Classification of Tower Cranes: Differences Between Top-Slewing and Bottom-Slewing

With the development of the construction industry, tower cranes, as large-scale lifting equipment used on construction sites, are mainly divided into top-slewing and bottom-slewing types. We differentiate between these two based on their structural characteristics and slewing (rotating) methods.

I. Top-Slewing Tower Cranes:

In top-slewing tower cranes, the tower does not rotate; instead, it is the jib (working arm), counter-jib, and other components above the slewing bearing that rotate around the centerline of the tower through a slewing mechanism. Depending on usage requirements, they can be further categorized into traveling, fixed, attached, and self-climbing types.

• Traveling Tower Crane: Capable of moving along tracks, this type offers a broad working range and is widely applied in multi-story building construction.

• Fixed Tower Crane: When the base of the crane is fixed on tracks or the tower is directly anchored to a foundation, it becomes a fixed tower crane, characterized by longer jibs.

• Attached Tower Crane: This type has its tower connected at intervals to the building via attachment rods. It uses a tower extension device allowing the upper slewing part to increase in height with the building, suitable for high-rise construction.

• Self-Climbing Tower Crane: Installed inside elevator shafts or similar openings, this crane ascends within the shaft using hydraulic cylinders according to the progress of construction. It saves parts of the tower structure, provides extensive service coverage without occupying construction site space but requires certain building structure conditions.

II. Bottom-Slewing Tower Cranes:

The slewing bearing in bottom-slewing models is located between the base and the turntable, causing all working mechanisms except the travel mechanism to rotate together with the turntable. Besides the track-mounted type, there are also crawler-mounted and truck-mounted versions that use crawler chassis and tire chassis as travel devices. These types can be easily dismantled, assembled, and relocated, are lightweight and flexible, and are widely used in multi-story building construction.

Through the analysis of these two types of tower cranes, one should have a clear understanding of the differences between top-slewing and bottom-slewing tower cranes. Any questions are welcome for further discussion.