The crankshaft

The crankshaft, sometimes usually
abreviated to crank , is the part of an
engine that translates reciprocating
linear piston motion into rotation. To
convert the reciprocating motion into
rotation, the crankshaft has "crank
throws" or " crankpins", additional
bearing surfaces whose axis is offset
from that of the crank, to which the
"big ends" of the connecting rods
from each cylinder attach.