so this makes it:
worm gear 2:25
next stage 10:35
next stage 9:29
final stage 18:37
648:187775 (and it does not factor smaller)
factor in the encoder (7*4) and you get
162 revs per 1314425 encoder steps or 8113.7345679012 encoder steps/rev
so we have been off by 0.42% in our measurement of all chain lengths, or around 10-12mm in motor spacing measurements (and at about 1500mm of chain, one tooth off)
no wonder we have been going nuts trying to get things accurate
We owe a LOT to the people who reported the positioning error