Tower cranes are commonly used lifting machinery equipment at construction sites, used to lift construction materials such as steel bars, wood corrugated, concrete, and steel pipes. One of the important parts of the tower crane is the slewing drive device. Tower cranes can be divided into lower slewing and upper slewing tower cranes according to the rotation mode of the tower body structure. Today we will talk about the difference between upper and lower slewing cranes.
The slewing drive is usually composed of worms, slewing bearings, housings, motors and other components. Since the core components of the structure are slewing bearings, it can bear axial force, radial force, and tilting moment at the same time. In the existing structural design of mechanical products, there are many forms of composition, but the types of structural parts are basically the same.
Upper slewing tower crane is with the slewing support, balance weight, and the main mechanism at the upper end. The advantage is that when the tower body does not rotate, the lower structure of the tower body can be simplified and the lifting and joints are convenient. The disadvantage is that when the building exceeds the height of the tower, the rotation of the crane is restricted due to the influence of the balance arm. At the same time, the center of gravity is higher, the wind pressure increases, and the weight increases, which increases the total weight of the whole machine.
The tower body of the jack-up tower crane is also assembled by standard sections, which is actually a kind of assembled tower crane. But it is also equipped with a jacking and sectioning system. After installation, it can be jacked and sectioned at any time. This feature is more prominent. The advantage of jack-up tower crane is that it can be attached and can be raised very high, so it is especially suitable for middle and high-rise buildings and bridge construction. It is the most common use tower crane in my country’s existing tower cranes. Jack-up tower cranes are all top-rotating, because they have to be attached and do not allow the tower to rotate.
The lower slewing tower crane is with the slewing support, balance weight and main mechanisms at the lower end, the boom is installed on the top of the tower body, and the tower body, counterweight and all mechanisms are installed on the turret and rotate together with the turret. . This type of tower crane has a low center of gravity, good stability, and small bending moments on the tower body (the bending moment of the upper slewing tower crane is borne by two diagonally arranged main chords, and the lower slewing tower The bending moment is shared by the four chords). In addition, because the balance weight is placed in the lower part, it can be erected by itself and transported as a whole. The disadvantages are: higher requirements for the slewing support, and limited use height. The cab is generally set on the lower turret, and the operating sight is not open.