How to calculate the capacity for slewing bearing?

Slewing bearings are bearings of large dimensions (> 400 mm) used in different applications, such as cranes, turning tables, excavators, wind turbines etc.. Their main function is to connect structural parts, allow relative rotation between them and transmission of loads. This article mainly introduces how to calculate the capacity for slewing bearing.

Here are the main points of the article:

• The capacity for slewing bearing

• How to calculate the capacity for slewing bearing?

1.The capacity for slewing bearing

When slewing bearing is needed for the equipment, there is a lot of confusion about the structure of slewing bearing. In fact, there are differences in the bearing capacity. How to improve the bearing capacity of slewing bearing under the premise of not changing the installation size of slewing bearing is a very challenging problem.

The structure of slewing bearing, four-spot bearing, double-volleyball bearing . If the bearing is not emphasized, the general four-spot slewing bearing is adequate for the rotation movement and load requirements, excavator slewing bearing, bottle blowing machine slewing bearing, tower crane slewing bearing, automobile crane slewing bearing, injection molding machine slewing bearing and so on.

If the installation size is not changed, the bearing capacity of slewing bearing should be improved. Priority should be given to the increase of the ring height and the increase of the steel ball, then the bearing capacity of the double volleyball slewing bearing should be changed to the double volleyball slewing bearing and the third row of roller slewing bearing.Of course, the cost of slewing bearing is going to go up as well.

2. How to calculate the capacity for slewing bearing?

The standard calculation methods for bearing evaluation are based on some assumptions which take into account only axial Fa and radial Fr loading of the slewing bearing. On the other hand, most of large slewing bearings are also loaded with an overturning/tilting moment MT (Fig. 1).

Some simple expressions for the determination of contact force distribution between the rolling elements and the raceway, based on this kind of external loading, can be found in technical literature. According to an expression from [7] the maximum contact force between the axial roller and the raceway can be determined as:

nFDn M Q aL

Tmax 4 ±  = (1)

This expression considers that the vertical contact load linearly varies across the diameter of the raceway (i.e. sinusoidal distribution). However, if slewing bearing rings undergoes considerable deformations during operation this method does not give enough accurate results. Numerical simulations or specialized calculation approaches for the determination of contact load distribution should be used in such cases.

The numerical calculations were performed with the computer program Abaqus/Standard [9] as a static simulation with elastic material properties taken into account. Due to the symmetry of the problem, a 1/8 model was employed (Fig. 2a). The numerical model consisted of approx. 100,000 8-node linear brick elements. The contact between the roller and the raceway was defined as “hard” contact (Fig. 2b). The P. Göncz et al. / Procedia Engineering 10 (2011) 1196–1201 1199 contact loading was prescribed as a vertical displacement (in direction of y) of the roller segment. The resulting contact force Q was then determined for every vertical displacement from the results of the numerical simulation. 

We hope the introduction of this paper will be helpful for you to know about slewing bearing. Our company specializes in producing all types of slewing bearing. If you need slewing bearing, please contact us.