Product Overview
The 51D080RD2NHSA2CEE1NNN032 is a mid-displacement bent-axis axial piston variable motor from the Danfoss Power Solutions (formerly Sauer Danfoss) Series 51, 51D080 frame size. The Series 51 includes three mounting configurations: 51V (SAE flange), 51D (DIN flange), and 51C (cartridge-mount for direct installation into planetary drives). The 51D080 features a DIN flange configuration with a bent-axis architecture and spherical piston design, specifically engineered for closed-circuit hydrostatic transmissions.
The 51D080 offers a maximum displacement of 80.7 cm³/rev (4.92 in³/rev), minimum displacement of 16.1 cm³/rev (0.98 in³/rev), and a 5:1 control ratio. Rated flow is 250 L/min (66 US gal/min), maximum flow is 323 L/min (85 US gal/min), maximum corner power is 403 kW (540 hp), rotary group inertia is 0.0071 kg·m² (0.1685 lb·ft²), and weight is approximately 32 kg (71 lbs). Series 51 motors typically offer rated pressures of 350–400 bar, with maximum pressure up to 510 bar (51 MPa). The 51D080 operates within a rated speed range of 2200–5600 rpm and a speed range of 2200–7000 rpm.
The 51D080 employs a bent-axis design in which pistons contact the drive plate through spherical ends, replacing the slipper design found in conventional axial piston motors. Spherical pistons are less affected by centrifugal forces at high rotational speeds, enabling maximum speeds up to 7000 rpm. Motors normally start at maximum displacement, providing maximum starting torque for high acceleration, then reduce displacement as speed increases.
The motor offers complete interchangeability: DIN flange mounting dimensions, splined shaft (ANSI or DIN standard), and port configuration are identical to the original Sauer Danfoss specification. The 51D080‘s configuration code (e.g., 51D080RD2NHSA2CEE1NNN032) corresponds to specific control, mounting flange, shaft, and port configurations. Every unit undergoes 100% simulated duty-cycle testing before shipment.
Brand Note: Sauer Danfoss was formed in 2000 through the merger of Sauer-Sundstrand and Danfoss Fluid Power, fully acquired by Danfoss A/S in 2013, and officially renamed Danfoss in September of that year. The Series 51 hydraulic product line is currently operated by Danfoss Power Solutions. The 51D080 is widely used in hydrostatic travel drives for harvesters, sprayers, telehandlers, and road rollers.
Technical Specifications
51D080RD2NHSA2CEE1NNN032 (Primary Model)
Model: 51D080RD2NHSA2CEE1NNN032
Brand Series: Sauer Danfoss / Danfoss Series 51 / 51D
Motor Type: Bent-axis axial piston variable motor, DIN flange configuration
Maximum Displacement Vg max: 80.7 cm³/rev (4.92 in³/rev)
Minimum Displacement Vg min: 16.1 cm³/rev (0.98 in³/rev)
Control Ratio: 5:1
Rated Pressure: 480 bar (48 MPa, reference: Series 51 general data)
Maximum Pressure: 510 bar (51 MPa)
Rated Speed: 2200–5600 rpm
Speed Range: 2200–7000 rpm
Rated Flow: 250 L/min (66 US gal/min)
Maximum Flow: 323 L/min (85 US gal/min)
Maximum Corner Power: 403 kW (540 hp)
Rotary Group Inertia: 0.0071 kg·m² (0.1685 lb·ft²)
Mounting: DIN 4-bolt flange
Shaft Type: Splined shaft (ANSI or DIN standard)
Port Connections: Main pressure ports: SAE flange; remaining ports: SAE straight thread O-ring boss
Control Options: Proportional, hydraulic pilot, electro-hydraulic (N1, HZ, E1, E2, E7, F1, F2, T1, T2, TA, TH, EP, EQ, L1, L2, L7, D7, D8, HS)
Displacement Limiter: Mechanical minimum/maximum displacement limiters
Weight: Approximately 32 kg (71 lbs)
Fluid Compatibility: Mineral oil, biodegradable fluids, fire-resistant fluids
Series 51 Other Displacement Sizes (Series Reference)
