Propane problems

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.
Recoiled_monsteR
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Mon Jul 16, 2012 1:20 pm

Well, I made a propane meter for my cannon. I am having a problem with get enough.......how to say it....uumph out of it. It really doesn't crack like it did with hairspray or shoot as far. I think it might be that the chamber size is too small, a .87:1 chamber to barrel ratio. It really cracks with a light projectile but heavier ones it kinda just blows it out. Any thoughts on what the problem could be? I have messed with propane % and that helps a little.
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jackssmirkingrevenge
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Mon Jul 16, 2012 1:22 pm

have you tried altering the ratios a little, higher or lower? your calculations might be a little off, and if the mix isn't right then performance will suffer. Note that noise is not always equal to the best ballistic performance ;)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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8tonsemi
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Mon Jul 16, 2012 1:23 pm

Have you tried the chart on advanced spud. com. It's exactly what you need. Google it and it should come up.
Recoiled_monsteR
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Mon Jul 16, 2012 1:28 pm

Yes I have adjust propane % up and down and have figured out what works best. I just am not getting the power out of it. I used to be able shoot potatoes, walnuts, and ear corn so far you could barely see it, now it just kinda lobs it not really up to it's previous ballistic performance. I have an air ram built into it, making for a recoiled gun like a field gun so I think it is robbing too much of the expanding gasses so I think I have to either shorten the air ram or make the chamber bigger. My thought was that there is not enough expanding gases supply both. Maybe the propane is not getting mixed good enough? Maybe I should add a chamber fan?
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8tonsemi
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Mon Jul 16, 2012 1:30 pm

A chamber fan is necessary when using propane. It helps mix the gases and get air into the tank when you open the back of the gun. And what type of ignition are you using.
Recoiled_monsteR
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Mon Jul 16, 2012 1:35 pm

I am using an electronic grill ignitor with 2 points of ignition
jsefcik
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Mon Jul 16, 2012 1:48 pm

Recoiled_monsteR wrote:I am using an electronic grill ignitor with 2 points of ignition

for 10-20 bucks get a stungun! =)
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jackssmirkingrevenge
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Mon Jul 16, 2012 1:51 pm

Some pictures of your setup will help us help you :)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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8tonsemi
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Mon Jul 16, 2012 1:57 pm

for 10-20 bucks get a stungun! =)[/quote]

Stun guns aren't legal in alot of places.
Recoiled_monsteR
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Mon Jul 16, 2012 2:02 pm

still the ignitor was half the cost of a stun guns that i can find. I'll try to get some pictures up, they are on a micro SD card in my phone and I think I misplaced my converter to SD. I'll see if I can find it
jsefcik
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Mon Jul 16, 2012 2:20 pm

Recoiled_monsteR wrote:still the ignitor was half the cost of a stun guns that i can find. I'll try to get some pictures up, they are on a micro SD card in my phone and I think I misplaced my converter to SD. I'll see if I can find it
i got two stuns, one was 10 other was 20
Recoiled_monsteR
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Mon Jul 16, 2012 2:29 pm

Lucky......the ones I can find go for $30 on the cheap end, but I always keep my eyes peeled for a good deal at gun shows and other festivities
jsefcik
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Mon Jul 16, 2012 2:31 pm

Recoiled_monsteR wrote:Lucky......the ones I can find go for $30 on the cheap end, but I always keep my eyes peeled for a good deal at gun shows and other festivities

do you want where i got mine from?

for my big bertha cannon i needed something very powerful,my chamber alone is 4 feet
Recoiled_monsteR
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Mon Jul 16, 2012 2:32 pm

But, the electronic ignitor works great and I got a discount 'cuz I work at the hardware store I bought it from :wink:
Recoiled_monsteR
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Mon Jul 16, 2012 2:35 pm

Sure, where did ya get your stun guns? Always figured it'd be nice to have a stun gun ignitor. Prolly will need it in the future, I want to make a 3" barrel field gun essentially. Still workin out the kinks and designing it. Eventually I am gonna build a 1/2 scale soviet SU-152 and this is how come i am working on a recoiling, propane powered cannon. Figured I'd test it out on a small scale before I went and made a behemoth of a potato field gun.
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