Twisted Handrail Solution?


I need to model a handrail that twists as it arcs around the spiral stair. The bottom of the rail will be at the top once you’ve ascended the stairs.

I’ve tried loading FredoScale (and its library) into both SU2014 and 2015 with no luck. SU tells me it’s installed, but there is no change to any menu. It simply isn’t there.

Here’s what needs to happen:

Does anyone have any suggestions? I’ve wasted about 12 hours on this so far and need a fresh outlook.



You can have a look at the plugin follow me and rotate


I have a stand-alone plugin called Spirix that is free and will do what you need. It’s spirix.rb and you can download it from

Give it a look and reply back here if you need help with it.

[edit] Here’s a quick staircase I did with Spirix:


What you have drawn is not enough information. A stair has a rise and run at least and the png of course does not carry enough info to support a model. Fredo’s scale will not work and less you do it in sections probably not Curviloft either. You know the hand rail needs to rotate X degs top to bottom but just in small increments as you go top to bottom while staying perpendicular to the " center" line. Given you inexperience I would suggest try the rail first, stair second. If you want to do the stair then there are other design parameters unless you don’t care about them. There are plugins but maybe you should learn how to use some of SUs native tools??
Here is link to Sage site with number how to help , scroll down about 1/3 to find helical info
More work some is required Grass Hopper:(


FredoScale appears in the Tools menu in a flyout of Fredo6 Collection.
it should also be available as a toolbar to turn on.

but if you’re going to use FredoScale, you might as well get ShapeBender too. :wink:


This is done with CurviLoft…


Mac - For the handrail, it would appear to the other respondents that I offered enough information. The actual dimensions of the stairs are irrelevant to the plugins. They need a shape to model and a path to do it over. The twist is what was creating problems with the native tools. When you rotate the face, SU changes the modeled shape’s initial dimensions.

To be fair, this isn’t for a handrail. I put that in so that others searching for a solution might be able to find this thread. It was also an easier way to describe what I need to model than “twist with curvature with rise”.

@Cotty - Unfortunately, follow me and rotate won’t work. It’s a great plugin but relies on the segmentation of the curve to create surfaces. Even at the crazy level of 180 segments with a 1 deg twist, the faces were visible. It would also be a nightmare to render later on. Thanks for the suggestion!

@Jeff - Fredo showed up after two hard reboots of my Mac. Go figure. I do already have ShapeBender As you generously demonstrated, the solution requires them to play nice. Thank you!

@Cotty - I’ll be looking into Curviloft too.



You can change this with the soften edges window… (the lines will be there with all solutions!)


i tried it with curviloft too… can’t get it to rotate past 90º without serious deformation… what’s needed is the ability to change the seam location… in curviloft, you can see fredo has thought of it (the little box/arrow at the seams when running the command) but if you click on one, you get a message that the feature is not yet implemented… theoretically, you should be able to drag the seam around the profile shape to control twisting


There’s also an extension that will draw a helix around a centerline. Here’s a link to more information about it:

I haven’t used this extension, so I don’t know how well it works.


“twist with curvature with rise”

I initially thought that Spirix would create this, but the geometry doesn’t quite come out right for what you’re looking for. However, a new feature now fixes that problem.

The surface below was generated by a 2.5" square (defined by eight points) rotated 180 degrees about the centroid in its own plane while sweeping 90 degrees about the z-axis from about 33" away while rising 24" parallel to the z-axis. I specified 100 segments for the surface in order to provide a more granulated result. This still isn’t exactly how you spec’d it since it follows a helix that passes through the centroid, not the corner. While my preliminary test doesn’t yet use centroid offsets for this operation, it should be easy enough to add such that it should then exactly create the surface you’re looking for.

This new feature is not available yet, but it seems like it would be nice to have.


Here’s my version using Chris Fullmer’s Component Stringer (Step 1) & Fredo6’s CurviLoft (Loft by Spline - Step 2)

The Component Stringer allows you to maintain the dimensional girth as the twist proceeds along the curve.



I think this is what Tau was looking for:

I’ve attached the SketchUp file as well.

rail.skp (204.1 KB)

I’ve also attached a new version of Spirix. If you already have Spirix, you will need to move it to another directory to avoid conflicts. If you use the new version and open the above SKP file, you can click on “Spirix | Create Surface” and review the parameters stored with the model. Delete the surface and run “Create Surface” with the current parameters and you can create the surface again. Or try different values, etc.

spirix.rb (30.4 KB)


They responded to your post and if that answers what you want that is you call.
It should be noted your OP stated the issue was for spiral stair and you post was just a png. => 2 dimensional. The link I provided to you gives a number or approaches to design a spiral stair and for the rail you will have to have a 3d solution, but since you were “fooling” us I guess that does make any difference any way you get what effort you put into what you ask.