XCMG XE700B Final Drive Sprocket Rim Assembly
Product Specifications
Professional Overview: XCMG XE700 Final Drive Sprocket Rim Assembly
The Final Drive Sprocket Rim Assembly for the XCMG XE700 is a critical and highly stressed component within the machine's travel system. The XE700 is a large mining and heavy-duty excavator, typically in the 70-ton class, designed for the most demanding applications, including quarrying, mining, and major earthworks.
This assembly represents a critical sub-component of the complete final drive. Understanding its specific role is key to maintenance and operational efficiency.
1. Primary Function and Strategic Importance
While the term "Final Drive Sprocket Rim Assembly" can sometimes refer to the entire final drive, it most precisely denotes the output sprocket and its immediately connected components that are responsible for the final interface with the track chain.
Its core functions are:
Power Transmission: It is the direct mechanical interface that meshes with the track chain's bushings, transmitting the immense torque generated by the final drive's planetary reduction system into linear movement.
Load Bearing: It supports a portion of the machine's weight and withstands the heavy loads and shock impacts from the track chain during operation, digging, and travel on uneven ground.
Steering and Maneuvering: It is subjected to extreme stresses during counter-rotation steering (where one track moves forward and the other backward).
On a machine of the XE700's size, the forces involved are enormous, requiring a component built for ultimate strength and durability.
2. Key Components of the Assembly
The "Sprocket Rim Assembly" typically consists of the following key parts:
Sprocket Rim (The Sprocket Itself): This is the main toothed wheel. It is manufactured from high-carbon, high-alloy steel (such as 40CrMnMo or similar) and undergoes rigorous heat treatment processes like induction hardening or carburizing. This creates an extremely hard, wear-resistant tooth surface to resist abrasion from the track bushings, while maintaining a tougher, more ductile core to absorb shock loads without cracking.
Hub/Bearing Carrier: The central part of the assembly that houses the large tapered roller bearings. It allows the sprocket to rotate smoothly on its axle while supporting radial and axial loads.
Mounting Flange or Bolts: This is the interface that connects the sprocket assembly to the output flange of the final drive's planetary gear carrier. These are high-strength, precision bolts torqued to very specific values.
Seals: Critical seals protect the internal bearings of the sprocket assembly and prevent grease from leaking out. On many large excavators, this area is protected by an external labyrinth seal or flinger to deflect dirt and debris away from the primary lip seals.
Important Distinction: This assembly is a sub-component of the larger Final Drive Assembly, which includes the hydraulic motor, multi-stage planetary gear reduction, and the gear case. The sprocket rim assembly is the final output of this larger system.
3. Technical Specifications & Performance (Typical for XE700 Class)
While exact OEM specifications are proprietary, the final drive sprocket for a 70-ton excavator like the XE700 will have characteristics typical for its class:
| Parameter | Estimated Specification / Feature | Implication |
|---|---|---|
| Number of Teeth | Approx. 16 - 19 teeth | Optimized for engagement with the track chain to provide smooth power transmission and maximum durability. |
| Pitch | Matches XE700 track chain pitch (e.g., 260 mm / 8.5") | The distance between the teeth must perfectly match the track chain's pitch for proper meshing and to prevent accelerated wear. |
| Material & Hardness | Alloy Steel, Induction Hardened to 55-60 HRC | Provides exceptional resistance to the abrasive wear caused by the track chain bushings. |
| Torque Capacity | Extremely High (>150,000 Nm) | Designed to handle the massive torque output from the final drive's planetary reduction system. |
4. Design and Durability Considerations
Split Rim vs. Solid Design: For larger excavators, the sprocket is sometimes a split rim design. This allows for the outer worn ring to be replaced without replacing the entire hub and bearing assembly, offering significant cost savings over time.
Hardfacing: It is common to apply hardfacing weld material to the sprocket teeth as a preventative measure or to rebuild slightly worn teeth, extending the component's service life.
Precision Machining: The sprocket must be perfectly concentric and balanced to prevent vibration, which can damage the final drive's internal gears and bearings.
5. Common Failure Modes and Maintenance Best Practices
Common Reasons for Failure:
Abrasive Wear: The gradual wearing down of the sprocket teeth due to friction with the track chain bushings. This is a normal process but is accelerated by contamination (sand, grit) and poor lubrication.
Chipping or Tooth Breakage: Caused by severe shock loads (e.g., hitting a solid rock ledge at speed) or material fatigue.
Improper Meshing (Mismatch): Occurs if a new sprocket is paired with a severely worn track chain (and vice versa). The mismatched profiles cause high point loads, accelerating wear on both components. They must be replaced as a set.
Bearing Failure: If the bearings within the hub fail, it can cause the sprocket to wobble or seize, leading to catastrophic damage to the sprocket and the final drive.
Loose Mounting Bolts: Can lead to sheared bolts, damage to the mounting flange, and failure of the assembly.
Essential Maintenance:
Regular Inspection: Daily visual checks for broken or cracked teeth, unusual wear patterns, and signs of oil leakage from the hub seals.
Track Chain & Sprocket Compatibility: Always measure track chain wear (e.g., via pitch elongation). Replace the sprocket and the track chain as a matched set to prevent accelerated wear.
Bolt Integrity: Periodically check the tightness of the sprocket mounting bolts to the manufacturer's specified torque using a calibrated torque wrench.
Cleanliness: Keep the final drive area free of packed material, which can trap heat and abrasives against the seals and sprocket.
