Selecting the correct slewing ring configuration is critical for performance and cost. The choice between an external and an internal gear is a common dilemma. This guide provides a technical comparison to inform your decision-making process.

Torque and Load Capacity:

• External Gear: Offers a larger pitch diameter for a given bearing OD, providing higher torque capacity. Ideal for applications requiring high torque at low rotational speeds under heavy loads.

• Internal Gear: Has a smaller pitch diameter, which may limit torque but often allows for a more compact overall design with the drive components protected inside the gear circle.

Space and Envelope Constraints:

• External Gear: Requires space around the bearing's outer diameter for the gear and pinion drive. This increases the system's overall footprint.

• Internal Gear: The drive pinion engages inside the gear circle, leading to a more compact envelope. This is advantageous in space-constrained designs like certain robotic applications or compact machinery.

Mounting, Sealing, and Maintenance:

• External Gear: Simplifies mounting as bolt holes are unobstructed. Gear teeth are easily accessible for lubrication and inspection but are more exposed to contaminants.

• Internal Gear: Offers inherent protection for the gear mesh from environmental debris. However, access for maintenance and mounting can be slightly more complex.

Cost Considerations:
Generally, externally geared rings can be more cost-effective for larger diameters due to simpler machining of the external teeth. Internal gearing may involve more complex machining processes.

Conclusion:
Choose an external gear for high-torque, heavy-load applications where space is not the primary constraint and ease of maintenance is valued (e.g., cranes, excavators). Opt for an internal gear when maximizing compactness and protecting the gear mesh is paramount (e.g., stacker cranes, some wind turbine designs).