Product Overview
The A2FM56/61W-VBB040 (Material No. R902160910) is a core model within the 56 frame size of Bosch Rexroth’s A2FM Series of bent axis axial piston fixed displacement motors. The A2FM Series features an axial tapered piston rotary group of bent-axis design, developed for hydrostatic drives in open and closed circuits, suitable for both mobile and stationary applications.
The A2FM56/61W-VBB040 has a nominal displacement of 56.1 cm³/rev, with a nominal working pressure of up to 400 bar and maximum pressure of 450 bar, making it an ideal power component for high-pressure heavy-duty hydraulic drives. The motor employs a 40° bent-axis design, where pistons act directly on the drive shaft flange through a tapered configuration to generate torque, offering high power density, compact dimensions, high overall efficiency, and good starting characteristics.
Model code breakdown: A2FM = bent axis fixed displacement motor; 56 = nominal displacement 56 cm³/rev; 61 = series 6, index 1; W = bidirectional rotation (viewed on drive shaft); V = FKM (fluoroelastomer) seals; B = DIN 6885 parallel keyed shaft; B = 4-hole mounting flange; 040 = threaded ports A and B at side and at rear; 0 = without valve; without speed sensor.
The motor features one-piece tapered pistons with piston rings, ensuring efficient sealing and long service life. The FKM seal material enables compatibility with mineral oil and HFD hydraulic fluids (selected sizes), adapting to demanding industrial environments. As a drop-in replacement, the motor is fully compatible with the OEM Rexroth specification in mounting interface, shaft end configuration, and performance characteristics, enabling direct replacement without hydraulic circuit or mounting bracket modification. Every unit undergoes 100% simulation-based testing prior to shipment, covering displacement calibration, torque output, pressure holding, and internal leakage.
Technical Specifications
All parameters below are based on Bosch Rexroth official technical documentation, verified supplier technical pages, and industry-standard specifications:
A2FM56/61W-VBB040 Technical Specifications:
Complete Model: A2FM56/61W-VBB040
Material Number (MNR): R902160910
Brand: Bosch Rexroth
Product Series: A2FM series, Series 61, bent axis fixed displacement motor
Product Type: Bent axis axial piston fixed displacement motor
Nominal Displacement: 56.1 cm³/rev
Nominal Pressure: 400 bar (5802 PSI)
Maximum Pressure: 450 bar (6527 PSI)
Maximum Speed: 3750 rpm (Series 61, Size 56 reference)
Maximum Flow: 210 L/min (Series 61, Size 56 reference)
Theoretical Torque (@ Δp = 400 bar): 356 N·m
Drive Type: Bent-axis design, pistons acting directly on drive shaft flange
Mounting: 4-hole mounting flange (ISO / SAE standard)
Drive Shaft: DIN 6885 parallel keyed shaft
Port Connection: Threaded ports A/B, at side and at rear
Direction of Rotation: Bidirectional (viewed on drive shaft)
Seal Material: FKM (fluoroelastomer)
Hydraulic Fluid: Mineral oil, HFD (selected sizes); sizes 5 to 200 compatible with HFB, HFC
Operating Temperature Range: Dependent on selected seal material
Weight: Approx. 20.8 kg
A2FM Series Other Model Specifications Reference (Series 61):
A2FM10: Displacement 10.3 cm³/rev, max speed 8000 rpm, torque 65 N·m @400 bar
A2FM12: Displacement 12.0 cm³/rev, max speed 8000 rpm, torque 76 N·m @400 bar
A2FM16: Displacement 16.0 cm³/rev, max speed 8000 rpm, torque 100 N·m @400 bar
A2FM23: Displacement 22.9 cm³/rev, max speed 6300 rpm, torque 144 N·m @400 bar
A2FM28: Displacement 28.1 cm³/rev, max speed 6300 rpm, torque 178 N·m @400 bar
A2FM32: Displacement 32.0 cm³/rev, max speed 6300 rpm, torque 204 N·m @400 bar
A2FM45: Displacement 45.6 cm³/rev, max speed 5600 rpm, torque 290 N·m @400 bar
A2FM56: Displacement 56.1 cm³/rev, max speed 5000 rpm, torque 356 N·m @400 bar
A2FM63: Displacement 63.0 cm³/rev, max speed 5000 rpm, torque 400 N·m @400 bar
A2FM80: Displacement 80.4 cm³/rev, max speed 4500 rpm, torque 508 N·m @400 bar
A2FM90: Displacement 90.0 cm³/rev, max speed 4500 rpm, torque 572 N·m @400 bar
A2FM107: Displacement 106.7 cm³/rev, max speed 4000 rpm, torque 680 N·m @400 bar
A2FM125: Displacement 125.0 cm³/rev, max speed 4000 rpm, torque 796 N·m @400 bar
A2FM160: Displacement 160.4 cm³/rev, max speed 3600 rpm, torque 1016 N·m @400 bar
A2FM180: Displacement 180.0 cm³/rev, max speed 3600 rpm, torque 1144 N·m @400 bar
Note: Specifications are based on Bosch Rexroth official technical documentation, verified supplier technical pages (SP Spare Parts, Hydraulikfiltershop, Xeriwell, Bossgoo), and industry-standard specifications. The A2FM Series covers a complete product matrix with displacements from 5 to 1000 cm³/rev. Always verify against the complete model code and consult the latest Rexroth official technical documentation during selection.
