Propeller or Turbine rotation
 

I'm animating a turbine engine kind of like the one in the pod race inStar Wars episode 1. Is there a Mel script to make the turbine turn all the time without having it to key frame it?

just use a exprestion.. there just what you want. there will be sevral examples in the help files for just what your wanting to do with rotation based on time.

Let's say your object is named propeller and you want to rotate it around the Z axis. Then the expression could be as easy as:

propeller.rz = frame;

If you want to control the speed, you could add a custom attribute to your object (let's say speed) and change the expression to:

propeller.rz = frame * propeller.speed;

This way you can key the speed attribute and control the speed of the rotation.

Why not just keyframe 10 frames and then set it to cycle with offset. It will spin forever.