Advanced Cannon: The Breechloading 70mm

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.
Cy4ka
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Fri May 24, 2013 8:19 pm

Hey everyone. Here's my first "advanced" cannon that is propane, not "spray-and-pray." I built it as an over/under design.

I have some quick disconnects on the hoses I should've used on all ends but two are hose barbs coming off the meter. Oh well. The hoses have paint on them or something once it all falls off I'll either leave it red or wrap it with blacktape.

I went for a OD green/military color look.

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It's a 4" pvc chamber and 3"/70mm barrel. I built a way to load the breech from the top intead of chucking cans down the front. The main armature I welded extra pipe I had laying around and the cannon is mounted to that.

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It has a 12v fan I wired to a pushbutton and two 9v batteries.
The firing mechanism is a piezo button above the breech and two stainless electrodes in the chamber.

Open breech:
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Closed breech:
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When I get vid of it firing I'll post it. I'llhave to jsut shoot regular cans out of it for posting cause they don't like you talking about shooting pyro payloads, etc...

It's pretty heavy but it's awesome.

I wanted a 6" chamber and 3" barrel but didn't want to pay for the fittings so the chamber had to be a little longer for the 4" but I think it looks fine and is well balanced as you hold it. I think if Iused a 6" chamber the barrel would stick out farther than the chamber to the point it would want to tip down when you hold it. Right now the center of gravity is pretty much right where you hold it and fire it so it's staying like this.
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I'll make a rocket-launcher type next, hopefully out of all steel, and it will fire glass bottles full of napalm and stee.... I mean nevermind...
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MrCrowley
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Fri May 24, 2013 8:28 pm

Complete awesomeness! You pulled off that design really well, I love it.
and it will fire glass bottles full of napalm and stee.... I mean nevermind...
I'll pretend I didn't see that :wink:
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King_TaTer
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Fri May 24, 2013 10:17 pm

It's always refreshing to see a great looking advanced combustion. Well done.

I like the military green look. Have you considered multiple spark gaps in your chamber? Such a large chamber would definitely from more than one.
I can't wait to see the damage video and watch that mule kick.

Once again, great looking cannon man.
Materials links:
<a href="http://www.discounthydraulichose.com/">Discount Hydraulic Hose</a>
<a href="http://www.buyfittingswholesale.com/#">Buy fittings wholesale</a>
<a href="http://www.flexpvc.com/">Flex PVC</a>
<a href="http://www.murrayequipment.com">MEI
</a>
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Labtecpower
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Sat May 25, 2013 2:13 am

Awesome cannon!
Nice job on the breech, that really puts it ahead of a lot of combustions.

Point of criticism: it seems like you used DWV fittings for the gun.
With a spray and pray this normally not a problem, but with your metering system it might pose a safety hazard.
If you've ever seen PVC shards you know why :roll:
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jackssmirkingrevenge
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Sat May 25, 2013 2:20 am

Pretty sweet, love the handle. Reminds me of the chainSAW :D

[youtube][/youtube]
Last edited by jrrdw on Sat Oct 19, 2013 10:06 am, edited 1 time in total.
Reason: Fixed video.
hectmarr wrote:You have to make many weapons, because this field is long and short life
Cy4ka
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Sat May 25, 2013 9:39 am

ChainSAW! LOL! Awesome. Didn't see that before.
Point of criticism: it seems like you used DWV fittings for the gun.
No I made sure they were all sch20 PVC at least but I did drop the reducer fitting while putting the chamber fan in and it shattered :( but they are crappy to begin with. I got a new one and was careful to put all inlets through double wall areas.

I wear plate armor and a kevlar helmet when I shoot it so hopefully I won't get murdered if it ever failed. Main reason I want the next one to be all steel anyway.
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MrCrowley
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Sat May 25, 2013 4:25 pm

Cy4ka wrote:No I made sure they were all sch20 PVC at least
Contrary to what most sites on the internet say, Sch40 (or Sch20) is not an indicator of pressure rating so it is likely that the fittings are still 'DWV' (or at least not rated for pressure).

This might clear up any confusion:
http://www.spudfiles.com/spud_wiki/inde ... sure_rated
Cy4ka
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Sat May 25, 2013 9:20 pm

Hmm. Well, I'll let ya all know if it blows up.
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Hubb
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Sun Jun 02, 2013 8:20 pm

I'll let ya know that I think this cannon looks fantastic!! Great job.
Cy4ka
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Wed Jun 12, 2013 10:50 am

Hasn't blown up yet but I'm still waiting to get vid of it. Something's going on with my regulator I think (cheap harbor freight one) I need like 88-90psi so I figured why even have a regulator but somehow it only lets 60 psi into the meter down the hose and there's no leaks so something isn't working correctly and I suspect it's the crap regulator. Maybe I'll just leave it off.
sw5amped
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Sun Jun 16, 2013 8:27 am

Hey bro
Great job on that gun!!! I never leave comments on other people's guns but ill give credit where credits due! The fabrication is excellent and I like the up right prop bottle. I make compound rounds for my guns that work awsome. Id love to whip u up a few. 3" monsters!!!! Lol. Keep in touch!
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Tombstone
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Fri Aug 02, 2013 11:46 pm

Nice gun buddy! very well designed and made, looks sweet and the color is perfect! Keep up the good work! :P
..."Cannons to right of him,
Cannons to left of him,
Cannons in front of him
Volley'd and thunder'd;
Storm'd at with shot and shell,
Boldly He rode and well,
Into the jaws of Death,
Into the mouth of Hell
Rode the Tombstone."...
anarchy08
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Sat Aug 03, 2013 9:23 am

Fantastic looking gun mate, kid you not, I had one exactly the same functionality wise even the propane meter system.

notice I said HAD.

to cut a long story short she went up on me, had safety's on at the time no serious injury.
The hand that held the belly of the thing felt like I just 'high fived' a bus going the opposite direction on the freeway.

did the same as you, gas inlet through the double walls, even had large ratchet hose clamps around it as a means to hold the handle in place.

150mm x 400~ chamber reduced to 40mm golfball barrel in the over under style that looks so darn good. Internal chamber fan and twin spark strip

must have put 100 rounds (Golf balls)down range before out of nowhere she just popped on me, no visible stress fracture externally or any other indications.

Beware, DWV will go, 'When' is what you have to think about

Gorgeous gun btw don't let me detract from that.
thought about tripod and remote ignition?
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