GM05 SAI Radial Piston Hydraulic Motor 39-191cc 250bar

Product Overview

The GM05, GM1, GM2, GM3, GM4, GM5, GM6, GM7, and GM9 are crankshaft connecting rod radial piston hydraulic motors from the SAI GM series (also known as “internal five-star motors”)—low-speed high-torque (LSHT) radial piston hydraulic motors. The series features a crankshaft connecting rod radial piston architecture with multiple pistons radially arranged in a star configuration.

The GM series motors represent a comprehensive upgrade from SAI’s previous M, L, and P series, incorporating decades of field experience with multiple design improvements in casing strength and internal dynamic component load capacity. The series is renowned for its high continuous power ratings, high mechanical efficiency, and high volumetric efficiency, with reduced internal specific loads minimizing heat generation and its negative effects.

The GM series covers displacements from 39 to 12000 cc/rev with torque ratings from 200 to 48000 N.m. Rated working pressure is 25 MPa (250 bar) with peak pressures up to 450 bar.

The GM18, GM21, GM35, GM38, and GM60 belong to the Nabtesco GM series travel motors (Final Drives)—integrated units combining hydraulic motor, planetary gearbox, and parking brake in a single housing, specifically designed for crawler excavator travel drive systems. The GM18 is for medium excavators, GM21 for 20-25 ton class excavators, GM35 for 30-35 ton class excavators, GM38 for 20 ton class excavators, and GM60 for large excavators.

Important Note: The “GM” series designation is used by both SAI (Italy / licensed manufacturing) and Nabtesco (Japan) for different types of hydraulic motor products. SAI GM series are standalone radial piston motors, while Nabtesco GM series are integrated travel motor final drives. Please confirm the required model based on equipment type and mounting interface.

Designed as 100% interchangeable direct replacements for original SAI GM series and Nabtesco GM series motors, these products match OEM specifications in mounting dimensions, porting interfaces, and performance characteristics. Every unit undergoes 100% simulated duty cycle testing prior to shipment, validating volumetric efficiency, mechanical efficiency, and sealing integrity under actual operating load conditions.

Technical Specifications (Bulleted List)

SAI GM Series (GM05, GM1, GM2, GM3, GM4, GM5, GM6, GM7, GM9)

General Specifications:

• Brand: SAI (Italy) / Licensed Manufacturing

• Product Type: Crankshaft Radial Piston Hydraulic Motor (Internal Five-Star Motor)

• Rated Pressure: 250 bar (25 MPa)

• Peak Pressure: Up to 450 bar (model dependent)

• Displacement Range: 39 – 12000 cc/rev

• Torque Range: 200 – 48000 N.m

• Continuous Speed: 225 – 1000 r/min (model dependent)

• Rotation Direction: Reversible

• Structure Type: Crankshaft connecting rod radial piston, 5-9 pistons

• Circuit Type: Open circuit

GM05 Series (GM05-60 to GM05-200)

• Displacement Range: 39 – 191 cc/rev

• Peak Power: 33 kW

• Max Speed: 800 – 1000 rpm

• Piston Bore: 25 – 45 mm

• Specific Torque: 0.62 – 3.04 Nm/bar

• Rated Pressure: 250 bar

• Peak Pressure: 280 – 450 bar (model dependent)

GM1 Series (GM1-100 to GM1-350)

• Displacement Range: 99 – 314 cc/rev

• Peak Power: 45 kW

• Max Speed: 600 – 1000 rpm

• Specific Torque: 1.54 – 4.90 Nm/bar

GM2 Series (GM2-200 to GM2-630)

• Displacement Range: 192 – 623 cc/rev

• Peak Power: 59 kW

• Max Speed: 650 – 900 rpm

• Specific Torque: 3.00 – 9.73 Nm/bar

GM3 Series (GM3-350 to GM3-1000)

• Displacement Range: 352 – 987 cc/rev

• Peak Power: 80 kW

• Max Speed: 400 – 700 rpm

• Specific Torque: 5.49 – 15.4 Nm/bar

GM4 Series (GM4-600 to GM4-1300)

