Union Mods for Burst Disk

A place for general potato gun questions and discussion.
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PeteS
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Joined: Wed Sep 11, 2013 5:53 pm
Location: Maryland
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I started with a standard 1-1/2" union from Home Depot. It looked basically like this:
Image

I then chucked the pieces up in my lathe and ground the tapered faces flat. It could be done with a belt sander, grinder, or even files if you have the patience. The modified product looks like this:
Image

Next comes a gasket. It goes on the side toward the chamber. I cut it with a scissors, so there was some excess both inside and outside, and contact cemented it to the union. Then I ground the excess off with a dremel tool drum sander attachment. The rubber is 1/16" stuff from Lowes, found in the plumbing section. The result looked like this:
Image
Sorry that is a little out of focus, but you should get the idea.

Initial tests seem to indicate that this modified union works well.

I hope that is helpful to someone.
[center]My wife upon seeing my latest hybrid and hearing an explanation of it:
"That really isn't a potato cannon anymore, is it?"
[/center]
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noname
First Sergeant 4
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Joined: Mon Apr 10, 2006 9:19 pm
Location: Bay Area, CA

My union isn't nearly as angular as yours is, for whatever reason. The chamber side is mostly flat, and the angled part of the barrel side extends maybe 1/16" into the chamber side's angled face.
Seeing how well your mods turned out makes me wish I had a lathe... Maybe this summer I'll turn one side of my bench grinder into one. I could also try using my bench grinder but getting it flat would be a chore.
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20140124_181938 (800x600).jpg
User avatar
PeteS
Specialist
Specialist
Posts: 179
Joined: Wed Sep 11, 2013 5:53 pm
Location: Maryland
Contact:

noname wrote:My union isn't nearly as angular as yours is, for whatever reason. The chamber side is mostly flat, and the angled part of the barrel side extends maybe 1/16" into the chamber side's angled face.
Seeing how well your mods turned out makes me wish I had a lathe... Maybe this summer I'll turn one side of my bench grinder into one. I could also try using my bench grinder but getting it flat would be a chore.
If you had access to a belt sander the flat surface might make finishing up the job easier. Interesting how different your union is. It looks like it has a lot of flat on the concave side and none on the convex one.
[center]My wife upon seeing my latest hybrid and hearing an explanation of it:
"That really isn't a potato cannon anymore, is it?"
[/center]
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noname
First Sergeant 4
First Sergeant 4
Posts: 2698
Joined: Mon Apr 10, 2006 9:19 pm
Location: Bay Area, CA

This should be good to go! I'll be able to test fire in a couple weeks when I go back to school.
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union.jpg
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