Helical Balustrade

sketchup
modeling
curve

#1

Hello,

I posted last week with some issues surrounding a helical staircase I am drawing up and gratefully received lots of help and was able to sort the problem, however I am now having a similar issue with a different part of the helical staircase. I understand that where the straight run turns into the helix on the staircase the the angle of ascent changes and I know how I want to blend the two bits together but I have not Idea how to create the shapes required. I have tried various plugins to help including Curve Maker and Draw Parametric Curves but I still cannot get the two sections to blend. I have attached the file which has my model on the left (darker grey) and the rough model I am working from on the right which shows the look I am trying to go for. If anyone could help me figure out how to create the desired shape that would be much appreciated.

Thanks
Thomas

helical_balustrade.skp (720.0 KB)


#2

If by ‘blend’ you mean ‘have the same slope’ where they join, you can’t do it at the same time as having the handrail (top of the balustrade) a constant height above the slope of the treads.

To do both, you will have to lengthen the straight stretch of staircase horizontally by having a bigger ‘going’ (wider treads).

Or you can fudge it by making the slope the same at the join, but with the handrail too low at the bottom of the helical section, and too high at the top of the upper helical sections respectively.

You can work it out for yourself with a piece of paper or thin card, or a SU drawing. Calculate the perimeter of the quarter circle. Draw the elevation of the slope of the straight section from the side, extend left and right by the quarter circumference, then extend the slope lines to the ends.


#3

At my computer now - here’s what I mean as a drawing.

Quarter helix stairs v2a.skp (836.5 KB)

The radius of the helix is approx 37". Quarter circumference is 37*PI/2.0 = 58" approx.

I’ve drawn the handrail line at 39" above the tread.


#4

Hi, thank for looking at this again! By blend I don’t necessarily mean have the same slope but just flow into each other more, which could allow the balustrade to increase in height if that is what you mean? On the SKP I uploaded, the rough model I’m working from has an organic sort of shape which just sort of flows all around but I am struggling to recreate it myself. As it is currently the straight run of the balustrade isn’t actually completely straight, today I added a small curve to it as per the plan which I thought would make it slightly easier to blend but so far I’ve had no luck!

Thanks again
Thomas


#5

Another one of the features of my stair maker plugins handles smooth transitions. You need to provide a good path and the plugin does the rest.

Here is an example of a curved an twisted handrail. Set up a thinner rectangular handrail and you can use it for a stringer.


#6

Oh - here is the skp file

curved parts.skp (677.1 KB)


#7

thanks, I’ll take a look!

Thomas