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Oh boy, I think I'm gonna blow my cannon apart!

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Technician1002 » Thu Apr 30, 2009 3:18 pm

jmccalip wrote:It's finally coming together! I just need to make the wooden supports and I'll be done. My jigsaw is broken so this might take a while though...


I was testing the piston with only 15 PSI in the chamber, and when I pulled the trigger it let out a loud BOOM!!!. No funny noises or delayed hissing. It was instant. Good thing I had the bumper in there.


I'm going to attach a miniature sharpie to the bumper so I can see how much the spring compresses.


Congratulations on first pop.

On my 2 inch first test was at about 30 PSI in the house.. :shock: I about had to go change underwear. I didn't think 30 PSI would do that. :D You will want a good bumper. Enjoy and again congratulations.
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Unread postAuthor: jmccalip » Thu Apr 30, 2009 4:57 pm

Technician1002 wrote:Congratulations on first pop.

On my 2 inch first test was at about 30 PSI in the house.. :shock: I about had to go change underwear. I didn't think 30 PSI would do that. :D You will want a good bumper. Enjoy and again congratulations.



Thanks.

And thanks for helping me.

It's kinda scaring me at 25 PSI. I used to have a 4', 4" chamber sprinkle valve cannon triggered by the solenoid only, and all it did at 50 PSI was make a pitiful farting noise with no recoil. The piston cannon is a monster compared to this, even at 25 PSI.


:lol: It does have a fair bit of recoil. I can picture in my mind the 90 degree elbow snapping off, but maybe I'm just paranoid.


It leaks slightly out the barrel with my PVC piston. I think the pressure is seeping through the bolt/nut in the middle. Should be an easy fix.

Image
Do to the weight on the pilot side, I need a separate support for it.

Image
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Unread postAuthor: Technician1002 » Thu Apr 30, 2009 6:11 pm

jmccalip wrote:

:lol: It does have a fair bit of recoil. I can picture in my mind the 90 degree elbow snapping off, but maybe I'm just paranoid.


It leaks slightly out the barrel with my PVC piston. I think the pressure is seeping through the bolt/nut in the middle. Should be an easy fix.


Be sure to use a spacer and tie the barrel down. You don't want barrel whip from breaking things.

As for the leak, Put some air in it, Tip it up, and pour a cup of water in it.

:) No problem seeing where the bubbles come from now.
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Unread postAuthor: jmccalip » Thu Apr 30, 2009 6:17 pm

Technician1002 wrote:
jmccalip wrote:

:lol: It does have a fair bit of recoil. I can picture in my mind the 90 degree elbow snapping off, but maybe I'm just paranoid.


It leaks slightly out the barrel with my PVC piston. I think the pressure is seeping through the bolt/nut in the middle. Should be an easy fix.


Be sure to use a spacer and tie the barrel down. You don't want barrel whip from breaking things.

As for the leak, Put some air in it, Tip it up, and pour a cup of water in it.

:) No problem seeing where the bubbles come from now.


Put a spacer where? There is only an 1/8" gap between the tee and elbow. Maybe everywhere there is a gap, I guess it couldn't hurt.

I plan on 2 or 3 wooden supports with metal cable ties for the barrel, reinforcement for the 2" fitting coming off the tee, and a final support for the pilot.

I'll just hold off until I get the entire thing assembled, and then you guys can OK it. :lol:
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Unread postAuthor: Technician1002 » Thu Apr 30, 2009 6:29 pm

jmccalip wrote:
Put a spacer where?

When you attach the barrel to the valve it hang over the chamber.. Tie it down.

jmccalip wrote: I'll just hold off until I get the entire thing assembled, and then you guys can OK it. :lol:


Maybe a good idea :D

This guy has his barrel tied down well.
http://www.spudfiles.com/forums/the-spudinator-2000-t17850.html
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Unread postAuthor: dewey-1 » Thu Apr 30, 2009 6:33 pm

Looking good so far!

I recognize that flow control regulator.
That one is from Harbor Freight.
They work great as a fill port valve due to the small size.
I use one on each cannon that is built.
I even did a 3D drawing of it.

Have fun with that valve! :)
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Unread postAuthor: jmccalip » Sat May 02, 2009 5:28 pm

Ok, I got every assembled and ready to fire. I just need some lube for the o-ring and maybe a cool paint job. I'm thinking maybe gray fittings and black tube. Any thoughts?


Also, how do you KNOW if your bumper is going to work at high pressure? I use a 5" long 80lb spring, and 2" of a foam pool noodle. How can I be sure at 60PSI, so I don't blow myself apart?

Maybe a better question, what have you used successfully as a bumper for a 2" piston.
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Unread postAuthor: inonickname » Sat May 02, 2009 9:10 pm

jmccalip wrote:Ok, I got every assembled and ready to fire. I just need some lube for the o-ring and maybe a cool paint job. I'm thinking maybe gray fittings and black tube. Any thoughts?


Also, how do you KNOW if your bumper is going to work at high pressure? I use a 5" long 80lb spring, and 2" of a foam pool noodle. How can I be sure at 60PSI, so I don't blow myself apart?

Maybe a better question, what have you used successfully as a bumper for a 2" piston.


Place it on a flat surface, put some plywood over it and smack it with a mallet or hammer. You'll soon see if it's good enough.
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Unread postAuthor: jmccalip » Sun May 03, 2009 9:19 pm

Here's a sneak peak.


I test fired into some unsupported 3/4" plywood and it went right through at 20 PSI. At 40PSI, it went about 1/2" into a solid 2x4.


I had a spare 4" sch40 coupling and reducer that I machined down to slide perfectly over the 2" male/female adapters and 3" tee connecting the barrel. It's solid as a rock now. This insures that mishandle or barrel snap will not damage the delicate 2" threaded fittings.
Image
Complete with adjustable hop-up. I'll have to test it in the open field to verify how well it works.
Image


The problem is the cannon is LOUD when it fires. The sound is just a huge piercing crack...I don't want to attract unwanted attention.
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Unread postAuthor: Technician1002 » Mon May 04, 2009 12:43 pm

jmccalip wrote:
The problem is the cannon is LOUD when it fires. The sound is just a huge piercing crack...I don't want to attract unwanted attention.


A longer barrel will quiet it down considerably along with lower pressure. In a test, I tried an overly large barrel on the marshmallow launcher and launched a tennis ball at 110 PSI. The clank of the valve is noisier than the actual shot.
[youtube]http://www.youtube.com/watch?v=ZUTXomfdLTE[/youtube]

The tank, not shown in the video is the 54 cubic inch marshmallow cannon.
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Tennis ball barrel2.jpg
Marshmallow cannon with the 7 foot tennis ball barrel.
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