My Cannons

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.
Canuck
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Sun Jun 08, 2008 9:05 pm

My Dads into HVAC (Heating Ventilation and Air Conditioning) so if theres scraps from a job, he lets me use them. Thats how i made my pneumatic. I had to buy most of the stuff for my combustion though. Will a shorter barrel help it perform any better? I usually have a plug of paper and put a small projectile in front of it. Do you guys think Hero Anti-Static work like Static Guard? It's highly flammable, says the label...
Canuck
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Mon Jun 09, 2008 5:37 pm

Sry to double post..BUT I think I found why my cannon isnt performing up to "par". Right now I have a 1:1 C:B ratio. Cutting 15" off the barrel, I will achieve .7:1!! Think it'll perform better? I'm also going to try out anti-static spray, sometime this week. Let me know what you guys think.
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xpitxbullx
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Mon Jun 09, 2008 5:45 pm

Cutting the barrel won't lower it to .7/1, it will raise it in the other direction. I don't know the dimensions of your gun but imagine it will be around 1.3/1

Jeff
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starman
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Mon Jun 09, 2008 5:52 pm

Canuck wrote:Sry to double post..BUT I think I found why my cannon isnt performing up to "par". Right now I have a 1:1 C:B ratio. Cutting 15" off the barrel, I will achieve .7:1!! Think it'll perform better? I'm also going to try out anti-static spray, sometime this week. Let me know what you guys think.
DON'T cut your barrel...pleeeease... geeze. :roll: 1:1 is great!!
Canuck
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Mon Jun 09, 2008 5:59 pm

It is? Must be the fuel im using then, cause a rock with a plug (Whats the plugs called that you put behind a projectile to make a better seal? Sry for my ignorance :lol:) will fly about 100ft. Thats the best I've gotten so far. Thats with Rubbing Alcohol though. I think that anti-static spray will be better. I've looked at a different site and they said a C:B ratio of 1.5:1 was the best performing. Are they correct?

Thanks,

Canuck
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starman
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Mon Jun 09, 2008 6:06 pm

Canuck wrote:It is? Must be the fuel im using then, cause a rock with a plug (Whats the plugs called that you put behind a projectile to make a better seal? Sry for my ignorance :lol:) will fly about 100ft. Thats the best I've gotten so far. Thats with Rubbing Alcohol though. I think that anti-static spray will be better. I've looked at a different site and they said a C:B ratio of 1.5:1 was the best performing. Are they correct?

Thanks,

Canuck
That would be a sabo... .8:1 is considered ideal under the right conditions (good fuel mix, spark gaps, fan etc.) but 1.5:1 to no slouch either.

Rubbing alcohol works OK but it isn't the best. Try some good ole Aquanet...anything with methyl-ethyl ether in it, usually works great.

Also Jeff (aka Pitbull) was a real fan of Gumout Carb & Choke Cleaner until he had a road to Damascus conversion to metered propane....uummm right Jeff?
Canuck
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Mon Jun 09, 2008 7:11 pm

Sabot, thats it! Would pure methanol do well?
The big reason for me cutting the barrel down, is the size of the bloody thing, lol. It goes from he back of my trunk, through my rear seat (folded down of course), and up to my shifter! Knocking 10" off would make alot of room but would bring the C:B ratio up to 1.2:1. lol, I'm sry for nagging on, but would it make much of a difference? I'm still learning about how much change it takes to the C:B, to really effect performance.

Thanks again,

Canuck
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starman
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Mon Jun 09, 2008 7:46 pm

Canuck wrote:Sabot, thats it! Would pure methanol do well?
The big reason for me cutting the barrel down, is the size of the bloody thing, lol. It goes from he back of my trunk, through my rear seat (folded down of course), and up to my shifter! Knocking 10" off would make alot of room but would bring the C:B ratio up to 1.2:1. lol, I'm sry for nagging on, but would it make much of a difference? I'm still learning about how much change it takes to the C:B, to really effect performance.
Sorry yes sabot with the "t".. :wink:

No a 1.2:1 will still have fine performance. .5 to 1.5:1 is a good performance window for most combustion guns...spray and prays aren't as predictable though...too many variables in play. Still these numbers will hold for them as well.

Keep in mind the first number represents the chamber volume, second number the barrel.
It goes from he back of my trunk, through my rear seat (folded down of course), and up to my shifter!
'Tis the price a spudder must pay my man... 8)
Canuck
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Mon Jun 09, 2008 7:50 pm


Sorry yes sabot with the "t".. :wink:

No a 1.2:1 will still have fine performance. .5 to 1.5:1 is a good performance window for most combustion guns...spray and prays aren't as predictable though...too many variables in play. Still these numbers will hold for them as well.

Keep in mind the first number represents the chamber volume, second number the barrel.
It goes from he back of my trunk, through my rear seat (folded down of course), and up to my shifter!
'Tis the price a spudder must pay my man... 8)
I guess eh. I'll just have to expereiment with it. Thanks, everyone, for all your help.
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n-strike
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Mon Jun 09, 2008 7:59 pm

I thought the chamber to barrel ratio thing was for the size of the pipe used. I didn't know it was for the length.
Philbob1
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Mon Jun 09, 2008 8:08 pm

It is for the volume,

Volume of the chamber : Volume of barrel
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xpitxbullx
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Mon Jun 09, 2008 10:32 pm

I love that metered propane now. If it wasn't for that, gumout is my spray-n-pray backup.

You should be fine cutting up to 1/3 of that barrel off. That will bring your ratio from 1:1 to 1.5:1 and that's still within what people here would call the standard.

First number is still the chamber volume in relation to the barrel (represented as a 1)

Jeff
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jr
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Mon Jun 09, 2008 11:40 pm

If I were you I would try and find a better sabot. You may be loosing pressure around the projectile and since combustions don't have a lot of pressure that is a bad deal.

try a potato and see how far it goes.

That is a nice long cannon you got there, welcome to SF.
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ammosmoke
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Tue Jun 10, 2008 12:17 am

xpitxbullx wrote:I love that metered propane now. If it wasn't for that, gumout is my spray-n-pray backup.

You should be fine cutting up to 1/3 of that barrel off. That will bring your ratio from 1:1 to 1.5:1 and that's still within what people here would call the standard.

First number is still the chamber volume in relation to the barrel (represented as a 1)

Jeff
I was under the impression that using carb/engine cleaners is a bad practice. I don't think that using such a strong chemical is a good idea.
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