3d Poly Line Role?

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3d Poly Line Role?

Postby Wes Mossing » Fri Jun 12, 2009 7:37 am

I have a problem I wonder if anyone can help. I have a 2.8m ID pipeline with a 4 cut miter bend and have to layout a saddle for each section. The 4 cut miter has a 55.49 degree horizontal bend combined with a 36.8425 degree vertical bend. The true bend on the pipe is 63.04 degrees with the role of course. If I could just built the pipe in 3d polylines and role it you could then profile it to come up with coordinates but I can’t seem to do that. If anyone has any ideas it would be much appreciated or at least let me know who or what I could use to solve this.

Thanks, Wes Mossing
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Postby Richard Sands » Fri Jun 12, 2009 2:29 pm

Wes I'm not exactly sure of what you are asking. Can you create a 3D polyline by making your pipeline in 2D then give it Mscad points at ends and intersection (with the appropriate grades applied to each section).
So you now have the points in 3D. Join them with a 3D polyline and play with that.
If you wanted more control you could create an offset line 1.4 each side and give those points also, and using COGO create whatever intersections you need.
may need a mix of COGO and trigonometry to get them all in 3D.
not sure if that helps?
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Postby Wes Mossing » Fri Jun 12, 2009 3:37 pm

Yes Richard I have tried that. Starting with 2d lines showing C/L pipe and the pipe walls as if the complete section of pipe was laying on the ground on a flat surface. At that point it is a deflection of 63.04 degrees. The next step and appears to be simple but I can't get it, is to rotate 3 dimensionally so the first section of pipe stays on the flat surface until the last section is sloping at 74.9%. Then ultimately coordinating the uderside of the pipe to set the saddles before they fly the pipe in.
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Postby Richard Sands » Fri Jun 12, 2009 4:46 pm

To me I would tackle this with trig calculations.
You know the inclination of the pipe and so can in effect apply a difference in height irrespective of its direction,probably not getting it across too well!! may sounds silly but get a piece of fencing wire or something you can use as a demo and bend it how its supposed to look and then study the maths involved. Draw the indivual triangles that make up the figure (pipeline elements) and work from those.
Then bring those back into Mscad and apply coordinates as required.
4 cut mitre bend - have I missed something? - not sure if thats significant?
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Postby Jason Poitras » Fri Jun 12, 2009 10:03 pm

Hi Wes,

Have you explored using spherical coordinates? In the help file search for "Spherical coordinates". This allows you to draw lines in 3d space at specific lengths and angles.

When working in 3D space it is sometimes easier to move your coordinate system around using the UCS command as you draw the entity. Once you get the geometry right, you can switch back to WCS and then coordinate the linework.

As Richard suggests, the pipe can be computed using simple trig functions. Rotate and create a UCS so that the X/Y plane is of the side profile of the pipe.
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Postby Wes Mossing » Wed Jun 24, 2009 11:58 am

Thanks Richard and Jason.
I was off for a few days and had figured this out. I started with the "draw 3d cylinder" comand and was able to draw each section of pipe at the centerline lengths then using "rotate 3d" along the proper axis (this part took a while) was able to put the sections of pipe together. Then again using the rotate 3d was able to rotate the mitered section of pipe and place it in the exact location (this part took even longer). I also then expoded the cylinders and fillited the linework thus creating the exact pipe. Also then I could re-draw the 3d faces so rendering realy gave it a nice presentation.

We had a couple people doing the trig calcs and once I had the model and brought there points in you could instanly see that trig sucked, cad kicked a$$!

Wes...
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