Are you trying to determine when a single layer of the coil has reached the far lip (and presumably needs to reverse to form a new layer), or when the layers of the coil have built up to the required outside diameter?
I am trying to determine when a single layer of the coil has reached the far lip in order to properly reverse to form a new layer.
Stopping exactly on the far lip is required in order to properly reverse to the new layer and keep a tight packing without overlaps. When using a single average value for the wiere diameter, the accumulation of error over thousands of turns yields inconsistent results (i.e. the wire will stop before or after (spool unto itself) the far lip).
Basically, I am trying to find a way that will guarantee that the wire will always stop exactly at the far lip.