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Here is my first attempt.

Built a combustion cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Here is my first attempt.

Unread postAuthor: longshot1068 » Sat Nov 19, 2005 3:36 pm

well, it isnt anything spectacular, but seeing as I got most of my info to build it from this forum it shouldnt be a total bummer to you guys. I finally built my first REAL spud gun and im getting just over 1/10 of a mile on 22 PSI of propane. The total length of the cannon is 8 feet. The chamber is 4" x 36" and the barrel is 1.5" x 60". I was surprised at how loud the report is from this thing! Sounds like a shotgun :). It isnt painted and doesnt have an official name yet ( been calling it my ,Tater Tosser). Hope your not too dissappointed in my first attempt. your opinions are respected and welcome.
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Unread postAuthor: CS » Sat Nov 19, 2005 5:22 pm

Spectacular for a first build! There is only one thing that I can see to complain about which is the use of duct tape. (gives off a ghetto look) Whats your CB ratio it looks a little out of control? 4:1? Your chamber is way to big know that I think about it. Why does your barrel have a reducer in the middle of it? Good job on the propane injection by the way. I could of only wished that my first spud cannon was this nice.
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Unread postAuthor: longshot1068 » Sat Nov 19, 2005 6:01 pm

There is still some fine tuning to do, I only did some quick research on this forum before delving into the project. I think th cb ratio is appx 4.54:1 if memory serves me correctly. the reducer in the middle of the barrel isnt really a reducer. I ran my 1.5" barrel thru a peice of 2" to help stiffen the barrel a bit, the reducers are modified to allow the barrel to run thru and to hold the 2" in place. Im going to do some more looking around to find a better remedy for the cb ratio, im assuming ( only cuz im still new to this) that the closer to 1:1 that I am the better?
Thank you for the compliment, it means alot to hear it from a veteran.
The duct tape was merely to hold the igniter wires out of the way but im thinking about using some wire loom to make it prettier. If there is any more advice that you would like to share, I would love to hear it.
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Unread postAuthor: TalonXxX » Sat Nov 19, 2005 6:46 pm

hmmm pics arent working for me :( anyone else have this prob? it'd be nice to see it...
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Unread postAuthor: longshot1068 » Sat Nov 19, 2005 7:31 pm

I notice that they arent there myself, I will try to resubmit the pics.

**EDIT** All better now enjoy!
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Unread postAuthor: saladtossser » Sat Nov 19, 2005 9:38 pm

wicked meter.
did u let the kid shoot waist height?
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Unread postAuthor: boilingleadbath » Sun Nov 20, 2005 12:36 am

About the ratio:
It's not hurting you, per se; a large ratio gives you more power, but it would have been better to make your chamber (say 18") shorter and use those saved inches to make your barrel longer... No matter, though - just something you might want to keep in mind next time.
You might try getting a 2" or even 3" barrel as long as your 1.5" - you'd get more power, even if it is a bit heavier. Note that this is not because you have moved the ratio closer to 1:1. Thinking that mearly being closer to the full-rescource-utilisation ratio gives you more power is deceptive - a better way to think of it is that, because of the larger diameter (and thus area) of the pipe, you have more force pushing on the tater... and of course, energy is related to distance*force.
(the 3" barrel won't have 4 times the muzzle energy of the 1.5" barrel though - mostly because the pressure declines as the gas expands to fill the barrel, and partly because of flow restrictions as it passes through the 2" threaded coupling. You will get worse preformance through the 3" barrel than the 2" barrel with light ammo because of this flow issue, but it shouldn't be an issue for ammo less than... 20-30 grams. [only an estimate, not calculated])

Your "sleaving" of the 1.5" pipe is rather unique - most people don't do it for their sch 40. Probably impoves accuracy... it'd be interesting to get a test on that, if anyone with a bit of money and some free time wants to do so.
If someone does so, please don't clamp your launcher like the burnt lakte tests - people don't do that in normal usage, so it's not an accurate description of the barrel accuracy. Resting it on a table should be fine, though.
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Unread postAuthor: longshot1068 » Sun Nov 20, 2005 8:36 am

the sleeving was put on to improve to improve the rigidity of the barrel, much like having a heavy (match Grade ) barrel on a distance/target (sniper) rifle. The thought behind it was to prevent the barrel from wobbling around as the charge was touched off and the gun was subjected to recoil and muzzle rise. Ive been resting the butt end of the chamber on the ground and firing it much like a mortar, and this thing has surprisingly been placing shots within 20 feet of one another with no real means of aiming it. I tried to design the meter for 36 PSI which called for a 4.5 " length of 1.5" tubing but forgot to take into accoumt for the rest of the peices that added to the capacity of the meter. I had to mess around thru trial and error to figure out that im getting the same charge as intended but at 22 PSI.
we went thru alot of propane yesterday, torch tanks, but put almost 10 lbs of spuds downrange. This hobby is addictive and now I see why it gets so advanced while chasing greater distances. Im smitten. Keep up the great job guys with this forum and I appreciate the useful input, we shall try to make do you proud.

As far as my son shooting it from the hip, He's still a bit too small to hold this bugger by himself but he love to be there when we shoot it. He's only 3 , but we'll learn him right early!
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