Answer: flywheels

AnswerCrossword Clue
FLYWHEELSParts of some engines
FLYWHEELSHeavy rotating disks
flywheelsFLYWHEEL, a heavy disk used in machinery
flywheelsA heavy revolving wheel in a machine that is used to increase the machine's momentum and thereby provide greater stability or a reserve of available power during interruptions in the delivery of power to the machine