Gluing Back Together CPVC?

rcman50166 · Mon Apr 12, 2010 11:12 pm

So I found some clear PVC in my university's machine shop and then I saw another and thought, "If they were only longer I could make a combustion cannon." So I want to glue them if at all possible. Can anyone reccomend an adhesive?

Hubb · Mon Apr 12, 2010 11:21 pm

How about super glue? It should support a basic combustion launcher.

Gaderelguitarist · Mon Apr 12, 2010 11:40 pm

I would suggest gluing the joint, as well as making a bracket that would hold the completed chamber together with a compressive force similar to that achieved with a basic C clamp.

If I were in your situation, I would do the above, as well as strengthen the glued joint with a coupling of some sort.

rcman50166 · Mon Apr 12, 2010 11:51 pm

Hubb wrote:How about super glue? It should support a basic combustion launcher.

Well after a little math, assuming combustion is equivalent to 100 psi, There would be 678 lbs of force or 238 psi of pressure on the glue. Would you let super glue support that?

Gaderelguitarist wrote:I would suggest gluing the joint, as well as making a bracket that would hold the completed chamber together with a compressive force similar to that achieved with a basic C clamp.

If I were in your situation, I would do the above, as well as strengthen the glued joint with a coupling of some sort.

I want to keep a clean look, a brace would be sloppy looking.

EDIT: I find that super glue (Cyanoacrilate) has a shear strength of 1000 PSI. This gives me a safety factor of 4.169. Is this good enough for spudfiles?

Gaderelguitarist · Tue Apr 13, 2010 12:07 am

I want to keep a clean look, a brace would be sloppy looking.

Perhaps. But remember it doesn't have to look sloppy. Build up a thickness of plywood longer than the chamber, cut it into the shape of a gun stock, pistol grip, etc. Then just remember to leave a rectangular cutout for the chamber to sit in with perpendicular pieces hugging the front and back of the chamber. If painted before attachment, the whole setup could look quite clean.

rcman50166 · Tue Apr 13, 2010 12:14 am

Gaderelguitarist wrote: If painted before attachment, the whole setup could look quite clean.

lol but if I paint it, it will defeat the purpose of clear pvc.

Also I edited the earlier post:

rcman50166 wrote:
EDIT: I find that super glue (Cyanoacrilate) has a shear strength of 1000 PSI. This gives me a safety factor of 4.169. Is this good enough for spudfiles?

Technician1002 · Tue Apr 13, 2010 1:52 am

Make sure you know for sure what that clear plastic is made of. If it is PVC, then PVC glue and joints can be used. If it is polycarbonate, superglue might not bond to it. Test a small drop of superglue on an end that will be covered by a fitting. After it is set, see if you can peel the glue off. If you can peel the glue off, then don't use that glue.

PVC cement on poly tubing will dry and can be easily peeled off. PVC cement on PVC pipe will soften and bond to the PVC.

I do not recommend using plexiglass for a combustion cannon. It is brittle and will craze and crack with stress leading to shrapnel when it fails. Plexiglass is solvent welded with a compatible solvent glue.

Gaderelguitarist · Tue Apr 13, 2010 12:09 pm

lol but if I paint it, it will defeat the purpose of clear pvc.

I'm sorry, I meant paint the wooden portion. Event with a shear strength of 100 PSI, I don't think I'd trust it. The worst that can happen though is it will fail and split at the seam, rather than explode into a million clear bits.

jhalek90 · Tue Apr 13, 2010 4:31 pm

Just use a coupler.

That is.... if it is truly pvc.

One strip of white (or other color) could actually look really good.

Better yet, use a T and then use it to hide your spark plug... and wire.

mikespahn · Wed Apr 21, 2010 9:26 am

Gaderelguitarist wrote:
I want to keep a clean look, a brace would be sloppy looking.
Perhaps. But remember it doesn't have to look sloppy. Build up a thickness of plywood longer than the chamber, cut it into the shape of a gun stock, pistol grip, etc. Then just remember to leave a rectangular cutout for the chamber to sit in with perpendicular pieces hugging the front and back of the chamber. If painted before attachment, the whole setup could look quite clean.

i agree with this. a colored stripe (coupler) in the middle wouldn't look that bad and if you make a stylish brace you could strengthen and enhance appearance.

on a side note since no one has said this... all the clear pvc that i have ever seen had a bluish tint to it. that doesn't appear to, so how sure are you that it is in fact pvc? also if it is, does it have any marking to describe pressure rating?