PCR-3B-12A-P-8486A Nachi Swing Motor 1399 N·m 21.6 MPa

Product Overview

The PCR-3B-12A-P-8486A is a swing motor assembly built on the Nachi PCR series platform, in the PCR-3B specification. The product features an integrated design combining a swash plate axial piston motor, planetary reduction gearbox, and brake into a single compact housing, specifically engineered for 360° swing drive of the upper structure on 3.5–5 tonne class mini excavators.

The PCR series is Nachi’s swing drive solution for compact construction machinery, covering five specifications from PCR-1B to PCR-5B, suitable for 2.5 to 8 tonne class excavators. The series employs an integrated architecture where the axial piston hydraulic motor is directly linked to a planetary reduction gearbox; hydraulic pressure acts upon the piston motor to deliver torque, which is then amplified through the planetary gearbox for controlled rotation of the excavator’s upper structure. The PCR-3B-12A-P-8486A offers a maximum displacement of 507 cm³/rev, maximum swing torque of 1,399 N·m, maximum hydraulic pressure of 21.6 MPa, and a weight of approximately 37 kg, suitable for 3.5–5 tonne class excavators.

The model code PCR-3B-12A-P-8486A decodes as follows: PCR designates the swing motor series, 3B is the specification code (PCR-3B), 12A is the variant code, P is the port configuration code, and 8486A is the special option code (potentially relating to seal material, brake configuration, or surface treatment). Specific suffix meaning should be confirmed with Nachi or an authorized dealer through the complete selection manual.

Engineered as a form-fit-function replacement for original Nachi PCR-3B series swing motors, this model maintains identical mounting flange dimensions, shaft specifications, and port locations, enabling drop-in interchangeability without modification to the host machine’s mounting interface or hydraulic circuit. Each unit undergoes 100% simulated load testing prior to shipment, validating output torque and volumetric efficiency against original specifications.

Technical Specifications 

• Model: PCR-3B-12A-P-8486A

• Original Brand: Nachi

• Series: PCR Series Swing Motor Assembly

• Product Type: Swash plate axial piston swing motor + planetary reduction gearbox + brake integrated assembly

• Design Feature: Swash plate piston motor, planetary reduction gearbox, integrated parking brake, shockless relief valve

• Maximum Final Displacement: 507 cm³/rev

• Maximum Swing Torque: 1,399 N·m

• Maximum Hydraulic Pressure: 21.6 MPa (216 bar)

• Applicable Excavator Weight: 3.5–5.0 tonnes

• Weight: Approx. 37 kg

• Lubrication: Hydraulic oil lubricated (no gear oil change required)

• Brake: Integrated negative-type parking brake

• Relief Valve: Integrated shockless relief valve

• Operating Temperature Range: −20°C to +50°C

• Mounting: Flange mounting, identical to original

• Circuit: Open circuit / Closed circuit

• Matching Reduction Gearbox: PCL-120 planetary reduction gearbox

Key Technical Advantages

1. Integrated Motor-Gearbox-Brake Design

The core advantage of the PCR-3B-12A-P-8486A lies in its highly integrated architecture. Conventional swing systems require separate installation of a hydraulic motor, planetary reduction gearbox, and brake — three independent components occupying significant space with complex installation. The PCR series integrates all three into a single compact housing, with the axial piston motor directly connected to the planetary reduction gearbox and the brake integrated into the motor body. This design significantly reduces installation space, particularly suitable for mini excavators with limited swing platform interior space, while simplifying machine hydraulic layout and reducing component count and potential leakage points.

2. Maintenance-Free Gearbox with Hydraulic Oil Lubrication

The PCR-3B-12A-P-8486A’s reduction gearbox is lubricated by the excavator’s hydraulic oil, eliminating the need for separate gear oil changes. Conventional swing drive gearboxes require periodic replacement of dedicated gear oil; the PCR series eliminates this maintenance step through hydraulic oil lubrication, significantly reducing maintenance costs and downtime throughout the equipment’s lifecycle while reducing failure risk from gear oil degradation.

3. Built-in Shockless Relief Valve with Smooth Swing Control

The PCR-3B-12A-P-8486A features a standard shockless relief valve that automatically limits hydraulic shock peaks during swing start and stop, ensuring smooth rotation of the upper structure and eliminating hydraulic shock-induced vibration and noise. The valve provides cushioned braking during swing stop, reducing impact loads on the swing gearbox and swing bearing, extending critical component service life while improving operator comfort.

4. Negative-Type Parking Brake for Safe Slope Operation

The PCR-3B-12A-P-8486A features an integrated negative-type parking brake that automatically locks the swing mechanism when hydraulic pressure drops, ensuring safe parking of the excavator on slopes. The brake operates on a spring-applied, hydraulically-released principle, maintaining braking even during unexpected system pressure loss, providing reliable safety assurance for both operator and equipment.

Application Areas

The PCR-3B-12A-P-8486A is designed for swing drive systems of 3.5–5 tonne class mini excavators, compatible with the following machines:

• Komatsu: PC40MR, PC50, PC50-7, PC55-7, PC56-7, etc.

• Kobelco: SK35, SK50, SK60SR-8, etc.

• Case: CX50B, CX55C, CX56B, etc.

• IHI: IS20, IS55, IS60, etc.

• JCB: 85Z, etc.

• Volvo: EC45, EC55B, etc.

• Yanmar: VIO45, VIO50, VIO55, etc.

• Sany: SY75, etc.

• Yuchai: YC35, etc.

Additionally, PCR series swing motors are widely used in concrete pumps, cranes, and drilling equipment requiring precise swing control.

Expert Maintenance Tips

1. Hydraulic Fluid Cleanliness Control: The PCR-3B-12A-P-8486A features precision clearances in the piston and distribution pairs. Maintain hydraulic fluid cleanliness at ISO 18/15 or NAS Level 9 or better. Replace hydraulic fluid and filter elements every 1,000 operating hours or annually, with filter element filtration accuracy no less than 10 μm.

2. Reduction Gearbox Lubrication Inspection: The product uses hydraulic oil lubrication without gear oil replacement, but checking gearbox oil level and quality every 500 operating hours is recommended. If oil emulsification or metal particles are found, inspect internal seals and gear wear.

3. Brake Performance Testing: Periodically check the negative-type parking brake effectiveness. Ensure the swing mechanism locks reliably when brake supply pressure is zero; otherwise, inspect brake springs and friction plate wear.

4. Shockless Relief Valve Setting Verification: Verify the shockless relief valve opening pressure every 1,000 operating hours, ensuring it provides proper cushioning during swing start and stop. If swing action exhibits shock or abnormal noise, inspect valve function.

5. Mounting Alignment Requirements: During installation, ensure the motor output shaft and swing bearing gear mesh precision. Flange faces must be clean and burr-free, with bolts tightened diagonally to the specified torque. Apply appropriate grease to spline mating surfaces to prevent corrosion.

6. Restart After Extended Storage: For motors stored over 6 months, manually rotate to confirm free rotation before restart. Run at low pressure under no load for 10 minutes, confirming normal case temperature and leakage before gradually applying load.