Barrel Support

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Postby Velocity » Sun Feb 11, 2007 1:43 pm

I have recently finished a coaxial pneumatic. The OD of the barrel is .75", and the ID of the chamber is 1.255". While this cannon works, it seals very unreliably, for the barrel support which I built was a strip of copper bent in an attempt to center the barrel. This support does not work very well, and the piston is almost always sealing the barrel at an odd angle.

I need some suggestions on a barrel support which will not decrease flow, and will center the barrel. The easiest solution would be to just pound a nail 1.25" long through the barrel and that would support it; however, due to my configuration, I cannot do such a thing. I would need to pound a nail through the entire coaxial chamber and through the barrel; this would be difficult, and probably lead to leaks.

My idea would be to take 1.25" PVC rod, and cut a .75 hole in the center. On the remaining material, I would drill as many holes as possible, to allow the air to flow through the support and out the barrel. Would this decrease flow a lot?

Thanks
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Postby Arborman495 » Sun Feb 11, 2007 2:09 pm

Just take two pieces of flat pvc and cut them to fit between the chamber and the barrel. Thin them down to where they are very skinny and epoxy them about 8- 10"? up the chamber
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Postby Suppresive Fire » Sun Feb 11, 2007 4:41 pm

I take 4 .25in wide strips of whatever is on hand (lexan, wood, metal) and attach them to the barrel about 1/2 way up.
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Postby sgort87 » Sun Feb 11, 2007 7:22 pm

Why can't you use a machine screw through the chamber wall and through the barrel? The threads will seal on the PVC and should not leak.

You could use maybe 4 screws around your chamber that all thread into the barrel.
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Postby Numbuh 16 » Mon Feb 12, 2007 12:56 pm

Just cover it in larger PVC.... If that works.

Also, wood.
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Postby Velocity » Mon Feb 12, 2007 6:36 pm

Numbuh 16: If I covered the barrel in larger PVC, it would support it, but air would not be able to pass this support, and therefore performance would suffer greatly.

Gort: A screw would be difficult to thread through precisely, but I suppose it could be done as long as I took my time. One problem I see is flow reduction in the barrel. Because the barrel is so narrow, any obstruction, even the size of a screw, would hurt performance a fair amount. Usually I would not care, but with this current gun, i'm going for the max
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Postby Freefall » Mon Feb 12, 2007 7:02 pm

So you want a support that has less cross-section than a screw? Good luck.

What's wrong with using a couple (I'd use three) screws from the outside in to center your barrel? The screws don't have to penetrate the barrel, they'd just hold it in place.
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Postby clide » Mon Feb 12, 2007 7:04 pm

Just thread three of them through enough to touch the barrel at 3 points, they don't have to go through the barrel.

Edit: bah Freefall beat me, must have hit reply right after I clicked on the thread.
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Postby BewareOfDog » Mon Feb 12, 2007 10:09 pm

<img src="http://img.villagephotos.com/p/2003-9/398596/coaxsocrassy.GIF">
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Postby Bone-23 » Tue Feb 13, 2007 11:38 am

<IMG>http://i19.photobucket.com/albums/b188/bonedrummer/spuds.jpg</IMG>

dunno how to make pictures show up...
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