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Bazookair - My first Co-Axial

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: microman171 » Sun May 04, 2008 3:07 am

Fair enough... Im not joking about the fitting though... The end cap cracked and the pipe boke off inside it. Wow $2000!!! After I get my degree I am going to move to USA. The glue is lasting and the highest I go is 100 PSI because that is what the pump's guage is rated to. I agree that this is cutting corners, but the truth is the fittings break before the glue and for me that is reassuring enough for me.
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Unread postAuthor: Killjoy » Sun May 04, 2008 3:32 am

@Mrcrowly and kablooie,
You know normally I would agree with you guys, but for many years I used super glue to glue pvc joints, ranging from 1/2" pvc to 3" pvc, and even at pressures over 150 psi the joints held, and continued to hold every time I used the cannon. You're on ground which your not familiar with so try not to get to worked up about this.

I have a number of cannons which still work and hold together despite having the joints glued with super glue, the SBC-500 is one and its almost 2 years old now and have been abused to no end without failure. Also at my job we build air cannons and water rocket launchers using super glue to glue the PVC joints for the kids, and we have yet to have any joint failures. Thats 1000s of joints glued with super glue, for hundreds of kids, over a 10 year period, and no failures to be heard of (and some of the stuff from ten years ago I personally know is still being used.

Super glue will work fine for gluing PVC joints. However it must be properly applied or it will fail, just like pvc cement or epoxy. Since I have no clue how you super glued your joints micro, I can not say whether your cannon is likely to fail or not, but my point is that super glue does work fine for gluing PVC joints.

That said, I'm still not gonna recommend you continue to use this cannon though, especially since you're sealing parts with hot glue suggests an improper super gluing technique. MrCrowley is right, spend the damn money and get PVC cement and primer and do it right. Only when you are familiar with the correct way should you move on to trying other things (like JSR and his epoxy).

I like the cannon but am wary about the risk. Just build another one just like it with the PVC cement and primer and enjoy the glory of a safer cannon.
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Unread postAuthor: MrCrowley » Sun May 04, 2008 3:58 am

The fact that he says he has leaks too, doesn't go down well.

Something like JB-Weld could also hold PVC fittings up to 100psi, but would I do it even if it was cheaper? No. It's not worth the risk.


I know you think the fittings break before the glue, but that simply does not always happen. Explain to me why would 270psi rated PVC blow at 110psi then?

Thinking you're safe because you used superglue, is something I wouldn't even think about.

Does it even have a pressure rating, the glue? Even if it is several hundred PSI, it doesn't apply to the same material with the same strength, and the fact that it leaks is proof of this.


but the truth is the fittings break before the glue and for me that is reassuring enough for me.

So on the packet of the glue it says "This glue can hold pressure rated PVC fittings over 18BAR (260psi) with the use of a compressed fluid or gas"?


Edit:
After I get my degree I am going to move to USA

Wow, how do you plan on doing that? Do you have relatives over there?

What you doing for your degree?
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Unread postAuthor: microman171 » Sun May 04, 2008 4:35 pm

Thanks for the advice guys! I am going to invest in some PVC primer. Is it okay to use the primer on its own? Or do I have to buy both? I will use new fittings and new pipe. I don't want to risk any explosion etc. How should I attach the end cap? Right now there is nothing holding it on (don't worry I haven't fired it). How should I secure it so it can come on and off? Rather than use primer (which I know is pure solvent) and glue (Which is solvent and PVC mixed together) is there any solvents I can use that people have had known to work?

I too would rather be safe than sorry.

EDIT- Okay I have just got all the new parts and solvent welded them together. The PVC cement and primer BOTH say for pressure and non pressure applications. There is definatly a lot of satisfaction in knowing that it is done properly!

Thanks for you warnings
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Unread postAuthor: MrCrowley » Sun May 04, 2008 11:17 pm

You use the primer with the solvent.

You should do this:
http://www.spudfiles.com/forums/solvent ... t3009.html

I did, and even got a certificate and pen to go with it. :)
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Unread postAuthor: biggsauce » Sun May 04, 2008 11:19 pm

Yeah the primer/cement combo, when done properly, should make your parts one piece of pvc.
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Unread postAuthor: Killjoy » Mon May 05, 2008 1:13 am

I did, and even got a certificate and pen to go with it.

I did it too but I didn't get a pen, just a certificate. I think some asshole stole the pen out of the package before I got it.
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Unread postAuthor: microman171 » Mon May 05, 2008 1:22 am

I went down to the local mitre 10 and bought what I needed. All solvent welded together! I will take the course next weekend when I have some extra free time.

Wow the fumes are scary! I was in the garage with the doors open and WELL ventilated but the fumes were still strong!

How should I attach the end cap? I dont want it to be permanent.
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Unread postAuthor: MrCrowley » Mon May 05, 2008 1:41 am

With threaded PVC fittings.
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Unread postAuthor: dongfang » Mon May 05, 2008 8:34 am

Hi,

Mate, I've had 270psi, that's right PN18(same as your fittings) pipe and fittings blow up on me at 110psi and that's when I used the proper glue and primer solvent welding techniques.


How the heck did that happen? Have you told the story somewhere?

Regards
Soren
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Unread postAuthor: MrCrowley » Mon May 05, 2008 2:08 pm

Yeah several times. Not quite sure, the only thing I can think of is rapid compression and decompression. I probably fired the gun 20 times in half an hour.
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Unread postAuthor: microman171 » Mon May 05, 2008 11:44 pm

Cant I use screws or something? I saw it on your GB gun
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Unread postAuthor: OuchProgramme » Mon May 05, 2008 11:53 pm

microman171 wrote:
How should I attach the end cap? I dont want it to be permanent.


Oh dear...
I laughed so hard when i saw that


DUH its gonna be permanent if you use glue+primer

Put primer on both end cap+piping
Put glue on both end cap + piping

Or like what Crowley said: Threaded fittings + teflon
I feel sorry for ya bud.
I'm not hating, just laughing
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Last edited by OuchProgramme on Mon May 05, 2008 11:54 pm, edited 1 time in total.

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Unread postAuthor: MrCrowley » Mon May 05, 2008 11:53 pm

microman171 wrote:Cant I use screws or something? I saw it on your GB gun

Yeah but they can leak if you don't use o-rings. I couldn't find the right o-ring so i just ended up glueing it on. The piston is pretty damn reliable, no cockups and it's been going strong for almost a year.
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Unread postAuthor: starman » Tue May 06, 2008 12:07 am

microman171 wrote:Fair enough... Im not joking about the fitting though... The end cap cracked and the pipe boke off inside it. Wow $2000!!! After I get my degree I am going to move to USA. The glue is lasting and the highest I go is 100 PSI because that is what the pump's guage is rated to. I agree that this is cutting corners, but the truth is the fittings break before the glue and for me that is reassuring enough for me.


Geeze, how much is a can of primer where you live?....$4 or so for 8 oz here in the states.

I'm with Crowley on this. Glue the stuff the way you are supposed to for crying out loud. Enough super glue to do those PVC joints isn't exactly free.

Edit: Sorry looks like you've already headed down the primer trail...good job...I'll shut up now.... :roll:
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