AA2FM63/61W-VSD520 Rexroth Hydraulic Motor 63cc 450 bar

Product Overview

The AA2FM63/61W-VSD520 is a bent-axis axial piston fixed displacement motor built on the Bosch Rexroth A2FM Series 61 platform, in the A2FM63 size (63 cm³/rev displacement). The motor features a bent-axis design with conical piston rotary group, engineered for hydrostatic drives in both open and closed circuits. It offers a nominal pressure of 400 bar, a peak pressure of 450 bar, a total pressure limit of 700 bar, and can withstand pressure change rates up to 9000 bar/s, suitable for highly dynamic hydraulic systems.

The model code AA2FM63/61W-VSD520 decodes as follows: AA2FM designates the bent-axis fixed motor series, 63 is the displacement size (63 cm³/rev), 61 is the series designation (Series 61), W indicates bidirectional rotation, and VSD520 is the combination code for mounting flange, port configuration, and shaft type. The motor’s fixed displacement design eliminates the need for variable adjustment mechanisms, simplifying system integration and minimizing maintenance risks.

The A2FM Series 61 is an upgraded version of the classic A2FM series, specially adapted for the US market (SAE version) with SAE flange or threaded working ports. Series 61 optimizes the materials and machining processes of the piston pair and port plate while maintaining the high efficiency of the bent-axis design, further improving volumetric and starting efficiency.

Engineered as a form-fit-function replacement for original Bosch Rexroth AA2FM63 series motors, this model maintains identical mounting flange dimensions, shaft specifications, and port locations, enabling drop-in interchangeability. Each unit undergoes 100% simulated load testing prior to shipment, validating output torque and volumetric efficiency against original specifications.

Technical Specifications 

• Model: AA2FM63/61W-VSD520

• Material Number: R902160055

• Series: Bosch Rexroth A2FM Series 61

• Motor Type: Bent-axis axial piston fixed displacement motor

• Design Feature: Bent-axis configuration, conical piston rotary group, fixed displacement

• Displacement (Vg): 63 cm³/rev (3.84 in³/rev)

• Nominal Pressure (p nom): 400 bar (40 MPa / 5,801 PSI)

• Peak Pressure (p max): 450 bar (45 MPa / 6,527 PSI)

• Total Pressure Limit: 700 bar

• Max. Pressure Change Rate: 9,000 bar/s

• Max. Speed: 4,000–4,500 rpm

• Min. Speed for Uniform Motion: 50 rpm

• Continuous Viscosity Range: 10–400 mm²/s

• Optimum Viscosity Range: 16–36 mm²/s

• Hydraulic Fluid: Mineral oil HLP (DIN 51524)

• Cleanliness Level (min): ISO 4406 20/18/15

• Seal Material: FKM

• Cold Start Temperature: −25°C

• Max Temp at Port T: +103°C

• Rotation: Bidirectional

• Mounting: SAE flange (ISO 3019-2 standard)

• Shaft Type: DIN 5480 splined shaft or parallel keyed shaft

• Weight (approx.): 20–25 kg (varies by configuration)

• Working Ports: SAE flange or thread

• Optional Features: Integrated pressure relief valve, counterbalance valve (BVD/BVE), flushing and boost-pressure valve

Key Technical Advantages

1. Bent-Axis Conical Piston Design with High Starting Efficiency

The AA2FM63/61W-VSD520 employs a bent-axis design with conical pistons that transmit force through tapered contact with the drive plate. The conical piston rotary group provides self-centering capability within the cylinder bores, reducing the risk of uneven wear. The bent-axis design delivers high mechanical efficiency during low-speed starting, with uniform motion starting at 50 rpm without stick-slip or speed fluctuation. This design maintains stable volumetric efficiency at the nominal pressure of 400 bar, with the high-pressure side requiring a minimum of 25 bar to maintain hydrostatic film integrity.

2. High Power Density and High Total Efficiency

The A2FM Series 61 motor is renowned for its high power density and very high total efficiency in the hydraulic industry. It achieves a high pressure rating of 400 bar nominal and 450 bar peak within a compact structural envelope, delivering an excellent power-to-weight ratio. Series 61 is specially adapted for the US market, with SAE flange mounting and SAE port connections ensuring seamless integration with US-standard machine hydraulic systems.

3. High Dynamic Response and Pressure Shock Resistance

The motor can withstand pressure change rates up to 9,000 bar/s, allowing rapid reversals without cavitation risk. The total pressure limit of 700 bar protects the rotating group against shock loads. This characteristic makes the AA2FM63 particularly suitable for highly dynamic hydraulic drive applications requiring frequent start-stop and forward-reverse switching, such as excavator travel drives and roller drives.

4. Flexible Mounting Configuration and Functional Extensibility

Working ports are available in either SAE flange or threaded configurations to suit different system requirements. The motor can be optionally equipped with an integrated pressure relief valve for additional safety protection. Counterbalance valves (BVD/BVE), flushing valves, and boost-pressure valves can also be mounted directly onto the motor, simplifying system piping design and reducing external connection points and leakage risks. FKM (fluorocarbon) seals provide compatibility with high-temperature and chemically aggressive media.

Application Areas

• Construction Machinery: Excavator travel drives, wheel loader travel drives, roller travel drives

• Agricultural Machinery: Combine harvester travel drives, self-propelled sprayers

• Mining Equipment: Mining truck travel drives, underground transport equipment

• Material Handling: Forklift drives, reach stacker travel systems

• Industrial Drives: Closed-circuit hydrostatic transmission systems, winch drives

• Specialty Vehicles: Concrete mixer truck drives, municipal service vehicles

Expert Maintenance Tips

1. Shaft Alignment Requirements: The bent-axis motor’s conical piston rotary group is sensitive to radial forces. During installation, ensure the coaxiality deviation between the motor shaft and drive-end spline does not exceed 0.05 mm. Excessive radial forces will accelerate wear on the piston tapered surfaces and drive plate, degrading volumetric efficiency.

2. Hydraulic Fluid Cleanliness Control: The A2FM series motor features precision clearances in the piston and distribution pairs. Maintain hydraulic fluid cleanliness at ISO 4406 20/18/15 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.

3. Viscosity and Temperature Management: Maintain viscosity between 10–400 mm²/s during continuous operation, with the optimum range being 16–36 mm²/s. Cold starts are possible down to −25°C, but the system should be gradually warmed to normal operating temperature after startup. Oil at port T should not exceed +103°C during extended duty; excessive temperatures accelerate seal aging and fluid degradation.

4. Closed-Loop Flushing Requirements: When used in closed circuits, a flushing valve is recommended to maintain case temperature below 80°C. Inspect case drain leakage every 200 operating hours; normal leakage should remain below 5 L/min. A sudden increase indicates potential wear on the piston-to-bore clearance or the distribution plate.

5. Restart After Extended Storage: For motors stored over 6 months, manually rotate the shaft 2–3 revolutions to confirm free rotation, then run at low pressure (10 MPa) under no load for 10 minutes, confirming normal case temperature and leakage before gradually applying load.