A6VE28HAXT/63W-VAL020A Rexroth Motor 28cc 450 bar

Product Overview

The A6VE28HAXT/63W-VAL020A is a bent-axis axial piston variable plug-in motor built on the Bosch Rexroth A6VE Series 63 platform, in the A6VE28 displacement size (28.1 cm³/rev). The motor features a bent-axis design with an axial tapered piston rotary group, engineered for hydrostatic drives in both open and closed circuits, and can be directly integrated into mechanical gearboxes. It offers a nominal pressure of 400 bar, maximum pressure of 450 bar, maximum speed of 5,550 rpm (at Vg max), maximum flow of 156 L/min, maximum output torque of 179 N·m (Δp=400 bar), and a weight of approximately 16 kg.

The defining design feature of the A6VE series is its plug-in structure — the motor’s mounting flange is located at the center of the case, combined with a recessed center flange that allows the motor to be directly plugged into a mechanical gearbox without needing to observe installation tolerances or configuration specifications, achieving an extremely space-saving compact integration. This design is particularly suited for direct drive gearbox integration in pavers, rollers, and similar equipment. The A6VE28HAXT/63W-VAL020A features HAXT control (automatic control related to high pressure), automatically adjusting displacement through hydraulic signals for load-adaptive control. The model has mature application validation in the drive systems of Wirtgen W100CF, W120CF, and W130CF pavers.

The model code A6VE28HAXT/63W-VAL020A decodes as follows: A6VE28 designates the series and displacement size (plug-in variable motor, 28.1 cm³/rev), HA is the control device series code (automatic control related to high pressure), XT is the control variant code, 63 is the series designation (Series 63), W indicates bidirectional rotation, and VAL020A is the port configuration, shaft type, and special option code.

Engineered as a form-fit-function replacement for original Bosch Rexroth A6VE28 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: A6VE28HAXT/63W-VAL020A

• Material Number: R902004238

• Series: Bosch Rexroth A6VE Series 63

• Motor Type: Bent-axis axial piston variable plug-in motor

• Design Feature: Bent-axis configuration, axial tapered piston rotary group, recessed center mounting flange, plug-in design

• Maximum Displacement (Vg max): 28.1 cm³/rev (1.71 in³/rev)

• Minimum Displacement (Vg min): ≈ 0 cm³/rev (infinitely variable)

• Nominal Pressure (p nom): 400 bar (40 MPa / 5,800 psi)

• Maximum Pressure (p max): 450 bar (45 MPa / 6,525 psi)

• Maximum Speed (Vg max): 5,550 rpm

• Maximum Speed (Vg < Vg max): 8,750 rpm

• Maximum Speed (Vg min): 10,450 rpm

• Maximum Flow (qV max): 156 L/min (41.2 US gal/min)

• Maximum Output Torque (Δp=400 bar): 179 N·m (132 lb-ft)

• Rotary Stiffness (Vg max to Vg/2): Cmin = 5,670 Nm/rad, Cmax = 18,100 Nm/rad

• Moment of Inertia (Rotary Group): 0.0014 kg·m²

• Maximum Angular Acceleration: 47,000 rad/s²

• Filling Capacity: 0.5 L

• Rotation: Bidirectional (W)

• Mounting: Plug-in (recessed center flange, direct mechanical gearbox insertion)

• Control Method: HAXT — Automatic control related to high pressure

• Circuit: Open circuit / Closed circuit

• Housing Material: Cast iron

• Weight (approx.): 16 kg (35.3 lb, port plate 02 configuration)

• Operating Temperature: 30–90°C

• Compatible Machines: Wirtgen W100CF, W120CF, W130CF pavers

Key Technical Advantages

1. Bent-Axis Tapered Piston Design with High Power Density

The A6VE28HAXT employs the classic bent-axis design of the Bosch Rexroth A6VE series, with pistons arranged at an angle to the drive shaft, transmitting torque through spherical contact between tapered pistons and the drive plate. This design achieves a nominal pressure of 400 bar and maximum pressure of 450 bar at 28.1 cm³/rev displacement, with maximum output torque of 179 N·m, offering high power density and excellent starting efficiency. The bent-axis axial tapered piston motor uses structurally simple piston rings for sealing within the cylinder bore, ensuring stable volumetric efficiency under high-pressure conditions.

2. HAXT High-Pressure Related Automatic Control with Load Adaptation

The HAXT control device provides automatic control related to high pressure (HA series), where motor displacement is automatically adjusted based on system operating pressure. As load pressure increases, displacement automatically increases to deliver greater torque; as load pressure decreases, displacement reduces and speed increases, achieving constant-power control characteristics. This control method is particularly suitable for hydrostatic drive systems in pavers and similar equipment requiring automatic torque and speed matching under varying operating conditions.

3. Plug-In Design with Direct Gearbox Integration

The A6VE28’s mounting flange is located at the center of the case. The recessed center flange design allows the motor to be almost completely inserted into the mechanical gearbox, achieving an extremely space-saving compact installation. The motor can be directly slid into the mechanical gearbox without needing to observe configuration specifications or installation tolerances. This design eliminates couplings and external mounting brackets in paver drive and travel drive applications, reducing system component count and potential failure points, while improving drive system rigidity and alignment precision.

4. Wide Control Range with High-Speed Capability

The A6VE28’s displacement is infinitely variable from Vg max to Vg min = 0, providing an exceptionally wide control range. At full displacement, the motor delivers maximum torque of 179 N·m for heavy-load starting and climbing conditions; at minimum displacement, maximum speed reaches up to 10,450 rpm for high-speed travel requirements. The A6VE series offers multiple displacement sizes from 28 to 250 cm³/rev for flexible matching.

Application Areas

• Pavers: Wirtgen W100CF, W120CF, W130CF cold milling machines and pavers drive systems (A6VE28HAXT/63W-VAL010VBA-S companion)

• Rollers: Bomag and other brand roller drive systems

• Construction Machinery Travel Drives: Excavator and loader travel drive systems

• Industrial Hydraulic Transmissions: Industrial drive scenarios requiring compact integration and high efficiency

• Other Mobile Applications: Various mobile hydraulic systems requiring plug-in variable motors

Expert Maintenance Tips

1. Plug-In Mounting Notes: Before installation, ensure the gearbox input shaft spline and motor output spline are clean and free of damage, with no burrs on mating surfaces. Do not strike the coupling or motor shaft end during installation, to avoid damaging internal bearings and rotating components.

2. Case Filling and Venting: Before initial installation or startup after extended idle periods, fill the motor housing with clean hydraulic fluid to prevent dry friction on piston pairs during startup. The case drain port must be connected separately to the reservoir, with return lines below the minimum oil level.

3. HAXT Control System Maintenance: Periodically verify the response characteristics of the HAXT high-pressure related automatic control mechanism. Check control response linearity every 500 operating hours, confirming displacement regulation matches system load. If response is sluggish or non-linear, check control valve spool wear and pilot circuit pressure.

4. Hydraulic Fluid Cleanliness and Viscosity Management: Recommended optimum viscosity range is 16–36 mm²/s (at operating temperature). 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.

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.