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