Super glue for pneumatics?!

[sirspuddest]

So, I just got my buddy into spud gunning a few weeks ago, and he got the bug REAL bad. He's built a combustion, a mini, and a pneumatic over the course of the past couple weeks.

Anywho, he built his pneumatic using SCH40 PVC and dollar store super glue. I told him he was insane, and that he was probably gonna kill himself.

Well, he proved me wrong, I guess. He's charged and fired the cannon up many times now (150+ PSI - he's gone as far as 180), and it doesn't leak or anything.

I still don't trust the thing, and I won't go anywhere near it, but super glue seems to be holding just fine.

Any thoughts on this? Personally, I don't trust it one bit, but I figured I'd ask the experts what they thought about it.

[Xerxys]

I find myself making the same slightly sarcastic comment on two forums in one day, both with a bit before explaining it, but here goes:

If you find yourself using it, always hold it in your mouth so when it blows your death will be quick.

But hey if it hasn't blown yet it might not.

and tell him to build a safer one and put the other on his wall.

[kablooie]

Super glue is not good. Anything that's not pvc primer/glue is bad news (with the exception of well applied epoxy). I guess it's better than hot glue, but I predict that cannon will violently disassemble itself when your friend least expects it. Do your friend a favor and cut his cannon to peices and burn it. No, I'm just kidding, but at least warn him again.

[Killjoy]

Alright here's the truth:
Super glue does work well for gluing PVC parts together. The capillary action pulls the glue evenly into the gap. However this has to be done properly and if done incorrectly could create a weak bond and be extremely dangerous. If done right though, the bound can withstand up to 150 psi safely and last for many, many years (my sbc-500 was super glued together and it still works great with no failures, and I've seen other cannons ten years old glued the same way that still have not failed).

And now here's the reality:
Nothing will beat the bond that PVC primer and cement creates because it basically welds the two pieces together. It also was intended for gluing PVC and designed for it so it will produce the best bond.

Unless you in a tight fix, you should always use PVC cement and primer no matter what. Seeing as I can not review your friends super glued joints for safety, I can not condone the use of it or request it be disposed off. However if it does not leak then the joints are probably sufficiently glued and should be fine.

Now with all that said, you friend should never take the cannon over 150 psi again. PVC pipe is not designed for use with compressed gases and when it fails it will resemble something much like a fragmentation grenade. Generally 125 psi is the recommended limit but 150 psi seems to be ok.

[jackssmirkingrevenge]

Most of my launchers are held together by high strength adhesive that was never intended for PVC, and have been taken to 400 psi without a single failure.

I have no experience with cyanoacrylate adhesives personally, but if done well - correctly prepared surfaces etc. - I see no reason why one couldn't make a perfectly safe launcher in this manner.

[starman]

...and be sure you use the purple primer....

[Hubb]

The only bad experiences I've had with super glue and PVC is the fact that I always seem to get a drop on my fingers, which tends to attract another finger...

I've never had a problem with super glue and PVC, CPVC, or any other type of plastic.

[Hydra]

The only bad experiences I've had with super glue and PVC is the fact that I always seem to get a drop on my fingers, which tends to attract another finger...

I've never had a problem with super glue and PVC, CPVC, or any other type of plastic.

Same here, you always get super glue on your fingers everytime you use it, even if you wear gloves are something. It gets really annoying...

But seriously, I dont want to risk using super glue, PVC Cement is your friend..

[starman]

The only bad experiences I've had with super glue and PVC is the fact that I always seem to get a drop on my fingers, which tends to attract another finger...

I've never had a problem with super glue and PVC, CPVC, or any other type of plastic.

Same here, you always get super glue on your fingers everytime you use it, even if you wear gloves are something. It gets really annoying...

But seriously, I dont want to risk using super glue, PVC Cement is your friend..

...And long curing epoxy for tough to weld joints in coaxials....it is your friend as well.

[THUNDERLORD]

I'm not sure what psi a car cylinder generates(?).
But I owned a chevy 305 with one cracked and the mechanic repaired it with JB weld!

BTW, I am finishing a project and I just need to add epoxy to the threads on the blow nozzle into the sprinkler valve.
Now I might just run and super glue it. Course if it doesn't hold, the cannon will fire by itself!
( I always point them in safe direction anyway so...).

[MrCrowley]

I wouldn't trust the dollar store bought stuff.

It can work well, really well. But eventually breaks under repeated stress.

I managed to bond a vice at school together because of a bet with a teacher. He said the cheap stuff is just as good. Well he was right until I fixed weights to the vice to keep stress on the bond and after a minute or two it came apart. But when it first bonded I couldn't break it.

[sirspuddest]

Wow, that's surprising.

So, the general consensus seems to be that, if you use it right, super glue will work just fine for pneumatics - even if primer and cement are the preferable choice.

And I watched him while he glued it - he slathered the fittings and pipe in glue before and after he pressed them together. He definitely did not skimp on the glue.

Oh well, I guess I can relax when he brings that cannon around from now on.

[THUNDERLORD]

....
Oh well, I guess I can relax when he brings that cannon around from now on.

Don't include myself on the "general consensus"! I mentioned glueing metal threads into the valve to hold better, not pipe joints.

The difference is superglue is an adhesive. And PVC glue actually welds the parts into one piece.
I don't ever trust anything 100% though. (Helps take precaution).

[jr]

I plan on sticking to my good old pipe cleaner and pvc cement. I value my life and the money I invest in my toys!

[sirspuddest]

Okay, it finally failed the other day.

The end cap/tire valve assembly finally blew off the other day, and hit him right in the ankle. The pipe and fittings are all fine, as well as his ankle, but I think this was a good wake up call for him.

I never trusted it, really, and I made this clear to him, so it was awfully hard to resist jumping on an opportunity to say "Told ya so!", but I managed to keep quiet. I did get a good laugh, though, once I realized that nobody had been hurt.

So, yeah. This just reaffirms what I've always thought - I'll stick with good old primer and cement, or epoxy.

Tell ya what, though. I almost had to change my pants after it blew off.

I've been an avid shooter my entire life, and that's still one of the loudest bangs I've ever heard. My ears were ringing for a good three or four hours after the incident.