HELI (CQCTRACK): ODM-Engineered Final Drive Wheel / Track Sprocket Assembly for KOMATSU PC1250 Mining Excavators (Part No. 21N2731191)

HELI (CQCTRACK): ODM-Engineered Final Drive Wheel / Track Sprocket Assembly for KOMATSU PC1250 Mining Excavators (Part No. 21N2731191)

HELI (branded as CQCTRACK), a global ODM (Original Design Manufacturing) leader in severe-duty undercarriage solutions, specializes in engineering and producing mission-critical drive assemblies for ultra-class mining equipment. This technical dossier provides an exhaustive exposition of our Final Drive Wheel / Track Sprocket Assembly—a fully integrated, high-performance solution designed as a direct, superior-grade replacement for KOMATSU part number 21N2731191, engineered explicitly for the KOMATSU PC1250 heavy-duty mining crawler excavator.

1. Product Overview: Integrated Final Drive Sprocket for Severe-Duty Propulsion

The Final Drive Wheel/Sprocket Assembly is the nexus of power transmission in a crawler excavator. For mining-class machines like the Komatsu PC1250, this component does not merely transmit torque; it must withstand catastrophic torsional stress, radical shock loads from tramming over blasted rock, and constant abrasive wear. A failure here results in complete machine immobility and exorbitant repair costs. HELI’s ODM approach fuses the sprocket and final drive interface into a single, reliability-optimized assembly, designed to outperform in the harshest mining environments.

• OEM Part Number: KOMATSU 21N2731191.
• Target Machine: KOMATSU PC1250 Heavy-Duty Mining Crawler Excavator.
• Core Function: Serves as the final reduction gear and track-engaging sprocket in one integrated unit. It directly mounts to the travel motor output, converting high-speed, low-torque rotation into low-speed, high-torque track movement.
• Primary Engineering Objectives:
  1. Maximize Gear Tooth Bending Strength & Pitting Resistance at the final reduction stage.
  2. Optimize Sprocket Tooth Hardness & Toughness to resist abrasive wear and impact from the track chain.
  3. Ensure Absolute Integrity of the Splined or Bolted Hub Interface to prevent fretting or catastrophic disengagement.
  4. Provide Superior Seal Protection for the internal planetary gear system against fine particulate contamination.

2. Material Science & ODM Engineering Methodology

Our design philosophy is preemptive, targeting the specific failure modes observed in PC1250-class mining operations.

A. Metallurgical Foundation & Material Certification:
The assembly is manufactured from two distinct, application-specific alloy steels:

• Gear/Sprocket Body: We employ a case-hardening alloy steel such as SAE 9310 (or DIN 18CrNiMo7-6). This nickel-chromium-molybdenum steel is selected for its exceptional core strength (≥ 1100 MPa UTS) and outstanding hardenability, allowing for a deep, hard case without compromising the ductile, fatigue-resistant core necessary for gear teeth and sprocket lugs.
• Internal Planetary Gears & Shafts: For these high-contact stress components, we may utilize vacuum-degassed, carburizing-grade steels (e.g., SAE 8620) to ensure a clean microstructure free from inclusions that could initiate pitting or spalling.
• All incoming material is certified with mill test reports and subject to in-house spectrographic verification.

B. Advanced Forging & Rough Machining:
Critical structural elements begin as precision-die forged blanks. This process:

• Aligns the Grain Flow along the contour of the gear teeth and sprocket lugs, increasing fatigue life by a factor of 2-3x compared to machined-from-barstock alternatives.
• Eliminates Internal Porosity & Improves Density, creating a homogeneous structure capable of withstanding high-cycle loading without internal crack initiation.

C. Precision CNC Machining & Gear Manufacturing:
The forged and normalized blanks undergo multi-axis CNC machining and specialized gear cutting.

