Based on some cool info found on the forums, I shortened my chamber to make a .8:1 C:B and increased the size of the suppressor. It still has a bang, but it is quieter than before by quite a bit. And it's difficult to tell subjectively, but I'd say the potato comes out faster than before.
The spray and pray method has its shortcomings, as you all know, and I'm feeling that now. Been reading up on propane meters and I'm starting to work on a design. I think I'm aiming for more portable than something huge and awesomely powerful...
I also have an idea for a butane-powered (metered???) pill-bottle mini.
Anyway, the current gun's specs are:
48" barrel, last 12" drilled for suppression. So for the C:B ratio, I used 42" for the calculation. Chamber is 4" x 8" (shortened from 16"!!) although I forgot to include the volume of the handle in the calculation... I may fill the handle.
Ignitor is a standard CharBroil piezo, inserted directly into the chamber via the handle, and sealed with high-temp RTV.
Desert camo paint job with Krylon "Super Flat" Fusion spray paint, tan and brown.
[youtube][/youtube]
I did a quick "damage video" today:
[youtube][/youtube]
CPCII Revised, with action video
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Boom_erang
- Private 4
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- Attachments
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- Further modified simple combustion cannon with 4"x8" chamber and 42" barrel with suppressor.
Last edited by Boom_erang on Mon May 26, 2008 8:44 pm, edited 1 time in total.
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ALIHISGREAT
- Staff Sergeant 3
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nice looking cannon, i like the paintjob 
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you want power... go .8:1 or a bad ratio and burst discs.. burst discs allow the pressure to build up some before they burst.
"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
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SpudFarm
- First Sergeant 3
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and that means you can use a shorter barrel...ilovetoblowthingsup wrote:you want power... go .8:1 or a bad ratio and burst discs.. burst discs allow the pressure to build up some before they burst.
"Made in France"
- A spud gun insurance.
- A spud gun insurance.
no problem... even if it isn't .8:1, i believe boogieman did some testing that showed using burst discs would improve the performance if it was a bad C:B ratio... look on http://www.advancedspuds.com somewhere for his testing with it.
"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
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Boom_erang
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Kostaki,kostaki wrote:I dont get the .8:1 c:b more power i thought the ideal ratio was 1.5:1
So did I, based mainly on info from Spudtech here: http://www.spudtech.com/content.asp?id=6.
However, after reading some of the threads here (I'm still a newbie, by the way), and especially after seeing the data here:
http://www.burntlatke.com/jpg600/15cb-graph.gif
http://www.burntlatke.com/jpg600/25cb-graph.gif
http://www.burntlatke.com/jpg600/cb-graph.jpg
And noticing that regardless of barrel diameter, the .7:1 or .8:1 ratio produces the most projectile speed.
Albeit this is for a metered propane system... But I suspect that for spray -n- pray guns, if the fuel mix is even close to optimum, that this ratio would still hold true. It certainly seemed to make a difference on mine!
-B
nice work. i love the paint job and thats one mighty silencer lol.
2 thumbs up!
2 thumbs up!
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bigbob12345
- Staff Sergeant
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Thats one puurty cannon
I really like the paint job, makes my painting look bad
I really like the paint job, makes my painting look bad