Pete Zaria's Over/Under Combustion

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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Pete Zaria
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Tue Jan 23, 2007 12:13 am

Squeaks,
Thanks for the input. I've already used ProMeter to find the right pressure for the meter pipe, however, I don't know for sure, but I think my pressure gauge reads 7-10psi high, so I may just experiment and find the best mix.
I'm working on finding a 2" camlock locally. I agree, that would be very cool.

I really like the feel of the gun now. It's kind of barrel-end heavy because of the ball valve and all the metal hardware there, but it's not bad. I can't wait to shoot it tomorrow. Waiting for the glue to dry is the hardest part.

I'll post pics tomorrow and a video as soon as I have time to find some cool targets to destroy.

Peace,
Pete Zaria.
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Pete Zaria
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Tue Jan 23, 2007 8:40 pm

IT'S DONE!!!

All I have to say is WOW! It's unfathomably loud. The first time I fired it, I didn't have hearing protection on.. I won't make that mistake again. Everything works wonderfully. Thanks so much to everyone that helped me along the way.

It's too dark outside to get good pictures now; I'll take some tomorrow.

Peace,
Pete Zaria.
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MrCrowley
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Tue Jan 23, 2007 8:43 pm

Muzzle flash? Perfect at night time :P
I can't wait.

Note: Anyone planning to post a cannon soon do it now, or wait a few weeks,it will get ignored for some time, when this cannon comes out :P
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Pete Zaria
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Tue Jan 23, 2007 9:29 pm

Here's a few pics I just took inside. I'll post some better ones and some damage pics, and hopefully video, in the next day or two.

Meter side:

Image

Tank side:

Image

Image

Spark strip:
Image
Back of spark strip:
Image

More tomorrow.

The fan controller and 12v battery are in the front grip, there's a BBQ sparker currently in the rear grip. On the inside of the chamber, I used 10g insulated wire so that it can handle a stun gun in the future. All I'd have to do to upgrade to a stun gun is replace the wires going from the handle to the bolts with thicker wire. But this BBQ sparker is jumping all the gaps on the spark strip just fine, so I'll leave it be for a while.

I've been launching spuds with this new gun outside for the last little while... I can't tell you how far they're going because its dark out, but I can tell from the kick and sound that they're going way farther than my old gun. I have a tree about 50' from my back deck that I shoot spuds at a lot. With the old gun, when you shot a spud at it, there was the BOOM from the gun, then about half a second later, SPLAT. Now, with this gun, there's almost no delay at all between the CRACK and the SPLAT. Awesome.

Peace,
Pete Zaria.
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MrCrowley
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Tue Jan 23, 2007 9:47 pm

HOLY SH*T, nice gun,like the dual handles :P Whats with all the zip-ties?
Is the fuel meter pipe crooked?
Apart from that great cannon,it was worth the wait. :twisted:
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Pete Zaria
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Tue Jan 23, 2007 9:51 pm

The zip ties hold the handles, propane meter, and propane tank on. I could have used huge hose clamps (dryer hose clamps) instead of zip ties, but the zip ties are black (look better, IMHO) and are cheaper.

I'm going to attach a piece of 3" pipe to hold the propane tank.

The propane meter is a bit crooked, but it's OK, I'm not quite done with it. I'm going to make some nice spacers to hold it to the cannon, and straighten it out. Probably tomorrow.

Thanks a bunch for the comments. I hope everyone enjoys the damage pics I'll post soon.

Peace,
Pete Zaria.
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Tue Jan 23, 2007 9:51 pm

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Last edited by SpudBlaster15 on Wed Jul 14, 2021 12:58 pm, edited 1 time in total.
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Pete Zaria
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Wed Jan 24, 2007 7:27 pm

Today I fired the cannon 10 or 15 times (stopped because my neighbors called...) with zero misfires. Distance was dependent on the quality of the potato's seal in the barrel. I got a hang time of 19 sec with a small-ish, good-sealing chunk of spud. Distance estimated at 400 yards. I can't wait to get the 10' stick of SDR-21 and play with golf balls. I have lots of them laying around :)
I discovered the best propane mix seems to be two "shots" at 70psi. I think my gauge might be reading a few psi high though, but whatever, it works every time, so I'm happy.
I added a shoulder strap, and started working on a longer barrel and silencer.

The fan stopped working for a little while. After investigation, I found the problem was because it had shifted slightly (it's friction-fit into the 4" pipe) and the blades were pinching against the frame. I corrected this problem by inserting a coat hanger with a small hook bent onto the end through the 1.5" vent valve, grabbing the fan, and pulling it forward slightly. It runs now, and it seems to be staying put. If it continues to move, I'll open up the chamber and glue it in place, I guess.

To come:
Paint whole gun glossy black.
Laser pointer sight
Hotter ignition - stun gun or battery-powered grill sparker?
Maybe:
Propane regulator? Is it worth it? The meter works fine unregulated...
Mount propane tank in 3" pipe?

As to destruction video... I found a 233 MHz green iMac in my garage. I have no use for it. Unless someone wants it and is willing to pay shipping, I'm thinking about having it play a DVD, and shooting it with a concrete-filled caulk tube while it's on. The only problem is what to do with the pieces. Where I live, it's illegal to throw away electronics in the trash - pollution and all. If someone can figure out what I can do with the junk that won't A) cost me any money, or B) be illegal, I'll blow up the iMac on video for your pleasure. Ideas?

Peace,
Pete Zaria.
SpudBlaster15
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Fri Jan 26, 2007 2:00 am

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