Hi all - got an interesting query. We have a staircase to model and detail design: I've attached a model, which has been created by a colleague. I've not looked into it in depth yet, but will be doing as you read this! The basic dimensions have been supplied by an architect and we have to fill in the blanks.

The issue is the staircase stringers: the specified material for these is 100x250x10 RHS (although if it makes life easier this could be fabricated - i.e. four pieces of 10mm thick plate welded together). We think the outside stringer can be made, but the inside is throwing up some funny shapes, which is making us a bit worried about producing a nice model and further still, fabrication.

Any questions, please ask and feel free to make suggestions!

For any interested parties, I had a dig into this and the solution I found was to take the 3D sketch, add points evenly distributed along it's length to act as references, then added planes on which to sketch (reference: point, perpendicular to line) sketch the profile of the RHS, repeat up the length of the 3D sketch then loft between profiles, then finally shelling and adding fillets to the loft.

This seems acceptable, but I'd still welcome other options.

• http://files.engineering.com/getfile.aspx?folder=6763770f-e4af-491b-8ce5-d6

I haven't previewed the attached file, but your solution sounds like overkill to me. So long as the same profile is continuous along the length, you should only require 1 sketch (or just use weldments, which will already have the sketch for RHS250x150x10 in it).

If you definitely want to do it from your own sketch, and are using a 3D path, you need to sweep the section sketch along the 3D path. Not loft. And if it doesn't look as you'd expect, play around with the appropriate setting for profile orientation (I'd suggest using "normal to path", which I think is the default anyway for sweep).

If you're interested, it's definitely worth having a look at the attached file. It's the geometry of the curve that produces the odd results when using a sweep: it's like there isn't quite enough information for the profile to be guided along the path, hence my move to lofts, which enabled me to better control the path of the profile.

The finished model, although actually not very heavy on parts count, is quite impressive and when it gets built I'm sure it'll be a belter!

unfortunately, I can't open that file in SW2011

David