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Unregulated C02 powered piston BB gun, need feedback.

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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Unregulated C02 powered piston BB gun, need feedback.

Unread postAuthor: Leonard » Sun Apr 06, 2008 11:30 am

Hello!
I'v been waiting for the parts for this launcher for a while but the first version of it if finnaly assembled. you can take a look at the attachments. The first picture is the whole piston/pilot area assemble and the second is the piston, the Te and the piston housing taken appart.

As you can also see, i'v attached a safety pop-off valve on the launcher (115 psi). At first there was only the gauge, but i over-pressurized the launcher by mystake and the blowgun opened by itself. I will definetly need to upgrade that blowgun to a spring powered ball valve.

Im a little disapointed with the power. I'v only taken it to 110 psi max because of the blowgun pressure rating (125 psi) and the safety valve. It can pierce trough 3 layers of beer cardboard, the airsoft bb then stops halfway trough the fourth layer. So i need advice.

Is my pilot volume too high? Could it be that my piston moves too much or not enough? (it moves about 3/32 inch) Is my blowgun not efficient enough to pilot the piston? Is my chamber too small? (it is rather small indeed, a 1/2 elbow and a quarter inch Te.)

Also, when i press the blowgun VERY lightly, i lose the pressure without moving the piston. Is my piston not tight enough?

Well, that's about it. I guess i could have posted this in the discution section, if it's not in the right place feel free to move it.

Thanks guys!
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Unread postAuthor: Hubb » Sun Apr 06, 2008 11:35 am

Drop the popoff and gauge, upgrade the trigger to a 1/4" ball valve, increase chamber size, and run that bad boy at its full potential. I'm pretty sure you will not be disappointed with a 6mm plastic projectile coming out of a 800 or more psi launch.

To answer your question, it is probably the small chamber.

As far as the actual launcher goes, it looks good.
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Re: Unregulated C02 powered piston BB gun, need feedback.

Unread postAuthor: Ragnarok » Sun Apr 06, 2008 11:45 am

Leonard wrote:...and the blowgun opened by itself.

That would be because it's on back to front. Other than that, it looks like a decent plinker.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 06, 2008 12:12 pm

Small calibres need high pressure for power, especially in your case where you're using CO<sub>2</sub> which is a heavier gas than air. Ditch the blowgun and take it to maximum pressure ;)
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Unread postAuthor: Mitchza89 » Sun Apr 06, 2008 8:15 pm

That's a nice little gun ya have there mate. Hate to sound like an old record, but yeah... Ballvalves are one of the best way to pilot your gun at high pressures. Their flow compared to a blowgun, is a hell of a difference plus I'm confident that the blowgun WILL leak at 300+ PSI. Every single one that I've had, has. With that said, cranking up the pressure much past that, is gonna be a bit pointless if your gonna lose all that lovely CO2 out the blowgun. As for the piston, I used a self machined rubber stopper. With small bore guns at a decent pressure, your sealing face will get ripped off a hell of alot. This shitted me after a while so I eventually just thought "bugger it.....I need something thats ALL rubber..."

But yeah.... Just have a tinker with ya plinker and I'm sure you'll be fine mate. Trial and error is the best way to learn with spudguns :D.

All the best,

Mitch.
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Unread postAuthor: DYI » Mon Apr 07, 2008 5:09 pm

You'll be limited by the relatively low speed of sound and particle speed in CO<sub>2</sub> quite a while before you reach 800 psi, in my opinion. Try using helium, and you might be impressed by the results. If you choked the flow enough, you could simply feed unregged helium through it until it reached the desired pressure, then turn off the flow. This could be done without an expensive regulator, as long as you were *extremely* careful.
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Unread postAuthor: Matheusilla » Fri Apr 18, 2008 9:36 am

Nice little gun you got there. Sounds to me like you have a poor seal around the piston.
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Unread postAuthor: iknowmy3tables » Mon Apr 21, 2008 2:05 pm

the chammber is small for low presures , the blowgun is on backwards, the weak parts are the CO2 filler, unless it's ment for shocks, the blow gun, and of coure the saftey pop off, the high presure equivelent of a blowgun is the presure washer handle
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