Certain masses oscillating about the z axis are tiltable about {HEAD ~ the x axis}, while {TAIL ~ some others} are tiltable about the y axis 
Certain masses oscillating about the z axis are tiltable about { HEAD ~ the x axis } , while { TAIL ~ some others } are tiltable about the y axis
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH