Product Overview
The MB350AS200BS09 is part of the Eaton Dowmax MB Series axial piston motor platform. The Dowmax MB/ME Series is Eaton’s classic low-speed high-torque hydraulic motor line, featuring a unique double swashplate design with up to 22 opposed pistons. Compared to conventional radial piston motors, this architecture delivers significant advantages in power-to-weight ratio, low-speed smoothness, and operating efficiency, reducing speed fluctuations, flow drift, and pressure ripple by as much as 50%. The Dowmax Series spans 13 displacement sizes from 99 to 4,097 cm³/rev, with rated torque ranging from 432 to 15,990 Nm and maximum speeds from 200 to 1,000 rpm, extensively deployed in marine deck machinery, swing drives, drilling rigs, and excavator slewing systems.
The specific model covered in this document — MB350AS200BS09 — is the MB350 frame size (350 cm³/rev displacement) with integrated mechanical brake. In the model code, MB designates the Dowmax motor series with mechanical brake; 350 indicates the displacement frame size of 350 cm³/rev; AS200 specifies the mounting flange and shaft configuration; and BS09 denotes the brake and seal configuration. Dowmax MB Series motors can be equipped with friction brake assemblies, and the rear cover can optionally include hydraulically controlled brake balance valves and relief valves. The motor is manufactured to original Eaton Dowmax specifications with 100% drop-in interchangeability, requiring no modification to mounting interfaces, port positions, or hydraulic connections. Every unit undergoes 100% simulated operating condition testing at the factory, including rated pressure loading, volumetric efficiency verification, seal integrity assessment, and low-speed smoothness validation prior to shipment.
Technical Specifications
MB350AS200BS09:
Series / Type: Eaton Dowmax MB Series axial piston motor with mechanical brake
Displacement: 350 cm³/rev (21.34 in³/rev)
Design: Double swashplate axial piston, opposed piston arrangement, up to 22 pistons
Rated pressure (continuous): 28 MPa (280 bar / 4,061 psi)
Peak pressure: 31.9 MPa (319 bar / 4,626 psi)
Rated torque: 1,530 Nm (156 kgf·m)
Rated speed: 660 rpm
Maximum speed: 800 rpm
Rated power: 106 kW (144 PS)
Direction of rotation: Bidirectional
Mounting: Standard flange mount
Output shaft: SAE/DIN standard spline
Brake type: Integrated friction brake, spring-applied hydraulically released
Housing material: High-strength cast iron
Approximate weight: 60 kg
Note: The rated pressure, torque, and speed values above are derived from the general technical data of the Dowmax ME350B same-displacement frame size. For precise technical specifications of the MB350AS200BS09, always consult the official Eaton Dowmax technical manual or the product nameplate data.
Dowmax MB/ME Series displacement range (for reference):
ME100: 99 cm³/rev (rated torque 432 Nm, rated speed 1,000 rpm, power 45 kW)
ME150: 152 cm³/rev (rated torque 667 Nm, rated speed 600 rpm)
ME175: 175 cm³/rev (rated torque 765 Nm, rated speed 600 rpm)
ME300B: 300 cm³/rev (rated torque 1,320 Nm, rated speed 660 rpm, power 90 kW)
ME350B: 350 cm³/rev (rated torque 1,530 Nm, rated speed 660 rpm, power 106 kW)
ME600B: 600 cm³/rev (rated torque 2,620 Nm, rated speed 500 rpm)
ME750B: 750 cm³/rev (rated torque 3,280 Nm, rated speed 450 rpm)
ME850B: 848 cm³/rev (rated torque 3,708 Nm, rated speed 400 rpm)
ME1300A: 1,345 cm³/rev (rated torque 5,250 Nm, rated speed 200 rpm)
ME1900: 1,868 cm³/rev (rated torque 7,290 Nm, rated speed 140 rpm)
ME2600: 2,578 cm³/rev (rated torque 10,070 Nm, rated speed 110 rpm)
ME3100: 3,104 cm³/rev (rated torque 12,120 Nm, rated speed 110 rpm)
ME4100: 4,097 cm³/rev (rated torque 15,990 Nm, rated speed 75 rpm)
Note: The key distinction between the MB and ME Series is that the MB Series is equipped with a mechanical brake as standard, while the ME Series is the brake-less version. Actual displacement values should be confirmed against official technical documentation.
Key Technical Advantages
1. Double Swashplate Design with Opposed Multi-Piston Architecture
The MB350AS200BS09 employs Eaton Dowmax’s unique double swashplate design with up to 22 opposed pistons. Compared to conventional radial piston motors, this architecture significantly reduces speed fluctuations, flow drift, and pressure ripple — reducing pulsation by as much as 50%. The opposed piston arrangement balances radial forces generated by individual pistons, reducing bearing radial loads and extending bearing service life. The double swashplate design enables smooth operation even below 5 rpm, providing an ideal solution for swing drive and tool drive applications requiring precise speed control.
