Connecting two pipes/profiles

Hi,
My problem looks very simple but if you try it, it’s not so easy.

One rounded rectangle profile 49mm x 14mm and circle profile pipe radius 7mm.

2pipes

How to connect them (two lines show direction) to make air duct?

My try with Fredo Loft and with out-of-the box SketchUp :slight_smile:

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200404A_Air_Duct.skp (171.1 KB)

Interesting problem. As far as I know there are no single “Follow Me” solutions that will generate the curve in a single operation. But there is a reasonably straight forward design approach that yields good results. It is a bit more complex that what can be demonstrated in a quick video … so I attached a .skp file that sort of leads you through it. This simple demo was done with simple surfaces (zero thickness) … but the same approach will work equally well with “real” thickness to the duct.

To construct Duct 1 start with one circle circle … pull that to the desired length of the connection.
Then split that in half … and grab the half circle of what will be the the “oval” end of the connection … and move it out the desired end of the oval. Make that a group. Copy the group to make the other end of the connection … scale it by -1 to make the mirror image … bring the two ends together. Explode both ends. Connect the two inside corners of each side with a single straight line on each side … which will fill in the connection on each side with a simple triangle. Make a Group out of the finished connection … and “Soften/Smooth Edges” as you do it. Duct 1 is finished.

Duct 2 starts with the same circle on one end … and with a second, smaller circle (with the smaller radius of the oval end) … set the smaller circle at the desired length of the connection … on the same center line of the larger circle… Make a four sided surface between the two circles … using one line on the center line of the two circles … lines on the radius of each circle … and a fourth line connecting the ends of each radial. Then select one of the circles … and do a “Follow Me” using the four sided surface. This will generate a cone surface that connects the larger circle on one end to the smaller circle on the other end. Split that in half … and as before, grab the half circle of what will be the the “oval” end of the connection … and move it out the desired end of the oval. Make that a group. Copy the group to make the other end of the connection … scale it by -1 to make the mirror image … bring the two ends together. Explode both ends. Connect the two inside corners of each side with a single straight line on each side … which will fill in the connection on each side with a simple triangle. Make a group out of the finished connection … and “Soften/Smooth Edges” as you do it. Duct 2 is finished.

But the duct in your example is a bit more complex … it has flats on both the sides and the ends. That I am calling Duct 3. To make Duct 3 … start exactly as with Duct 2 … with the larger circle on one end … and with a smaller circle (with the radius of the corner of the end) … set at the desired length of the connection. And as before, make a four sided surface between the two circles … using one line on the center line of the two circles … lines on the radius of each circle … and a fourth line connecting the ends of each radial. Then select one of the circles … and do a “Follow Me” using the four sided surface. This will again generate a cone surface that connects the larger circle on one end to the smaller circle on the other. From this save only a quarter of the cone … and then grab the quarter circle of what will be the the “corner” of the connection … and move it out the desired position at the corner of the “oval” end of the connection oval. Make that a group. Copy the group to make the other side of the connection … scale it by -1 to make the mirror image … bring the two sides together. Explode both sides. Connect the two inside corners with a single straight line … which will fill in the connection on that one end with a simple triangle. Make a group out of the finished end connection. Copy this group to make the other end of the connection … scale it by -1 to make the mirror image … bring the two ends together. Explode both ends. Connect the two inside corners of each side with a single straight line on each side … which will fill in the connection on each side with a simple triangle. Make a group out of the finished connection … and “Soften/Smooth Edges” as you do it … and Duct 3 is finished.

My guess is that once you work through Duct 1 … it will be obvious how to make the Duct 2 and Duct 3 shapes. Equally obvious is that there is nothing to be gained by doing a full 360 degree “Follow Me” to generate the “cone shapes” for Duct 2 or Duct 3. 180 degrees will suffice on Duct 1 and Duct 2 … and 90 degrees is all that is required on Duct 3.

So there you have it. These written directions ended up being a bit more tedious than I had expected … so I could lead you through the process with a quick screen share if that would be more helpful. But then, the .skp models make be sufficient. The key is to develop the connection first … and then add the rest of the duct to the connection … making the complete duct. My guess is that you started with the two ends … and then got stuck trying to connect the two ends.

Good luck, you are welcome contact me if you get stuck.

Regards,

E. Godsey

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Equally easy if you do an offset first so it is a pipe. Just separate the corners.

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Wow great technique!

Sorry I wasn’t addressing you with my comment @egodsey, I was referring to @endlessfix and how it could be done the same but already offset.

Your technique is much simpler … and thus (in my opinion) superior to my scheme of starting with the circles.
Thanks for sharing

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Lot of different ways to go about this, that’s one of the fun parts of SketchUp. @Box is right of course about the offset, thanks for lighting a fire under me. Here is a version for making the same duct with a 1mm wall thickness with native tools.

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Your technique is impressive … and fast. But you are mistaken on the wall thickness. Do a Section and you will find that the wall thickness “as measured in the video” is correct ONLY for the walls that are perpendicular to the base (horizontal plane). All of the other walls are something less than that … specifically: WTM times cosine of AWV.

Where:

WTM is Wall Thickness as Measured on the horizontal plane

AWV is Angle of Wall off Vertical

Regards,

E. Godsey

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This is totally true, as the end fittings are at an angle relative to the wall as you pointed out, one of the two has to be a different thickness than 1mm. This could be corrected by sizing the planes at the two end connections up to a thickness that yields a true 1mm wall. But then the end fittings would have odd internal diameters, I picked the ends to be standard as that’s where the fit usually counts. It depends on the manufacturing process and the end use goal. Good catch though.

I suppose you could do the whole operation on a single surface object, and, as a last step, add thickness with Joint Push Pull.

Yup, JPP would be great here, I was just trying to “go native”. But with the end plates positioned as like this , angled to the wall, you would still have to pick one of the two to be 1mm.