JMDG8-800 Radial Piston Hydraulic Motor 810cc 20MPa High Torque

Product Overview

The JMDG8-800 and JMDG6-750 are crankshaft connecting rod radial piston hydraulic motors from the JMDG series (also known as “external five-star motors”)—low-speed high-torque (LSHT) radial piston hydraulic motors. The series features a five-piston eccentric shaft structure with five pistons radially arranged at 72° intervals in a five-star configuration.

The JMDG series motors are designed and manufactured according to Italian standards with adaptations for the Chinese market. Key components are machined on imported machining centers and CNC equipment, with castings produced using polyester sand ductile iron precision casting. All seals and high-strength hexagon socket screws are imported from Germany, Italy, and Taiwan.

Designed as 100% interchangeable direct replacements for original JMDG 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.

The JMDG series is widely applied in hydraulic transmission systems for petroleum, chemical, mining, marine, and construction machinery—particularly suited for injection molding machine screw drives, winches, drums, various rotary mechanism drives, and tracked or wheeled travel drives.

Technical Specifications 

JMDG8-800

• Model: JMDG8-800

• Series: JMDG8 Crankshaft Connecting Rod Radial Piston Motor (External Five-Star Motor)

• Theoretical Displacement: 810 ml/r

• Rated Pressure: 14–20 MPa

• Max Working Pressure: 16–25 MPa

• Rated Torque: 1661 N.m

• Max Output Torque: 1888–2396 N.m

• Speed Range: 4–400 r/min

• Max Power: 120 kW

• Weight: Approx. 120 kg

• Structure Type: Crankshaft Connecting Rod Radial Piston

• Piston Quantity: 5 pistons (five-star configuration)

• Rotation Direction: Reversible

• Operating Oil Temperature: 20°C–80°C

JMDG6-750

• Model: JMDG6-750

• Series: JMDG6 Crankshaft Connecting Rod Radial Piston Motor (External Five-Star Motor)

• Theoretical Displacement: 754 ml/r

• Rated Pressure: 14–16 MPa

• Max Working Pressure: 16–20 MPa

• Rated Torque: 1546 N.m

• Max Output Torque: 1760 N.m

• Speed Range: 4–350 r/min

• Max Power: 110–112 kW

• Weight: Approx. 110 kg

• Structure Type: Crankshaft Connecting Rod Radial Piston

• Piston Quantity: 5 pistons (five-star configuration)

• Rotation Direction: Reversible

• Operating Oil Temperature: 20°C–80°C

Note: Pressure and torque parameters may vary across different manufacturers and configurations. Please refer to the corresponding technical manual for specific model details.

Key Technical Advantages

1. Crankshaft Connecting Rod Radial Piston Design for Extreme Torque Output

The JMDG series employs a crankshaft connecting rod radial piston architecture with five radially arranged pistons at 72° intervals. Roller bearings between the crankshaft and connecting rods deliver high mechanical efficiency. This design enables the motor to deliver massive torque at low speeds—the JMDG8-800 achieves up to 2396 N.m maximum output torque.

2. Five-Piston Eccentric Shaft Structure for Low-Noise Operation

The eccentric shaft design with lower excitation frequency five-piston configuration delivers exceptionally low noise output. This makes the JMDG series particularly suitable for indoor equipment and work sites with strict noise requirements.

3. 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 JMDG series units. No machine modifications are required—simply replace and resume operation, minimizing downtime and reducing maintenance costs.

4. 100% Simulated Duty Cycle Testing for Extreme Environment Reliability

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

5. Excellent Low-Speed Stability with Wide Speed Range

With optimized structural design reducing friction losses and improving sealing performance, JMDG series motors deliver exceptional low-speed stability—operating smoothly at speeds as low as 1 r/min. The wide speed range spans from 3–4 r/min minimum to 400–500 r/min maximum.

6. High Starting Torque with Superior Efficiency

Starting mechanical efficiency reaches 0.9 or higher, ensuring reliable torque output during heavy-load start-up. Roller bearing support between the crankshaft and connecting rods further enhances mechanical efficiency.

7. Precision Casting with Imported Machining – Quality Assurance

Castings utilize ductile iron precision casting, with critical components machined on imported machining centers and CNC equipment. All seals and high-strength fasteners are imported from Germany, Italy, and Taiwan. Precision machining of critical friction pairs ensures long-term reliability under high-load and high-impact conditions.

8. Low Oil Sensitivity with Wide Temperature Adaptability

JMDG series motors exhibit low sensitivity to oil quality and operate normally across oil temperatures from 20°C to 80°C. This characteristic enables stable operation even in applications with less-than-ideal fluid cleanliness conditions.

Application Areas

• Construction Equipment: Excavator travel drives, tracked travel mechanisms, rotary mechanism drives

• Building Machinery: Concrete mixers, tower crane rotary drives

• Mining Equipment: Mine hoists, mining transport equipment travel drives

• Injection Molding Machinery: Injection molding machine screw drives

• Marine & Port: Winch drives, drum drives, deck machinery

• Petroleum & Chemical: Oil drilling equipment, chemical machinery hydraulic drives

• Metallurgical Machinery: Metallurgical equipment hydraulic drives

• Hoisting Machinery: Hoists, crane rotary and travel drives

• Agricultural Machinery: Large agricultural machinery travel drives

Expert Maintenance Tips

1. Housing Pressure Limits: JMDG series motor housing working pressure is 0.1 MPa, with maximum pressure of 0.5 MPa. Ensure the case drain line is unobstructed during installation to prevent seal damage from excessive housing pressure.

2. Pre-Installation Preparation: Before using the JMDG series motor, read and understand the complete 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.

3. Working Pressure Selection: JMDG series hydraulic motors have continuous working rated pressures of 16 MPa, 20 MPa, and 25 MPa. Select the actual working pressure based on the motor’s service life requirements.

4. Oil Temperature Control: Ensure the hydraulic system operating oil temperature remains within the 20°C–80°C range to prevent viscosity reduction and seal degradation from excessive temperatures.

5. Seal Maintenance: Use OEM-specification imported seals to ensure sealing performance and service life.

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