Bosch Rexroth A4FM Piston Motor

The Bosch Rexroth A4FM is a fixed displacement axial piston motor of swashplate design, engineered for hydrostatic drives in both open and closed circuits. Unlike bent-axis motors, the A4FM offers a specific geometric profile ideal for applications where installation space is limited. It delivers high output torque and speed with a nominal pressure rating of up to 400 bar, making it suitable for heavy-duty mobile and industrial machinery.

Key Features:

Series: Series 10, Series 32
Type: Fixed Displacement (Swashplate)
Sizes: 22 to 500 cm³/rev
Pressure: 400 bar (Nominal) / 450 bar (Peak).

Product Overview The Rexroth A4FM Motor is designed for rigorous performance. Its axial piston swashplate construction ensures a constant flow-to-torque conversion ratio. The output speed is directly proportional to the inlet flow, while the output torque increases with the pressure differential. The A4FM is particularly valued for its compact axial length and integrated valve technology options.

Why Choose Rexroth A4FM?

High Pressure Capability: Capable of handling nominal pressures of 400 bar and peak pressures up to 450 bar (Series 32), providing exceptional power density.
Compact Integration: The swashplate design allows for a compact envelope, often featuring integrated auxiliary valves (counterbalance valves, relief valves) directly on the port plate.
Versatility: Can be used as a pump in specific applications (charge pump or auxiliary drive).
Efficiency: Low start-up torque losses and high volumetric efficiency.

Common Applications:

Construction: Track drives, Wheel drives.
Drilling: Top drives for drill rigs.
Winches: Hoisting gear.
Industrial: Mixer drives, Conveyor belts.

Specification	Value / Description
Product Type	Fixed Displacement Axial Piston Motor
Design	Swashplate Design
Series	Series 10 (Standard), Series 32 (High Pressure)
Displacement Sizes ( $V_g$ )	22, 28, 32, 40, 45, 56, 63, 71, 80, 90, 107, 125, 160, 180, 200, 250, 355, 400, 500 cm³/rev
Nominal Pressure	400 bar (Series 32) / 280 bar (Series 10)
Peak Pressure	450 bar (Series 32) / 350 bar (Series 10)
Max. Speed ( $n$ )	2000 – 4500 rpm (depending on size)
Mounting	ISO 3019-2 (Metric Flange)
Ports	SAE Flange Ports (Side or Rear)
Common Part Numbers	Model Code Structure: A4FM[Size]/[Series][Rotation]-[Shaft][Seals][Ports] A4FM 28 / 32W-VPB01… (28cc, Series 32) A4FM 56 / 32W-VSB02… (56cc, Series 32) A4FM 71 / 32W-VPB02… (71cc, Series 32) A4FM 125 / 10W-PPB02… (125cc, Series 10) A4FM 250 / 30W-PPB02… (250cc, Series 30) Note: “W” usually denotes Reversible direction of rotation.