a pair of pinions, {HEAD ~ each} having {TAIL ~ an outer teeth gear thereon}; and 
having
a pair of pinions , { HEAD ~ each } having { TAIL ~ an outer teeth gear thereon } ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH