How do I get pipes tightened at precise angles?

[Stokestack]

Hi all. I have a non-plumbing scenario that nonetheless involves regular pipe.

I'm using 3/4" pipe to mount a driveway mirror on a vertical wooden beam. The mirror is in a wooden frame that I built, to which I plan to attach a flange to accept the pipe. I plan to get the pipe to the desired position by using relatively short nipples and elbows.

I've attached a picture that shows just the first experimental placement of a couple lengths of pipe for size. I'm mounting a flat mirror above and to the side of the near-useless convex mirror put up by the landlord; this adds to the mounting complexity.

This assembly needs to be adjustable in all directions for testing, and then secured at the desired position and angle. It also needs to be quite strong and resist rotation. Thus the fundamental problem: You never know exactly which direction an elbow is going to end up when it's fully tightened.

It seems to me that the only way of controlling the final angle is by putting a union in every leg of the assembly that requires rotation. Then I can rotate the assembly as desired and tighten the union. Does this make sense? For example, I'll have to replace the vertical pipe in the picture with two shorter lengths and a union in between.

In a real plumbing scenario, where plumbers need to route pipe using elbows, do they tighten the elbows as much as they can until they reach the desired angle, then secure them with sealant? This won't work for my application, but I'm curious.

Any other ideas? Thanks!

 

[Terry]

You don't need to fully tighten. Make it tight, with some still to go. Stop when it's where you want it. A bar of soap will lube the threads, or tape and/or dope.

 

[Sponsor]

 

[PorcelainVacation]

Since it doesn't need to be water tight, you can add a set screw if you need it to be tight in a position where it isn't.

 

[Jadnashua]

The difference between tight enough and it won't go any more is often more than one full turn, but you may need a bigger wrench to do it.

 

[Stokestack]

Thanks for the replies, guys.

The pipes do in fact need to be fully tightened; or at least the last one does, because it's going to be holding a considerable weight (the mirror within a large wooden frame) that will want to flop over if the thing isn't tight.

 

[OnlyinCali]

Why not put a couple of tack welds on it once in desired location? Or small through bolt?

 

[Jadnashua]

Tight enough and even tighter can usually be a full turn with a good sized wrench. A setting pipe dope verses one with PTFE in it, or even some thread locking compound could be used since it doesn't need to be watertight. The red Locktite is really hard to break loose once it sets. WOrks in critical things like in an engine, etc.. You would likely need more than you would with a straight thread, but around the end where it gets compressed via the taper should be enough.

 

[Stokestack]

Thanks, guys.

I ended up only needing two length of pipe, so I put unions in each.

I don't have a welder and really don't want to drill through iron elbows to place set screws, so I think this'll work. I'll post pics when I'm done.

 

[wrbix]

Blue LocTite

 

[Stokestack]

Thanks, but this application requires that I be able to adjust the angles and then tighten them instantly; no waiting for threadlock. Two unions ended up working perfectly. Here's the final result.

Now we can see the relevant oncoming traffic full-size, and not a bunch of other crap we don't care about.