Drive units are slow-speed and high-torque devices that are a combination of a hydraulic motor with a braking system that operates automatically when the power supply to the motor is turned off, and a gearbox that increases the torque of the set.
To a unit consisting of a hydraulic motor, brake and gearbox , depending on the adopted design solution, additional structural elements may be attached to allow the installation of a chain in the tensioning system. The purpose of such a set is to facilitate the performance of chain length correction during shortening or lengthening operations.