• Displacement Range: 402 – 1316 cc/rev

• Peak Power: 100 kW

• Max Speed: 350 – 600 rpm

• Specific Torque: 6.27 – 20.5 Nm/bar

GM5 / GM5A Series (GM5-800 to GM5-2000)

• Displacement Range: 526 – 2007 cc/rev

• Peak Power: 120 kW

• Max Speed: 250 – 500 rpm

• Specific Torque: 8.22 – 31.3 Nm/bar

GM6 Series (GM6-1700 to GM6-3000)

• Displacement Range: 1690 – 3041 cc/rev

• Peak Power: 170 kW

• Max Speed: 250 – 400 rpm

• Specific Torque: 26.4 – 47.5 Nm/bar

GM7 Series (GM7-2000 to GM7-4300)

• Displacement Range: 1373 – 4298 cc/rev

• Peak Power: 250 kW

• Max Speed: 300 – 450 rpm

Nabtesco GM Travel Motor Series (GM18, GM21, GM35, GM38, GM60)

General Specifications:

• Brand: Nabtesco (Japan)

• Product Type: Travel Motor / Final Drive

• Structure Type: Integrated hydraulic motor + planetary gearbox + parking brake

• Control Type: Two-speed available (model dependent)

• Circuit Type: Closed circuit

• Rotation Direction: Reversible

GM18

• Applicable Equipment: Medium excavator travel drives

• Features: Integrated hydraulic motor + planetary gearbox + parking brake

GM21 (GM21VA Series)

• Applicable Equipment: 20-25 ton crawler excavators (Komatsu PC138USLC-8, etc.)

• Control Type: Two-speed travel motor

• Main Variants: GM21VA-A-43/76-2, GM21VA-A-44/79-1

GM35 (GM35VA / GM35VL Series)

• Applicable Equipment: 30-35 ton crawler excavators

• Applicable Brands: Volvo EC240, etc.

• Features: Integrated hydraulic motor + planetary gearbox + parking brake

• Nominal Pressure: 32 MPa

GM38 (GM38H / GM38VB / GM38VL Series)

• Applicable Equipment: 20 ton crawler excavators

• Applicable Brands: JCB JS210, Kobelco SK200-8, etc.

• Features: High-strength integrated cast housing, high impact load resistance

• Pressure Rating: High-pressure design for heavy-duty conditions

GM60 (GM60VA Series)

• Applicable Equipment: Large crawler excavators

• Applicable Brands: Kobelco SK330-8 / SK350-8, Sany SY305, Sumitomo SH350, etc.

• Features: Integrated hydraulic motor + planetary gearbox + parking brake in compact housing

Key Technical Advantages

SAI GM Series

1. Crankshaft Radial Piston Design for High Torque Output

The GM series employs a crankshaft connecting rod radial piston architecture with radially arranged pistons. Radial injection cylinder feed eliminates direct hydraulic axial loading of the motor casing. Larger cylinder feed channels reduce power loss with high flows. The GM series delivers torque from 200 to 48000 N.m, meeting requirements from light-duty to ultra-heavy-duty applications.

2. High Continuous Power with Superior Efficiency

Through reduced internal specific loads combined with high mechanical and volumetric efficiency, GM series motors deliver exceptional continuous power ratings while minimizing heat generation and its associated negative effects. Cylinder trunnions with hydraulic balancing reduce friction, wear, and heat generation, enabling operation with higher powers and improved efficiency.

3. High-Capacity Bearings with Reinforced Castings

High-capacity bearings support applications requiring high lifetime, high power/pressure, and high external loads. Stronger castings with internal reinforcement ribbing provide increased casing strength and stiffness for higher internal and external load capacity. Larger cylinder trunnions deliver increased strength and stiffness with reduced specific loads.

4. 100% Interchangeability – Zero-Modification Drop-In Replacement

Manufactured to exact OEM mounting dimensions, porting specifications, and performance standards, these motors achieve 100% interchangeability with original SAI GM series units. No machine modifications are required—simply replace and resume operation, minimizing downtime and reducing maintenance costs.

5. 100% Simulated Duty Cycle Testing for Extreme Environment Reliability

Every motor undergoes 100% simulated duty cycle testing before shipment, validating performance under rated pressure (250 bar) and peak pressure conditions—ensuring long-term reliability in demanding injection molding, mobile, and industrial applications.

