The structure and function of the slewing drive of the truck-mounted crane

Slew Drive

The structure and function of the slewing drive of the truck-mounted crane

Slew Drive Structure

The slewing drive device of the truck-mounted crane includes a hydraulic motor, a brake and a reducer.


1.Hydraulic Motor

Convert the pressure of hydraulic oil into rotational mechanical energy and transmit the rotational motion to the reducer.


The brake is inside the hydraulic motor and brakes the output shaft of the hydraulic motor.


The reducer of truck-mounted crane is composed of a two-stage reduction planetary gear transmission. It is decelerated through the gear transmission device and transmitted to the output shaft of the reducer.

Slewing Bearing

Abnormal noise problem of excavator slewing bearing

It is normal for the new slewing bearing to make a uniform sound of rolling steel balls when it is idling. It will disappear after a period of running-in after installation. If there is a loud sound or special noise, you should pay attention.

1. The mounting surface is uneven and the mounting bolts are loose

2. There is a foreign body in the slewing bearing

3. Abnormal noise caused by a problem with the grease

4. Raceway and rolling body are severely worn

Conclusion: you should not be careless when there is abnormal noise in the excavator slewing bearing, you must check and solve the fault in time.

Slewing Gear Ring Bearing Drive

Slewing Gear Ring Bearing & Slewing Gear  Drive

Rotary gears are usually divided into two types, one is the rotary gear support bearing, the other is the rotary gear drive
Slewing gear support bearings are composed of an inner ring and an outer ring, usually one of which contains the gear. Together with the connecting holes on the two rings, they are easily and quickly wired through the adjacent link components for optimized power transmission. Slewing gear bearing raceways combined with rolling elements and cages are designed to withstand loads acting individually or in combination in any direction.
Rotary gears can be used in various industries such as aerospace, heavy equipment, industrial machinery, medical systems, mining, oil and gas, etc., and are the key to many industries and play a vital role.
The slewing gear support bearing is different from ordinary bearings, the difference is that it has a gear that can adjust the rotation. The machine transmits and adjusts the direction of the mechanical products fixed on the slewing bearing through the dynamic sensing system installed on the slewing gear bearing. and take advantage of special constructs:

It maintains the overall balance, effectively guarantees the radial force generated in the work, and ensures the balance.

The rotary gear drive is a kind of turntable fixed in the gear box, which can safely bear the radial and axial load force, and drives the rotation of the turntable through the rotation of the turbine. Rotary gear drive is a gearbox composed of gears, bearings, seals, casings and motors.
The rotary gear drive is a modification of the worm drive mechanism. It dates back to the Renaissance period, when the Greek mathematician Pappus devised a worm drive. Da Vinci also used the slewing gear drive trim in many of its machines.

The driving force of the rotary gear drive comes from the rotational force given by the motor to the worm, and the gear on the worm is adjusted by the gear on the electric turntable. This combination mode reduces the rotation speed of the turntable, increases the torque, and can drive heavier objects.
Slewing gear drives can be applied to solar trackers, wind turbines, elevators, hydraulic machinery, telescopic arms, cranes and other equipment.

Large Diameter Slewing Bearings

LDB high quality large diameter slewing bearing

The high-quality large-diameter slewing bearing produced by LDB leads the world, and has more than 20 years of experience in the design, development and customization of large-diameter ball bearings. LDB’s high-quality service has won unanimous praise from customers.

LDB oversized bearing combination

The range of oversized bearings currently produced by LDB includes large diameter slewing ring bearings, single row bearings, double row four point bearings, triple row ball bearings, and also offers a variety of custom designed special bearings.

The slewing ring bearings produced by LDB include external, internal and gearless bearings. Among them, the bearing with gear needs to be determined according to the actual situation.

Multifunctional application of LDB large slewing ring bearing

The large diameter bearings produced by LDB are used in various fields, and different designs meet different needs. This includes construction machinery such as excavators and drilling rigs, as well as mining, construction and offshore wind turbines.

LDB one-stop bearing solution

LDB offers a range of system solutions. The large diameter slewing bearing of LDB is perfectly combined with the LDB slewing drive. According to customer requirements, we provide corresponding electric or hydraulic motor control technology, so that customers can choose more easily and quickly.

LDB large slewing bearing high quality, high reliability

All components of large slewing rings produced by LDB meet the highest standards in terms of functionality and are able to meet customer needs even under extreme conditions. LDB implements a strict management program to ensure product reliability and long service life.

