CF

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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Blitz
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Wed Apr 16, 2008 10:05 pm

*** UPDATE - 23 Apr 2008: Electrical system posted here.

So here's my pseudo build-log for those who were interested in my upcoming cannon. I chose the name CF, because the chamber has just over 1CF of volume, thought it was fitting. :) Please note, the tee/elbow and the flange assembly are dry-fitted and have not yet been glued. I barely had enough energy to pose the cannon for pictures let alone prep and glue those fittings.

Basic information

- The chamber is 6" ID, 60" long excluding the fittings.
- The barrel is 4" ID, 120" long excluding the tee/breech.
- The cannon weighs about 70lbs right now, it will weigh about 130lb when complete (stand, electronics, and breech block). No, I never wanted this to be hand-held. :P
- The propane meter will be approx. 22" of 3/4" piping, but I will calculate the total volume with the fittings before making this official.
- The cannon will feature a vertical sliding-wedge breech block for quick reloading of large ammunition. This is really the main reason I started this project -- the rest is just cake.

So yeah, it's a big gun, there's larger but this is respectable. Whatcha think so far? I have not shown any of the electronics yet, I haven't fully gathered what I need yet.
Attachments
Down the chamber, from the flange.
Down the chamber, from the flange.
The end of the chamber.  So far, using flanges is the most economical method I've found to plug up the end of the chamber.  Since it's 6" ID, I plan on making a nice sliding spark strip that can be easily serviced without jamming my arm down the chamber.  I have lots of room, might as well take advantage of it!
The end of the chamber. So far, using flanges is the most economical method I've found to plug up the end of the chamber. Since it's 6" ID, I plan on making a nice sliding spark strip that can be easily serviced without jamming my arm down the chamber. I have lots of room, might as well take advantage of it!
Down the barrel, from the breech.
Down the barrel, from the breech.
The breech end.  Over this fitting, I will be machining a vertical sliding-wedge breechblock and housing.  This will probably be the most time-consuming (and rewarding) section.
The breech end. Over this fitting, I will be machining a vertical sliding-wedge breechblock and housing. This will probably be the most time-consuming (and rewarding) section.
The cannon in all its glory.  Showed to give you a basic view of its configuration.
The cannon in all its glory. Showed to give you a basic view of its configuration.
Last edited by Blitz on Wed Apr 23, 2008 1:33 am, edited 1 time in total.
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TwitchTheAussie
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Wed Apr 16, 2008 10:12 pm

Nice size bud. She'l be pretty sweet when done. WHat are you using to power the spark strip?
Raise your horns if you love metal.
spudgunning is like sex, once you've tasted, you can't wait til next time.
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Blitz
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Wed Apr 16, 2008 10:15 pm

It's likely that I'll be using a stun gun only because of the sheer size of the chamber. But I will be experimenting with that next week.
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pizlo
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Wed Apr 16, 2008 11:28 pm

You have a perfect set up for a piston valve!
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Blitz
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Wed Apr 16, 2008 11:58 pm

It would take forever to fill up with my compressor. The chamber has half the volume of my compressor as-is! (It's 15 gallons)
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starman
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Thu Apr 17, 2008 12:16 am

Ahh so there it is. I didn't really grasp the scale of the thing until I realized those were standard 6' foldout tables underneath.. :shock:

So a breech loader...don't forget to calc the elbow volume into the tank size.

What have you decided on for ammo?
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Blitz
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Thu Apr 17, 2008 12:25 am

starman wrote:Ahh so there it is. I didn't really grasp the scale of the thing until I realized those were standard 6' foldout tables underneath.. :shock:

So a breech loader...don't forget to calc the elbow volume into the tank size.

What have you decided on for ammo?
Applesauce jars. :)

I have also made some ammunition out of 3" PVC scraps. Along with my breech, I am designing an extractor that'll pull casings out of the breech when opened. Just like the real thing, though I may have to make it lever-operated instead of automatic, but that's fine.
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psycix
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Thu Apr 17, 2008 6:07 am

Its big, its powerful, its clean and all together: SUPERB!
You should hold that with two man (or alone if you can) and feel the recoil :D
BLAM!

I assume your breech loading system will be a very interesting design.
Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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TwitchTheAussie
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Thu Apr 17, 2008 7:02 am

This is gonna be one sweet sexy momma' :D
Raise your horns if you love metal.
spudgunning is like sex, once you've tasted, you can't wait til next time.
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brother361
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Thu Apr 17, 2008 1:29 pm

awesome so this is the beast
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Blitz
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Wed Apr 23, 2008 1:40 am

Bump, updated. :) See top of the thread.
brother361
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Wed Apr 23, 2008 7:14 pm

so i guess this is what your big a** gun is goin to turn out to be
[youtube][/youtube]
Last edited by brother361 on Wed Apr 23, 2008 7:19 pm, edited 1 time in total.
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bigbob12345
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Wed Apr 23, 2008 7:18 pm

Wow that thing is enormous
Dont see too many cannons out there with a chamber that large
im extremely impressed

and brother361 copy and paste the url not embed code

Edit: brother nevermind
Ive always been impressed by when he hits the tree and half of it falls over.
Last edited by bigbob12345 on Wed Apr 23, 2008 7:24 pm, edited 1 time in total.
brother361
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Wed Apr 23, 2008 7:20 pm

bigbob12345 wrote:Wow that thing is enormous
Dont see too many cannons out there with a chamber that large
im extremely impressed

and brother361 copy and paste the url not embed code
i know i messed up i fixed it your too fast
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Blitz
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Wed Apr 23, 2008 9:56 pm

Well, that cannon's got a larger diameter chamber, but I have more volume. It also has a shorter barrel.

It also weighs less than half of my design right now, and his does have the portability of being handheld. I did not design my cannon to be handheld at all, going for structural intergity and the luxury of some of the nicer things a combustion cannon can have.

It's also muzzle-loaded, whereas mine will have a quick-opening vertical-wedge breech.

Elevating and traversing will be operated by a hand crank, worm-gear setup. The mount will be small enough to transport with my truck, though.

So I guess they're similar only in size -- but my cannon will definitely be larger and less mobile. But I think it'll also be more powerful though, with more volume, a propane metering system. HGDT calculated 4800ft/lb of muzzle energy with a 3lb projectile, though I did that using exactly a 60" chamber. With the elbow and breech, it's going to be more than that so teh figure will definitely change.
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