CAT 383-2129 COLLAR-GD

CAT 383-2129 GD is a boom balance spring assembly for Caterpillar mini excavators, commonly used at the boom-stick/linkage articulation point in models such as the 303CR/304CR. Its core functions are to balance the weight of the boom, buffer operational impacts, and assist in hydraulic mechanism reset. Below is precise technical and application information:

Core Technical Parameters
Item Details
Part Model: CAT 383-2129 (3832129) GD Boom Spring Assembly, unit weight approximately 3.2 kg, assembly includes main spring, upper and lower lifting lugs, locating pin, dust cover, and shock absorber.

Core Materials: Main Spring (60Si2MnA spring steel, wire diameter 12 mm, hardness HRC 45-50, fatigue life ≥10^6 cycles); Lifting Lugs (SAE 1045 steel, tempered HB 220-260); Dust Cover (Nitrile Rubber NBR, oil-resistant and wear-resistant); Shock Absorber (Polyurethane) PU (Shore Hardness 85A)

Key Dimensions: Free length 480 mm, compressed installation length 320 mm, total coils 8, effective coils 6, spring mean diameter 80 mm, both ends flat ground, center distance 150 mm, lug bore diameter 25 mm, fitting pin diameter 24 mm

Rated Parameters: Operating temperature -30℃ to +120℃, rated installation load 18 kN, stiffness 120 N/mm, maximum compression 180 mm, ultimate load 35 kN, suitable swing angle ±15°

Suitable Working Conditions: Mini excavator boom auxiliary balance, suitable for medium and low loads, frequent start-stop and vibration conditions, compatible with NLGI 2 lithium-based grease

Compatible Models: CAT 303CR/304CR/305.5E2 mini excavators (boom-stick, boom-link), 903C loader (rocker arm-boom)

Accessories Compatible with: Pins 175-4039, Bolts 106-7773 (M12×25), Grease fittings 1U-8878, Dust rings 453-2164. Core Functions and Structural Features:

Boom Balancing: Offsets part of the boom weight, reduces hydraulic cylinder load, decreases energy consumption, and improves operating efficiency.

Impact Buffering: Spring elastic deformation absorbs articulated impacts, protecting pins, bushings, and mounting structures, suitable for vibration conditions in construction machinery.

Reset Assistance: Spring rebound force assists in boom/stick reset, reducing operating force, suitable for frequent operation scenarios.

Reliable Protection: Dust covers + buffer pads prevent mud and sand intrusion, reduce wear on lifting lugs and pins, and extend component life.

Easy Installation: Assembled design, bolt fixing is sufficient, no additional adjustments are required, and old parts can be directly replaced.

Installation and Maintenance Points

Installation Specifications: Clean components, mounting surfaces, and pins; remove burrs and oil stains. Check springs for cracks, lifting lugs for deformation, and dust covers for damage.

Position according to the installation length; symmetrically pre-tighten bolts (torque 80 N·m). After installation, ensure there is no sticking or abnormal noise during swinging; clearance ≤ 0.3 mm.

Fill with lithium-based grease. After a 5-minute test run, add more grease to ensure proper lubrication.

Maintenance Recommendations: Add grease every 250 working hours. Check for wear and deformation every 800 hours. Replace the spring when permanent deformation > 5 mm or lifting lug wear > 0.2 mm.

Avoid prolonged overload compression to prevent spring fatigue and breakage.