51D060: Max displacement 60.0 cm³/rev (3.66 in³/rev), min displacement 12.0 cm³/rev (0.73 in³/rev), rated flow 216 L/min (57 US gal/min), max flow 264 L/min (70 US gal/min), max corner power 336 kW (450 hp), weight approx. 28 kg (62 lbs)
51D080: Max displacement 80.7 cm³/rev (4.92 in³/rev), min displacement 16.1 cm³/rev (0.98 in³/rev), rated flow 250 L/min (66 US gal/min), max flow 323 L/min (85 US gal/min), max corner power 403 kW (540 hp), weight approx. 32 kg (71 lbs)
51D110: Max displacement 109.9 cm³/rev (6.71 in³/rev), min displacement 22.0 cm³/rev (1.34 in³/rev), rated flow 308 L/min (81 US gal/min), max flow 396 L/min (105 US gal/min), max corner power 492 kW (660 hp), weight approx. 44 kg (97 lbs)
51D160: Max displacement 160.9 cm³/rev (9.82 in³/rev), min displacement 32.2 cm³/rev (1.96 in³/rev), rated flow 402 L/min (106 US gal/min), max flow 515 L/min (136 US gal/min), max corner power 644 kW (864 hp), weight approx. 56 kg (123 lbs)
51D250: Max displacement 250.0 cm³/rev (15.26 in³/rev), min displacement 50.0 cm³/rev (3.05 in³/rev), rated flow 550 L/min (145 US gal/min), max flow 675 L/min (178 US gal/min), max corner power 850 kW (1140 hp), weight approx. 86 kg (190 lbs)
Note: Series parameters are compiled from the Sauer Danfoss Series 51 technical data table.
51V / 51C Mounting Variants (Series Reference)
51V060–51V250: SAE flange mount variable motors, displacement sizes corresponding one-to-one with the 51D series
51C060–51C250: Cartridge-mount variable motors for direct installation into compact planetary drives, further reducing overall drivetrain dimensions
Key Technical Advantages
① Bent-Axis Spherical Piston Design — High Speed and High Power Density
The 51D080 employs a bent-axis architecture in which pistons contact the drive plate through spherical ends, replacing the slipper design found in conventional axial piston motors. Spherical pistons are less affected by centrifugal forces at high rotational speeds, enabling maximum speeds up to 7000 rpm — significantly higher than typical axial piston motors of equivalent displacement. For direct-drive applications requiring high rotational speeds (travel drives, railway equipment), this characteristic eliminates the need for reduction gearing and simplifies the drivetrain. The 51D080 achieves a maximum corner power of 403 kW, offering power density significantly superior to equivalent axial piston motors.
② 5:1 Large Control Ratio — Wide-Range Stepless Speed Control
The 51D080 achieves a displacement control ratio of 5:1 (80.7 to 16.1 cm³/rev). After starting at maximum displacement for maximum torque, the motor progressively reduces displacement as speed increases, enabling wide-range stepless speed control without altering pump output flow. This characteristic allows smooth transitions between low-speed high-torque and high-speed low-torque operating conditions, ideal for travel-drive systems with varying load demands. Series 51 motors incorporate mechanical minimum and maximum displacement limiters to ensure displacement regulation operates within safe limits.
③ DIN Flange Configuration — Standardized Mounting for European Equipment Platforms
The 51D080 features a DIN 4-bolt flange mounting configuration. Compared to the SAE flange version (51V), the DIN flange offers broader compatibility with European equipment platforms (Claas, Ponsse, Bomag, etc.). The standardized DIN flange mounting dimensions and splined shaft configuration enable direct replacement of equivalent Sauer Danfoss original motors without modifying mounting brackets or piping. DIN flange and SAE flange motors share identical core hydraulic parameters, differing only in mounting interface.
