GM1-300-1HD40 SAI Radial Piston Motor 290cc 250bar

Product Overview

The GM1-300-1HD40 is a mid-displacement radial piston hydraulic motor from the SAI GM series, GM1 frame size. With a displacement of 290 cm³/rev, it delivers a rated working pressure of 250 bar, peak pressure of 300 bar, continuous speed of 350 rpm, maximum speed of 650 rpm, and theoretical specific torque of 4.52 N·m/bar. The model code decodes as: “GM1” = series and frame size, “300” = displacement group, “1H” = standard single-speed configuration, “D40” = 40mm splined shaft and associated port configuration.

The GM series motors employ a classic five-piston radial oscillating-cylinder design driven by an eccentric crankshaft, delivering smooth low-speed high-torque output across a wide speed range. The GM1 sub-series covers displacements from 99 cm³/rev to 314 cm³/rev, with a uniform rated pressure of 250 bar and peak pressures ranging from 280 to 425 bar depending on displacement specification. The GM1-300 offers a peak pressure of 300 bar, suitable for medium-pressure heavy-duty drive applications.

The motor offers complete interchangeability: mounting dimensions and over 80% of internal components are interchangeable with the original SAI GM1 series motors, enabling drop-in replacement without hose or flange modification. Every unit undergoes 100% simulated duty-cycle testing before shipment, covering full-load pressure cycling, thermal balance verification, and shock-load validation.

Technical Specifications

• Model: GM1-300-1HD40

• Brand Series: SAI GM Series / GM1

• Motor Type: Radial piston, fixed displacement, low-speed high-torque

• Displacement: 290 cm³/rev

• Rated Working Pressure: 250 bar

• Peak Pressure: 300 bar

• Continuous Speed: 350 rpm

• Maximum Speed: 650 rpm

• Theoretical Specific Torque: 4.52 N·m/bar

• Piston Diameter: 48 mm

• Shaft Stroke: 32 mm

• Peak Power: 48 kW (65 HP)

• Mounting: Flange mount

• Shaft Type: 40 mm splined shaft (D40 configuration)

• Rotation: Bi-directional

• Weight: Approximately 31 kg (reference: GM1-100 equivalent)

• Operating Temperature Range: -20°C to +80°C

Note: Specifications are compiled from SAI GM1 series official technical data and industry standard references. The GM1-300 is listed at 290 cm³/rev in most technical documents, with a 304 cm³/rev variant also available.

Key Technical Advantages

① Five-Piston Radial Oscillating-Cylinder Design — Low-Speed Smoothness and High Starting Torque

The GM1-300-1HD40 utilizes a five-piston radial arrangement with eccentric crankshaft-driven oscillating cylinder assemblies. The sequential firing of multiple pistons ensures continuous torque output even at extremely low speeds, with a minimum stable speed of 1 rpm that effectively suppresses stick-slip behavior. Starting torque reaches over 90% of theoretical value, excelling in winch, slew drive, and other high-inertia breakaway applications.

② Wide Speed Range — Adaptable to Diverse Operating Conditions

The speed range of 350 rpm continuous and 650 rpm maximum covers applications from precise positioning to rapid slewing. Combined with a minimum stable speed of 1 rpm, the motor offers significant advantages in hydraulic systems requiring wide-range stepless speed control, enabling full-range drive from extremely low to moderate-high speeds without additional reduction gearing.

③ High Volumetric Efficiency and Cavitation Resistance

The piston-to-bore running surfaces are precision-lapped with optimized port window design, maintaining low internal leakage across a wide pressure range. The motor also exhibits excellent cavitation resistance, effectively suppressing cavitation damage in closed-loop circuits or systems with frequent direction changes. SAI official documentation states that “high mechanical and volumetric efficiency and excellent cavitation resistance make them ideal products for any circuit that requires reliability, high performance, and speed control”.

④ Compact Lightweight Design — High Power Density

Despite a displacement of 290 cm³/rev, the GM1-300 weighs only approximately 31 kg, offering superior power density compared to equivalent axial piston motors. The compact design provides significant packaging advantages in space-constrained installations such as marine deck machinery and injection molding machine clamping units.

⑤ Splined Shaft and High-Capacity Bearings — Radial Load Capability

The D40 configuration features a 40mm splined shaft conforming to DIN 5462 standards, paired with high-capacity output bearings that directly accommodate radial loads from belt, chain, or gear drives. The output shaft supports bi-directional rotation, simplifying directional valve configuration in hydraulic circuits.

Application Areas

• Marine: Deck machinery, hatch cover drives, winches

• Injection molding: Clamping mechanisms, turntable drives

• Lifting & transportation: Crane slew and hoist mechanisms, windlasses

• Mining & drilling: Geological prospecting equipment, drill rotary drives

• Metallurgical machinery: Continuous casting auxiliary drives, rolling mill auxiliary transmissions

• Construction machinery: Excavator swing drives, compactor travel drives

• Light industry: Plastic machinery, packaging machinery hydraulic transmission systems

Expert Maintenance Tips

Pre-Installation Inspection: Verify flatness and cleanliness of the mounting flange mating surface. Spline shaft-to-coupling or drive-wheel fit must conform to DIN 5462 standards (40mm spline); avoid interference fits that could damage the spline. Use bolts of strength class 8.8 or higher, tightened in diagonal sequence to specified torque.

Casing Oil Filling: The casing must be filled with clean hydraulic oil before initial start-up. Fill through the highest casing port until oil overflows from the level port. Dry starting causes metal-to-metal contact between piston and bore surfaces without lubrication, resulting in irreversible damage.

Fluid Cleanliness: Maintain system oil cleanliness at NAS 8 (ISO 4406 18/16/13) or better. The precision-matched piston-to-bore surfaces are sensitive to particulate contamination; excessive contamination accelerates wear and causes volumetric efficiency degradation.

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 piston-pair wear, and preventive maintenance should be scheduled. Also inspect the spline interface for abnormal clearance increase or wear marks.

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 piston-bore interfaces and bearings.