# Ellipse to circle transition elbow

Hello, I’ve enjoyed using sketch up to design components for tools in my wood shop. I’ve been working on a dusk collector elbow that needs to be 3D printed as spare parts are no longer available from the manufacturer. I’ve been practicing creating circles, using them along with the follow me tool to make simple elbows, but I am stuck figuring out the best way to transition from an ellipse to a circle along that path. I would be looking to emulate the part in this photo as best I can. Any tips? I’ve been using the sketchup at my local library, so I am unsure if any add-ons would be available to me.

Have a look at this, especially from 1:30 onwards to 1:50. The rest is also quite informative.

1 - make circle
2 - extrude it
3 - scale one end solid from circle to ellipse
4. Use Shape Bender expansion for make elbow

(@Guido), @jbkozy, since your profile indicates that you are using the free web version you can’t use extentions to make things easier.
You need to use the scale tool and apply an decremental factor to each cross section of the elbow: from factor 1x to factor say 0.7x, dividing the difference (1-0.7) by 14 to get the decrement on the first and each subsequent factor. (see example image below)
So 1x
1-0.0214 = 0.9785x
1-0.0214-0.0214 = 0.9571x
1-0.0214-0.0214-0.0214 = 0.9357x

1-(14x0.0214) = 0.7x

You can do it natively like this:
1 circle
2 pulling out
3 scaled at one end to an oval
4 division of the length of the resulting solid into the necessary number of segments
5 rotation of each segment by the value equal to alpha / number of segments
6 tea and smile

My guess is if it’s for an extractor you aren’t too concerned with aesthetics. so here is a simplified version of what @Wo3Dan is suggesting.
By using only three segments it does the job without much faffing about, you can add more segments to the path and scale each to get a nice smooth curving transition if that’s what you need. Nothing here can’t be don’t in the web version, even the section plane to remove the inner face. If you don’t remove that face it will not show as a solid.

Edit: I’ll probably just confuse things with this, the inner face was created as I hit ctrl with PP out of habit because it is often needed to get rid of some edges, but if you don’t do that the face will not form therefore not needing to go inside and delete it. But it never hurts to pop inside and have a look.

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