Enclosed are three plots.  "fricVSvcG05" is the scan of friction vs. a
unitless arm velocity over the quantity Lattice spacing times natural
frequency of arm in vertical direction.  "fricVSvcG07" is the same. These
plots are with the coefficient of restitution of 0.5 and 0.7 respectively.
poVC193G07 is a Birkhoff-Poincare plot at g=0.7, with normalized
velocity=1.93 (where it peaks).
At normal velocity=2 it does not look periodic.
I will write up my findings this afternoon/evening and send it to you ASAP.

Tyson