• Gear Tooth Generation: The final drive gear teeth are cut using CNC gear hobbling followed by profile grinding to achieve AGMA Class 11 or higher accuracy. This ensures perfect meshing with the internal planetary gears, minimizing noise, heat generation, and localized stress.
• Sprocket Tooth Profile Optimization: The external sprocket teeth are milled with a modified involute profile and optimized root fillet. Our ODM design may include asymmetric tooth geometry to better manage the asymmetric load distribution during track engagement and disengagement, reducing peak stress.
• Hub & Interface Machining: The mounting hub, splines (or precision bolt circle), and seal-running surfaces are finish-machined to tolerances of IT6 or better. This guarantees perfect concentricity, eliminates imbalance, and ensures a leak-proof interface with the final drive housing.

D. Proprietary Multi-Stage Heat Treatment:
Different zones of the assembly undergo tailored thermal processes.

1. Deep-Case Carburizing: The entire gear/sprocket body is subjected to a computer-controlled, deep-case gas carburizing process.
2. High-Pressure Gas Quenching: A controlled, high-pressure gas quench minimizes thermal distortion while achieving the desired martensitic case.
3. Cryogenic Treatment (Optional for Severe Service): For maximum dimensional stability and wear resistance, components may undergo deep cryogenic treatment to transform retained austenite into martensite.
4. Double Tempering: A two-stage tempering process relieves internal stresses and sets the final mechanical properties.
   • Resultant Specifications:
     • Gear/Sprocket Tooth Case Depth: 7.0 – 8.5 mm at 550 HV.
     • Surface Hardness: 60 – 64 HRC.
     • Core Hardness & Toughness: 38 – 42 HRC with high Charpy V-notch values.

E. Assembly, Sealing & Final Integration:
Precision-ground internal planetary gears, bearings, and high-performance seals are assembled in a climate-controlled clean room.

• Sealing System: We utilize labyrinth seals combined with heavy-duty, multi-lip radial seals manufactured from hydrogenated nitrile butadiene rubber (HNBR) for superior resistance to heat, abrasives, and lubricant breakdown.
• Lubrication: Assemblies are filled with high-performance, extreme-pressure (EP) synthetic gear oil specified for mining applications.

3. Mining-Grade Quality Assurance & Performance Validation

Every assembly is subjected to a conclusive validation protocol:

1. Geometric & Dimensional Metrology: Full 3D CMM inspection verifies gear tooth geometry, sprocket pitch, hub dimensions, and assembly concentricity.
2. Hardness & Microstructure Analysis: Case depth verification via micro-hardness testing and metallographic examination of sample coupons.
3. Non-Destructive Testing (NDT): 100% MPI of all critical surfaces and 100% UT of high-stress areas (tooth roots, hub fillets).
4. Run-In & Performance Test: Each unit undergoes a loaded run-in cycle on a test rig that simulates operational torque and speed. This test verifies:
   • Smooth, quiet operation.
   • Absence of oil leakage.
   • Correct bearing pre-load and temperature rise.

4. The HELI (CQCTRACK) ODM Advantage for Mining Fleets

• Integrated Design for Reliability: We engineer the sprocket and final drive interface as one system, eliminating potential mismatch and weak points found in separately sourced components.
• Predictable Lifecycle in Abrasive Environments: The combination of premium metallurgy, deep-case hardening, and optimized gear/sprocket geometry delivers extended, predictable service life, reducing unscheduled downtime.
• Direct Replacement with Enhanced Specifications: Designed for seamless interchangeability while incorporating material and design improvements informed by field data from mining applications.
• Full Vertical Manufacturing Control: From forging to final assembly, our in-house control ensures traceability, supply chain security, and consistent, mining-grade quality.

Disclaimer: KOMATSU, PC1250, and part number 21N2731191 are trademarks of Komatsu Ltd. HELI (CQCTRACK) is an independent ODM manufacturer of heavy-duty undercarriage and drive components. Our products are engineered based on our proprietary designs to be mechanically and functionally interchangeable with the referenced OEM parts for the stated application. This document implies no affiliation, endorsement, or sponsorship by Komatsu Ltd.