{TAIL ~ Piston machine}, which operates either as an engine or as {HEAD ~ a working machine}, the piston machine comprising: 
{ TAIL ~ Piston machine } , which operates either as an engine or as { HEAD ~ a working machine } , the piston machine comprising :
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH