6-1/2X9 Np633994f

Here is the English version of the description of railway wheel hub bearings (Type 7, typically referring to tapered roller bearings):

Structural Features

Tapered roller bearings are separable bearings, where the inner ring assembly (with rollers and cage) and the outer ring can be installed separately. They feature conical raceways on both the inner and outer rings, with tapered rollers arranged between them.

Classification and Characteristics

1. Single-row Tapered Roller Bearings
Clearance needs to be adjusted by users during installation.
 Moderate load capacity. Examples:
30200 series: Smaller size.
30300 series: Larger size and higher load capacity.
 31300 series: Higher radial and axial load capacity.

2. Double-row Tapered Roller Bearings
 Clearance is pre-set at the factory, requiring no user adjustment.
 Composed of two inner rings, two outer rings, two sets of tapered rollers, and two cages.
Capable of bearing radial and axial loads simultaneously. Examples:
 32000 series and 32200 series: High load capacity, suitable for heavy-duty applications.

3. Four-row Tapered Roller Bearings
Clearance is factory-set.
 Composed of four inner rings, four outer rings, four sets of tapered rollers, and four cages.
Extremely high load capacity, mainly used in extra-large mechanical equipment (rarely for railway wheel hubs, more common in large rolling mills, etc.).

Load-carrying Characteristics

• Can withstand significant radial loads and unidirectional axial loads. To transmit axial loads in the opposite direction, another bearing must be installed symmetrically.

• Load capacity is related to the angle of the outer ring raceway: the larger the angle, the higher the load capacity.

Application Features in Railway Wheel Hubs

• Adapt to complex load conditions during railway vehicle operation, including radial loads from the vehicle's own weight and cargo, as well as axial loads from starting, braking, and cornering.

• Single-row tapered roller bearings are often used in wheel hub positions where installation adjustment flexibility is needed and load requirements are not extreme.

• Double-row tapered roller bearings are applied in wheel hubs requiring high load capacity, strict clearance control, and no on-site adjustment (e.g., wheel hubs of some passenger or freight trains, varying by vehicle design and working conditions).

Installation and Maintenance

• For single-row bearings: Pay attention to clearance adjustment during installation.

• For double-row and four-row bearings: Focus on installation accuracy and fit requirements, as clearance is pre-set.

• Regular maintenance includes inspecting wear and lubrication conditions to prevent failures affecting train safety and stability.

• Installation may require special tools, with slightly higher difficulty than some other bearing types.

Material Requirements

• Mainly made of bearing steel (e.g., GCr15) with high hardness, wear resistance, and toughness to ensure performance and service life under high loads and high speeds.

• Cage materials: Brass, aluminum alloy, or engineering plastics (e.g., nylon) to separate rollers and reduce friction.

• Sealing materials: Nitrile rubber, fluororubber, etc., to prevent dust/water intrusion and lubricant leakage.

This description focuses on the application and technical characteristics of tapered roller bearings in railway wheel hubs, covering structural design, classification, load capacity, and maintenance requirements.