# Rotation around one axis (Mechanical)

I am completely new to Blender and I have trouble solving a rather trivial problem.

I have a model of a machine which parts can only rotate around a given axis.

For example: Imagine a tank with its turret. The platform of the turret can only rotate in a circle around the y-axis (height axis). I wanted to archive this with a simple cylinder and a rotating plate on top.

I watched tutorials on rigging but using armature seemed the wrong move since it mainly bends instead of rotating the object. Is there a way to force the armature bone to only be able to rotate? If thats possible I could assign every part of the machine one bone with fixed axis rotation and a fixed offset to the next part of the machine.

Which technique should be used to archive the given task?

You can add a Copy Rotation constraint to them pointed to one Empty, then just rotate the empty on that axis by pressing R+Z.

Now when you rotate the empty all the other objects follow that rotation.

• thanks for the fast response! To be sure, the empty object the source of the rotation even though it gets set as target by all objects referencing to it? – Wandang Feb 28 '15 at 18:29
• It is the target of them all, and all are affected by that one empty. You can even duplicate the object and the settings and link are the same. – VRM Feb 28 '15 at 18:29
• This worked as expected. Unfortunately the objects are far away from the origin of ordinates. So the axis is a bad reference for now. None the less your answer was right to the topic – Wandang Feb 28 '15 at 18:46
• OK, can you change the origin using Ctrl+Shift+Alt+C > Origin to Center of Geometry? – VRM Feb 28 '15 at 18:55

I found a very simple solution by playing around.

Go to the timeline. Insert a Delta Rotation Keyframe at the start.

Then go to the object panel and change the Delta Rotation values of the particular axis you wish to rotate. And then just add a new Delta Rotation keyframe. There you have a very simple animation of a rotation on a single axis.