Product Overview
The 51V250-R-F2-N-EQ-A7-J-Y-E1-CCA-140-AA-F3-15-16 belongs to the Danfoss Series 51 family of bent axis variable displacement piston motors, featuring spherical piston and bent axis construction engineered for closed-loop hydrostatic transmission systems. Manufactured to original technical standards with precision-matched critical components, these motors deliver true drop-in interchangeability with genuine Danfoss/Sauer units. Every motor undergoes 100% simulated operating condition bench testing before shipment, validating volumetric efficiency, pressure retention, and control response characteristics.
The Series 51/51-1 motors feature a large maximum/minimum displacement ratio of 5:1. Motors start at maximum displacement, providing maximum starting torque, and reduce displacement as speed increases — covering a wide speed range without changing pump flow. The 51V version is equipped with proportional control, enabling stepless displacement regulation in combination with a Series 90 pump or other closed-circuit pump.
Technical Specifications
Full Model: 51V250-R-F2-N-EQ-A7-J-Y-E1-CCA-140-AA-F3-15-16
Series: 51V250
Motor Type: Bent Axis Variable Displacement Motor
Maximum Displacement (Vg max): 250.0 cm³/rev [15.26 in³]
Minimum Displacement (Vg min): 50.0 cm³/rev [3.05 in³]
Displacement Ratio: 5:1
Rated Pressure: 420 bar
Peak Pressure: 480 bar
Maximum Speed: 4000 rpm
Rated Flow: 550 L/min [145 US gal/min]
Maximum Flow: 675 L/min [178 US gal/min]
Maximum Corner Power: 850 kW [1140 hp]
Weight (approx.): 86 kg [190 lb]
Mass Moment of Inertia: 0.0480 kgm² [1.1580 lb·ft²]
Control Type: F2 Proportional Control
Mounting: SAE 4-bolt flange
Direction of Rotation: Bi-directional (CW/CCW)
Main Pressure Ports: SAE flange
Remaining Ports: SAE straight thread O-ring boss
Key Technical Advantages
1. Bent Axis Spherical Piston Design — High Volumetric Efficiency & Power Density
The spherical piston and bent axis drive principle achieves near-contactless operation through hydrostatic pressure balancing between the piston and cylinder bore. Compared to swashplate designs, the bent axis configuration delivers higher power density and lower case heat generation at equivalent displacement. The 51V250 achieves a maximum corner power of 850 kW, among the highest in the 250cc displacement class.
2. 5:1 Large Displacement Ratio — Wide Speed Range
The 51V250 displacement varies continuously from 50.0 to 250.0 cm³/rev, enabling a single motor to cover the full operating envelope from high-torque launch to high-speed travel. The motor starts at maximum displacement for maximum torque and automatically shifts to lower displacement as speed increases, significantly optimizing system energy utilization.
3. High-Pressure Capability — Heavy-Duty Adaptability
With a maximum working pressure of 420 bar and peak pressure of 480 bar, the 51V250 is engineered for continuous heavy-duty operation in construction machinery. The valve plate and cylinder block end faces undergo precision lapping and surface hardening to maintain stable hydrodynamic lubrication under high pressure differentials. The housing is cast from high-strength nodular iron and pressure-tested after precision machining.
4. Proportional Control Integration — Stepless Regulation & System Protection
The F2 proportional control configuration enables stepless motor displacement regulation in response to pilot pressure signals, with response characteristics bench-calibrated for linearity. The pressure compensator automatically reduces displacement when system pressure reaches the set threshold, limiting torque output to prevent system overload. The compensator features a low pressure rise (short ramp), ensuring optimal power utilization throughout the entire displacement range.
5. Precision Matched-Lapping Process — Low Noise & Long Service Life
Critical kinematic pairs — including piston-cylinder bore, valve plate-cylinder block face, and drive plate-piston ball head — are manufactured using matched-lapping processes with clearances controlled at the micron level. This ensures uniform oil film stiffness across all kinematic pairs, effectively suppressing pressure and flow pulsation for low-noise operation while substantially reducing localized contact stress.
Application Areas
Forestry Machinery: Ponsse Elephant, Valmet 890.1/890.3 forwarder hydrostatic travel drives
Construction Machinery: Bomag BW 219 DH, Dynapac CA 302 roller travel drives
Road Sweeping: Johnston street sweeper hydrostatic drive systems
Mining Equipment: Underground LHD loaders, drill rig travel systems
Material Handling: Reach stackers, container handlers travel drives
Specialty Vehicles: Snow removal vehicles, airport de-icing vehicles hydrostatic drives
Expert Maintenance Tips
Installation Notes:
The motor housing must always remain filled with hydraulic fluid. Installation position is discretionary, but the housing must be primed through the case drain port before first startup.
Main pressure ports use SAE flange connections; remaining ports are SAE straight-thread O-ring boss. Tighten to specified torque values (110 Nm for 250 frame size cover screws).
Closed-circuit systems must incorporate an independent braking system. Do not rely on the hydrostatic transmission for holding braking.
Ensure pilot control circuit cleanliness during installation; proportional control pilot pressure must be within the calibrated range.
Operating & Maintenance Guidelines:
Select hydraulic fluid viscosity based on operating temperature, maintaining optimum viscosity range (VG46 or VG55 recommended).
Periodically monitor case drain flow. Abnormal increases typically indicate accelerated internal wear.
Verify proportional control pilot pressure settings at regular intervals using calibrated gauges at the provided gauge ports.
Replace hydraulic fluid and filters after the first 500 hours of operation; thereafter, determine change intervals based on oil analysis results.
After extended storage, manually rotate the shaft to confirm freedom of movement and bleed air from the highest point of the housing before restart.
