Generally speaking, the driving device is mainly composed of the following three parts:

1) Driving machine, such as electric motor, hydraulic motor in hydraulic drive (including hydraulic power source), internal combustion engine driven by internal combustion engine, etc.

2) The transmission device mainly includes deceleration, reversing and braking devices.

3) The rotary pinion engages with the large tooth ring on the rotary bearing device to realize the rotary movement of the rotary part.

In order to ensure the reliable operation of rotary machinery and prevent overload, it is generally necessary to install limit torque limiter in the transmission system. Most of the driving machines use electric motors, but most of the mobile slewing cranes use internal combustion engines. Rotary driving components mostly adopt gear (or needle wheel), there are also individual cranes using driving roller or rope traction.

According to the use and structure of the crane, the rotary drive device can be arranged according to two schemes:

The driving part is installed on the slewing part of the crane, and the last stage of the big gear ring (or pin wheel) is installed on the rack of the non-slewing part. In the slewing mechanism of the port crane, the vast majority of them adopt this form.

The driving part is installed on the non-slewing part of the crane, and the last stage of the big ring (or pin wheel) is installed on the slewing part of the crane, which is sometimes used in some large fixed column crane, tower crane.