When maintaining the slewing bearing of a commercial crane, it is necessary to know the basic parameters of the slewing bearing so that the slewing ring can be conveniently repaired or replaced.
1, safety factor
Because the bearing does not often bear the full load during the work, the rotation is relatively stable, the impact is small, the speed is slow, and the slewing bearing that meets the requirements of the safety factor can basically meet the requirements of the bearing. When the safety factor of the bearing is lower than the recommended value, the requirement for the rigidity of the bearing race is correspondingly increased. The deformation and tilting of the raceway can cause additional load on the bearing and aggravate the early failure of the bearing. If the safety factor does not meet the maximum load application of the slewing bearing, damage to the slewing bearing may result.
2, ball diameter Dw
D = KC
Where: K is the ball diameter coefficient; C is the width of the bearing outer ring.
Based on design experience, it was concluded that the steel ball diameter coefficient was selected within the following range.
K1=0.25 to 0.28
K2=0.22 -0.24
Where: K, K2 are the diameter coefficients of the main thrust and reverse thrust steel balls, respectively. Therefore, the diameters of the main thrust and reverse thrust steel balls are
Dw1 = (O.25 - 0.28)C
Dw2=(0.22-0.24)C
3, the ball group diameter circle Dpw
Dpw1 = 0.5 (D1 + d1) where: D is the diameter of the center circle of the outer ring, and d is the diameter of the center circle of the hole of the inner ring, as shown in Figure 2. Dpw1 can be adjusted slightly based on the diameter and length of the inner and outer ring mounting holes. Reverse pitch ball group pitch circle diameter DpW2 DpW1+Dw1-Dw2.
4, contact angle
Due to the large overturning moment of the bearing and the poor stress conditions, the contact angle is much larger than the conventional value. At present, both domestic and foreign take 75 to 90 degrees.
5. Ditch curvature coefficient
In order to meet the heavy load requirements, the groove curvature of the bearings used in marine cranes is highly loaded and special designs are made. In designing, taking into account the slower bearing speed, do not have to consider the effect of temperature rise, the groove curvature coefficient should be appropriately reduced, improve the degree of closeness, thereby increasing the bearing capacity, the current groove curvature coefficient f = 0.515 ~ 0 .525, with equal inner and outer curvatures.