6. Modular Design with Broad Compatibility

GM series maintains compatibility with shafts, adaptors, and distributors of the preceding M, L, and P series motors. Component standardization increases modularity and flexibility for displacement interchangeability, spare parts management, and option configurations. A reduced number of components enables a simpler and more reliable design. Compatibility with non-polluting oils is supported.

7. Wide Displacement Coverage with High Speed Range

The GM series covers displacements from 39 to 12000 cc/rev with continuous speeds from 225 to 1000 r/min. The wide speed range with excellent low-speed stability enables both low-speed high-torque and high-speed requirements from a single motor.

Nabtesco GM Travel Motor Series

1. Integrated Compact Design

Nabtesco GM series travel motors integrate hydraulic motor, planetary gearbox, and parking brake in a single housing, minimizing external connections and simplifying travel system maintenance.

2. High Impact Load Resistance

High-strength integrated cast housing provides exceptional structural rigidity and resistance to impact loads for heavy-duty excavator travel applications.

3. Two-Speed Control for Flexible Operation

Models such as the GM21 support two-speed travel control, enabling flexible speed selection across varying terrain conditions.

Application Areas

SAI GM Series

• Injection Molding Machinery: Screw drives

• Construction Equipment: Roller travel drives, tracked travel mechanism drives

• Hoisting & Transport: Hoist winches, drum drives, rotary mechanism drives

• Mining Equipment: Mining and construction machinery hydraulic drives

• Metallurgical Machinery: Heavy metallurgical equipment hydraulic drives

• Petroleum & Coal Mining: Oil drilling equipment, coal mining machinery hydraulic drives

• Marine Industry: Marine deck machinery hydraulic drives

• Geological Drilling: Geological drilling equipment hydraulic drives

• Light Industrial Machinery: Light industry hydraulic transmissions

Nabtesco GM Travel Motor Series

• Crawler Excavator Travel Drives: GM18 (medium), GM21 (20-25T), GM35 (30-35T), GM38 (20T), GM60 (large)

Expert Maintenance Tips

SAI GM Series

1. Pre-Installation Preparation: Before using the GM series motor, read and understand the complete SAI instruction manual. For first commissioning, fill the motor housing with hydraulic fluid using a filling unit with filtration not less than 10 µm. Never operate the motor without fluid.

2. Case Drain Pressure Monitoring: Radial piston motors are sensitive to housing backpressure. Ensure the case drain line is unobstructed and returns to a separate oil tank to prevent seal damage from excessive housing pressure.

3. Coupling Alignment: Precise alignment between the motor shaft and drive shaft is required with minimal tolerance. After installation, manually rotate the coupling to verify smooth operation.

4. Oil Cleanliness Control: Recommended system filtration not less than ISO 4406 18/13. Regular oil analysis is recommended with filter change intervals adjusted based on contamination levels.

5. Working Pressure Selection: GM series rated pressure is 250 bar with peak pressures up to 450 bar. Select the appropriate pressure grade based on the duty cycle of your specific application—avoid prolonged operation at peak pressure levels.

6. Regular Inspection Schedule: Regular inspection of the hydraulic system and motor is recommended. Check hydraulic fluid level daily and monitor operating temperature, noise levels, and case drain flow regularly. Abnormal increases may indicate internal wear or seal degradation.

7. Rotation Direction: GM series motors feature reversible rotation—confirm inlet/outlet port connections based on actual requirements during installation.

Nabtesco GM Travel Motor Series

1. Pre-Installation Inspection: Before installing the travel motor final drive, ensure the gearbox mounting flange and spline interface are clean and free of contaminants.

2. Brake System Check: Nabtesco GM series integrates a parking brake—confirm brake oil line connections are correct and brake pressure meets requirements after installation.

3. Travel Motor Bleeding: Before first commissioning, perform bleeding of the travel motor final drive to ensure no air remains in the housing.

4. Regular Inspection: Regularly inspect the travel motor final drive for noise levels, operating temperature, and leakage. Abnormal increases may indicate internal wear.

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