How to Intersect Pipe Bend Groups for Turbo Manifold


I have drawn 90 degree pipe elbows, and when I overlap them for a merge of the two parts I cannot successfully Intersect Faces. Best case it draws lines on the inside and outside surfaces of the pipe at the overlaps, but I cannot get a notch cut out of a section of pipe. I have tried each pipe elbow as component made Unique, as a group (not Component), every which combination of exploding and Intersect Faces option, on both Pro and Make machines.
How does one solve this?
Thank you in advance.

1.75 od 2.5 radius 90 pipe elbow .12 wall 2 pipe group experiment.skp (261.6 KB)


Try cutting one elbow with Intersect, then copy, flip, assemble. No grouping involved. Thus:



Still a problem but thank you Gully for this step forward!

I’m glad to see that work for a flat plane and I will use it for cutting the final off-axis 4-pipe merge off at its base to mount to the turbo flange.

Please see this turbo merge collector:
header collector mockup better oil pan split 1-31-2016.skp (300.9 KB)

The pipes in this model (what I’m actually building) intersect at only non-flat planes, instead at curved warped bends. This is the problem.

To add another wrinkle, I want to draw and 3D print an outer layer shell to use as a cut jig/stencil over each pipe elbow so I can trace the physical pipe elbow cut lines and then reference the angle of the jig’s ends so the pipe cut angles are same as the model (flush) prior to welding.

Best I’ve come up with as a workaround is to possibly instead make each pipe elbow a solid, which would at least allow use of solid tools, hopefully. But I can’t get that to work either:
1.75 od 2.5 radius 90 pipe elbow solids 2 pipe group experiment.skp (178.2 KB)

Any help is massively appreciated! Thank you in advance.


First, and perhaps foremost, your elbow is in fact a solid in the sense used in SU with one very minor, easily correctable issue, namely, the centerline/path. Strictly speaking, an edge floating in space that does not bound a face is considered debris–the kind of junk cleaning plugins go after and remove. So, with a triple-click and a hit of the Delete key, the line is gone from all instances of the component, which is instantly recognized by Entity Info as a Solid Component.

Second, if you intend using the Intersect command to have two or more objects cut each other and fuse together along the cut lines to form a single, complex object, they must both (or all) be in the same context, that is, either in the same group or component or in none at all. If you were using Pro, you could leave all the components separate and use the Solid Tools to combine them into a single solid, but you can achieve the same effect using the Intersect command with Make.

If you want a single outer shell, you can simply spin-off a new component without an ID and use that to make the manifold. That is, leave them as instances of a component to distribute/arrange them, then explode them and combine them.



Gully wow you are amazing. You know such subtle nuances of SketchUp!

I understand points first and second, saving to Evernote!
Last point I’ll figure out with more practice.

I finally had some long overdue success notching out a pipe with your tips, and will continue to expand on the implementation of it until (hopefully) it is finished. Thank you Gully!

The goal is not to combine the 4 pipe elbows into one complex object, but instead to end up with 4 individual pipe sections that each look uniquely notched out like this:

Does the method you described allow for that final pulling apart? (kind of like a cut sheet for each separate pipe elbow). I am assuming yes with enough clever copying and undoing and combining components and using solid tools and hiding / something with the “pipe shells” it should work! I absolutely cannot wait to 3D print the eventual completed model, and test fit it and then put it on my desk as my first every 3D CAD success. Thanks in large part to you!


You needn’t be so effusive, friend: I am merely a garden variety Sage. Besides, it would seem I haven’t told you anything you can actually use, yet.

Sure, this is doable. Since the four notched pieces are to be unique, they must be separate components, not four instances of the same one.

When you invoke the Intersect Faces command, the lines of intersection appear in whichever context was active when the command was invoked. So you can simply enter each elbow group in turn, selecting all and picking Intersect Faces with Model. After the Intersect command, just remove the excess material (the cutout) and move on to the next elbow.

Maybe each elbow should be a separate component with one instance positioned twisting around its brethren and a second instance out in the open where you can get at it.



My $0.02 on the matter, to improve quality and efficiency:
Scale the thing up 100 times
Change the number of the segments of the circles to at least 48.
Change the arc segments to at least 24.
Work only with the outside of the pipes, you can’t cut the inside as the outside in one cut anyway.
Crete a copy of each of the two groups and use Substract from the Solid tools- first on the copy then the original. Then intersect with a plane, representing the plate.
Put them together and chose which of the pipe to let untouched and which to cut. Maybe now you decide to change the angle a bit so they won’t intersect that much. Don’t be afraid to start over, it’s just a 3d model. In real life you know how hard is to get those cuts right, especially with the inside cuts.
After all is done successfully scale down 0.01 and all is good.
At the end you can give them thickness using Joint Push&Pull plugin.
If you still want to cut the pipes in a realistic way, you need to intersect the outside of the pipes only, then the inside with the inside only then connect the two(outisde and inside) cuts.


Can’t wait to implement all of these approaches. Lots to play with. Thank you.


Ely good lord you’ve done the whole thing! Thank you so much for all the information! Going to implement all of it!

The last part,

then connect the two(outside and inside) cuts.

How would / did you connect these two cuts?


It’s not that much of a deal you know, once you get to know Sketchup a bit.
If you have the nerve you can connect it by hand with the line tool otherwise you can use the Curviloft plugin, that can be found on Sketchucation.


Worked on it for a long time and only now am really understanding what you said :slight_smile: I thought I understood it but didn’t really “get it” until I saw this method not working. Going to go back yet again and do it exactly as you recommended. Hoping to finally get it this time. This one was made strictly with solid tools, no intersects. I now see the limitations of solid tools, though it was fun to see how far they could go, and dang they are easy to use.


If you weld them from inside, which now seems a better approach being given the fact that the pipes are so closer, this may work !


I had the same thought, weld them together at the accidentally beveled inside joint. Better though for scavenging and airflow if the original sharp joint edges are maintained.
You do bring up a more important question: How the heck can this be welded?
My thought is to weld each volute pair together, then flatten their base with a belt sander, and weld each volute set to its half of the flange. But it looks like some inside welding is going to be essential, since there is that interior inaccessible inch. Inside welding where the pipe meets the flange is common enough in turbo header fabrication. That can be made to be a very clean solution with beveling before welding.

As for how to mate them at their intersection, I love the idea of using solid tools to subtract one pipe causing a flush fit-up to the other, then using a solid of the interior empty space to cut its mate. So one overlaps the other rather than the two having a shared butt joint. Possibly stronger, probably a lot easier to hand fabricate. Might be better, might be worse. TBD.

Though a bigger issue for now is the 2.5" radius pipes still take up a 4" vertical space. I want that closer to 3", so going to redo it with one or some of:

  1. Tighter radius pipes.
  2. Thinner wall material, 0.065" wall vs 0.120" wall.
  3. Slightly smaller inside diameter pipe than 1.5". In that 1.38-1.50" ID range.