BM4 Series Orbital Hydraulic Motor | BM4-630 BM4-390 BM4-245 BM4-500

The BM4 Series low-speed, high-torque (LSHT) orbital hydraulic motors manufactured by Chengyuan Hydraulic are heavy-duty engineering solutions fully cross-referenced to global Eaton Char-lynn 4000 series technical standards. Engineered to perform as primary rotary driving elements, this series adopts an integrated shaft distribution architecture coupled with an advanced Geroler gear set design to deliver steady and high torque outputs even at extremely low velocities. Focused on the targeted displacement matrix provided—BM4-245, BM4-310, BM4-390, BM4-500, and BM4-630—we have reinforced the internal structural fluid channels and bearing matrix. Every single BM4 motor undergoes 100% full-load test mapping for start-up torque efficiency and thermal-leakage boundaries, ensuring flawless 100% original-place interchangeable plug-and-play compatibility.

Technical Specifications :

• Core Product Series: BM4 Series Shaft-Distribution Geroler Orbital Hydraulic Motors (Char-lynn 4000 Equivalent)

• Displacement Platform Architectures:

  • BM4-245 (245 $cm^3/rev$)

  • BM4-310 (310 $cm^3/rev$)

  • BM4-390 (390 $cm^3/rev$)

  • BM4-500 (500 $cm^3/rev$)

  • BM4-630 (630 $cm^3/rev$)

• Continuous Operational Pressure: 160 bar – 205 bar (Slightly reduced for higher displacement sizes)

• Intermittent Peak System Limit: 200 bar – 240 bar

• Max. Continuous Output Torque: From 590 N·m (BM4-245) up to 1210 N·m (BM4-630)

• Max. Continuous Speed Boundary: From 150 rpm (BM4-630) up to 380 rpm (BM4-245)

• Max. Continuous Power Output: 12 kW – 20 kW

• Drive Shaft Interface Matrix: Standard $\phi 32$ / $\phi 38$ / $\phi 40$ Cylindrical straight shaft with parallel key, or 14-tooth involute splined configuration

• Main Port Dimensions: G1/2 or G3/4 British Standard Pipe Thread (BSPP), with an independent G1/4 case drain port

Key Technical Advantages:

• Advanced Geroler Component Metallurgy: Unlike standard sliding-contact gerotor structures, the BM4 series features hardened rollers on the stationary outer ring teeth. This rolling friction design minimizes startup mechanical resistance, enabling the motor to release over 88% of its theoretical torque at startup and preventing low-speed “stiction” or crawling.

• Monoblock Shaft Distribution & Reinforced Tapered Bearings: The timing mechanism and the output shaft share an integrated drive link configuration, protecting distribution timing from severe external radial loads. The load section utilizes heavy-duty tapered roller bearings that absorb substantial axial and radial forces directly from hoist winches or vehicle wheels.

• High-Resilience Backpressure Viton Shaft Seals: The front output shaft is fitted with a heavy-duty, high-pressure Viton lip seal backed by internal check-valve routing. This setup allows short-duration backpressure shocks up to 100 bar on the return line without immediate failure, though a dedicated case drain line is always optimal.

• High-Tensile QT500-7 Enclosures for Heavy Duty Operations: The main casing is cast from premium QT500-7 ductile iron, delivering a dense molecular micro-structure. Under consistent 20 MPa peak cycles, housing micro-deformation is virtually zero, keeping critical tolerances perfectly balanced.

Application Areas:

• Agricultural & Forestry Machinery: Infeed mechanism drives for combine harvesters, heavy-duty lawn mower cutter heads, and forestry harvester attachments.

• Construction & Environmental Engineering: Drill pipe rotation drives for mini crawler rigs, street sweeper brush rotators, and small excavator swing drives.

• Marine Hoist & Deck Winch Elements: Net haulers for fishing vessels, compact anchor winch drums, and small hydraulic boom hoist winches.

Expert Maintenance Tips:

• An Independent, Unrestricted Case Drain Line is Critical for Shaft Seal Longevity: Although internal check valves are included, you must route a dedicated line from the G1/4 case drain port back to the reservoir below the oil level during heavy-duty or multi-motor series operations. Leaving the drain plugged under heavy loads causes case pressure spikes that blow out the shaft seal and cause external leaks.

• Purge Air and Perform a 15-Minute No-Load Break-in Run Prior to System Commissioning: New or recently serviced motors contain trapped air. Before running under load, fill the motor case with clean hydraulic oil through the case drain port and vent the air until a solid column of oil appears. Running a motor dry will score the internal Geroler surfaces and link splines.

• Maintain System Operating Temperature Below 60°C: Orbital motors depend heavily on proper oil viscosity. Running continuously above 60°C lowers fluid viscosity, causing a sharp drop in volumetric efficiency and risking metal-to-metal contact. Ensure the cooling circuit is active and use premium ISO VG 46/68 anti-wear hydraulic oil.