how can you do a Spiral Sweep

[crarchitect]

Hello again Reviteers,

Is there any way to create a spiral sweep? What we are trying to create is a Roof element that is a section of a spiral. The basic idea [which we can't seem to figureout!] would be to sweep a simple section along a 3D spiral path.

Can we do that in REVIT? I considered a using the spiral staircase generator but that provides limitations during an early massing excercise.

As always, any help is much appreaciated,

Oh, by the way, our principle here, Fred, just said, "tell AUGI this solid modeling is great!" (and HE is the guy who provided the above questions, too!) I guess 7.0 massing tools has them quite excited...

[beegee]

You may be able to get the result you want using a ramp, as per the image below, but it all depends on the "sweep profile " you want.

Ramps can only be rectangular profiles.

[shaunv68276]

If you work smartly with reference planes and arcs one can achieve spiral sweeps with any profile easily

[Merlin]

If you work smartly with reference planes and arcs one can achieve spiral sweeps with any profile easily
...Wow!...So how DID you work those arcs and reference planes?

John Mc

[PeterJ]

He has fixed it I would guess with a series of reference planes running at angles and then extruded the star shape along a path mapped out using those ref planes as a work plane. I think I posted something similar a while back in a discussion on spiral columns.

The problem as I recall is that to make a mathematically true spiral that looks correct in all views you really need to extrude along a sinusoidal path and this (known as lofting I think in some other packages) is not available to us. Shaun's demonstration is a good approximation though.

[shaunv68276]

In an elevational view I set up ref planes (at the required angle) & name them. Then in plan set the work plane and draw an Arc. Do this to every work plane. ( until completing 360 deg ) then simply create\sweep\pick path & load the profile to the path. before finishing the family copy up the amout of spirals you need and there you are.!

[beegee]

That method works well for most situations but does have some limitations.

As PeterJ said, a true helix requires a sine curve, whereas this method uses planes that intersect at sharp angles, which can cause problems with the junctions of some sweep profiles. In most cases, these junctions can be hidden or approximated though.

The other problem I've found, is that Revit does not allow a sweep path with ellipse or spline segments together with a profile having non straight lines.

[Merlin]

That method works well for most situations but does have some limitations.

As PeterJ said, a true helix requires a sine curve, whereas this method uses planes that intersect at sharp angles, which can cause problems with the junctions of some sweep profiles. In most cases, these junctions can be hidden or approximated though.

The other problem I've found, is that Revit does not allow a sweep path with ellipse or spline segments together with a profile having non straight lines.
hmmm....yes, I can see that now.....I suppose you could always construct a solid in AutoCAD (I have a little LISP programme to do a helix) and import it but that's a pretty undesirable way of going about it....by the way BG....were you at KarelCAD's REVIT Launch today?

John Mc

[Mr Spot]

Yeah, BG we missed you. Too busy i guess.

[beegee]

Someone has to keep AUGI going seeing as everyone else is enjoying themselves in vegas. ;)

[Merlin]

Someone has to keep AUGI going seeing as everyone else is enjoying themselves in vegas. ;)
....yeah, yeah, yeah....!;)
by the way, Chris!...I was the guy you were talking to with Terry just after it finished. That was good insight you guys gave. Thanks....The directors here have now given me a task (a multi-residential hi-rise) with it (finally), but I'm finding, because I'm unpracticed at it, that I'm learning much of it from scratch....Would you believe I'm having trouble with moving, copying and arraying?!?!..(@*&%! idiot!)

cheers,
John Mc