Hi, I have some gears rotated at 120 degrees from center, and i want them to copy the rotation of the z axis rotation of the top one, since it’s centered on…center…
but when i tried, the gear just wobbles about. I have my transformation orientations saved and labeled, but i don’t know how to apply them to these rotated gears, and have them stick while they are attempting to copy rotation of something with its own orientation (in this case, global).
If you are building a gear train, you are best to use Drivers not copy rotation constraints. Then the problems will go away, the gears can easily rotate about their local axes making the Drivers easier to setup and the whole system easier to animate over say multiple rotations of each gear. An image of your gear train or a blend file would be a good idea by the way thus enabling us to help you easier. To rotate an object about its own axis, just type a value into the appropriate box on the Object panel or to rotate about its own X axis you can type R X X and a value. Using the double X key means local X axis whereas one X would mean global X axis. Don’t forget that if you use driver expressions you must enable Autorun Python Scripts in User Preferences, or they won’t work.
Cheers, Clock (no longer an EU citizen grumble, grumble, moan and curse)
Here’s the basic arangement of my 3 gears. The way they are set up, copy rotation causes wobbly rotation. I tried drivers but they also caused wobbly rotation. gears120.blend (572 KB)
Maybe there is a way to match the rotation, a step im missing.
This is the easiest way - just press Play to see them move. Do NOT apply the rotation to the gears or they will wobble!
Cheers, Clock. 
gears120.blend (683 KB)