How would you build the top rail for a handrail of a spiral stairs

[Joe Carrick]

Joe,

The reason that the rail is segmented is because when you edit the 3D molding line by changing it's End Z value, you really are not forming part of a spiral, you are just rotating the arc in one plane.
Try the same thing with a nearly completed circle and you will see that the arc stays coplanar and just rotates in the one plane.

You can't actually define different start and end heights for a 3D polyline arc - they always default to coplanar.

Glenn,

Take a good look at the 3D PLine dbx (Selected Arc Tab). The Start and End Coordinates (x,y,z) can be edited.

[Glenn Woodward]

Joe,

I have had a good look at the dbx, and I know those settings are there.
But giving the Start Z and End Z different values doesn't create a helix - it just tilts the arc in 1 plane.
Can you demonstrate to me how you can create a helix from a 3D molding polyline arc (say an arc covering 300°).
Or drag one of your arcs so that it nearly forms a circle.
No point doing it with a small arc, because you cant see the result.

I maintain that you can't create a helix from and arc - but I am always willing to be proved wrong.
What I believe you are doing is tilting the arc in one plane and ending up with this:

[Joe Carrick]

Glenn,

Check Posts 22, 23, 26 & 27. Those were created exactly exactly as I indicated. I've been using this method for several years. The one thing that you can't do is make a helix of more than a 359 degree arc because then it's a circle that connects the start and end points and doesn't allow different z heights.

OTOH, since I only use 30 degree segments and rotate/replicate them at specific z increments it may be that you are correct. The smaller arc segments may make the distortion be too small to see. IAE, it works for me.

[Glenn Woodward]

Joe,

I know that you can make an approximation of a helix by multicopying a small piece of tilted 3D molding arc, as per your posts.
Can you please tell me how I can make a 3D polyline arc spanning 300° using 1 molding polyline arc.

[Joe Carrick]

Hey Scott,

I watched the entire video - way to long....................................

You could have saved a lot of time by just paying me to do one for you - I don't charge that much and you would have a better stairway I could have even made an Escherian Version for you

BTW, these can be adjusted for height, width or depth. You could even make them elliptical instead of circular.

[Joe Carrick]

His and Hers - for the couple that has everything

[Joe Carrick]

Joe,

I know that you can make an approximation of a helix by multicopying a small piece of tilted 3D molding arc, as per your posts.
Can you please tell me how I can make a 3D polyline arc spanning 300° using 1 molding polyline arc.

Glenn,

You were absolutely correct in your statement that changing the end z values simply titled the arc. Since I had not tried to do it with a larger arc I didn't realize that's what was happening. This is why I started the thread in Suggestions requesting a "Helicoil Molding Pline" tool.

I've also experimented with the Ramp Railings but that's not a true Helicoil either as the Molding doesn't get properly "warped" thruout the coil. About every 90 degrees there is a disconnect as the warp has to be restarted. Basically, the cross section of the molding should be the same (it shouldn't be angled off of level) at every point along the Helicoil. Presently it appears to be level only at the center of a 90 degree arc segment.

[Joe Carrick]

So at this point in time I simply use the 30 degree arc segment, copy rotate about the centerpoint with a z delta equal to the difference in start/end point z values to get the full number of degrees that I need. I then display it in 3D and create a symbol of it. The symbol can be stretched within a reasonable range (width,depth,height) without being noticeably distorted. I generally start with 8" as my vertical delta because most spiral stairs will have a riser height of 7-1/4" to 8-3/4" which falls within code limits for Spiral Stairs. I also start with a 36" radius arc for similar reasons - ie: 30"-42" is the normal range.

[Joe Carrick]

OK Scott,

Here's my basics. I start with the individual components (all of which are symbols I made before)

1. 6" Post - about 4' tall with a spherical cap
2. Tread - 32-33 degrees so that the next one will overlap - top of tread at 9"
3. 2" diameter 30 degree handrail section (Arc converted to PLine - Lock Start - set end z to 9") - move up 41" so that it's 32" above the tread at the nosing
4. Place Balusters - in my case 1" round

The 2nd pic shows all these things together.

Next I rotate/replicate the Treads, Balusters & Handrail about with a delta z=9", angle = 30 degrees.
Depending on how may copies I made I then adjust the post height.

The third pic shows a 16 tread assembly which can be converted into a symbol that can be stretched to match the desired floor height and stair radius.

The advantage to using this method is:

1. I can reuse just a few different pre-made symbols (the things that the fabrication shop does in the real world.
2. Each component has it's own material named to match the component (post, tread, handrail, baluster, etc)
3. Once the final stair has been converted to a symbol it can be stretched vertically within about a 10-15% range without being too distorted. The Railing, Riser Height, Post & Balusters all stretch together.

The 1st pic shows another stair with just 13 treads - it's so easy to make any size I need. If I need a special railing or some other custom feature I just add it to the repeatable unit.