Spiral Stringer for Stairs

[spardacus]

I wonder if someone might offer insight here ...

I have a staircase following the outside diameter of a round tank - inside diameter of stair is approx 200 feet, while the height is approx 80 feet. I have created the treads easily enough with a multiple clone set at a 1? angle and a -8" Y value.

Now as I attempt to create the stringers (support under steps) I have tried a bezier and a portion of a helix to execute a rail extrude with a rectangular cross section. However, the top of my stringer is nice and vertical and correct, but as it extrudes along the rail down and around my rectangular cross section twists and ends up "laying over" as seen in the linked page.

http://www.creativeresource.org/lw/spiralstringer.html

Any clues?

Thank you.

i am spardacus

[mlinde]

So the treads, rails, and posts are correct, you are concerned about the angling of the stringers. I would use a rail extrude with a box squared on the x/y, then use booleans to cut the stringers from the box.

Did you try that?

[spardacus]

I use Boolean quite often ... love the boolean ... however, I sure thought the rail extrude or some helix arrangment would address this a bit more directly.

Slice out the stringers with a boolean from a bezier shape, huh? Guess I'll try that.

BTW - speaking of Booleans, I can't seem to get booleans to add together. Should this allow me to create shapes like building block joined together then edit their "union"?

What does the Boolan Add and union get me? I use subtract all the time, but the add and union don;t make any visible sense to me???

thanks mlinde ... your input is always inspiring.

i am spardacus

[mlinde]

Originally posted by spardacus
BTW - speaking of Booleans, I can't seem to get booleans to add together. Should this allow me to create shapes like building block joined together then edit their "union"?

What does the Boolan Add and union get me? I use subtract all the time, but the add and union don;t make any visible sense to me???

Example: two layers of objects. One is a box with 3 segments in each plane. The second is a cylinder in the center of the box that extends outside the box. The cylinder is in the foreground, the box is in the background.

Boolean "Add" will add the geometry of foreground & background layers together, so the foreground layer now has both object layers combined into one.

Boolean "Join" will combine the two layers so that the outside shape is one object, the cylinder inside the box is removed.

Boolean "Intersect" will leave just the part of the cylinder that was inside the box.

Boolean "Subtract" will leave just the part of the cylinder that was outside the box.

[mlinde]

Image for the above example