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trasher

Built a pneumatic 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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trasher

Unread postAuthor: tape fist » Fri Mar 06, 2009 12:59 am

First the reason behind the name and then the spec`s.I have been planing on building a piston valve for my next cannon for about a week and when i finally built it i was severely disappointed when the hot glue kept on grabbing the 1 in. pipe.since i didn't want my investment to go to waste i scraped it and made this.Hence trasher.surprisingly it is drastically better then my first air cannon and im very happy :) but i would still like to attempt a piston valve cannon. :(

Chamber:1 in. sch 40 PVC
Barrel:1/2 in. sch 40 bolt action barrel
Valve:sprinkler valve
activation:blowgun valve
Air source:Bike pump
pressure gauge:160 psi
tested pressure so far:100 psi

Chamber
Image
sprinkler valve
Image
barrel
Image
suppressor
Image
open suppressor
Image
Fully assembled-sorry couldn't get a full one
Image

Questions i have for more experienced builders
Is the suppressor i made doing anything and if it is it there any way i can improve it?
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Last edited by tape fist on Fri Mar 06, 2009 2:43 am, edited 1 time in total.

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Unread postAuthor: starman » Fri Mar 06, 2009 2:35 am

Not a bad effort tape, especially for a punt. Can you show a little more detail on your breach load mech...?

Your can photo is virtually worthless...way out of focus.
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Unread postAuthor: tape fist » Fri Mar 06, 2009 2:56 am

Not a bad effort tape, especially for a punt. Can you show a little more detail on your breach load mech...?


I got the idea off of this instructable.
http://www.instructables.com/id/SSPU7XQF6B7Q5Y1/?InstructImages The only thing i did differently is scale down to a 1/2 in. barrel sleeved in a 1 in pipe.I also added o rings to make an air tight seal and added a old handsaw handle.

Your can photo is virtually worthless...way out of focus.

I will get better photos up later.Not enough light where i took it. :(


thanks for commenting
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Re: trasher

Unread postAuthor: Lentamentalisk » Fri Mar 06, 2009 3:11 am

tape fist wrote:Questions i have for more experienced builders
Is the suppressor i made doing anything and if it is it there any way i can improve it?


Basically you have the right concept, but about 100x too small. Put a soda bottle on over the end of your cannon, and you will get much better results. Remember, for suppressors, the bigger the better. At no point is there such a thing as being too large. Also, if you fill the suppressor with steel wool you will get some improvement.
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Unread postAuthor: psycix » Fri Mar 06, 2009 3:34 pm

Nice cannon! Clean build.

Some comments:
-You could take that T-piece with the pressure gage out of your pilot volume and tap the gage in something else. Like in the chamber, or maybe even right into the sprinkler. This will increase performance a little.
-How well does your bolt seal? Did you add an o-ring or something (even duct tape) to seal it?
-About the suppressor:
It works, but it could be more efficient. Besides increasing the volume, you could also build a suppressor working in another way.
Make it vent air out to the outside. In order to slow the air vented out, add baffles. May create a short hiss if the baffles are not obstructing enough, but surely does the best job suppressing the bang.

When going for increasing volume, you could also make an expansion chamber around the barrel (Like a coaxial launcher) but in this case, the chamber is part of the suppressor.


Also, if you fill the suppressor with steel wool you will get some improvement.
Mainly for combustions, to cool the gases.
Does work like baffles, obstructing the air though.
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Unread postAuthor: tape fist » Sat Mar 07, 2009 1:26 am

-How well does your bolt seal? Did you add an o-ring or something (even duct tape) to seal it?


I used o rings to make it air tight.
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Unread postAuthor: Lentamentalisk » Sat Mar 07, 2009 2:32 am

psycix wrote:
Also, if you fill the suppressor with steel wool you will get some improvement.
Mainly for combustions, to cool the gases.
Does work like baffles, obstructing the air though.


I have done a fair amount of research on the topic, and what I gleaned is this:
Yes, steel wool has a much bigger effect on combustions, because it cools the gases. It does, however help in pneumatics, not so much because it slows the gases, but because it reflects sound waves back on themselves, canceling eachother out. Ideally one would calculate exactly the shape and positioning of all of your baffles, to perfectly cancel the sound waves, but for us, some times the best we can do is just send them all in random directions, and hope that they will tend to cancel.
Make no mistake though, for a pneumatic, baffles are far more important than the steel wool.
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