Complex sentence: A swashplate is a device used in mechanical engineering to translate the motion of a rotating shaft into reciprocating motion, or to translate a reciprocating motion into a rotating one to replace the crankshaft in engine designs.
Split into simpler sentences: A swashplate is a device used in mechanical engineering to translate the motion of a rotating shaft into reciprocating motion. Conversely it can translate a reciprocating motion into a rotating one and can be used to replace the crankshaft in engine designs.