Curved Spiral Truss

[Josh Schulman]

I'm trying to make a curved spiral truss and can't figure out any way to do it. I'm also trying to make a spiral object from the above truss. Any thoughts?

Thanks!

[Benson Shaw]

Can you describe more or point to an image, or post an image or sketch, eg a 2d plan view?

Idea:

Draw the center axis, and a 3d object representing the cross section (3d triangle)

Make the triangle tubular with Model>Extrude Along Path using a 2d circle for profile.

Select the axis & tubular triangle then Edit>Duplicate Along Path.

Connect the corners with NURBS curves. EAP with a 2d circle to make them tubular. I connected 2 sets of corners and only one has EAP.

If there are is a lot of this, make the triangle EAPs into symbols.

Also note that Vectorworks has a 2d spiral in the 2d tool set, and a 3d helix command in the Model>3d PowerPack pulldown.

HTH

-B

Edited August 31, 2012 by Benson Shaw

[Josh Schulman]

Sure, imagine a paper towel tube that has been opened or maybe a popped can of biscuit dough.

[img:center]http://lh3.ggpht.com/_0WlJg3o4BSI/TYFl9u1HYtI/AAAAAAAAAWc/Tj-Tt-rAEIM/IMG_3126%255B3%255D.jpg[/img]

The idea is that every closed section of the spiral is 13' and each open section is 6' There are a total of 4 twists.

Does that make sense?

[Benson Shaw]

OK, the Tube is not so hard

Total turn is 13? + 6? = 19?

Total rise is 4 turns x19? = 76?

First the 3d helix (I started in Front View):

1. Draw a vertical 2d line, L = 76?

2. Model>3d Power Pack>Create Helix Spiral

# Turns = 4

Assign start & end radius (eg 5?)

Click OK, spiral appears on drawing

Now the opened biscuit dough tube:

1. Draw a vertical 2d line, L=13?, Convert to NURBS

2. Snap low endpoint of NURBS to low endpoint of Spiral

3. Select NURBS and Helix

Model>Extrude Along Path

Enable both Lock Profile Plane and Fix Profile

Click OK & wait a few seconds - Open tube appears on drawing.

4. If thickness is desired, apply the Shell tool. But use a copy, because you loose the source objects when shelling.

What are the truss elements?

-B

Edited August 31, 2012 by Benson Shaw