This series of the actions are repeated to provide {HEAD ~ a continual reciprocal movement} of {TAIL ~ the piston} 
of
This series of the actions are repeated to provide { HEAD ~ a continual reciprocal movement } of { TAIL ~ the piston }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL