this is straight from the late big jim




The common belief that a Hemi wound armature is equal to 1/2 turn less is an old-wives tale or an "R/C Urban Legend". The fact is that the Voltaic Principle states that in order to make a magnet loop of maximum strength a coil of wire must cross itself when wound around an iron core. Since the last turn of a Hemi wound armature coil does not cross itself, it's believed that it's equal to a half turn less. This is ludicris!

Since it's impossible to make an armature with only 1/2 a turn of wire less of the total, no one can say what is equal to that, since no one has made one.
If one were to take the last coil off of a Hemi wound armature and the last coil of a Mabuchi cross-wrapped armature and measure them they would find that the difference in length is something much shorter than 1/2 turn around the stacks.

So I wonder what basis that person used (who made this up) to determin that a Hemi wound armature is equal to 1/2 less?