SpudFiles

Hello all... (Betcha haven't seen my face around for a while)

But I do need your help once again.

I need to figure out a way to attach 2 (or possibly 3) 2" PVC couplings together, in a row so that a 2" pipe can slide into all of them when they are attached.

I was thinking of maybe sliding them onto a two inch pipe, and JBwelding the edges together, or possibly putting thin rings of some material around the joins and JBwelding those.

These couplings will be holding cartridges for a single shot grenade launcher i designed, so obviously they have to be inline for a 2" pipe to slide into it.

Opinions?

thanks

you could weld them but then you would need a pvc welder and pvc welding rod. woudn't 2" couplings fit inside 2 1/2" pipe rather snug?

@grumpy: facepalm.jpg :/

@ilovetoblowthingsup: how solid do these couplings have to be attached? What forces are acting on them?

[quote="markfh11q"]@grumpy: facepalm.jpg :/]

ok ill bite what does that mean?

I would try this.

After dremel tooling the inside ridges down so the pipe will slide through, with a disk sander, carefully sand flat the ends of all the couplers, or the ends that will connect to each other. This will allow for a solid connection between them.

Then, build a "dumbbell" out of 2 2" to 1" reducer bushings. Cement the reducers together with a short piece of 1" pipe. You may have to sand off the hex or the ridge around the outside. You can then use this dumbbell to align the 2 couplers while cementing the couplers together without worry that you will cement the aligning tube. Use a very small amount of cement to where none or only small amount will leak inside.

After welding, push the alignment dumbbell out. If you leaked some cement on the inside, you may need to cut the dumbbell in half before pushing it all the way out.

grumpy wrote:ok ill bite what does that mean?

I think it may be a comment on your "PVC welder", but don't hold me to that.

As for whether 2" couplings will fit in 2.5" pipe.... it might work, but I don't know US pipe fits like that, not having any experience with them. Ask me about UK copper fits like that, and I'll tell ya though.

So, you want a couple unions joined end to end that you can slide the pipe into and then still be able to remove the pipe at will? Even if you remove the central ridge the couplers are going to be a very tight fit on the pipe. If you need to be able to remove the central pipe with minimal force, you'll probably need to either grind the ID of the couplers bigger, grind the OD of the pipe smaller, or cut a very narrow lengthwise cut in the pipe then reglue the cut closed to reduce the pipe's OD by a bit.

How strong does it need to be?

Dremeling out the ridge in the couplers would be one way to go but it can be kind of hard to reach that far into the coupling.

Do you have a power miter saw? Chop the ends of the fittings square, making them flat enough to be joined together. Chop the fittings in half to remove the central ridge completly (easier than Dremeling). For 3 fittings you would have 6 "half-coupler" pieces with no central ridge. The ends are all square and true and can be glued together.

Or, you can take another coupler and slice it into ~1" long rings. Cut the rings open so it looks like a "C" (only need a saw kerf width as the open part of the "C"). Boil the rings in water and, while hot, force over another coupler to reform the ID of the C to be about the same as the original OD. Assemble the coupler halfs using the C rings as "couplers for couplers". A bead of PVC glue can be run around the fillet where the Cs sit on the couplers. That should be more than strong enough if this part does not need to be pressure rated.

Actually, in answer to Jimmy's "tight fit problem" - have you considered looking for slip couplings? These are usually a bit more expensive, but they're designed to let the pipe move freely through them.

This is usually either to allow replacement of cracked sections in fixed pipes, or to provide support for a pipe that may move lengthways.

They might be useful here - I personally used them to support the movable barrel (for breech loading) on HEAL.

Ragnarok wrote:

grumpy wrote:ok ill bite what does that mean?

I think it may be a comment on your "PVC welder", but don't hold me to that.

ok , i just assumed that people like me that use alot of pvc in building cannons and such would also know about welding pvc.

pvc welder http://www.laramyplasticwelders.com/torchpage.html

pvc welding rod http://www.usplastic.com/catalog/produc ... t_id=11514

welding school http://www.plasticweldingschool.org/tech/techtips.php

It has to be strong enough in order to support a) a cartridge being slid in and out..

b) strong enough to be slid back and forth- as an M203- slides forward and back.

c) strong enough to withstand a reasonable impact.

oh jimmy- im going to sand out the ID of the coupler a bit as well to allow the pipe to slide easily in and out

I think what i'll try is jimmy's technique- actually maybe a combination of the two.

I'll glue the half couplers together, and then glue the "C" pieces over the joints as well.