Curved Staircase Railing Losing Orientation


#1

Hey all!

I’m having trouble figuring out how to model a railing for a curved staircase. I have made a guide line for the elevation change and radius the railing should follow, but when I use the “follow me” tool, the face of the railing ends up rotating as it moves around the angle, ending up turned on it’s side by the end of the stairs. I’ve looked for extensions like flowify and upright extruder, but the same issue persists.

My railing is your standard with the irregular face.

I hope this is a common issue and I’m just not smart enough to find the answer! Any help is appreciated, and thank you!

-Mike


#3

You could also look at “profile builder” if upright extruder isn’t working for you, although technically the profile should run perpendicular to the angle of the stair rise and not “upright” (vertical) and Eneroth’s tool should work.

the first gif with the single helix is Eneroth’s extruder, the one with two in it shows SU (which twists) and profile builder, which runs as you want?

The nice thing about profile builder is that you can change profile size, offset etc afterwards on the extrusion without haveing to start from the beginning. see other gif


#4

Eneroth Upright Extruder accomplishes the task when you use the Set “Upright” Vector From Edge option.
Use a vertical edge as the upright vector.
https://extensions.sketchup.com/en/content/eneroth-upright-extruder

UPDATE

Example Model
Eneroth Upright Extruder Example.skp (371.5 KB)

Prior to extrusion, the model was scaled up x100 to avoid issues with missing faces.


#5

My stairmaker plugin uses a strategy that more closely emulates the actual geometry used when building the stair and handrail.

  1. the path used for handrail is at the top of the stair since that would more closely represent height of handrail and building codes.

  2. when we do a bent lamination we use the same form for the handrail as we use for bending the stringers. The geometry works the best if the stringer’s geometry is at the front of the riser line.

Internally my script uses a polygon mesh and I have not had the need to scale 100 X - even with a fairly detailed handrail.


#6

While a little exaggerated on the angle, you can see the difference between a profile that is extruded from an upright position to that perpendicular to the path. A real world handrail would have its profile perpendicular to the angle as its a solid piece of wood being positioned at different angles…
The blue is perpendicular and the yellow upright.


#7

I’ve replicated the twisting effect of the built-in follow me tool, and I think I understand why. The fact is a handrail can’t just change direction (in plan) without geometry problems. I tried making a model that shows what’s happening.

I think when a profile goes from one segment of a path to the next with the follow me tool, it’s probably being done as a simple miter, like when you miter trim going around a corner. The mitered turn has to happen along a single plane, and you can find such a plane with any two line segments as the vector cross product of the two. (or completing the triangle by creating the third edge as I did in the model) What you really want a handrail to do is follow a series of ramps in a way, but turning ramps don’t intersect cleanly like you would want. (Look closely at the intersection, there’s a scene for that.) What does miter cleanly is using this common plane from one line segment to the next. That plane is rotated outward slightly from the first ramp, and that, I think, is what makes the profile seem to rotate incrementally as it goes from one segment to the next.

Spiral Handrail_2017.skp (474.1 KB)


#8

I guess in the real world we might be limited by miters unless this could be steam bent.
Attached a file that has a rail profile drawn with Profile builder. Just for a look, to see if it/how it might be doing things differently than the native push/pull.

Spiral Handrail_2017_B.skp (1.3 MB)


#9

Not exactly steam bent usually, but glued up laminations clamped to a jig is what I’ve typically seen.

Yes, Profile Builder is doing it differently than native follow me, and more like what you would want a handrail to do. What version of PB are you using? (I have 2 and need to get 3 soon)

Turning on Show Hidden Geometry is revealing. The flat bottom is not a series of quadrilateral inclined planes, but triangulated to accommodate the twisting action. You can see the same in @gkernan’s stringers too where the top surface is triangulated.


#10

Yes, much cleaner.
PB does offer a “follow me” option for some reason?
I’m now using PB3. Upgraded, and while it offers much more functionality, it has become more complex and I’ve found things don’t work as easily as before?.. guess I just need to dig in some more.

This guy does some nice steamwork https://www.dailymotion.com/video/x6fonje


#11

Great replies everybody! Thank you for the help!

In the end I figured out what part of my issue was. It worked as intended if I built my railing in sections instead of one continuous run. By trying to do it all at once, I could never set the correct upright vector as the railing moved not only along the curve, but also up a 90 degree goose neck at the top of the flight. I was able to do the total railing in 3 separate sections, then come back and fix the geometry at the butt joints.

An unintended consequence was that I got to try out a couple new extensions I didn’t know existed, so thank you very much to everyone!

-Mike


#12

Glad you got is sorted. The collision of sloping, turning, plumb and level geometry is often harder than you think. Roof rakes and eaves is another place with these troubles.

BTW, for anyone who’s interested in such stuff, I recommend this book as a reference: A Treatise on Stairbuilding & Handrailing. It shows you just how much old school stairbuilders knew back in the day.


#13

I am and I have just ordered a copy. Thanks for the heads up Robert!


#14

The Staircase — 2 Vol. Set

By John Templer


#15

Interesting and out of print, unfortunately. Totally different coverage of the subject including plaintiffs and expert witnesses.