{HEAD ~ The pistons} are connected to a crankshaft via {TAIL ~ two connecting rods} which are pivotally connected to the same crank pin 
are connected via
{ HEAD ~ The pistons } are connected to a crankshaft via { TAIL ~ two connecting rods } which are pivotally connected to the same crank pin
HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH