Rexroth AA2FM fixed displacement axial piston hydraulic motor

The AA2FM is a fixed-displacement, bent-axis design axial piston motor manufactured by Bosch Rexroth. Unlike swash-plate axial piston units, the bent-axis architecture tilts the cylinder block relative to the drive shaft at a fixed angle (typically 25°, 30°, or similar depending on frame size). This geometry gives the AA2FM a few structural advantages: shorter piston stroke for a given displacement, high pressure capability, and excellent efficiency across a wide speed range.

How the AA2FM Motor Works

Understanding the internals makes troubleshooting and specification far easier.

The Bent-Axis Piston Arrangement

In a bent-axis motor, the cylinder block sits at a fixed angle to the output shaft. Pressurized oil enters through the valve plate, forcing pistons in the cylinder block to extend. Because the cylinder block is angled relative to the shaft, the pistons push against the shaft flange, converting linear piston force into rotary torque. The fixed angle means displacement per revolution never changes — hence "fixed displacement."

The Valve Plate and Porting

Oil distribution happens through a valve plate (also called a port plate) that times the high-pressure and low-pressure ports as the cylinder block rotates. In the AA2FM configuration, this plate is engineered for reduced pressure ripple and quieter operation compared to older generations — a big part of why Rexroth markets this line for noise-sensitive mobile applications.

Bearing and Shaft Support

The AA2FM uses a robust bearing arrangement (typically tapered roller bearings) to absorb both radial and axial loads directly at the shaft, which is one reason these motors tolerate side loads from sprockets, pulleys, or direct-coupled pumps better than many swash-plate alternatives.

Common Applications

Construction equipment: Concrete mixer drums, compactor drums, and travel drives on skid steers or compact track loaders

Material handling: Winches, conveyor drives, and slewing drives on cranes

Agricultural machinery: Fan drives, auger drives, and header drives on combines

Marine and offshore: Deck winches and anchor handling systems

Industrial machinery: Rotary tables, mixers, and any application needing constant-torque, bidirectional rotary output

Installation and Maintenance Considerations

1. A case drain line is mandatory. Running an AA2FM without a properly sized case drain back to tank will cause seal failure and overheating almost immediately.

2. Check shaft seal pressure rating. If the application involves back-pressure in the case drain line, confirm the shaft seal can handle it — exceeding the rated case pressure is one of the most common failure causes in the field.

3. Filtration matters more than people think. Axial piston motors have tight piston-to-bore clearances; contamination control (ISO 4406 cleanliness targets per Rexroth's recommendations) directly determines service life.

4. Verify mounting flange and shaft spline match your specific frame size. SAE flange and spline standards vary by displacement class, and mismatches are a frequent ordering mistake.

5. Monitor for unusual noise or vibration, which often signals bearing wear or valve plate scoring before a catastrophic failure occurs.

For more information on the AA2FM hydraulic motor, please visit https://www.baolilaihydraulic.com/product/.

Specifications

Selection Table

Q1: How long does an AA2FM motor typically last?

A1: Service life varies enormously with fluid cleanliness, pressure levels, and duty cycle, but well-maintained units in properly filtered systems commonly run tens of thousands of hours before requiring bearing or seal service.

Q2: What fluids is the AA2FM compatible with?

A2: Standard mineral-based hydraulic oils are typical; biodegradable and fire-resistant fluids are supported in many configurations but require seal material verification (Rexroth specifies compatible seal codes for each fluid type).

Q3: What is the price and delivery time of the AA2FM hydraulic motor?

A3: The specific price and delivery time will be provided based on the specific model you provide.

Q4: How to purchase an AA2FM hydraulic motor?

A4: You can visit https://www.baolilaihydraulic.com/contact/ to contact us and purchase our products through various methods.