I am currently working on a 4-bar chain mechanism in Blender and have encountered an issue with the rotation of the bones. Here's the setup:

  1. I started by adding a series of bones, with the last bone being named Bone.004. The first bone (Bone) serves as the fixed link in the chain.

  2. I set Bone.004 to be the child of the first bone (Bone) in the chain. In other words, Bone is the parent of Bone.004.

  3. I applied an IK (Inverse Kinematics) constraint to the Bone.003 to Bone.004 connection. However, when I rotate the active bone (Bone.003), I expect to see two cranks rotating 360 degrees each.

  4. The problem I am facing is that the bones are not rotating as expected. Instead of the two cranks rotating 360 degrees, the bones seem to be rotating individually around themselves.

I believe this issue might be related to the length and fixed nature of the first bone, causing a disruption in the intended rotation. I would greatly appreciate any insights or suggestions on how to resolve this problem and achieve the desired rotation of the bones in my 4-bar chain mechanism.

Thank you in advance for your assistance.

Attachement: https://i.imgur.com/aG1lPNE.gif

Update: I Selected Bone.004 and ensured that it is not parented to any other bone.

  • $\begingroup$ Hello and welcome. Instead of having users go through links and external sites please use the builtin tools to embed images in your post. See How to upload an image to a post? or GIF $\endgroup$ Commented Jun 7, 2023 at 20:16
  • $\begingroup$ Hello Ramos, Thank you for your response. I appreciate your guidance. As a newbie, I apologize for not using the built-in tools to embed images in my post. I will make sure to follow the instructions you provided in the future. Your support is invaluable as I continue my learning journey with Blender. Best regards, Arif. $\endgroup$ Commented Jun 8, 2023 at 14:31
  • $\begingroup$ You have a fixed bone and a control bone. Just use a 2-chain IK for the other two bones in the 4-bar. Lock all but a single axis on both of those bones. In 4.0.1, this works fine, giving you a full 360 degrees rotation on your crank bones. $\endgroup$
    – Nathan
    Commented Feb 15 at 18:51


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