The Rexroth-style Axial Piston Fixed Motor A2FE is a bent-axis design unit engineered for hydrostatic transmissions in open and closed-circuit applications. By utilizing a rotating group with a 40-degree bent-axis angle, the A2FE achieves high power density and favorable starting torque characteristics. The unit is designed for direct mounting onto mechanical gearboxes, where the motor housing is integrated into the output flange of the gearbox, significantly reducing the axial installation length. Compliance with ISO 1219 standards ensures interoperability within complex hydraulic circuits, while the robust internal bearing arrangement supports substantial radial and axial loads typical of high-torque industrial and mobile machinery.
For complete selection guidelines and cross-reference documentation on this product line, please consult our Rexroth replacement hydraulic products guide.
Technical Specifications and Performance Parameters
The following table details the standard operational parameters for the A2FE series, reflecting typical performance benchmarks for bent-axis motor configurations.
| Parameter | Unit | Specification Range |
|---|---|---|
| Displacement Range | cm³/rev | 28 – 250 |
| Max Pressure (Continuous) | bar | 350 |
| Max Pressure (Peak) | bar | 400 |
| Max Speed (n_nom) | rpm | 2,500 – 5,000 |
| Mounting Interface | – | ISO 3019-2 / DIN 24340 |
| Fluid Compatibility | – | HLP Mineral Oil (DIN 51524) |
Fluid Cleanliness and Contamination Control
The longevity of the A2FE rotating group—specifically the interface between the cylinder block and the valve plate—is strictly dependent on fluid cleanliness. Particulate contamination leads to abrasive wear, which increases internal leakage and degrades volumetric efficiency. To maintain the design life of the motor, the hydraulic system must adhere to a minimum cleanliness level of 20/18/15 per ISO 4406.
In high-duty cycles, “spool silting” in associated control valves can lead to erratic motor response. Filtration systems should be sized to manage the flow requirements of the specific displacement size, utilizing beta-rated elements (βx ≥ 75) to ensure the capture of fine metallic particles that could otherwise score the hardened steel surfaces of the pistons and cylinder bores.
Seal Elastomer Compatibility and Thermal Limits
The A2FE motor is typically supplied with either Nitrile Butadiene Rubber (NBR) or Fluoroelastomer (FKM/Viton) seals depending on the thermal environment and fluid chemistry.
- NBR (Nitrile): Suitable for standard mineral-based hydraulic fluids (HLP) within a temperature range of -20°C to +80°C. It offers excellent resistance to compression set but is susceptible to degradation in synthetic fire-resistant fluids.
- FKM (Viton): Mandatory for high-temperature applications (up to +110°C) or when utilizing phosphate ester-based fluids. FKM exhibits superior chemical stability; however, it requires careful monitoring of seal squeeze during installation to prevent extrusion under peak pressure spikes.
Engineers must verify that the case drain pressure remains within the manufacturer’s specified limits (typically < 2 bar continuous) to prevent premature shaft seal failure. Excessive case pressure, often caused by restricted return lines or undersized case drain plumbing, will lead to seal blowout and external leakage, compromising the integrity of the hydrostatic loop.