Unified quality management system

The LDB large slewing bearing is a trademark of excellent quality. In order to maintain high standards, LDB adopts advanced management methods, and strictly controls each development and production process, and all production processes are assembled in the computer data on file. This allows full control, monitoring and traceability. Processes are continuously improved through various assessments.

LDB large diameter slewing bearing adopts high quality raw materials

All components of LDB large diameter bearings are made of raw materials of the highest quality standards. Raw material parts are provided by qualified suppliers and audited regularly. For special raw materials, we manage production with standards that exceed the industry.

In addition to the use of 42CrMo4 alloy for large slewing ring bearings, polymer spacers are usually used for the cage between the bearing balls. However, brass alloy or steel is used as the material in extra large bearings, which can prevent corrosion and wear.

Slewing Bearing Installation Surface

Mechanical machining of the bearing connection surfaces on the connecting structure is required . The mounting position of slewing bearings must correspond to that shown in the drawing. If a transporting cross was delivered, it has to be removed before installation.

The corrosion protection can be removed with an alkaline cleaner. Cleaner must be prevented from coming into contact with the seals or the raceway. Remove the protective coating from the upper and the lower mounting surfaces of the slewing bearing as well as from the gear.

The corrosion protection can easily be removed, for example, using a biodegradable alkaline cleaner.

Rapid removal of the corrosion protection and low environmental impact.

The unhardened zone between the beginning and the end of the hardened region of the raceway is marked with an “S” on the inner or outer diameter of each bearing ring. On the gear ring, the hardness gap is marked on the axial surface. Wherever possible, the hardness gap “S” must be positioned outside the main load-carrying areas. If the main working area for the application is known, then the hardness gap of the ring loaded on the circum-ference must also be positioned outside the main load-carrying area.

The bearing must be completely screwed on for commissionings and test runs. Sufficient load / moment loan must be applied to avoid a slip-stick effect on the anti-friction bearing bodies.


Entanglement hazard due to exposed gear

  • Keep hands away from moving parts

The backlash is adjusted relative to the three gear teeth marked in green and should be 0.03 – 0.04 x module.After the final tightening of the bearing,the backlash should be rechecked over the entire circumference. A tip edge radius and a tip relief must be provided on the pinion.

How to maintain the slewing bearing during use?

We know that the quality of the slewing bearing itself is the main factor affecting the service life of the bearing, but no, because in addition to the quality of the bearing, there is also a very important issue, that is, the maintenance and maintenance of the bearing during its use, but, How to maintain the slewing bearing during use?

Lubrication of slewing bearing

Slewing Bearings

1. Lubrication

(1) Reduce friction and wear. In the mutual contact parts of the rings, rolling elements and cages that constitute the bearing, metal contact is prevented, and friction and wear are reduced.

(2) Extend the fatigue life. The rolling fatigue life of the bearing is extended when the rolling contact surface is well lubricated during rotation. Conversely, if the oil viscosity is low and the lubricating oil film thickness is not good, it will be shortened.

(3) Discharge frictional heat and cooling. The oil circulation method, etc., can use oil to discharge heat generated by friction or heat from the outside, and cool it. Prevent the bearing from overheating and prevent the aging of the lubricating oil itself.

(4) Others. It also has the effect of preventing foreign matter from entering the inside of the bearing, or preventing rust and corrosion.

2. Lubrication method

Bearing lubrication methods are divided into grease lubrication and oil lubrication. In order to make the bearing function well, first of all, it is necessary to select a lubrication method suitable for the conditions of use and the purpose of use. If only lubrication is considered, the lubricity of oil lubrication is dominant. However, grease lubrication has the advantage of simplifying the structure around the bearing. Compare the advantages and disadvantages of grease lubrication and oil lubrication.

Cleaning of slewing bearing

1. Selection of cleaning materials

As the cleaning agent, cleaning agent and kerosene are generally used. In addition, pay attention to sealing the cleaning agent when not in use to avoid the entry of external magazines and contaminating the cleaning agent. In the case of inattentiveness, cleaning the bearing with the contaminated cleaning agent will not only not have a cleaning effect, but will contaminate the bearing and cause the bearing to be polluted. Running brings stress.

