Engineering problem: Attaching two objects.

[Risu]

I've got this prop I'm working on that consists of a series of tubes. There's one point where a plastic tube meets a copper tube, the exterior diamaters are the same and the interior diameter of the plastic tube is smaller than that of the copper tube. Another tube fits inside this point and just barely fits. What is the best way to permanently attach these two pieces without adding any thickness to the inside wall of the plastic tube? Thanks in advance for any and all help. The whole piece relies completely on finding a way to solve this problem.

 

[DaddyfromNaboo]

Pictures ?

I am pretty sure that if you are replicating a prop the original one had the copper tube wth a bigger inner diameter, so that the acrylic tube could be stuck into it.

 

[Risu]

I'm actually building a steampunk-ish version of a prop. There used to be more material on the acrylic tube that I could have filed into a smaller OD and pressure fit the copper tube over it, but it had to be removed after a mishap. I'm thinking I could possibly use a dremel to take out some material from the inside of the plastic tube to make the ID's the same, then get another tube with an OD the same as the others' ID's and glue it between the two. I'm just not sure if that'll work.

 

[robstyle]

Pictures could solve the problem. Doesnt have to be the entire prop in the photo, just the troubled area in question.

 

[Kang]

Even though I know nothing of props, I have had my fair share of these problems. Pics please.

 

[Risu]

My camera battery is dead at the moment, but here's a quick cross section mock up if it helps.

On top is the current situation, on the bottom is what I think might work.

 

[Kang]

Are you trying to plug it into a hole?

 

[Meule]

If I understand correctly you want the plastic and the copper tube to attach to each other without a visible solution, right?
In stead of dremeling out the inside of the plastic tube, why not get a rod that fits nicely into the plastic tube and cover the other half of the rod with tape, so it'll fit in the larger diameter of the copper tube. Then just glue the rod into both tubes.

 

[Risu]

Because another tube has to fit inside the plastic tube and move freely and it's OD is a hair smaller than the plastic tube's ID.

 

[Node Nine]

I don't see why that would not work, though I would be more inclined to turn down the OD on the plastic tube to fit the copper rather than bore its ID. By turning down the plastic tube's OD you could avoid the "new tube" adapter all together.

Edit: Added image

 

[clonesix]

connecting plastic to copper with only the wall thickness? You can use super gluse or even epoxy. The bond will not have enough surface area for the joint to be very strong.

Your best bet is to get a copper tube in the right diameter, and solder then together.

 

[CustomCreations]

I would put a slight taper on the inside of the plastic tube, about 1-2mm in.... You can prob run a scalpel blade around the inside of the tube to do this.
Scuff the inside of the copper tube to make a good key- the scuff the same with the plastic tube.
Using a quality 2 part epoxy adhesive, bond them together.
By tapering the plastic, you have given a larger surface area for the glue to hold onto (as it can smear out onto the taper without affecting the join diameter)

You dont say if the plastic is clear or not- but you can now clean away the internal glue blobs once hardened by using a drill bit the right diameter, or a bit of sand paper double sided to a tube/dowel/round object.
Your internal piece should now move freely, and the glue will cover the join like a bridge, rather than face to face...

 

[TK-2126_MD]

Is this what u need it to look like????

 

[Darth Lars]

Replace it all with a single copper tube and paint one portion to look like plastic.

 

[Risu]

I can't remove or cover up any of the outside of the plastic tube. It has details cut into it which are part of the overall design. And it's not clear. And I'm not quite getting what that new diagram is supposed to be. There's a tube that just fits inside the ID of the plastic tube that moves from one end to the other, not two tubes inside the larger.

 

[AnubisGuard]

I think TK is misunderstanding your diagram as indicating two small tubes stuck next to each other inside one larger diameter tube.

 

[Servo]

I've got this prop I'm working on that consists of a series of tubes.

Are you making the internet?

http://www.youtube.com/watch?v=f99PcP0aFNE

 

[Risu]

I can never help but use that phrase whenever the opportunity arises.:lol