Wire-race bearings application

Stratosphere observatory for infrared astronomy.
An aluminum three-row wire-race roller bearing with a bolted steel gear ring for the rough adjustment of the telescope was applied. The telescope is in the rear of a converted Boeing 747.During the flight, a sort of “sliding roof” opens to enable the telescope to make astronomic observations in the infrared range.
Optical telescopes
Three-row wire-race roller bearing was designed for telescopes. The bearing rings are made of aluminium.The bearings enable the adjustment of the M2 mirror.In addition,a surface-hardened three-row precision bearing was supplied to adjust the M3 mirror.Astronomic faculties use these telescopes for their extensive research.
Articulated buses
Hybrid-type four-point bearing was manufactured for the articulation of buses, consisting of a wire race bearing part and a surface-hardened part.The majority of the articulated buses are referred to as pushers, i.e. the engine and entire drive unit are located in the rear section, in the trailer.This concept puts a lot of specific requirements on the articulation, such as buckling stability, for instance, which is achieved by means of a complicated electronically-controlled damping system.

UWE Wire-race Bearing Components

Wire races:Hardened or naturally hardened steels
Rolling elements:Bearing steel, also corrosion-resistant
Bearing rings:aluminium
Surface: corrosion-proof
• Steel normalized or hardened and tempered
Surface: corrosion-proof
• Stainless steel, selection as required(e.g. acid-resistant steels)
• Special steels, selection as required(e.g. magnetoresistive steels)
• Bronze(e.g. seawater-resistant bronze)
Rolling elements
• Bearing steel, also corrosion-resistant
Gear rings
• The material can be selected as for the bearing rings.
• The gearing cut into the ring can be hardened.
Material combinations
• Material combinations in one bearing are also possible (e.g. rings of aluminium and gear ring of hardened and tempered steel).
Design and dimensioning

Wire-race bearing special designs

There are few special types for UWE wire-race bearing
Four-row wire-race roller bearing
Particularly designed to transmit loads due to the different expansion behaviour of the outer and inner companion structure or to prevent radial clearance in this context.
Hybrid-type three-row wire-race roller bearing
The raceways of the outer ring are surface hardened, the raceways of the inner rings have a wire filling. Particularly designed to compensate raceway tilts due to the expansion of the inner companion structure.
Hybrid-type four-point wire-race ball bearing
The raceways of the inner ring are surface hardened, the raceways of the outer ring have a wire filling. Particularly designed to enable the necessary cast design to act at the same time as outer ring.
Four-point wire-race ball bearing
With integrated 4-way slip ring and retaining ring with spring suspension system. Particularly designed for the transmission of electric current and limitation of the frictional torque in case of a major deformation of the companion structure. Furthermore equipped with earthing plugs to compensate the potential between the bearing rings.
Three-wire race bearing
With integrated ring motor. Particularly designed to integrate the drive into the bearing.
Segmented wire-race ball bearing
Particularly designed for limited available space.

ship crane slewing ring

Key Specifications/Special Features of UWE ship slewing rings:
Inner diameter: 600- 4500 mm
Outer diameter: 700 - 5000 mm
Width: 56-300mm
Tooth processing module:M7-M25
Gear machining accuracy:<0.1
Max. Tapping diameter:M60
Gear optition: extenal gears,internal gears,no gears 
Rolling element: ball or rollers
Rolling element material: Chrome steel GCr15 or GCr15SiMn
Ring Material: 42CrMo, 50Mn, steel 45#
Seal: NBR
Normalizing hardness: 187HB-241HB
Quench & temper hardness: 229HB-269HB
Raceway hardness after quenching: 55HRC-62HRC
Sevice:OEM Service Offered/Design Service Offered/Buyer Label Offered

UWE ship crane slewing ring includes double row ball slewing ring, four-point contact ball slewing ring and three row roller slewing ring.Large size three row roller slewing ring is often selected for heavy duty deck crane, four-point contact ball or double row ball slewing ring are often selected for light duty deck cranes.Large shipboard crane with a three row roller slewing ring. The high load capacity and compact proportions of this type of slewing ring are ideally matched to the mast and base block proportions of the crane.Deep sea fishing vessels use ball slewing rings for shipboard cranes and net handling equipment.
UWE slewing rings are widely used in kinds of cranes, such as tower cranes, ship deck cranes, mobile cranes, railway cranes and so on.

