Derrick Crane are generally made of wood or steel. This crane has a simple production, easy assembly and disassembly, from the weight, limited by the construction site characteristics. Especially the lifting of large-scale components and the lack of large-scale lifting machinery, such lifting equipment even more of its superiority. But this type of crane need to set more cable rope, moving difficult. In addition, the lifting radius of small, poor flexibility. Therefore, the Derrick Crane is generally used for heavy components, lifting works more concentrated, the construction site is narrow, but the lack of other suitable large-scale lifting machinery.
Derrick Crane are non-standard cranes and are generally used in environments where the crane can not be lifted.
(A) the basic structure and classification of Derrick Crane
Derrick Crane structure: mast body, lifting system, stability system, power system
Mast body: mast, base and its accessories.
The mast is divided into a lattice and a solid (generally steel) crane in the form of a structure.
The lifting system is mainly composed of pulley block, guide wheel and wire rope.
The stabilization system mainly includes cable wind rope, ground anchor and so on.
Power system is mainly electric hoist, but also the use of hydraulic devices.
(B) Calculation of cable rope tension and cable rope selection
The cable wind rope is a stable system of the Derrick Crane, which is related to the safety of the crane and affects the shaft force of the mast. The tension of the cable rope is divided into working tension and initial tension.
1. The initial tension of the cable rope
The initial pull refers to the force that the mast is pre-tensioned when the mast is not working. The initial pull to take the work of the pull of 15% -20%.
2. Cable wind rope work pull
Working tension refers to the load on the cable crane when the Derrick Crane is in operation.
In the correct cable wind rope process layout, there is always a cable wind rope in the vertical and mast axis of the vertical plane, which is called "main cable wind rope."
3. Cable rope selection of the basic principles: all cable wind rope will be selected by the main cable wind rope.
When the cable wind rope is selected, the working tension of the main cable wind rope is based on the sum of the initial tension.
T = Tg + Tc
Where: Tg - the main cable wind rope work pull;
Tc - the initial tension of the main cable wind rope.
(C) the type of ground anchor, ground anchor calculation
Type: Buried, semi-buried, active and use of buildings
1. Full burial anchor can withstand a large pull, suitable for heavy lifting. When calculating the strength, it is usually necessary to check the horizontal stability, vertical stability and beam strength according to the soil condition and the beam material.
2. Activities to anchor by the force is not, suitable for change, expansion project. The level of stability and vertical stability need to be calculated when calculating its strength.