Vertical mold, sealing tube

[Dale Allen]

Hey all, thanks in advance.

Since I could not find a larger pipe today for my pressure chamber, I decided to try it vertical. Here is the rig using a dowel rod set in a bottom plug. I have a delrin centering plug for the top that is not shown here.
anyway, the brass tube does not fit tight on the dowel so what could I seal the ends with in this situation. I have clay, CA, 5-min epoxy, tape, glue gun, etc.

 

[longbeard]

I'm thinking a clay mold to fit the bottom of the tube then a rubber plug that you can get from lowes/home depot (put a little eyelet screw in the end of the plug) to fit the top of the tube. I dont cast this way, but just a thought. JMO


Harry

 

[Dale Allen]

Harry, I started to use that method but was also considering how to center the tube in the plastic mold. This is a plastic sleeve used of transporting pens. One end is sealed and the wood block on one end keeps the dowel, and thus the tube, centered in the mold. I had considered using small pieces of aluminum screen on the ends of rubber stoppers to center the tube. This use of a dowel seemed easier. Just have to seal the ends of the brass tube where it fits loose over the dowel. Maybe some teflon plumbers tape will work.

 

[Kenny Durrant]

I'm not very good a describing what I'm thinking but I'll try and hopefully it might help rather than confuse you. I use silicone plugs on both ends of my brass tubes and also a silicone stopper on the bottom of my mold. I took a straight pin and went all the way through the bottom of the stopper and secured the plug for the tube with the pin that holds it on the bottom and keeps it centered. I drill a small hole in the top plug to equalize pressure and I bend a wire that wraps around the mold then goes into the mold and into the hole in the plug to keep the top centered. I hope this might help. Good Luck

 

[Dale Allen]

Kenny. I think I see what you are saying!:bulgy-eyes:
You pin the stopper to the plug which I assume is the ID size of your mold and that centers the bottom end. Then the 'spring' like wire at the top centers the other end.
Question: what do you use for a mold? I used a plastic tube that may not release the resin and I may have to destroy the tube to get the blank out.
Here is a picture of the thing after I removed it from the pressure chamber.
I used teflon tape to make a better seal on the brass tube.
You also mentioned about a hole in the stopper to equalize the pressure. I was assuming that if the ends of the brass tube were not tightly sealed that the resin would be forced into the tube. Is that a false assumption?

The good news is there are no bubbles detected.
Bad news is that I really need to be patient and let this cure for a few days.:frown:

 

[Kenny Durrant]

Sorry I can't get my camera to down load pics to the computer or I'd show you what it looks like. That is true you want a tight seal with the plugs to keep the resin out of the tube. Others have said in the past that the heat generated from the resin setting has caused air to leak out from the ends of the tubes. By drilling a hole in the top plug only it allows the pressure to equalize within the tube and not causing it to leak where you don't want it to. I also use that same hole for the wire to keep the brass tube centered but the wire is loose enough to let air pass through if needed. I use a clear plastic tube for a mold and I make a cut from end to end and tape it back with scotch tape. I use black electrical tape to seal the tube to the bottom silicone plug. That way it makes it easy to demold everything. I hope this helps.

 

[Dale Allen]

Kenny, thanks again for the explanation.
It is now quite apparent to me that although I now have a very nice cast blank, the method has a major flaw.
I spent the better part of an hour getting that wooden stick out of the brass tube, Apparently the resin also makes a fairly good adhesive!
The teflon tape did not keep it from seeping inside the tube. What a pain!:frown:
I will re-design this using some rubber stoppers I have from a PR kit.
The hole in the stopper seems reasonable in that the resin will flow to the path of least resistance and that should not be inside the tube. We'll see!
I just don't know if a tight fit in the end is enough with all the heat and movement going on in there.