Winding Stair Stringer Issue

[Dadgad]

Right, who left without being paid, I know about that one, conspicuously deft and altruistic! No mention if he was wearing sandals, and walking 6 inches off the floor.

[Jack_O'neill]

In every generation there are true artists that rise above logic and normal possibility and produce things that the rest of us can just oooh and aaahhh at. This is one of those cases. Miraculous...maybe. Amazing...absolutely.

[dedmin]

Ok, thanks for the tip. But I only followed you correctly until the second step. I have extruded the 3D Polyline as a surface. But I don't follow the next step of offset or solid option. Can you elaborate a little more on that part?

 

To insure I did the first step correctly, I did:

EXTRUDE

MODE

SURFACE

 

Then I selected the 3D polyline and gave it a height of 16. I would like the stringer to be 2" x 16". I should also note I did this operation with the UCS set to W. I have now a nice surface which follows the 3d polyline but I don't follow the next step too well.

 

[dedmin]

Jack, yes I looked back at the other thread...must be having another senior moment. I was able to us THICKEN after I got the surface extruded and it's shaping up better now. I knew there had to be a way of doing this in AutoCAD, not just Inventor or 3DsMax.

 

I will try next to smooth out the stringer surface as it looks too segmented for Presentation work.

 

So has anyone ever heard of this website: http://www.stairporn.org They don't have any porn there, just stairs and if you're into designing stairs like I am, this is an amazing site for information and ideas. Funny URL though!

 

Traced over the 3d polyline with the spline curve (FIT POINTS)

Winding Stair Stringer.dwg

[sevdo2000]

Or just double click on 3D poly, type "S", enter

[dedmin]

Or just double click on 3D poly, type "S", enter

 

Exellent reminder sevdo2000:thumbsup:

[SEANT]

Let me take a moment to defend AutoCAD’s capabilities with regard to the SWEEP command.

 

The algorithm employed by AutoCAD has the primary function of maintaining a consistent cross section. When used with a faceted 3DPolyline, AutoCAD also maintains a clean junction at the miter.

 

Unfortunately, that often means that some other desired trait (outside faces parallel to the Z axis, for instance) are impossible to maintain. Not due to a limitation in AutoCAD – more like a geometric reality.

 

Bill, it sounds like you would prefer a smooth spiral anyway, so the techniques discussed previously should apply.

 

Conversely, if a person had a beautiful source of dimensioned lumber (Walnut, maybe), was not opposed to faceting, and wanted to assemble their own stringer, the miters could remain clean if some additional faceting were added to the top and bottom faces.

StringerAsSegments.dwg

[Bill Tillman]

Seant,

 

That's some nice work. But I think Jack (The Stairmaker) would agree with me that making that out of wood, would not be structurally sound. Metal perhaps where you could depend on welding and/or bolting together of things. No, the method I saw recently was for a small spiral stair which only when up about 120" total. The builder constructed the treads on the center pole, wrapped them all up in shrinkwrap to protect them from glue and then began by using clamps, screws and lots of wood glue to laminate up the curved stringer. When he was done it all looked like one solid piece of wood. His stringer had a core of dimesional lumber inside of it with some beautiful oak verneers to add strength and give it a finished surface.

 

The other limit would be the size of the lumber available. I think to make the stringer I've shown here would require steel framing which could be welded. The depth of the stringer alone would be about 16" to 18" and would require lots of clamps and glue to laminate up. Steel framing on the other hand could be wrapped in sheetrock and plastered over to give that concealed look.

 

As for the miracle stairs which are at the chapel in New Mexico, yes, I've read about them many times. Indeed this was a miraculous feat of carpentry in the time it was done. And who knows, it might have been an Angel of the Lord who came and went so mysteriously. The design is flawless but if you notice they do not let anyone walk up or down those stairs anymore for fear of structural failure. So I think it was just a really experienced carpenter who came along and helped those nuns out.

[SEANT]

No doubt, my attachment left numerous issues unresolved. It would be nice to find a customer willing to fund further development, though.

 

 

 

The purpose of the geometry was to illustrate the quirk, while addressing a particular requirement.

[Jack_O'neill]

 

As for the miracle stairs which are at the chapel in New Mexico, yes, I've read about them many times. Indeed this was a miraculous feat of carpentry in the time it was done. And who knows, it might have been an Angel of the Lord who came and went so mysteriously. The design is flawless but if you notice they do not let anyone walk up or down those stairs anymore for fear of structural failure. So I think it was just a really experienced carpenter who came along and helped those nuns out.

 

I wonder when they actually stopped using them. Been there for 133 years. Is the fear of structural failure caused by engineering concerns or the fact that we just eat too much now!

[robindemey]

In AutoCAD 2012 extrude the 3d polyline to a suface, then offset the surface to the needed thickness using the solid option.[ATTACH=CONFIG]31927[/ATTACH]

 

I have the same problem.

The solution from dedmin looks great, but I still can't do the following:

How do you exactly choose the hight of the stringer?

 

I have a helix that I'd like to extrude to a surface and then give a thickness.

But the stringer has to be exact 300mm high.

 

The stringer will be made out of stainless steel that will be bended (I don't know if that is the correct English word).

[ReMark]

The stringer will be "bent" I think is the terminology you are looking for.

 

The stringer in the original post may have been given a height using the EXTRUDE command.

[robindemey]

Thanks. Indeed bent :-).

 

You can't give it a height with the extrude command, because that is not the correct height. The height with extrude is the Z-height.

The height I need is the perpendicular height form top to bottom (the width for the stainless steel plate).

[ReMark]

Without seeing your drawing I cannot tell from your last statement what we are talking about. You wrote "...the perpendicular height...(the width for the stainless steel plate)."

 

Post a DWG file or an image and someone here will take a look at it.

 

Did you try using the THICKNESS command?

[robindemey]

Lol, posting a dwg from something you can't draw ;-).

 

What I mean is the following:

We'll take a steel plate from 300mm heigh, 8mm thick and lengt depending on the height of the staircase.

This plate we'll bent.

 

So I need to draw the stringer exactly 300 mm heigh.

[SLW210]

Draw it 8mm x 300mm and extrude along the helix.

[ReMark]

Draw it 8mm x 300mm and extrude along the helix.

That may well introduce the "twist" that Bill encountered which this thread was all about eliminating.

[robindemey]

Here's a picture:

 

Height 2 is 300

Height 1 is what you can adapt with extrude.

 

Extruding along a helix isn't possible.

[SLW210]

Sweep there is no twist.

 

You explode the helix then extrude, but as ReMark stated you are back to the twist problem.

[ReMark]

There is width, depth and height. Never use the same word to describe distances on two different planes.

 

Have you worked with Surfaces at all? Do you know that when you extrude a line it creates a surface and that surface can then be given a thickness? That is basically what was done for the stringer in Bill's original drawing.