Mechanic arm wit pistons, who can i animate this model...

I’m working in a some forestal machines animations, and one of the main troublesome things is the machines arms, that have pistons that have move in a logic specific way…

very hard to animate, and hard to explain so i’m posting some pics about my machine main positions…

if it wasn’t for those pistons it wold be very easy to put an armature on it… i also tried key shapes but the deformation during the animation is very odd for this kind of stuff.

please, anyone have an idea of how this can be properly animated?

*edit: sorry for the typing errors in the title, but i cant fix it…


Francis, keeping in mind that I’ve not animated something as complex as you are showing, I would tend to say this can be done with armature animation, just not in the typical sense that they’re used.

When using armatures on character animation, the desire and intent is to deform the actual mesh at the joints. But with what you are doing, you don’t want the meshes to deform with the armatures.

Thus, you can make the entire upper arm (for example) linked to a single bone (as a separate mesh object itself) and so forth. The primary challenge will be to maintain the pivot points of the bones to match those of the mechanics of the mesh. No scaling or twisting of the bones can be allowed either. I think there’s a way to limit the motions such that they can only pivot in a given axis, etc.

What you’re doing should be possible with an armature - it just takes thinking about it differently from “organic” motion. It is actually much more structured, since it is man-made and narrower in design scope than biologics.

Hi Francis,

Yeah, that will be easy… just joking. When mechanical rigging something I like to keep all the moving parts separate objects and parent them to the bones that will move them. This avoids the weight painting/vertice groups stuff. Bones have to have their head/tail positioned at the exact pivot points of the mechanical parts. I did a basic beginner type of tutorial on mechanical rigging that you can see here. From there on out, it’s a matter of adding extra bones for the hydraulic cylinders and constraints to get them to work. See attached screenshot of a landing gear setup I did. Basically, you move the bottom mesh, and everything else moves as needed.

Like I said, easy, hahahahhaa. Basically, I would rig the main parts of the arm. Once that works, insert bones as needed to rig the cylinders. It will be a lot of work if you don’t know rigging and constraints, don’t let my humor fool you…

I have no more advice than that…


A lot of what you’re doing can be achieved by parenting and constraints, as well as shifting the pivot points of objects to where they rotate around. There are some spots that require bones. It’s definitely possible to do, though. I rigged something similar a while back.

The tutorial titled “A tutorial on how to animate nice robots with pistons moving their arms, with tubes and springs.”, on this page, was really helpful,
it might be a bit outdated now, but the techniques are the same. Good luck!

I did it!

Tanks everyone, the tips and tutorials helped a lot.

wen the animation is completed i will be sure to post it.