A self centering construction 19 wherein said axial movement means comprises a second liquid spring operable in {HEAD ~ tension} and compression on {TAIL ~ each} of said liquid springs 
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A self centering construction 19 wherein said axial movement means comprises a second liquid spring operable in { HEAD ~ tension } and compression on { TAIL ~ each } of said liquid springs
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH