[HungryBear]

First lets pick a coordinate system. Since this is going to be "hand waveing" rather than math lets us a Cartesian system - X, Y, Z. the "plane of the swing" defined as X,Y and any above or below plane defined a Z. A cylindrical system may be more appropriate but harder to understand. and polar system would become impossible. So the swing plane is a flat X,Y plane and deviation above or below this plane is +/- Z. (Just geting started) Any engineers object?

hb