Product Overview
The 51C080-1-RD3NE2B1NNU1ACB045AAF00000 is an 80 cm³/rev displacement model from the Sauer Danfoss (Sauer-Danfoss) Series 51 bent-axis axial piston variable motor family, featuring spherical piston bent-axis design and electrohydraulic proportional control. Displacement is infinitely variable between 80.7 cm³/rev maximum and 16.1 cm³/rev minimum for a 5:1 ratio. Series 51 motors are designed primarily to be combined with other products in closed-circuit systems to transfer and control hydraulic power, making them ideal for travel drive and tool drive applications.
The model code breaks down as follows: 51C080 identifies the Series 51 C-type variable motor with 80.7 cm³/rev displacement; 1 indicates 51-1 generation design; RD3N is the rotation and shaft configuration code; E2B1 is the electrohydraulic proportional control type (24 VDC solenoid); NNU1 is the port and mounting configuration code; ACB045 is the regulator and control option code; AAF00000 is the standard option combination. This model corresponds to Danfoss part number 83002135.
Series 51 motors achieve a 5:1 maximum-to-minimum displacement ratio with high output speed capability, and are available with SAE, cartridge and DIN flange configurations. Motors normally start at maximum displacement, providing maximum starting torque for high acceleration. Controls may utilize internally or externally supplied servo pressure and may be overridden by a pressure compensator for optimized power utilization.
Every 51C080 unit undergoes 100% simulated operating-condition bench testing prior to shipment. Mounting flange, shaft end and port dimensions comply with SAE/DIN standards and are identical to the original Sauer Danfoss 51C080, ensuring true drop-in interchangeability with zero modification required.
Technical Specifications
Series 51 Frame Size Specifications:
51C060: 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 ~28 kg (62 lb), mass moment of inertia 0.0046 kg·m²
51C080 (This Model): 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 ~32 kg (71 lb), mass moment of inertia 0.0071 kg·m²
51C110: 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 ~44 kg (97 lb), mass moment of inertia 0.0128 kg·m²
51C160: 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 ~56 kg (123 lb), mass moment of inertia 0.0234 kg·m²
51C250: 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 ~86 kg (190 lb), mass moment of inertia 0.0480 kg·m²
51C080-1-RD3NE2B1NNU1ACB045AAF00000 Additional Specifications:
Model Code: 51C080-1-RD3NE2B1NNU1ACB045AAF00000
Manufacturer Part Number: 83002135
Type: Bent axis axial piston variable motor, spherical piston design
Displacement (Maximum): 80.7 cm³/rev (4.92 in³/rev)
Displacement (Minimum): 16.1 cm³/rev (0.98 in³/rev)
Displacement Ratio: 5:1
Rated Working Pressure: 480 bar (7,000 psi)
Peak Pressure (Intermittent): 510 bar (7,400 psi)
Rated Speed Range: 2,200–5,600 rpm
Maximum Speed: 7,000 rpm
Rotation: Bi-directional (clockwise / counter-clockwise)
Control Type: E2B1 electrohydraulic proportional control, 24 VDC solenoid, 14.7 W
Mounting Type: SAE 4-bolt flange / 2-bolt cartridge
Shaft Configuration: SAE or DIN splined shaft
Port Connections: Main pressure ports SAE flange; remaining ports SAE straight thread O-ring boss
Temperature Range: -40°C to +115°C
Weight: ~32 kg (71 lb)
Mass Moment of Inertia: 0.0071 kg·m²
Circuit Type: Closed circuit
Standard Features: Integral loop flushing valve, mechanical displacement limiters
Key Technical Advantages
1. Spherical Piston Bent-Axis Design for High Startup Torque and Wide-Range Efficiency
The 51C080 employs Sauer Danfoss Series 51’s signature bent-axis design, with the cylinder block angled relative to the output shaft and spherical pistons with piston rings acting against a thrust plate. Motors normally start at maximum displacement, providing maximum starting torque for high acceleration. The 5:1 wide displacement ratio (80.7/16.1 cm³/rev) enables a single motor to cover the full spectrum from low-speed high-torque to high-speed low-torque operation, significantly simplifying hydraulic system design.
