Snap and lock extrusion to reference line

[tbrown6608]

I am trying to create a Revit family for an air terminal designed to fit 360 degrees around a column enclosure. It will actually be 2 separate pieces placed back to back with each other around the enclosure. The air terminal requires 4 round duct connections on each half. I created the original air terminal with minimal difficulty but now the problem I am having is some column enclosures are larger than others. Now I am modifying the family so that I can specify the column size, overall size, height, etc. but also the duct connections need to stay centered. I've gotten a reference line arc that remains in the center of the air terminal as the size changes along with 4 other reference lines that go from the column side to the face (after spending a few hours of banging my head on the table trying to get all the parameters and formulas to work). What would solve everything at this point is if there were some way I could lock the round extrusions for each duct connection at the center of the circle to the intersection of the arc and the 4 lines. Or even forget about the arc and lock to the midpoint of the 4 lines. Does anyone know any way I can do this or any other ideas?

[CoreyDaun]

I understand what you are trying to accomplish, but could you post an image or even the family file so we can assess the situation?

[tbrown6608]

I've attached the .rfa file for this. I removed the connector elements but you will see the 4 round extrusions I am using for the connection points.

[CoreyDaun · Accepted solution]

The method I would probably use is to place a Reference Line across the diameter of the round extrusion, Group them, and copy the Group to the other locations. Create Reference Planes for the core angles, rotate the round extrusions to be perpendicular to these planes, and then place constraints. Refer to image below. Ask if you need more info...

[tbrown6608]

Excellent! That works. Thank you very much.