topic Re: Help plz - 3D modeling helical / helix pipe system transitioning to vertical runs. in AutoCAD Forum

Help plz - 3D modeling helical / helix pipe system transitioning to vertical runs.

michelleUQC9V — Tue, 20 Jun 2023 06:42:27 GMT

Really challenged trying to draw a twisted, angled pipe system in AutoCAD/Revit. I am struggling to transition from the main body of the helix to the straight vertical runs. (where it tapers at the bottom and twists back up through itself through the middle of the helix , as well as where it transitions up into a vertical pipe at the top/ outer diameter of the helix.

Attached is a 2D diagram of what I am trying to draw in 3D
Also attached is the closest helix + sweep work that I did to get something close to what I need to model.

Re: Help plz - 3D modeling helical / helix pipe system transitioning to vertical runs.

leeminardi — Tue, 20 Jun 2023 17:37:37 GMT

In the following I have created a helix with a radius of 1, a height of 3 and 3 turns. The helix's base is at 0,0,0. The green line is from 0,0,0 to the bottom end of the helix. The yellow line (its length is not important) lies on the XY plane, is perpendicular to the green line and has an end at the end of the helix.

We want the yellow line to have the same slope as the helix. We can compute the slope angle (theta) via:

theta = asin( pitch/(sqrt( (2*pi*r)^2 + (pitch)^2) ))

Note, sqrt( (2*pi*r)^2 + (pitch)^2) is the length of the helix for one turn.

Using rotate3d with the 2 point method, rotate the yellow line down by the angle theta about an axis defined by the green line. The result should look like this.

The yellow line will be used as a reference for editing a spline. Add a vertical line (cyan) at the bottom of the of the vertical line that passes through the center of the helix axis.

Create a spline with with 6 fit points as shown. The spline (white) should start at the end of the helix and end at the vertical red line.

Click the pulldown next to the spline and change to Control Vertices for editing.

Move the second CV from the helix end, and using osnap nearest, move it to the yellow line. This will ensure that the slope of the spline will be the same as the helix.

In the same manner move the next to the last CV to the cyan line.

We now have a spline with the appropriate slopes at the start and end. We now need to adjust the location of the other CVs.

Define a UCS with its x axis along the green line and its Y axis along the vertical red line

Use plan to view the XY plane.

With osnaps off and ortho mode active, move the CV's (but not the first two or last two) as shown.

Go to the right view and make the ucs active for that view

Move the CVs up or down (with ortho active) to yield a smooth shape that does not have a curvature reversal.

Edit the CVs as needed being careful the the active UCS is parallel to the view.

Re: Help plz - 3D modeling helical / helix pipe system transitioning to vertical runs.

michelleUQC9V — Tue, 20 Jun 2023 20:11:09 GMT

Omg. You're a friggin genius. Thank you for such a thorough step by step!
I'm going to give it a go myself. Wish me luck. 😄

Re: Help plz - 3D modeling helical / helix pipe system transitioning to vertical runs.

parkr4st — Thu, 22 Jun 2023 10:08:36 GMT

another way

the slope is a triangle length of hypotenuse is length of the helix, height is 3, in the autocad calculator enter

sqrt(sqr(19.0868)-sqr(3)) = 18.8495606 which is the horizontal run.

set the UCS properly and draw a triangle as in the attached

then the lines for the path with square corners, then FILLET the corners, changing the UCS as needed.

join the lines and helix for a path and COPYBASE.

sweep a circle for the OD, paste the path at the base point and sweep a circle for the ID if you want a hollow tube. Subtract ID fron OD which I didn't do in the attached.

The lines can be laid out in a multitude of directions to give the product you desire.