2. High Pressure Capability — 480 Bar Rated
The 51C080 supports 480 bar rated working pressure and 510 bar peak pressure, with rated flow of 250 l/min and maximum flow of 323 l/min delivering up to 403 kW maximum corner power. This power density offers significant advantages in travel drive and tool drive applications requiring high torque density.
3. E2B1 Electrohydraulic Proportional Control for Precise Displacement Modulation
The E2B1 control configuration features 24 VDC electrohydraulic proportional control drawing only 14.7 W, with a solenoid valve mounted on the multi-function block connecting the control valve spool end with pilot pressure or motor case. Controls may utilize internally or externally supplied servo pressure and may be overridden by a pressure compensator for optimal power utilization in both motor and pump modes. The pressure compensator features low pressure rise (short ramp), ensuring optimal power utilization throughout the motor’s entire displacement range.
4. Integral Loop Flushing and Mechanical Displacement Limiters
Series 51 motors incorporate an integral loop flushing valve as standard equipment in closed-circuit applications, maintaining circuit fluid cleanliness and temperature control. Mechanical displacement limiters allow the minimum displacement to be limited within the standard range via a set screw in the motor housing, while maximum displacement can be limited with spacers installed on the servo piston.
5. 100% Simulated Load Testing & Drop-In Interchangeability
Each 51C080 unit is bench-tested under simulated operating conditions prior to dispatch, covering pressure cycling, displacement response and thermal variation. Mounting flange, shaft end and port dimensions comply with SAE/DIN standards, matching the original Sauer Danfoss 51C080 exactly, enabling direct replacement without pipework or interface modification.
Application Areas
The 51C080 is deployed across demanding closed-circuit hydrostatic transmission applications:
Road Rollers: Bomag BW series, Dynapac CA series vibratory roller travel drives
Telescopic Handlers: Manitou MLT/MRT series, Merlo series
Skid Steer Loaders: Bobcat, Gehl, Mustang and other brands’ travel drive systems
Agriculture: combine harvester hydrostatic travel drives, reverse-PTO drivetrains in narrow-orchard tractors
Construction: asphalt pavers, trenchers, compact track loaders
Industrial: closed-circuit hydrostatic transmission systems
Expert Maintenance Tips
1. Control Signal Calibration and Displacement Verification: The E2B1 electrohydraulic proportional control requires control signal calibration after installation to confirm minimum and maximum displacement positions match the technical manual. Pilot control pressure should remain stable within the technical manual specified range with ±1 bar variation. If displacement response exhibits lag or drift, inspect the control spool for sticking and the pilot circuit for air entrainment.
2. Loop Flushing Valve Maintenance: The 51C080 features an integral loop flushing valve as standard. Periodically inspect its operating condition. Insufficient flushing flow causes circuit oil temperature rise and contamination accumulation, affecting motor life. Inspect flushing valve flow and pressure settings every 1,000 hours. Installation position is recommended with the control at the top or side.
3. Displacement Limiter Adjustment: Minimum displacement is adjustable via a set screw in the motor housing; maximum displacement is adjustable via spacers on the servo piston. After adjustment, verify displacement response matches the control system to avoid conflict between mechanical limits and electrical control.
4. Oil Cleanliness and Temperature Control: Maintain system oil cleanliness at ISO 4406 18/16/13 or better. Case drain temperature is affected by pressure and speed and is always higher than circuit temperature—system temperature must not exceed 115°C at any point. Replace hydraulic oil and filter after the first 500 hours, then follow a 2,000-hour or annual replacement cycle.
5. Drain Line Management: The drain port must return to the reservoir independently—housing back pressure must not exceed 2 bar. The drain line end must remain submerged to prevent air ingestion. After extended shutdown, fill the housing with clean hydraulic oil before restarting.
6. Periodic Spherical Piston and Cylinder Bore Inspection: Inspect spherical piston-to-cylinder bore clearance, piston ring wear and bent-axis bearing clearance every 2,000 hours. Abnormal efficiency loss or noise requires immediate shutdown and service. Use original specification parts when replacing piston groups to ensure fit accuracy.
