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PVC, cement and heat

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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PVC, cement and heat

Unread postAuthor: dongfang » Thu Sep 13, 2007 6:37 pm

Hi,

I have epoxied together an air chamber of 110mm PN16 PVC. That´s 4½ inch pipe! I am pretty sure that without some kind of press or vice, I would never be able to push the parts together well enough with solvent weld; it sets real fast and real hard.

But - before I put pressure on it - does anyone have a reason or some experience not to use epoxy on PVC? I did file the pipe ends and fittings rough, and I have seen other epoxy cemented parts fail before the cement joints failed (yes, my S-DSTV shot the bolt.... there was no damper on it).

I have also used the ghetto technique of heating PVC parts in hot water to reshape them slightly, such as expanding one 75 fitting by 0.5 mm to make it slip over another fitting. Does that damage/weaken the PVC?

I intend to test the result at 4-5 bar first (it´s all PN16, hehe) and later, when I have a decent pump, throw it in a lake and see what happens at 20 bar.. but if anyone can tell me already now that it will be a disaster, well...

Regards
Soren
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Unread postAuthor: pyromaniac » Thu Sep 13, 2007 7:19 pm

First hand experience right here buddy, Mopher man and I made our first gun useing epoxy. Simple under over coke bottle chamber ball valve.

Well the bottem elbow blew off and Wham! the coke bottle hits my face. I'd suggest useing pvc primer and cement.
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Unread postAuthor: iknowmy3tables » Thu Sep 13, 2007 7:20 pm

epoxy on fittings is okay but its more expensive and not as safe as good o'le pvc cement, for some epoxy types you can add acetone to thin it out this will also help it bond to the pvc and allow fitting to slide together

heating and shaping pipe is not that safe it would probaly be safer to grind down that amount rather then heating, avoid doing it but when you do use lower pressures

I don't know what pn16 is but 20bar seems pretty dam high for something that uses a ghetto method of construction
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Unread postAuthor: f.c » Thu Sep 13, 2007 7:46 pm

i heated some pipe today using a heat gun and joined it together. its being used in a combustion gun but is this safe to do ?
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Unread postAuthor: frankrede » Thu Sep 13, 2007 7:48 pm

It should, maybe adding a few screws might help
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Unread postAuthor: SpudBlaster15 » Thu Sep 13, 2007 8:00 pm

If you roughened the mating surfaces prior to applying the epoxy, the joint should hold at least as much pressure as the pipe is rated to.
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Unread postAuthor: Marco321 » Fri Sep 14, 2007 3:07 am

Hey
On my coaxial, i epoxied the barrel into the brushing on the chamber. The barrel blew out from the force exerted on it by the piston, it took alot of shots, and it blew at around 40psi.

EDIT: I didn't roughen up the surfaces properly....
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 14, 2007 4:01 am

It all depends on 2 things, the quality of the epoxy you're using, and the care with which you clean and roughen up the contact areas. I have never had a problem with epoxied joins and have been using 350psi+ for the past 2 years at least.
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Unread postAuthor: Marco321 » Fri Sep 14, 2007 4:07 am

jackssmirkingrevenge wrote:It all depends on 2 things, the quality of the epoxy you're using, and the care with which you clean and roughen up the contact areas. I have never had a problem with epoxied joins and have been using 350psi+ for the past 2 years at least.


yeah i agree, my joint wasn't as good as it should have been :roll:
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 14, 2007 4:10 am

Marco321 wrote:yeah i agree, my joint wasn't as good as it should have been :roll:


here's all you need to know ;)
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Unread postAuthor: Marco321 » Fri Sep 14, 2007 6:20 am

jackssmirkingrevenge wrote:
Marco321 wrote:yeah i agree, my joint wasn't as good as it should have been :roll:


here's all you need to know ;)


Ohh right, my bad, iv been using epoxy in all my joints :P
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Unread postAuthor: dongfang » Fri Sep 14, 2007 6:55 am

OK thanks everynbody. I feel comfy enough with putting pressure on the thing now.

I did roughen the surfaces, and even took care that the file "grooves" are more or less perpendicular to the direction of the force on the fittings.

One thing I like about esing epoxy on PVC is that I can reuse the fittings if I decide on a different chamber size. 110mm fittings are quite expensive here, about 25 UD$ for a reducer to 3" and another 25$ for an end cap. They can be salvaged by cutting a slice along the length of the pipe, and them smash it in with a hammer and a chisel near the ends. The pipe then relatively easily peels off the fittings.

Maybe I will give it some bolts, if for nothing else then because it looks cool. Well, nice and smooth 9mm bushings, with 6mm bolts to hold them.

Regards
Soren
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Unread postAuthor: grumpy » Mon Oct 08, 2007 11:12 am

jackssmirkingrevenge wrote:
Marco321 wrote:yeah i agree, my joint wasn't as good as it should have been :roll:


here's all you need to know ;)


very interesting link there jack :o
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Unread postAuthor: Gepard » Mon Oct 08, 2007 12:02 pm

I've just finished (they're curing as I type) making my chambers on my cannon and I used 110mm with the proper cement without any problems or difficulty and there were 16 joints so it wasn't a fluke :D.

In fact I found the 75mm ones harder as I couldn't get as good a grip on them :D
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Unread postAuthor: rna_duelers » Mon Oct 08, 2007 10:53 pm

Just use plenty of glue so it slides on easily.Use the proper glue and primers as they are designed to do a job of holding the pressure.
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