Hello,
I am pretty new to Kangaroo2, and this is my first time writing here. I am trying to simulate a cable (black) that slides along the vertices (theoretical trajectory in cyan) of a slender beam-based structure (red) anchored on the floor.
By pulling the black inextensible cable down, I would like the structure to deform while the cable points slide along the cyan path.
This is my attempt with no success:
OnMovingCurve_2.gh (24.5 KB)
Hope I was clear, and thanks in advance.
Emanuele
I’m not sure what deformation you’re expecting. Is this like a “tentacle” mechanism from animatronics where the cable is constrained by the boundary of the structure?
Is there a real-world example of this kind of thing? Could you draw the intermediate stages (relaxed, start to pull on the cable, fully deformed)?
I would say that your setup seems very complicated, with beams and supports and tendons and rods. Feels like it could just be two sets of Line Length constraints for the rungs and rails of the ladder. But without a clearer idea of the end result it’s hard to say.
Hi Tom,
many thanks for your prompt answer. Yes, exactly, it is like a sort of that long arm shown in the video. So, yes, that is a good real-world example.
I have used beams in the structure aiming for simplicity, but I believe the horizontal ones could be replaced with simple “rigid” lines. The longitudinal ones, instead, are perhaps necessary to model the bending/torsional structure response since it would be nice to see the behavior in both the 2D and 3D space.
The relaxed structure looks like the one I sent before, but simply straight:
I do not have a picture of the expected fully deformed shape, since that is what I would like to obtain. I may look like this:
with a bit of difference in the curvature close to the base, since, as you also said, the cable is constrained by the boundary of the structure and that should affect the deformation.
Hi Martin,
Thanks for your suggestion, I am trying to take the best out of your inspiration with no success. I may need to totally change the problem approach…
I had a chance to look at your file now. I’m not sure if I would use the Drag option to pull the structure downwards. A Length Line goal might be more useful.
To access the output a little easier and also unaffected by changing inputs, I’d put the Show goals in the first branches and then all other goals into one or as many branches as you wish.
pull-end-of-curve.gh (30.7 KB)
Thanks again Martin, I think you are right about the approach of not dragging but instead using Length Line goal.
However, the point is that the curve must keep its initial length, like a unstretchable cable, and keep sliding along the beams ends.
Here is my latest attempt:
OnMovingCurve_3.gh (28.8 KB)
Here it is very close to what I would like to obtain however the curve being dragged slides only vertically while I would like to have it to follow the deformed structure…
I think I understand now 
You want to keep the tendon points on what you call channel line. You can use the length factor on the rod goal to pull the beam ends.
OnMovingCurve_4.gh (30.9 KB)
