The working medium which has been compressed or expanded in one of the two piston working chambers can therefore also do {HEAD ~ work} in {TAIL ~ the third working chamber} 
in
The working medium which has been compressed or expanded in one of the two piston working chambers can therefore also do { HEAD ~ work } in { TAIL ~ the third working chamber }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL