SAI GM Series Orbital Piston Motor | GM1 GM2 GM3 GM5 GM7 | High Torque Radial Piston Motor

Chengyuan Hydraulic offers the GM Series (GM1, GM2, GM3, GM4, GM5, GM5A, GM6, GM7, GM9) and JMDG Series (e.g., JMDG6-700B/750) radial piston hydraulic motors, precision-engineered as premium replacements for SAI (Italy) industrial standards.

Utilizing a classic crankshaft and connecting rod structure, these motors are renowned for their exceptional mechanical efficiency and high starting torque in heavy-duty applications. Chengyuan ensures 100% Drop-in Interchangeability for all mounting flanges, shaft splines, and porting configurations. Supported by our 100% Simulation Load Testing, each GM motor is verified for low-speed stability and volumetric efficiency, providing continuous, smooth power for plastics machinery, marine deck equipment, and mining systems.

Technical Specifications 

• Series Category: GM Series / JMDG Series

• Displacement Range: 60 $cm^3$/rev to 12,000 $cm^3$/rev (e.g., GM2-200 is 200cc; JMDG6-700B is 700cc)

• Rated Pressure: 250 bar (25 MPa)

• Peak Pressure: Up to 350 bar – 400 bar (size dependent)

• Rated Speed: 1 rpm to 800 rpm (excellent ultra-low speed stability)

• Max Output Torque: Up to 40,000 Nm (for large GM7/GM9 models)

• Housing Material: High-strength Ductile Iron

• Sealing: High-precision wear-resistant composite seals (high-temp capable)

• Weight: 25 kg to over 500 kg (increases with displacement)

Key Technical Advantages:

• Crankshaft & Con-rod Balanced Design: The five-star radial layout uses hydrostatic balanced bushings between the connecting rod and crankshaft. This minimizes friction, achieving a starting torque efficiency of over 90%, ideal for heavy-load startups.

• High Volumetric Efficiency Distributor: Features a patented rotary distribution shaft, precision-ground to ensure minimal internal leakage. This allows for smooth operation even at speeds below 1 rpm without the “crawling” effect.

• Heavy-Duty Bearing System: Large internal roller bearings are designed to handle significant axial and radial external loads. In winch or wheel drive applications, these motors can operate under load without auxiliary support.

• Modular Flexibility: Supports integrated functional valve blocks (e.g., balance valves, relief valves) and mechanical brakes. Both single and dual-displacement models offer seamless integration with original systems.

Application Areas:

• Plastics Machinery: Injection molding screw drives and extruder rotation systems.

• Marine & Port: Winches, crane hoists, deck cranes, and steering gear.

• Mining & Construction: Roadheader cutter drives, heavy-duty conveyors, and wheel drive systems.

• Agriculture: Harvester drives and large-scale sprayer power systems.

Expert Maintenance Tips:

• Case Priming: Before the first startup, fill the motor case with clean hydraulic oil via the drain port to lubricate the crankshaft and con-rod bearings. Never start the motor dry.

• Case Drain Backpressure: The drain line must lead directly back to the tank. Backpressure should be kept below 2 bar; excessive pressure will damage the shaft seal and degrade performance.

• Vertical Installation: If the motor is installed vertically (shaft up), a special air bleed line must be installed to prevent air pockets that could cause insufficient lubrication of the upper bearings.