④ Extensive Control Options — Precise Power Management
Series 51 motors offer over a dozen control options including N1, HZ, E1, E2, E7, F1, F2, T1, T2, TA, TH, EP, EQ, L1, L2, L7, D7, D8, and HS. The 51D080 can be equipped with proportional control, hydraulic pilot control, or electro-hydraulic control for continuous displacement adjustment. The pressure compensator functions as a stand-alone regulator and operates in both motor and pump modes, ensuring optimal power utilization throughout the motor’s entire displacement range.
⑤ Compact Lightweight Design and Broad Fluid Compatibility
Despite a displacement of 80.7 cm³/rev, the 51D080 weighs only approximately 32 kg — power density significantly exceeding equivalent axial piston motors. Series 51 motors are compatible with mineral oil, biodegradable hydraulic fluids, and fire-resistant fluids. In forestry, mining, and other applications with specific environmental or fire-safety requirements, the motor can be adapted to the appropriate fluid without replacement, reducing system modification complexity.
Application Areas
Agricultural Machinery (Primary Application): Hydrostatic travel drive systems for Claas Lexion combines, New Holland CR series combines; self-propelled sprayers, grain transport vehicles, telehandlers
Compaction Equipment: Travel drive systems for Bomag BW series, Dynapac CA series vibratory road rollers
Forestry Machinery: Hydrostatic travel drives for Ponsse harvesters, Timberjack forwarders
Construction Machinery: Crawler dozer and railway equipment drive systems, Bobcat telehandler travel drives
Material Handling: Drive systems for Schaeff SKL834 and similar loaders
Mining & Drilling: Underground LHD travel drives, drill rotary drives
Industrial Transmission: Closed-loop hydraulic drive systems, test stand drives
Expert Maintenance Tips
Pre-Installation Inspection: Verify flatness and cleanliness of the DIN 4-bolt flange mating surface. The interface between spherical pistons and the drive plate is extremely precise; avoid impact or scratching during installation. Spline shaft-to-coupling fit must conform to DIN 5480 or ANSI standards; avoid interference fits. Tighten mounting bolts in diagonal sequence to specified torque.
First Commissioning: The motor casing must be filled with clean hydraulic oil before initial start-up. Series 51 officially requires that the installation position must ensure the housing is always filled with hydraulic fluid. Fill through the highest casing port until oil overflows from the level port. Series 51 motors typically start at maximum displacement, producing high instantaneous torque at startup; insufficient casing lubrication causes severe wear on spherical piston-to-drive plate contact surfaces. Closed-loop systems should complete charge pump circuit bleeding before startup.
Fluid Cleanliness and Temperature Control: Maintain system oil cleanliness at NAS 8 (ISO 4406 18/16/13) or better. Oil temperature should remain at least 16°C (30°F) above the pour point of the hydraulic fluid, with maximum temperature not exceeding Series 51 technical manual limits. Viscosity should remain within the recommended range to ensure volumetric efficiency and bearing life.
Control Adjustment Check: Periodically inspect proportional controller response linearity. If displacement regulation exhibits lag or non-linearity, inspect servo spool, shuttle spool, and pressure compensator operation. The Series 51 motor‘s control option can be identified by the end cap configuration; during maintenance, confirm the current configuration matches system requirements.
Scheduled Inspection: Check casing drain flow and output shaft spline wear every 500 operating hours. Under normal conditions, drain flow should remain stable; a sustained increase indicates accelerated wear of piston pairs or valve plate surfaces, and preventive maintenance should be scheduled. Also verify displacement limiter settings are correct, ensuring mechanical stops have not shifted due to vibration.
Long-Term Storage Protection: If the motor will be idle for more than 3 months, fill the casing with rust-preventive hydraulic oil and manually rotate the shaft several turns monthly to prevent corrosion or adhesion on spherical piston-to-drive plate contact surfaces. Perform a no-load run-in before returning to service.
