After Effects: Ferris Wheel, Pendulum Expression.
Write an expression to make sure that one object that is being rotated by another stays facing straight. Useful for certain pendulum animations, ferris wheels, bicycle cranks, etc. The first 5 minutes are setup and at 5:40 I begin showing the actual expression..... *-1
In addition to that expression there are a number of things that need to be parented the right way.