Bigfoot Howitzer

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.
Boomgobug
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Fri May 30, 2008 4:03 pm

Holy crap that is a big MOTHA!
How much it cost?
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STHORNE
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Fri May 30, 2008 4:26 pm

Man, nice work Spuddin! Very military-style gun.

But for a stand that big...the scale of the gun vs the stand is kinda out of proportion (stand is way bigger lol) but it still looks awesome.

I would have suggested a 6" double-chamber, over-under combustion at the least for a kick-ass stand that big, but that's just me lol :lol:

Still did a very good job though. Nice paint work too :wink:

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Spuddin
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Sun Jun 01, 2008 12:43 pm

Boomgobug wrote:Holy crap that is a big MOTHA!
How much it cost?
about $40 u.s.
as for the propane meter and fan i had that stuff laying around that i salvaged over time. as of now i dont use the meter because the gun does not like propane, it likes canned propellant such as solarcaine first aid spray, that sucks because i gotta clean the cap threads now after shooting it a few times. but the solarcaine is 3 times more powerful than propane.
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starman
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Sun Jun 01, 2008 1:34 pm

Spuddin wrote:
as for the propane meter and fan i had that stuff laying around that i salvaged over time. as of now i dont use the meter because the gun does not like propane, it likes canned propellant such as solarcaine first aid spray, that sucks because i gotta clean the cap threads now after shooting it a few times. but the solarcaine is 3 times more powerful than propane.
Propane is a little more sensitive to getting the mix right and sparks being in the middle of chamber, etc. If you get all that down pat, it is just as reliable.

I just saw your video and it is impressive! It's amazing, you can throw that baseeball as hard as you want to against that plywood and it will just bounce off or knock the board down...shoot the same baseball with a cannon and punch a hole right through it.

You have some fairly significant ft lbs flying out of that barrel.
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xpitxbullx
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Wed Jun 11, 2008 10:21 pm

You still going to add a softball barrel to this monster? That is some nice work. Hope you get the propane problem solved.

Jeff
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starman
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Wed Jun 11, 2008 10:34 pm

I meant to comment on this yesterday when you reposted the paint job. It looks great!!

I agree with Jeff, you would be so much happier if you got a solid metered propane solution going. One thing I might suggest there is to get your spark gaps out in the middle of the chamber rather than at the rear. The fan is tending to move the mixture away from the rear...propane being a little picky, is probably showing up a little lean back there where the spark lives.
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Spuddin
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Fri Jun 13, 2008 7:50 am

Spuddin wrote: UPDATE #2: i added the electric bbq ignitor and a spark strip with double sparks using small bolts.
even with the double spark strip and electric ignition it still wont shoot propane, i cannont figure it out, ive tried 5 to 40 psi.

as for the softball barrel i might leave the baseball barrel on and make a softball mortar instead.
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bigbob12345
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Fri Jun 13, 2008 9:25 am

ive tried 5 to 40 psi.
Well then maybe you should try 45-60psi too
Nice cannon though
Although I think it looked better without the camo or sheild but thats just me.
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Spuddin
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Fri Jun 13, 2008 10:13 am

bigbob12345 wrote:
ive tried 5 to 40 psi.
Well then maybe you should try 45-60psi too
i could but i think it would be a waste of propane because my meter is alot bigger (1.5") compared to 1/2" meters. although it is short it would not require much pressure, if i used the calculator right it said to use 10 psi but nothing happened.
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starman
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Fri Jun 13, 2008 10:27 am

Spuddin wrote:i could but i think it would be a waste of propane because my meter is alot bigger (1.5") compared to 1/2" meters. although it is short it would not require much pressure, if i used the calculator right it said to use 10 psi but nothing happened.
Oh...you do have a largish meter. I'm thinking you may need a smaller meter so you can pump the pressure up in it some...get a good injection shot into the chamber. I like to fit a meter that requires 50-60 psi to get the right volume.

Also, if your barrel is sealing the chamber, your meter will come to pressure equalization with the chamber and not evacuate all of the propane. Another reason to overwhelm it with pressure instead of volume.
Taavet
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Sun Jun 15, 2008 5:06 pm

yerrr... nice work mate, im planning my own altillery
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potatoflinger
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Sun Jun 15, 2008 6:30 pm

I don't know if you have already tried this, but since you are having trouble with your propane meter it might help. From what I can see in one of your videos, it looked like you weren't pushing the baseball all the way down the barrel, you were just pushing it in the length of the baseball bat. To get a good fuel mix, you would have to calculate your meter pressure using the volume of the chamber, plus the space in the barrel behind the baseball (which is pretty much part of your chamber). That could be the reason why your propane meter doesn't work.
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Sun Jun 15, 2008 9:25 pm

dude that is one awesome artil. u got there!
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