2. Cleaning precautions

(1) The disassembled bearing is cleaned, divided into coarse cleaning and fine cleaning, and placed in the container respectively, first put on the bottom of the metal mesh, so that the bearing does not directly contact the dirt of the container.

(2) During rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing, so be careful. In the rough cleaning oil, use a brush to remove grease and adhesions. After it is roughly clean, transfer to the fine cleaning.

(3) Fine cleaning is to carefully clean the bearing while rotating in the cleaning oil.

slewing bearings

Maintenance of slewing bearing

1. Maintenance method

(1) Check the state of the raceway surface, rolling surface, and mating surface, the wear of the cage, the increase of bearing clearance, and the damage and abnormality irrelevant to the decrease of dimensional accuracy.

(2) For small ball bearings, support the inner ring horizontally with one hand, and rotate the outer ring to check whether it is smooth. For separable bearings such as tapered roller bearings, the rolling elements and the raceway surface of the outer ring can be inspected separately.

2. Maintenance precautions

(1) In order to judge whether the disassembled bearing can be used, it should be checked after the bearing is cleaned.

(2) Special tools and disassembly steps and techniques should be used for bearing disassembly to avoid damage to the bearing due to the disassembly of the bearing for maintenance, which is not worth the loss.

(3) Since large bearings cannot be rotated by hand, pay attention to checking the appearance of rolling elements, raceway surfaces, cages, rib surfaces, etc. The higher the importance of the bearing, the more careful inspection is required.

The above is the summary of how to maintain and maintain the slewing bearing during the use of the slewing bearing. It can be seen that the maintenance skills in the use of the slewing bearing include lubrication, cleaning, and maintenance.

Bearing lubrication should pay attention to the selection of appropriate lubricants, pay attention to the distinction between coarse and fine washing when cleaning, and pay attention to disassembly, rotation and other issues when overhauling.

Light slewing bearings & Medium slewing bearings

Light slewing bearings & Medium slewing bearings

LDB manufactures many types and variants of slewing rings. The most common bearings in stock or with short lead times are:

  • Single row four-point contact ball slewing bearing
  • Single row crossed cylindrical roller slewing ring

These standard slewing bearings are described on the following pages and their performance data are listed in the relevant product tables.

LDB also manufactures various other types of slewing rings. For more information on these bearings, please contact LDB Application Engineering Services.

Single ball slewing bearings

Light slewing bearings

  • with an external gear
  • with an internal gear
  • without a gear

Medium slewing bearings

  • with an external gear
  • with an internal gear
  • without a gear gear

Single roller slewing bearings

Medium roller slewing bearings

  • with an external gear
  • with an internal gear
  • without a gear

Marine Propeller orientation device (POD)

Marine Propeller orientation device (POD)

LDB has a long history of providing a full range of slewing bearings for the azimuth positions of marine applications.

These highly tailored solutions cover outside diameters from 50 to 7 900 mm.

Our wide range of engineering expertise in bearings, seals, mechatronics, services and lubrication systems all contribute to the high quality of our marine solutions.

As proof, every bearing designed and produced for marine applications is subject to approval by certifying authorities.

Large Slewing Bearings

Large Slewing Bearings

Traditional energy Turret mooring systems and cranes

LDB has decades of experience partnering with oil and gas customers to develop large slewing bearings for the turret mooring systems and cranes used in offshore oil extraction ields.

Designed with a wealth of application knowledge and specialised sealing systems,large slewing bearings for traditional energy provide high reliability and performance in harsh conditions.An energy company makes use of the characteristics of large slewing bearings and uses the large slewing bearing with a diameter of 13.4m as an offshore drilling platform.

Additionally, LDB has developed monitoring detection systems to help ensure the safety of large cranes used in offshore platforms and we are able to conduct bearing inspections on site.

Material handling Cranes slewing bearing

Metals Ladle turrets Application

Metals Ladle turrets Application

Material handling Cranes slewing bearing

Material handling Cranes slewing bearing

Dockside and deck cranes are moving heavier loads, faster than ever before.

Drawing on deep application knowledge and using advanced FEM calculations to optimize designs,LDB slewing bearings for cranes increase reliability and bearing service life, while reducing maintenance costs.

Integrating LDB’s advanced condition monitoring technologies also boost uptime and productivity.

“To solve my technical issue, LDB signiicantly increased the slewing bearing’s service life thanks to advanced calculations and specially developed technical solutions.”- Material handling customer.

