GM1-200-1H-D40 SAI Radial Piston Motor 201cc 250bar

Product Overview

The GM1-200-1H-D40 is a mid-displacement radial piston hydraulic motor from the SAI (SAI Motori Idraulici) GM series, GM1 frame size. The motor employs 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 motor offers a theoretical displacement of 201 ml/r, rated working pressure of 25 MPa, peak pressure of 35 MPa, rated torque of 785 N·m, maximum power of 48 kW, continuous speed range of 1–800 rpm, and weight of approximately 31 kg. The model code decodes as: “GM1” = series and frame size, “200” = displacement group, “1H” = standard single-speed configuration, “D40” = 40mm splined shaft and associated port configuration.

The GM series is SAI‘s flagship radial piston motor product line, spanning nine frame sizes — GM05, GM1, GM2, GM3, GM4, GM5, GM6, GM7, and GM9 — with displacements from 59 cc/rev to 12000 cc/rev and peak pressures from 270 to 450 bar. Frame size displacement ranges are as follows: GM05 covers 39–191 cm³/r, GM1 covers 99–314 cm³/r, GM2 covers 192–623 cm³/r, GM3 covers 352–987 cm³/r, GM4 covers 402–1316 cm³/r, GM5 covers 526–2007 cm³/r, GM6 covers 1690–3041 cm³/r, and GM7 covers 1373–4298 cm³/r.

Series-Related Models: The GM2-630-7H-D40 in the original title belongs to the GM2 frame size, with theoretical displacement of 623 ml/r, rated pressure of 25 MPa, peak pressure of 28 MPa, rated torque of 2433 N·m, maximum power of 59 kW, and continuous speed of 650 rpm. The GM1-150, GM1-200, GM1-250, GM1-300, and GM1-320 are displacement variants under the GM1 frame, sharing mounting dimensions and over 80% of internal components with original SAI GM1 series motors.

The motor offers complete interchangeability: mounting flange, splined shaft, and port configuration are identical to the original SAI specification. Every unit undergoes 100% simulated duty-cycle testing before shipment.

Technical Specifications 

GM1-200-1H-D40 (Primary Model)

• Model: GM1-200-1H-D40

• Brand Series: SAI GM Series / GM1

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

• Theoretical Displacement: 201 ml/r

• Rated Working Pressure: 25 MPa (250 bar)

• Peak Pressure: 35 MPa (350 bar)

• Rated Torque: 785 N·m

• Specific Theoretical Torque: 31.4 N·m/MPa

• Maximum Power: 48 kW

• Continuous Speed Range: 1–800 rpm

• Maximum Speed: 800 rpm

• Piston Diameter: 40 mm

• Shaft Stroke: 32 mm

• Mounting: Flange mount

• Shaft Type: 40 mm splined shaft (D40 configuration, DIN 5480 standard)

• Rotation: Bi-directional

• Weight: Approximately 31 kg

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

GM1 Series Displacement Variants (Series Reference)

• GM1-100: Theoretical displacement 99 ml/r, rated pressure 25 MPa, peak pressure 42.5 MPa, rated torque 385 N·m, specific torque 15.4 N·m/MPa, max speed 1000 rpm, weight 31 kg

• GM1-150: Theoretical displacement 154 ml/r, rated pressure 25 MPa, peak pressure 40 MPa, rated torque 600 N·m, specific torque 24 N·m/MPa, max speed 1000 rpm, weight 31 kg

• GM1-175: Theoretical displacement 172 ml/r, rated pressure 25 MPa, peak pressure 37.5 MPa, rated torque 670 N·m, specific torque 26.8 N·m/MPa, max speed 900 rpm, weight 31 kg

• GM1-200: Theoretical displacement 201 ml/r, rated pressure 25 MPa, peak pressure 35 MPa, rated torque 785 N·m, specific torque 31.4 N·m/MPa, max speed 800 rpm, weight 31 kg

• GM1-250: Theoretical displacement 243 ml/r, rated pressure 25 MPa, peak pressure 35 MPa, rated torque 950 N·m, specific torque 38 N·m/MPa, max speed 700 rpm, weight 31 kg

• GM1-300: Theoretical displacement 290 ml/r, rated pressure 25 MPa, peak pressure 30 MPa, rated torque 1130 N·m, specific torque 45.2 N·m/MPa, max speed 650 rpm, weight 31 kg

• GM1-320: Theoretical displacement 314 ml/r, rated pressure 25 MPa, peak pressure 28 MPa, rated torque 1225 N·m, specific torque 49 N·m/MPa, max speed 600 rpm, weight 31 kg

• GM1-350: Theoretical displacement 340 ml/r, rated pressure 20 MPa, peak pressure 25 MPa, rated torque 1060 N·m, specific torque 53 N·m/MPa, max speed 550 rpm, weight 31 kg

Note: GM1 series variant parameters are compiled from SAI GM series technical data. The GM1-350 has a rated pressure of 20 MPa, differing from the 25 MPa of other variants.

