Hi everyone,
I’m trying to achieve this mechanism using Kangaroo, but I haven’t been able to get it working properly.
I added axis and position constraints, but when I move the slider, all the pieces suddenly “explode” or move in unexpected directions.
Could someone help me und
mechanicalfinguer.gh (282.8 KB)
erstand what I might be doing wrong? Am I using the wrong constraints, or is there a better way to set up this mechanism in Kangaroo?
Any advice would be greatly appreciated. Thank you!
You can attach the hinge points to the rigid bodies. I think it reduces the complexitiy of the definition.
The definition now works with the grab component.
mechanicalfinger_updown_grab.gh (283.8 KB)
This definition works with the target plane input. The confusing bit might be that you want the part to move in Z but the input on the support needs to be True for Z…
mechanicalfinger_updown_target-plane.gh (285.8 KB)
WOOOOoooOWWWWW, my mind just explooooooooded hahaha! 
Thank you so much @martinsiegrist for replying so quickly!!
Correct me if I’m wrong: does assigning coincident points basically mean that the mesh elements are sharing the same point? And because of that, there’s no need to use a concentricity constraint?
It’s honestly quite interesting—and a little strange at first! It’s very different from other software where you simply add constraints directly. But honestly, it works really well!!!
And yes, it’s definitely much lighter and easier to visualize this way. Thank you agaaaaain! 
=) =)
Okay, I think I’m starting to understand it better now!
I made a modification where I embedded a few points with loads into the rigid bodies.
This allows me to see at which point the system reaches equilibrium, as well as the relationship between the piston force and the force applied by the finger.
I think this could also be useful for sizing/dimensioning the mechanism, in case anyone is interested.
One more question: how could I make the movements slower and more damped, almost as if the mechanism were moving through oil?
Is there a way to increase the inertia of the pieces, or apply something like a drag/damping effect? Maybe some kind of velocity reduction on the moving points?
sorry there is the file
mechanicalfinger_updown_grab_load.gh (279.3 KB)
Yes, when you add the points to the rigid bodies and the tolerance is right, the rigid bodies will stick together. Also you don’t actually need to mesh the geometry for the rigid bodies. These can be nurbs too.
@DanielPiker shared this linkage definition ages ago:
This here is my copy of it:
rigid_body_linkage.gh (46.5 KB)
Not sure about dampening the movement. Try the bouncy solver…
Ahhh, thanks for the tip!!
Indeed, the Bouncy Solver works really well for this!
Do you know if there is a way to visualize the stress vectors at each point, including their magnitude and direction?
I’m trying to imagine a very basic kind of FEM (Finite Element Method) analysis using Kangaroo, just to get a visual representation of how the stresses are distributed. For example, I was thinking about something where a piece under stress could be colored according to the magnitude of the stress, something like this,
for example.
I have no idea about FEM / FEA
Maybe try search for ‘FEA @danielpiker’
You’ll find things like this:
thanks a lot @martinsiegrist !!!