Wind Turbine Bearings

Tunnel Boring Slewing Bearing

Scrap standard and service life of tower crane slewing bearing

All machines will experience wear and tear after a long period of use. When the parts exceed the service life or are damaged beyond repair, they should be scrapped and replaced. The tower crane slewing bearing is prone to failure and damage in the long-term outdoor harsh environment and high-load operation, so to what extent does it meet the scrapping standard of the tower crane slewing bearing?

Scrap standard of tower crane slewing bearing

slewing bearing

1. Slewing bearing raceway ring and rolling element wear and scrap

The wear of raceway rings and rolling elements is one of the common forms of scrapped slewing bearings. When there is raceway pitting on the surface of the slewing bearing, surface metal peeling and overall wear, abnormal noise, rolling element jamming and excessive clearance between the raceway rings will occur in the tower crane during operation, resulting in vibration and local impact. With the development of the state, the slewing resistance will continue to increase and the slewing function will be lost.

2. The slewing bearing cage is damaged and scrapped

In order to avoid mutual friction between the rolling elements, the tower crane slewing bearing usually adds a spacer cage between the rolling elements. The material of the cage is generally copper, plastic, powder metallurgy or mild steel. During the working process of the bearing, the cage does not transmit the load, but it moves with the rolling elements. When the cage is damaged or broken, there will be a sharp and ear-piercing abnormal sound. As the broken body of the cage is pushed and rolled by the rotating rolling body, it will cause serious damage to the raceway ring and the rolling body. At this time, the slewing bearing meets the scrap standard and can be replaced.

3. The slewing bearing gear teeth are damaged and scrapped

The gear meshing methods of tower crane slewing bearing include external tooth meshing and internal tooth meshing. When the surface of the gear teeth is excessively worn, cracks and broken teeth occur. The tooth side clearance of the tower crane slewing bearing gear teeth increases, causing the slewing bearing to lose its function immediately when the tooth is broken, and it cannot be repaired. At this time, the scrapping standard of the tower crane slewing bearing is reached.

4. The connecting bolts of the slewing bearing are damaged and scrapped

Although the connecting bolt of the slewing bearing is not the bearing body, the failure of the bolt will also cause the slewing bearing to fail to work. The damage of connecting bolts in tower crane work is also a common phenomenon. When a slewing bearing connecting bolt loosens or breaks, it often brings about a chain reaction of loosening and breaking of other bolts. At this time, the slewing bearing also needs to be replaced.

5. The slewing bearing is scrapped due to corrosion and burn damage

Due to the complex working environment of the tower crane slewing bearing, the situation that the bearing may encounter is also unpredictable. If it is corroded by corrosive substances such as acid and alkali during operation, it will damage the internal components of the bearing and cause the bearing to be scrapped.

Service life of tower crane slewing bearing

Slewing Bearings

Under a certain load, the number of revolutions or hours that a bearing experiences before pitting occurs is called bearing life. The service life of tower crane slewing bearing is affected by rotational speed, radial load, basic rated load, equivalent compliance, speed coefficient, and fatigue life coefficient.

1. Calculation formula of bearing life

L10–When the bearing load is P, the basic rating life (106 revolutions)

C–Basic dynamic load rating N


Ball bearing: ε=3

Roller bearing: ε=10/3

P–equivalent dynamic load (N)

The load on the bearing under actual conditions: A, R, converted into the load under the experimental conditions is called the equivalent dynamic load. For the bearing components, this load is variable. During the experimental study, the bearing life is 106 turns to The unit is more convenient (counter), but in actual production, the general life is expressed in hours, so it is necessary to convert L10×106=Lh×60n.

Slewing Bearings

2. Calculation method of tower crane slewing bearing life

(1) Knowing the bearing type, load and shaft speed, calculate Lh;

(2) Knowing the load, speed and life expectancy, calculate C, and select the bearing model.

Usually, the medium repair or overhaul limit of the machine is taken as the design life of the bearing, generally Lh’=5000, and the temperature coefficient ft should be introduced for the bearing working at high temperature


t≤120 125 150 200 300

ft 1 0.95 0.90 0.80 0.60

The above is the relevant content about the scrapping standard of the tower crane slewing bearing. The tower crane may affect its service life due to its complex use environment. At the same time, good maintenance and repair can also prolong the service life of the tower crane slewing bearing.