Modelling segmented boom

[mariomelendez]

Hello,

I'm trying to model one of these things:

It's basically a giant base, with a folding arm on it. The arm has several segments, so it can bend in different ways. The idea I have is to model it for site design purposes: laying out where to place it and how to fold it to get to a certain wall or element.

What I'm stuck on is the arm. I can't figure out how to get that arm to work right in Revit. In my family parameters I've created parameters for the 3 angles at the folding points. I create the arm segments, and put an angular measurement with the label linked to each angle in the parameters. The idea is that as I enter the angles, the arm will bend at those angles.

Problem is, when I change angles, the elements I've drawn get longer or shorter, which doesn't really work. If I set them to a fixed measurement, when I try to change the angle I get a "Constraint not satisfied" error. Seems Revit wants the length to change as the angle changes.

I tried switching to detail elements (a 3D model family is nice, but I'd be perfectly happy with a parametric detail item)... same problem: changing angles messes up the element lengths. 

Any ideas on how to go about this?

[ToanDN]

[I am playing devil advocate here so please forgive me.]

Why do you need to model the arm that move?  Are you trying to do some robotic simulation in Revit?  If it is for planning/spacing purposes, just use symbolic lines to draw the maximum/minimum reach, clearance space, blind spots etc... on plan and elevation of the family.

[mariomelendez]

Actually I did that initially.. some symbolic lines in the faimly plan view, and the manufacturer's movement curves in the family elevation as a CAD insert so they show up in model elevation views.

The problem I have is that I need a bit more detail for specific scenarios. A 10m circle is good for general planning, but when you're looking at a tight space or when you've got vertical issues, the best solution is to go into elevation view and flex the boom into position, and there you know you're not going to get a call at 11 PM telling you the thing's stuck on the upper floor slab and they can't get it out 

So that's where the idea of being able to alter the lines with specific angles comes into play. Sure, you could simply draw them using detail lines, but it gets kind of boring after 5 or 7 iterations.

[Anonymous]

I believe Toan may be correct that this may not be something that is a good idea to do... however, if you still want to do it.  I have had success by making nested face based families that allow you to accomplish what you are trying to do.  Probably best explained in a video:

Revit 2017 - How to make a family with Articulated arms

Good Luck 

[Alan.johnson1970]

You could model the mobile boom unit with multiple boom arms in the different positions and use yes/no visibility parameter to turn off the boom in certain positions. Set up a few types with the yes/no visibility options ticked / un-ticked to suit, so you could have a folded type, part folded type and fully extended type. You could then just change the boom type for each space scenario.

[ToanDN]

Below would be my approach if I need to do it.  I hope the file explains itself but feel free to ask if you want clarifications.

[Viveka_CD]

Hi @mariomelendez

Revit which will have certain constraint errors if you modify the angle of the arm. 

You can try modelling the difficult arm in Inventor or Fusion if interested, then import the stl file format in Revit.

Download trial here: https://www.autodesk.com/products/fusion-360/free-trial

Fusion 360 - Tutorial - Trebuchet - Swing Arm tutorial below:

You can also do a motion study if you are looking for a simulation.

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