The cranks of adjacent pairs of {TAIL ~ cranks} are interconnected by a common crankshaft, therefore {HEAD ~ all} of the cranks are interconnected and rotate together about a common axis 
The cranks of adjacent pairs of { TAIL ~ cranks } are interconnected by a common crankshaft , therefore { HEAD ~ all } of the cranks are interconnected and rotate together about a common axis
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH