# How to fix rotational constraint 'jumping' in rotation problem

I am rigging a set of gears (a car - wheels driving through a differential), and am taking the input as the wheel rotation. I've used parenting and constraints to link the gears. All goes well until I reach the point where I need to have the next gears rotation at 1/3 of the previous gear. Each method I have tried (transformation constraint, rotation constraint, and others, drivers, etc) all result in the correct rotation for only 120 (or 1/3 of a full rotation) before it flips on it's local axis and starts again. This is true for other fractions of the original rotation also. On a rotationally symmetrical gear this may not be a problem, or even visible, but my gear is not. It can easily be seen by selecting the target gear and turning on the local axis view. Does anyone now of a solution to this, to achieve a fluid, full, scaled rotation?

• Are you using euler angles in your calculation? Because they have some issues, most notably gimbal lock which could be the cause of jumpy rotations. It is better to use Quaternions instead. The Blender Wiki give a good overview over the different rotation modes. – maddin45 May 24 '14 at 20:33
• I am using the Eulerian system. I have wondered about quaternions being the solution, and have experimented a little in the past, but can't get to grips with it. How can I use constraints such as transformation constraint with this coordinate system? – zzero101 May 24 '14 at 21:22
• This Dr. Hirsig tutorial explains some limits & quirks of transformation constraints at about 5:30 vimeo.com/46063135 – dino808 Mar 20 '16 at 19:51

Here I have the source rotating -120 and the destination rotating 360. The key to having it rotate continuously is to tick the extrapolate check box.