{TAIL ~ The floating hinging point} is formed through two ball bearings , a fastening bolt , {HEAD ~ a coupling ring} , a bearing house , an intermediate ring and a self locking nut  
{ TAIL ~ The floating hinging point } is formed through two ball bearings , a fastening bolt , { HEAD ~ a coupling ring } , a bearing house , an intermediate ring and a self locking nut
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH