Pulley / Rope / Wire System in Kangaroo Grasshopper for Rhino

Dear Forum,
I’m working on a pulley-rope simulation for an puppetry artwork with a robotic arm at uni. For this I would like combine the movement of the robot arm over attached wires / ropes over pulleys to a not yet defined object (the puppet).
So far I have a simple rope I can control (thanks to this: rope in kangaroo - Grasshopper). But I dont have an idea to simulate a wire which goes over 1 or best would be 2 or more pulleys.
I’ve found the OnCurve goal component in Kangaroo but it seams not working (yet). Do you have an idea of how to solve this or the rope system at all?
Thanks for any hint or solution try, I keep you updated!
Have a nice evening, greets,
20220116-rope-v1.gh (14.3 KB)

Hi Martin,

I was trying to simulate an H-bot mechanism not too long ago, and several people on the forum were of great help. I think this thread may be of some help for your project as well.

Oh wow, very interesting thread! I will have a look at all the input there. :slight_smile:
Thanks for the fast reply.

Addition: I also tried out this about a custom pulley goal but I get errors from the goal and from the grab components right now.

Hi @martin.c.baier

The length sum goal in the thread Bruce linked above can be useful for more complex situations,
but if you know that the pulleys stay fixed and one end is the driver then things can be simplified.

Because the distance between the top 2 points stays fixed, you know that any change in the length of the segment on the left results in the negative of that change to the length of the segment on the right. So you can measure the distance and adjust the rest length like this:


simple_pulley.gh (16.7 KB)

edit - if you’re on Mac, you might need this for the grab tool.


Uh wow, thank you Daniel!!! I will try to combine the robot movement with the kangaroo simulation in the next days and post the result here. Best, Martin

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