Curved staircase supports?

[Wayne_Carlson]

I'm trying to draw a curved (not spiral) staircase.  The steps will be supported by plate steel bent in a compound curve.  

It makes sense to me to start with cylinders for the outer and inner diameters, then use intersections or cuts to leave the constant-width 'ribbons' for the end pieces.   Since Fusion 360 does not allow putting lines on the curved surface which would make life so easy, I'm trying to use planes or other projections to make the cuts.   How can I draw this and have it be accurate across the entire length?  It seems that projecting straight lines or planes is not the correct section.    I would extend the same technique for cutting balusters and bannisters.

Thanks for any assistance!

[davebYYPCU · Accepted solution]

There is not a lot of information to work with, but I think the coil command will be the starting command,

by using a combination of processes, I could knock up a quick example here - use your dimensins, should be OK.

Coil, Patch, Offset and Thicken, got me a step holding beam,

Coil command will go part way round the circumference, My example, 100 dia coil, 0.5 revolutions, and 100 high, gives a half turn and about 40 degree lift, used sq section.

Go to Patch environment, and offset the verical? face, offset distance "Zero"

Go to Model environment, turn off coil feature, thicken the patch surface by your thickness, (Solid Spiral Rail right there)

two sets of this process, same rotation, same height, inside and outside diameters will give usable framework to continue.

Not sure if linear pattern will climb the rail for steps and risers, didn't go that far.

Try something similar...

Browny

[Wayne_Carlson]

Thanks!   That looks very promising.   I'm very new to this and didn't even notice the coil as an option!   I'll start playing with it and see if I can get the parameters set to hit the marks I need to.

[davebYYPCU]

Ahhh, the the linear pattern for the steps and risers I had a fiddle with did not work, 

too advanced for me, I got the pattern to work, but the objects, did not retain their orientation.  

In other words the flat step at the bottom, was not a flat step at the top, each step had a bit more roll than the one before it.

There will be a way to get it done, just not sure how far to look outside the square at the moment.

Browny

[Wayne_Carlson]

Don't worry about the steps.   I already have them working fine.  I used a sketch of the steps from above and used push/pull to get the pieces I needed already curved.   Each step is a component and they assemble with rigid joints very well.  

I'm working the side supports, balusters and bannisters right now.  I'm using coil to make bodies to use to intersect with cylinders and other parts to get what I need.  When I get a good pic I'll post what I've learned.

[Wayne_Carlson]

This is how I successfully (I think!) built the outside support, baluster and banister details.   The inner ones work the same way with a different diameter.

This picture shows the square coil that I will use to intersect with oversize baluster bodies I had extruded from a sketch of their cross sections repeated in a circular pattern.   The steps are shown for reference.

Here are the balusters along with the coil which I've already rotated about the origin and moved up the Z axis to meet the floor.

Here are the balusters trimmed by using "Combine" with "intersect".  I selected "keep tools" and "new component".

The side support was built using another square coil, this time intersected with a cylinder of the desired thickness.   It was also rotated and moved in the Z direction to be at the proper position.

The banister is simply a round coil section.   I was able to attach it to the end baluster with a rigid joint

Here is the completed outer set of parts shown along with the steps.

For anyone who's curious, this is what my step component looks like.

From the top, you can see it's formed by two circles and radial lines.   I then used push/pull in the Z direction to form the various pieces to maintain the curved sides.

This is the step component from the side.

And then from the bottom.  The construction is welded steel on the sides which are attached by the angle irons.   The steps have a plywood subfloor piece plus finish flooring on top of the plywood.   Risers are shown made of the finish flooring but that probably won't be the case.  The step components were duplicated with copy/paste and joined with a single rigid joint between the back top edge of the finish flooring and the back bottom edge of the next riser.   This aligned them nicely into the complete curve.  I did not try to use joints to attach the angle iron to the side pieces.  They aligned nicely "as built".

The drawing will be a starting point for a Professional Engineer to work on structural calculations and to make recommendations on materials, sizes, and any changes needed in design.

Thanks again for your assistance.

[TrippyLighting]

Very nice explanation. Thanks for sharing!

[Wayne_Carlson]

I'm glad to share - hoping it'll help other beginners like me.

I meant to mention the other thing I learned...

When you create the coil, you specify the "section size" which for a square section is the length of each side.   This worked well for me as I could use the value of the height of the items I wanted to create.

BUT.... Initially I thought I would be clever and create a single "reference coil" for each side.   Then I could copy/paste/rename from the references and offset the upper and lower faces by the delta Z values I needed.  But I was WRONG.   The faces would be offset orthogonally to the surface, and the value I would specify would be used as the distance in that direction, not in the Z direction.   Of course this made perfect sense after I realized what was happening.  It would be nice to be able to specify an axis displacement value and let the software do the trig, but that doesn't seem to be in the cards.  So I just made separate coils with all the parameters the same except the section size.

[TrippyLighting]

I thought I post a link here on the creation of helical structures that does NOT involve the coil tool. Just in case it might be needed 😉

[Wayne_Carlson]

Thanks.  I scratched my head for a bit how it applied, but then I saw the screencast using loft.