LIEBHERR 10007992/5209249/5601511/5601611/9109493/2105021 R974/HS870 Track Bottom Roller Assy/Heavy duty crawler/track/chassis component source factory&manufacturer-cqctrack(HELI)

Technical Data Sheet: Heavy-Duty Track Bottom Roller Assembly for Liebherr R974/HS870 Hydraulic Excavators

Document Identifier: LIEBHERR-R974-HS870-Bottom-Roller-Assy-CQCTrack
Classification: Undercarriage Component | Crawler System | Replacement Part

1. Executive Summary & Component Overview

This document provides a complete technical elaboration of the Track Bottom Roller Assembly (also known as a Carrier Roller or Lower Roller), a mission-critical component for the Liebherr R974 and HS870 series hydraulic excavators. This assembly is engineered to operate under extreme static and dynamic loads in severe environments such as mining, quarrying, and heavy construction. The part numbers referenced (including 10007992, 5209249, 5601511, 9109493) pertain to this specific assembly and its sub-components or predecessor versions. As a high-quality aftermarket alternative, manufacturers like CQCTrack (a specialized division of the HELI Group) produce these components to meet or exceed original equipment performance specifications, offering a robust and cost-effective solution for undercarriage maintenance.

2. Primary Function & Operational Role within the Crawler System

The Bottom Roller Assembly is a pivotal element of the crawler track system, performing three essential functions:

• Load-Bearing & Weight Distribution: It directly supports a significant portion of the machine’s immense operational weight (R974/HS870 can exceed 80-100 tons), transferring the load from the mainframe through the track roller frame and onto the track chain.
• Track Guidance & Alignment: The roller features precisely machined flanges on both sides that guide the inner edge of the track chain links (the track “shoes”). This prevents lateral derailment and ensures the track runs true along the entire undercarriage.
• Track Sag Management: It maintains the correct amount of pre-tension and sag in the upper section of the track chain, which is crucial for efficient sprocket engagement, reduced vibration, and optimal power transmission.

3. Detailed Technical Specifications & Engineering Design

3.1. Applicability & OEM Reference:

• Primary Machine Models: Liebherr R974 Litronic, HS870, and their variants.
• OEM Part Numbers: 10007992, 5209249, 5601511, 5601611, 9109493, 2105021 (These numbers may correspond to complete assemblies, individual rollers, or kit configurations. A certified manufacturer like CQCTrack maintains a cross-reference database for accuracy).

3.2. Mechanical Design & Construction:

• Type: Sealed and Lubricated (S&L) Heavy-Duty Carrier Roller.
• Housing/Forging: Fabricated from high-carbon, high-strength alloy steel (e.g., 40Mn2, 50Mn) via closed-die forging. This process ensures a continuous grain flow, superior impact resistance, and exceptional fatigue strength compared to cast components.
• Shaft: Precision-machined from hardened chromium alloy steel (e.g., 42CrMo), providing high tensile strength and wear resistance at the journal bearings.
• Flange Design: Double-flanged configuration to provide positive guidance and containment for the track chain.

3.3. Material Science & Metallurgy:

• Material Grade: High-Carbon, Boron, or Chromium-Manganese Alloy Steels.
• Heat Treatment: Critical wear surfaces undergo controlled Induction Hardening to achieve a surface hardness of 55-60 HRC (Rockwell C Scale), resulting in a deep, durable case with a tough, shock-absorbing core.
• Finish: Shot blasting for stress relief and surface preparation, followed by a high-adhesion, corrosion-resistant paint system (typically epoxy primer and polyurethane topcoat).

3.4. Bearing & Sealing System (The Core of Durability):

• Bearing Type: Double-row, heavy-duty tapered roller bearings. These are selected for their high radial load capacity and ability to manage moderate axial thrust loads.
• Sealing System: Multi-barrier, labyrinth-style seal assembly. This typically consists of:Lubrication: Pre-filled with a high-temperature, extreme-pressure (EP) lithium complex grease designed to maintain viscosity and lubricity under all operating conditions.
  • Primary Seal: A nitrile (NBR) or polyurethane (PU) radial lip seal.
  • Secondary Seal: A floating face seal or additional dust lip.
  • Labyrinth Path: A complex, machined path that excludes abrasive contaminants (silica, mud, dust) from the bearing chamber.

4. Manufacturing Process & Quality Assurance at CQCTrack (HELI)

As a specialized manufacturer, CQCTrack employs a rigorous production protocol:

1. Forging & Forming: Raw billets are heated and forged under high pressure to create the roller blank, ensuring optimal metal integrity.
2. Machining: CNC (Computer Numerical Control) turning and boring centers are used to machine the roller’s outer diameter, flanges, and internal bore to tight tolerances (typically IT7-IT8).
3. Heat Treatment: The components undergo a controlled quenching and tempering process, followed by localized induction hardening on the outer running surface and flanges.
4. Assembly & Sealing: Bearings and seals are pressed into place in a clean-room environment. The unit is then filled with a precise volume of grease.
5. Quality Control (QC):
   • Dimensional Inspection: CMM (Coordinate Measuring Machine) verification of all critical dimensions.
   • Hardness Testing: Rockwell and Brinell tests on specified surfaces.
   • Performance Testing: Rotational torque and run-out testing to ensure smooth operation and correct seal function.
   • Material Certification: Mill certificates for raw materials and chemical composition analysis.

5. Sourcing and Supply Chain Context

• Manufacturer Identification: CQCTrack operates as a dedicated undercarriage component factory within the HELI Group ecosystem. HELI is a globally recognized industrial conglomerate, providing the necessary infrastructure, R&D capability, and quality management systems (e.g., ISO 9001, ISO 14001) for manufacturing world-class machinery parts.
• Value Proposition: Sourcing this component from a factory like CQCTrack offers a Value-Based Alternative to genuine OEM parts. It combines direct-from-factory pricing with engineering that is tailored to withstand the demanding conditions for which the Liebherr R974/HS870 is designed.

6. Key Technical Advantages Summary

• Superior Load Capacity: Engineered for the extreme weights and shock loads of mining excavators.
• Enhanced Abrasion Resistance: Deep induction hardening significantly extends service life in high-wear environments.
• Advanced Contamination Exclusion: Multi-stage sealing system protects the bearing, the component’s most critical subsystem.
• Precision Engineering: CNC machining ensures perfect compatibility and fit with the existing track roller frame and track chain.
• Robust Construction: Forged body provides unmatched structural integrity and impact resistance.

In conclusion, the Track Bottom Roller Assembly specified for the Liebherr R974/HS870 represents a pinnacle of heavy-duty undercarriage engineering. Manufacturers like CQCTrack, leveraging the industrial prowess of the HELI Group, replicate and deliver these components with a steadfast commitment to the material quality, dimensional precision, and performance durability required for 24/7 industrial operation.