Wednesday, 27 September 2017

Weird Railing Stuff - part 7a - Support Spacing Postscript

I mentioned in my previous post about handrail support spacing that the distance between supports is measured along the length of the handrail regardless of its angle, rather than a horizontal plan distance (which is used by other railing element spacing).  It turns out that it gets even weirder:

Revit Railings Get Weirder and Weirder

I thought I would check where it is measured on the handrail, and whether it takes into account a fillet radius if you have one.
  • On a horizontal railing, it measures support spacing on the underside of the handrail
  • On a sloping railing, the supports seem to be attached to the handrail a bit higher - you can snap to the top endpoint of the support.  In the example I tested, with a 75mm high support, the top is about 7mm vertically into the handrail.
  • This means that the spacing is measured slightly above the underside of a sloping handrail - this may vary depending on the angle and the type of support.  However, I have no desire to investigate any further - this is weird enough already.
  • If you have a curved transition from horizontal to sloping handrail (fillet radius), the support spacing measurement transitions (on a radius) from underside of handrail to somewhere above the underside.
  • This means that you cannot accurately predict where the supports will end up - unless you do a checking diagram like the one below.  I can tell you, this is the first and last one I will ever do!

 Extension to Floor

I know that you'd never put supports like this on a handrail with a vertical extension to the floor, but I just wanted to see what it does with the spacing:

The answer is that the supports get flipped to the outside of the handrail (what becomes the top when it turns the corner to be horizontal).  However, the spacing between the two supports as it goes from vertical to horizontal is not predictable.  In the example above, the typical spacing is 200mm (just to be certain it doesn't come away from the wall!), but the distance measured orthogonally between those two supports on the corner is only about 190mm - so we are adrift by 10mm.  As I said, it is not easy to predict exactly where the supports will end up.

If we had a start/end indent property, we could at least make a guess, then tweak the indent value until it is exactly where we want the first/last support - without having to unpin the supports (which has its own problems, to be discussed later).  Please go to the official Revit Ideas website and vote up my idea on this

Just to entertain you, here is what Revit does when you have a handrail extension to a wall - note that the support goes to the top of the handrail again (not that you actually want a support when the handrail fixes to a wall, of course!).

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