Yaw and Pitch Rolling Bearing Design Types

Modern wind turbines use large slewing rings at the root of each blade to enable pitch angle changes and thus aerodynamic performance and load control. Yaw bearings are used for angular realignment of the nacelle into the predominant wind direction. These applications require long periods in nearly stationary positions with large stochastic loads. Due to this demanding load environment and the fact that bearings exist in the critical load path, their design becomes critical to the safety and reliability of most turbine designs.
Large wind turbines (those rated at more than 250 kW) use ball or roller bearings with special configurations for blade retention pitch bearing and yaw bearing locations. The bearings consist of two ring-rolled forgings forming the outer and inner raceways and a complement of either balls or rollers. The inner and outer continuous-ring forgings have mounting holes that allow the bearing to be bolted directly to the supporting structures. The balls or rollers are inserted into the bearing through a radial cylindrical hole in one of the rings. The hole then is closed using a removable loading plug con-toured to the ball path or roller path surface. 
It is common practice to cut a spur gear integral with one of the bearing rings, especially for the yaw bearing application. Individual plastic spacers or thin section cage arc segments are used to separate the balls. The spacers are cylindrical with a hemispherical end. The individual rollers in the cross-roller bearing are separated by plastic, saddle-shaped spacers. The rollers in the cross-roller bearing alternate in their orientation to carry load.
The inner and outer rings are hardened from 250 to 300 Brinell hardness (HB). This is referred to as the “core hardness” of the ring. This core hardness should provide adequate core yield and fatigue strength, yet remain at a hardness low enough to facilitate machining of the rings, gear teeth, and mounting-bolt holes. The actual ball or roller path (rolling contact surface) is induction heated, quenched, and tempered to provide a hard surface or “case.” The surface hardness of the raceway is a minimum of 58 HRC (Rockwell C scale hardness). The depth of the hardened case is defined as the depth to a hardness of 50 HRC.
The two-row, eight-point contact ball bearing type is more costly to manufacture than the single-row, four-point contact ball bearing. In addition to having a second row of balls and separators, the two-row bearing must be repeatedly assembled and disassembled during manufacture to accurately measure and match the internal diametral clearance or preload of the two ball rows.
The main advantages of the eight-point contact ball bearing, as compared to the four-point contact ball bearing, are:
• Lower ball loads;
• Lower Hertz stresses;
• Less required case depth; and
• Increased fatigue life.

Bearing Design Criteria-wind turbine slewing ring

The proper design of a yaw or pitch bearing must satisfy five design criteria and the miscellaneous considerations listed below. Each of the following criterion is addressed in detail in this guide.
1. Bearing fatigue life (rolling contact fatigue)
2. Bearing static capacity
3. Adequate case depth and core hardness
4. Adequate lubrication (surface failure)
5. Friction torque
6. Miscellaneous
A. External bolting
B. Cages or separators
C. Integral seals
The relationships used in the method for determining the basic dynamic capacity in oscillation, life adjustment factors, and equivalent load are supplied in Section 4.

Effective Lubrication for Wind Power Bearing

A meaningful oil film thickness cannot be generated in a slowly and intermittently moving (oscillating) grease-lubricated yaw or pitch bearing. Therefore a clean grease with good boundary lubrication additives (especially for oscillating conditions) should be selected on the basis of experience for use in wind turbine yaw and pitch bearings. A seal system (integral or external) also is essential for achieving satisfactory operation.
A fretting-corrosion type of raceway and rolling element surface failure commonly is encountered in yaw and pitch bearings. The fretting corrosion appears as elliptical or rectangular footprints at ball or roller spacing in the bearing. The markings are tiny corrosion pits caused by the lubricant being forced out of the contact area (by a small load increase) and then not being able to re-enter the contact zone. The unprotected surface then is subject to corrosion pitting. Most grease rated for oscillation use can coat the rolling contact surfaces and maintain corrosion protection. In extreme cases, coating the raceways is an option. A TDC coating increases the bearing cost significantly but provides increased protection.
One manufacturer of wind turbine yaw and pitch bearings suggests using the Hertz contact stress limits given in Table 16 as means to limit fretting-corrosion types of failures.