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Sweep a handrail profile along an irregular helical curve in 3D?

JustinDT47Q
Explorer

Sweep a handrail profile along an irregular helical curve in 3D?

JustinDT47Q
Explorer
Explorer

Hello all I am in the custom iron railing business and would like to provide my client with a 3d rendering of what the railing return will look like at a landing. The shape will be a helix similar to a volute and retain the handrail section profile's vertical orientating (no banking or twisting or tilting along the path. I have been successful in the past, but only with a simple rectangle, by creating a mesh between two legitimate helixes and press pulling or extruding that. This is something I will need to know going forward, having a method of accurately creating these 3d renders in such a way I could use them for shop and installation drawings as well.

 

 

 

 

 

I am trying to replicate a shape like this...

Capture1.JPG 

 

This is what I keep having happen when I do get a successful sweep. This was broken up into three parts.

Capture.JPG

 

Anything you have or commands to try would be very much appreciated. This is my first post on the CAD forum, but I am stumped. Thank you

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5 Respuestas
Respuestas (5)

dany_rochefort
Collaborator
Collaborator

Extrude / Path is a good start. Your geometry must be a close polyline to extrude along a path and rotated in the axis of extrusion. Have a look at the attached dwg.

leeminardi
Mentor
Mentor
Solución aceptada

To get good control on twist I would use LOFT for curved sections of the railing,

 

For my first attempt at a 90° rising corner I used 4 cross sections.  I copied a cross section from the end of the bottom straight railing and then rotated it by 30° about the world Z axis. The 3rd section was rotated by 60°. The section for the beginning of the top straight section was rotated 90°. 

Note, the magenta line is a spline that was constructed using the CV method ensuring that the slope of the curve was tangent at the two ends to the straight railings to which they mate.

 

leeminardi_0-1644619048279.png

leeminardi_1-1644619089028.png

I did not like the result as the there was an undesirable twist/bulge midway through the curve which you can see better in the image below.

leeminardi_2-1644619352319.png

 

To correct this I rotated the 2nd and 3rd sections about their local Z axis. To gauge the amount of rotation I created construction lines from the top center of each straight railings (red lines) then used these to create a smooth spline (white) with CVs at each end and one at the intersection of the two red lines.  Using these 3 CVs ensured slope tangency at the ends. Using UCS OBject I could then use 2D rotate and adjust the rotation until the top center of the cross section was by the top magenta spline.

leeminardi_3-1644619767366.png

 

leeminardi_4-1644619809386.png

Note, I tried using sweep with guides and paths but could not get much control of the twist or teeter.   I think lofting is the best approach.

 

leeminardi_0-1644620359670.png

 

 

 

 

 

 

lee.minardi

Washingtonn
Collaborator
Collaborator

Do you have a plan and elevation view of the stairway as well as a cross-section of the railing you could post?

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R_Tweed
Advisor
Advisor

Using loft with one guide will resolve the roll problem. In my drawing I ran two lofts and then joined them using union. The first loft is at the base and the second is the long run. dwg is attached.

 

Screenshot 2022-02-16 100729.png

JustinDT47Q
Explorer
Explorer

This worked great for me! Thank you! I have tons of control of their twist and can tweak it in any direction to achieve the look I want. 

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