a planetary gear that meshes with each of {HEAD ~ the sun gear} and {TAIL ~ the ring gear}, and 
a planetary gear that meshes with each of { HEAD ~ the sun gear } and { TAIL ~ the ring gear } , and
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH