Product Overview
The F11 Series bent axis fixed displacement axial piston motor/pump is a field-proven heavy-duty hydraulic component from Parker Hannifin, recognized globally as a benchmark solution for high-speed, high-pressure hydraulic transmission. The series achieves operating pressures up to 420 bar (6,090 psi) and speeds up to 14,000 rpm, with displacement options spanning 5–19 cm³/rev in the small frame sizes, extended to larger displacements including F11-028, F11-039, and F11-058. The motors are suitable for both open and closed loop circuits, making them exceptionally versatile across mobile and industrial applications.
The specific model covered in this document — F11-039-MU-CE-K — is the 38.7 cm³/rev configuration with a 40° bent-axis fixed displacement design and bidirectional rotation capability. In the model code, F11 designates the product series; 039 indicates the theoretical displacement of approximately 39 cm³/rev; MU denotes the mounting flange and shaft configuration; CE specifies the control/valve plate configuration; and K indicates the special option code. The motor is manufactured to original Parker specifications with 100% drop-in interchangeability, requiring no modification to mounting interfaces, port positions, or hydraulic connections. Every unit undergoes 100% simulated operating condition testing at the factory, including rated pressure loading, volumetric efficiency verification, case pressure validation, and seal integrity assessment prior to shipment.
Technical Specifications
F11-039-MU-CE-K:
Series / Type: Parker F11 Series bent axis fixed displacement axial piston motor/pump
Displacement: 38.7 cm³/rev (2.36 in³/rev)
Design: Bent axis, fixed displacement, 40° shaft-to-cylinder barrel angle
Rated continuous operating pressure: 350 bar (5,075 psi)
Maximum intermittent pressure: 420 bar (6,090 psi)
Peak pressure: 480 bar (6,960 psi)
Maximum continuous speed: 4,200 rpm
Maximum intermittent speed: 5,200 rpm
Minimum speed: 125 rpm
Direction of rotation: Bidirectional (either A or B port as inlet)
Theoretical flow: up to 200 L/min
Theoretical torque at 100 bar: approximately 61.6 Nm
Mounting flange: SAE / ISO / CETOP standard flanges available
Shaft end: SAE / ISO standard spline
Bearing arrangement: Dual tapered roller bearings for high radial and axial load capacity
Housing material: High-strength cast iron
Maximum noise level: 80 dBA
Maximum radial shaft load: 400 kg (880 lb)
Maximum fluid temperature: 115°C (239°F)
Minimum fluid temperature: -40°C (-40°F)
Fluid viscosity range: 8–1,000 cSt
Approximate weight: 8–9 kg
F11 Series displacement range (for reference):
F11-005: 4.9 cm³/rev
F11-006: 6.0 cm³/rev
F11-010: 9.8 cm³/rev
F11-012: 12.5 cm³/rev
F11-014: 14.0 cm³/rev
F11-019: 19.0 cm³/rev
F11-028: 28.1 cm³/rev
F11-039: 38.7 cm³/rev
F11-058: 58.2 cm³/rev
F11-078: 78.2 cm³/rev
F11-110: 110 cm³/rev
F11-150: 150 cm³/rev
F11-250: 242 cm³/rev
The F11 Series shares the bent axis fixed displacement platform architecture with the F10 and F12 Series, with certain rotating group components (pistons, cylinder block, valve plate) exhibiting platform commonality. The F11 and F12 Series share service tools and select spare parts, streamlining spare parts management.
Key Technical Advantages
1. 40° Bent Axis Design for High Power Density
The F11 Series employs a 40° bent axis angle between the output shaft and cylinder barrel, enabling high displacement density and torque output within a compact envelope. Compared to swashplate designs, the bent axis architecture transmits piston force to the output shaft through a shorter, more direct path, yielding higher mechanical efficiency. The compact rotating group design enables the F11 Series to deliver high output power from a remarkably small package, achieving a power-to-weight ratio that outperforms comparable swashplate-type motors. The motor is suitable for both open and closed loop circuits, offering exceptional system adaptability across mobile machinery and industrial drive applications.
2. Unique Spherical Piston and Laminated Piston Ring Technology
The F11 Series features spherical piston ends that run directly in the output shaft socket, paired with laminated piston rings that provide superior sealing performance and thermal shock resistance. The engineering significance of the laminated ring design lies in its ability to adapt to micro-deformation of the cylinder bore under high pressure, maintaining consistent sealing contact. Under thermal cycling, the laminated construction offers thermal expansion compensation far superior to solid piston rings, effectively suppressing internal leakage. This design maintains high volumetric efficiency across a wide temperature and pressure envelope, minimizing energy loss and heat generation from internal leakage.
3. Gear Synchronization Mechanism for High G-Force Tolerance
The F11 Series utilizes a unique gear synchronization mechanism that precisely synchronizes output shaft and cylinder barrel rotation. This timing gear design makes the motor extremely tolerant to high G-forces and torsional vibrations, making it ideally suited for installation on moving machinery subject to frequent shock and vibration loading — such as saw drives, deck cranes, and skid steer loaders. The precision meshing of the synchronizing gears ensures that piston reciprocation within the cylinder bores maintains correct phase relationship, preventing piston side-loading and seal failure caused by synchronization errors.
4. Dual Tapered Roller Bearings for High External Load Capacity
The output shaft is supported by heavy-duty dual tapered roller bearings, capable of simultaneously accommodating significant radial and axial external loads. Maximum radial shaft load capacity reaches 400 kg (880 lb). For drive applications requiring direct mounting of gears, sprockets, or pulleys, this means the motor output shaft can directly absorb the radial forces generated by driven components without requiring a separate bearing support housing — simplifying system design and reducing installation costs.
5. High Speed Capability with Low Noise Operation
Thanks to lightweight piston design and a compact rotating assembly, the F11 Series tolerates very high speeds — up to 14,000 rpm for small displacement models, and 4,200–5,200 rpm for medium and large displacement models. The motor features a precision-engineered valve plate optimized for high-speed, low-noise operation, with a maximum noise level of only 80 dBA. For applications such as saw drives and fan drives where the motor operates in proximity to personnel, the low noise characteristic significantly improves the working environment.
Application Areas
Forestry equipment: Chain saw drives (the F11 Series is extensively applied in this domain thanks to its compact structure and high-speed capability)
Material handling: Deck cranes, hatch cover drives, skid steer loader travel drives
Construction equipment: Rotary drilling rig auxiliary drives, vibratory roller travel drives, excavator auxiliary systems
Oil & gas: Coil tubing units, drilling platform auxiliary drives
Agricultural machinery: Combine harvester auxiliary drives, self-propelled sprayer travel systems
Industrial drives: Machine tool drives, winch and conveyor drives (high starting torque applications)
Marine and offshore: Deck machinery, windlass drives
Expert Maintenance Tips
1. Fluid Cleanliness Control
The F11 Series operates with micron-level clearances between pistons and cylinder bores and between the valve plate and cylinder block face. Systems must be equipped with filtration rated to ISO 4406 20/18/13 or better (per Parker recommendation). In high-contamination environments such as forestry or construction job sites, shorten fluid change intervals and increase filter replacement frequency accordingly. Fluid viscosity should be maintained in the optimum range of 15–30 cSt (acceptable range 8–1,000 cSt).
2. Case Drain Flow as a Wear Monitoring Indicator
Case drain flow is a sensitive indicator of internal motor condition. Per Parker service manual procedure: run the unit at normal speed and pressurize the system to 150–200 bar, disconnect the drain line, and measure drain flow for one minute. Compare the measured value against Parker’s baseline specification for a new unit. A significant increase in drain flow may indicate piston-slipper wear or valve plate sealing degradation, warranting timely inspection and repair.
3. Pre-Start Case Filling and Air Purging
Before first startup after installation or repair, the motor case must be filled with clean hydraulic fluid through the highest case port until fluid overflows. The F11 Series bent axis architecture creates a complex internal case cavity geometry, and starting an un-purged motor can cause dry friction damage to piston ball ends and socket bushings.
4. Piston Ring Wear Inspection and Replacement Criteria
During teardown and repair, inspect the spherical piston rings for wear. Parker service manual specifies that piston rings with more than 50% wear on the spherical surface must be replaced. Additionally, all shaft seals and O-rings should always be replaced during any teardown procedure to ensure sealing reliability.
5. Installation Alignment and Spline Engagement
The F11 Series uses SAE/ISO/CETOP standard flange mounting. During installation, verify that the output shaft spline is properly aligned with the mating component. While dual tapered roller bearings accommodate substantial external loads, installation misalignment will significantly shorten bearing life. Tighten mounting bolts in stages to the specified torque value, and re-check torque after 500 operating hours.
6. Restart Procedure After Extended Shutdown
If the motor has been idle for more than three months, manually rotate the output shaft to confirm freedom of movement, and inspect the case oil level and shaft seal for leakage before restarting. Extended shutdown can cause oil film drainage from piston-slipper interfaces, creating a dry-start risk. Operate at low speed and reduced load for 10–15 minutes before returning to normal duty.