Key Technical Advantages
1. 40° Bent-Axis Design for High Power Density and High Starting Efficiency
The A2FM56 employs a proven 40° bent-axis design, where pistons act directly on the drive shaft flange through a tapered configuration to generate torque, enabling high power density within a compact size. This design allows the motor to deliver high torque at startup, offering excellent starting efficiency, particularly suitable for travel drive applications requiring frequent start-stop or loaded starting. Compared with swashplate designs, the bent-axis architecture provides a larger displacement range (for variable models) and higher power-to-weight ratio at the same displacement.
2. One-Piece Tapered Pistons with Piston Rings for Efficient Sealing and Long Life
The motor features one-piece tapered pistons with piston rings, where the piston rings provide efficient sealing performance, effectively reducing internal leakage and improving volumetric efficiency. The one-piece construction reduces the number of moving parts, lowering wear risk and enabling the motor to maintain stable volumetric efficiency and long service life under high-pressure conditions. Drive shaft bearings are optimized to provide the expected service life across the entire operating range.
3. High Pressure Rating with Wide Media Compatibility
With a nominal pressure of 400 bar and maximum pressure of 450 bar, the motor handles high-pressure heavy-duty applications. FKM seal material provides excellent high-temperature and chemical resistance, with compatibility for mineral oil and HFD hydraulic fluids. Sizes 5 to 200 are also compatible with HFB and HFC fire-resistant fluids, meeting diverse industrial environment media requirements.
4. High Overall Efficiency with Economical Design
The A2FM Series features high overall efficiency, where output speed depends on pump flow and motor displacement, and output torque increases with the pressure differential between high and low-pressure sides. The series offers finely graduated displacement sizes, allowing users to precisely select the most suitable specification for specific drive conditions, achieving system efficiency optimization. The economical design philosophy runs throughout the product series, reducing total cost of ownership while maintaining performance.
5. Complete Specification Coverage with 100% Simulation-Based Testing
The A2FM Series covers a complete displacement range from A2FM10 to A2FM1000, satisfying all requirements from precision industrial transmission micro-torque to high-power heavy-duty drive applications. Every A2FM56/61W-VBB040 undergoes 100% simulation-based testing prior to shipment, covering displacement calibration, torque output verification, pressure holding performance, and internal leakage detection. As a drop-in replacement, the motor is fully compatible with the OEM Rexroth specification in mounting dimensions (4-hole flange), shaft end configuration (DIN 6885 parallel keyed shaft), and performance characteristics, enabling direct replacement of the original motor.
Application Areas
Construction Machinery Travel Drives: Travel motors for excavators, loaders, and compactors, utilizing high starting efficiency for smooth starting and climbing
Rotary Drilling Rigs & Piling Machinery: Power head drives and auxiliary winch systems, utilizing high power density for compact layouts
Cranes & Material Handling: Hoisting mechanisms and slewing motors, utilizing high torque output for heavy-load lifting
Concrete Mixer Trucks: Mixer drum drive motors, utilizing economical design and reliable performance for long-term continuous operation
Mining & Tunneling Equipment: Hydraulic drive systems for roadheaders, roof bolters, and related equipment
Marine & Offshore: Deck machinery, winches, and propulsion system hydraulic transmission
Industrial Hydraulic Systems: Metallurgical equipment, presses, and test rigs requiring high-pressure fixed displacement drives
Agricultural Machinery: Travel and implement drives for harvesters, sprayers, and other equipment
Expert Maintenance Tips
Pre-Installation Checks:
Verify mounting flange (4-hole) alignment with equipment mounting surface; ensure surface is clean and free of burrs, flatness deviation not exceeding 0.01 mm/100 mm
Inspect DIN 6885 parallel keyed shaft mating surface for wear or corrosion; apply appropriate grease
The motor must be fully filled with clean hydraulic oil via the housing drain port and air bled during commissioning to prevent dry friction damage to piston/cylinder and bearings during startup
Confirm threaded port seals are intact; tighten diagonally to specified torque
Operational Maintenance:
Maintain hydraulic oil cleanliness to ISO 4406 18/16/13 or better; use pressure filters with ≤ 10 μm filtration accuracy
Periodically monitor hydraulic oil moisture and particle contamination levels; oil replacement recommended every 1,000 to 3,000 operating hours or every six months
Periodically inspect shaft seals for aging or leakage; shaft seals recommended for replacement every 5,000 hours or immediately when leakage exceeds 10 drops/minute
Periodically verify housing drain line is unobstructed; return back pressure must not exceed allowable limits
Periodically monitor motor operating temperature and noise level; abnormal increase may indicate internal wear or fluid contamination
In closed circuit applications with excessive oil temperature, consider installing a flushing valve to control heat build-up
Troubleshooting Guide:
Motor fails to rotate or speed abnormal: Check hydraulic system supply pressure; verify directional valve operation; check oil cleanliness
Insufficient output torque: Confirm system pressure reaches rated value (400 bar continuous / 450 bar peak); inspect piston rings and cylinder bores for wear
Abnormal noise or vibration: Check housing oil fill level; verify suction line is unobstructed; check mounting bolt tightness
External leakage: Inspect shaft seal for aging or damage; verify drain line back pressure is within allowable range
Excessive oil temperature: Check system for excessive internal leakage; verify cooling system operation; consider adding flushing valve in closed circuit applications
