the video... I see why my friends say I laugh like a dog or bird)

wasn't even sharpen either, the flat top was enough to dig itself into the wood, granted it is rotting after all
also dont mind my yet again, messy workspace, that photo was 3 months ago and cleaned it long after that lol