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