2. Low-Speed High-Torque Performance
At 350 cm³/rev displacement, the MB350AS200BS09 delivers a rated torque of 1,530 Nm, rated speed of 660 rpm, maximum speed of 800 rpm, and rated power of 106 kW. High torque is available even at very low speeds, enabling direct drive of large-diameter slewing mechanisms or winch equipment without gear reduction. For applications such as marine deck crane swing drives and hatch cover actuation requiring high torque at low speed, this characteristic simplifies the drivetrain design and reduces energy losses from intermediate transmission stages.
3. Integrated Mechanical Brake (MB Series Feature)
The defining feature of the MB Series is its integrated multi-disc friction brake at the rear of the motor. The brake operates on a spring-applied, hydraulically-released principle, automatically applying braking force upon loss of system pressure to ensure safe load holding during power failure or hydraulic system malfunction. For applications with stringent safety braking requirements — such as ship cranes and deck machinery — this integrated design eliminates the need for a separately configured brake, simplifying system integration and reducing installation space requirements.
4. High Power-to-Weight Ratio and Compact Construction
Thanks to the double swashplate design and opposed piston layout, the MB350 packs 350 cm³/rev of displacement capability within a compact housing, achieving a power-to-weight ratio that leads its class among low-speed high-torque motors. The unique Dowmax design ensures the motor consistently operates in its high-efficiency zone, enabling machines to operate under optimal conditions with optimum performance, energy efficiency, and safety. The compact structure enables high torque output within limited installation space — particularly important for marine deck equipment and port machinery with constrained mounting envelopes.
5. Wide Speed Range with Precise Speed Control
The MB350 operates across a speed range of 0–800 rpm with smooth performance throughout. For swing drive applications requiring precise speed control — such as ship crane slewing and drilling rig rotary table drives — the low-pulsation characteristics of the double swashplate design ensure accuracy and repeatability in the slewing process. The Dowmax MB Series can be optionally configured with rear cover relief valves, speed sensors, and balance valves, providing greater flexibility for system integration.
Application Areas
Marine and offshore: Ship deck crane swing drives, hatch cover actuation, windlass drives, winch drives, marine IHI hydraulic swing motors
Port machinery: Port crane swing drives, container handling equipment slewing systems
Construction equipment: Rotary drilling rig rotary table drives, excavator swing drives, TBM auxiliary drives
Mining machinery: Mine winch drives, drilling equipment swing drives
Metallurgy and heavy industry: Stacker-reclaimer slewing drives, large rotary table drives
Industrial applications: Heavy-duty industrial equipment requiring low-speed high-torque swing drives
Expert Maintenance Tips
1. Periodic Inspection and Maintenance of the Mechanical Brake
The MB350AS200BS09 is equipped with an integrated multi-disc friction brake. Inspect brake friction disc wear and brake piston seal condition every 1,000 operating hours. Brake release pressure must be set to the value specified in the Eaton Dowmax technical manual — excessive release pressure will damage seals, while insufficient pressure will cause brake drag and overheating. Replace friction discs when brake clearance exceeds specified limits.
2. Fluid Cleanliness Management Is the Primary Task
The MB350 operates with micron-level clearances between pistons and cylinder bores and between the valve plate and cylinder block face. Particulate contamination in hydraulic fluid is the leading cause of piston scoring and valve plate wear. Systems must be equipped with filtration rated to ISO 4406 18/16/13 or better. In ship engine rooms or dusty industrial environments, consider increasing filtration to ISO 4406 17/15/12 and shortening filter replacement intervals to 500–800 hours.
3. Case Drain Line Configuration Requirements
Case drain from the MB350 must be routed to the reservoir through the highest drain port, with case pressure strictly controlled within specified limits. Excessive case pressure will cause shaft seal failure; insufficient pressure will reduce lubrication and heat rejection effectiveness. The case drain line must terminate below the minimum oil level in the reservoir to maintain positive return flow under all operating conditions. For models equipped with a brake, the brake leakage oil circuit should drain independently and must not share the motor case drain line.
4. Pre-Start Case Filling and Air Purging
Before first startup after installation or repair, the motor case must be filled with clean hydraulic fluid through the highest case port until fluid overflows. The MB350 double swashplate axial piston architecture creates a complex internal case cavity geometry; starting an un-purged motor can cause dry friction damage between piston ball ends and the swashplate, leading to irreversible premature wear.
5. Output Shaft Spline and Mounting Alignment
During installation, verify that the output shaft spline is properly aligned with the mating component. For ship crane swing drive applications, installation misalignment will cause abnormal spline wear and bearing side loading, significantly shortening service life. Tighten mounting bolts in stages to the specified torque value and re-check torque after 500 operating hours.
6. Restart Procedure After Extended Shutdown
If the motor has been idle for more than three months, manually rotate the output shaft to confirm freedom of movement, and inspect the case oil level, shaft seal, and brake for leakage before restarting. Extended shutdown can cause oil film drainage from piston-slipper interfaces, creating a dry-start risk. Before restarting, replenish clean hydraulic fluid through the case fill port and operate at low speed and reduced load for 10–15 minutes before returning to normal duty.
