Animating a rigid linkage

I have tried this previously but my knowledge on animation and rigging for rigid linkage like this is limited at best.

I have a trailer model in Blender that has 4 rotating casters attached via rigid linkages to the central steering mechanisms, also connected by linkages. See picture:

I need to animate the model such that when the front ‘hound’ is rotated (right side center, has the long tongue sticking out of it) the linkage rotates the casters appropriately. What is the best way to do this? I have attached the base blend file as well.

SteeringAnimation.blend (4.15 MB)

I would do this with IK constraints:

Make sure you get the chain lengths correct on the IK constraints - they should only cover the number of bones in the chain (0 means go back to the root bone and will not work).

To operate; rotate the “hound-1” bone and you can also rotate the “hound-2” bone to lift the hound eye.

I have locked some rotation axes on the hound bones so it works properly.

Then “bone” parent the pieces to the bones (Select Mesh, SHIFT+Select correct bone in the armature, key CTRL+P => “Bone” - this assigns all the mesh to the bone so it moves as one. Assign the body to the root bone then you can move the whole model by moving this bone. The other major bones should be parented to “root” as I have done for various bones.

I’ll leave you to fit my armature to your model and finish off the other bits.

Here’s you blend file, with an armature added for reference: SteeringAnimation.blend (4.19 MB)

Cheers, Clock.

As I understood, rotating Bone.Rotate rotates both front- and back-axis, so:

Parent Bone.Front-L, Bone.Front-R and Bone.007 to Bone.ROTATE
Parent Bone.Back-L and Bone.Back-R to Bone.Back
Parent Bone.Back to GRAMMA
Parent Bone.ROTATE to GRAMMA
Give Bone.005 an IK-Constraint with Armature/GRAMMA as Target, and set Chain Length to 2
Give Bone.Back a Copy-Rotation-Constraint with Armature/Bone.005 as Target and Space set to Local Space

Now by translating GRAMMA and rotating Bone.ROTATE you can animate the gear.
Hope that helps.


Normally this amount of work isn’t something most people would do for free, but since I don’t get too much practice rigging here’s what I came up with:
SteeringAnimation1.blend (4.19 MB)

The rig has two layers. One with control bones, and the others are for the mechanical action. The same two sets are also in bone groups. This is pretty rudimentary, as there’s likely more that can be done with it. Little bit fiddly with a few IK sets, there might be a better way but that’s how I got it to work.

By the way that was a bit of a pain to setup centers, being that the mesh was all tris and selections had to be manually painted before snapping the 3D-cursor which was used to place bones. For working in Blender quads are much better as it’s possible to select edge rings a lot more quickly, etc. Things just flow with quad meshes, so that should be kept in consideration.

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If I had modeled it in Blender to start with I would never use tris like this. But these are from our Inventor files at work that were made for 3d Printing, so imported via stl file.

Thanks all for the replies, Ill have to look at them this morning.

Nice setup. myself looking for mechanical linkage tutorial for blender bone, but not much resources. yr replay give me a good understanding. Bone constraints/setup somehow nightmare to me, very difficult to follow blender manual. can u suggest any good article which can lead me toward working with complex mechanical rig setup. Once again thank u very much even after 3 yrs.