GM2-630-7H-D40 (Series Reference)

• Model: GM2-630-7H-D40

• Brand Series: SAI GM Series / GM2

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

• Theoretical Displacement: 623 ml/r

• Rated Working Pressure: 25 MPa

• Peak Pressure: 28 MPa

• Rated Torque: 2433 N·m

• Specific Theoretical Torque: 97.3 N·m/MPa

• Maximum Power: 59 kW

• Continuous Speed: 650 rpm

• Piston Diameter: 63 mm

• Shaft Stroke: 40 mm

• Shaft Type: 40 mm splined shaft (DIN 5480 standard)

• Weight: Approximately 51 kg (reference: GM2 series data)

Key Technical Advantages

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

The GM1-200-1H-D40 utilizes a five-piston radial oscillating-cylinder arrangement with eccentric crankshaft drive. Sequential firing of multiple pistons ensures continuous torque output even at extremely low speeds (minimum 1 rpm), effectively suppressing stick-slip. SAI official documentation states that GM series motors, “due to their very good low speed characteristics (the motors remain sensitive to flows down 0.5 l/min) and higher than average max. speeds for motors of similar design, have some of the widest specific speed ranges of any hydraulic motor.” High starting torque makes the motor excel in winch, slew drive, and other high-inertia breakaway applications.

② Hydrostatically Balanced Pistons and Hydraulically Balanced Cylinder Trunnions — Low Friction, Low Wear

GM series motor cylinder trunnions employ hydraulic balancing to reduce friction, wear, and heat generation, enabling operation at higher powers with improved efficiency. Cylinder feed channels are radially injection-designed, eliminating direct hydraulic axial loading on the motor casing, and larger cylinder feed channels reduce power loss at high flows.

③ High-Strength Castings with Reinforcement Ribbing — High Load Capacity

GM series motors feature stronger castings and internal reinforcement ribbing, increasing casing strength and stiffness to withstand higher internal and external loads. Heavy-duty bearing configuration with output shafts capable of radial loads and bi-directional rotation provides significant advantages in belt, chain, or gear drive applications with radial loading.

④ Wide Speed Range — Adaptable to Diverse Operating Conditions

The GM1-200 offers a continuous speed range of 1–800 rpm, achieving a speed turndown ratio of 800:1. Combined with a specific theoretical torque of 31.4 N·m/MPa, the motor provides significant advantages in hydraulic systems requiring wide-range stepless speed control, enabling full-range drive from extremely low to moderate speeds without additional reduction gearing. GM series motors can also operate in pump mode, realizing freewheel operation.

⑤ High Interchangeability and Modular Design — Simplified Maintenance and Spare Parts Management

GM series motor mounting dimensions and over 80% of internal components are interchangeable with original SAI products. Standardized component design enhances modularity and flexibility for displacement interchangeability, spare parts replacement, and option configuration. GM series motors can also be coupled with SAI single or double stage planetary gearboxes for shaft-end output, further expanding application range.

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

• Others: Petroleum and coal mining machinery, lifting and transportation equipment, geological prospecting equipment, etc.

Expert Maintenance Tips

Pre-Installation Inspection: Verify flatness and cleanliness of the mounting flange mating surface. The GM1-200-1H-D40 D40 configuration uses a 40mm splined shaft (DIN 5480 standard); spline shaft-to-coupling or drive-wheel fit must conform to standards, avoiding 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. GM series motors are compatible with non-polluting hydraulic oils.

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.

Bearing Life Reference: SAI recommends estimating bearing life according to the L10 life formula (per ISO 281:1990) under the condition of no radial load on the output shaft, referencing SAI official life curve graphs. For radial loading conditions, consult SAI Technical Department for other applicable graphs.

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.