Hydraulic Orbit Motor Selection Guide: BM Series, OMR, OMS, and More
What is a Hydraulic Orbit Motor?
A hydraulic orbit motor (also called a cycloid hydraulic motor or gerotor motor) converts hydraulic pressure into rotary motion using a gerotor gear set. These compact, high-torque motors are essential components in construction equipment, agricultural machinery, marine systems, and industrial conveyors.
Unlike axial piston motors, orbit motors are simpler, more durable, and significantly more cost-effective for medium-duty applications. At Seric Hydraulic, we manufacture a complete range of BM, OMR, OMS, OMM, BMP, and BZZ series hydraulic motors compatible with major international brands.
How Hydraulic Orbit Motors Work
An orbit motor consists of five main components:
- Gerotor Set (Stator and Rotor): The rotor orbits inside the stator, creating expanding and contracting chambers that convert fluid pressure into rotational force.
- Output Shaft: Transmits torque to the driven equipment. Available in straight shaft, splined shaft, and tapered shaft configurations.
- Valve Plate / Distributor: Directs fluid to the correct chambers as the rotor orbits.
- Front and Rear Covers: House the bearings and seal the motor.
- Seals and O-Rings: Prevent internal and external leakage.
The result is a motor that delivers high torque at low speeds without requiring a gearbox — ideal for winches, augers, sweepers, and conveyor drives.
Key Specifications When Choosing an Orbit Motor
1. Displacement and Torque
Displacement, measured in cm³/r (cubic centimeters per revolution), directly determines the motor output torque:
| Displacement Range | Series | Typical Torque | Applications |
|---|---|---|---|
| 50-200 cm³/r | BM1, OMP | 100-400 Nm | Small augers, fans, sweepers |
| 200-400 cm³/r | BM2, OMR, BMP | 400-800 Nm | Conveyors, mixers, small winches |
| 400-800 cm³/r | BM4, OMS, OMM | 800-1600 Nm | Heavy winches, crushers, forestry |
| 800-1250 cm³/r | BM5, BM6, OMT | 1600-2500 Nm | Mining equipment, marine winches, large augers |
Formula: Torque (Nm) = (Displacement × Pressure × 0.0159) ÷ (2 × π)
2. Operating Pressure
Most standard orbit motors operate at 10-20 MPa continuous with 22.5 MPa intermittent. For heavy-duty applications, Seric offers high-pressure models rated to 27.5 MPa (BM5, OMT series) with reinforced housing and premium seals.
3. Speed Range
Orbit motors typically operate at 10-800 RPM depending on displacement:
- High-speed models (200-800 RPM): BM1, OMR series for conveyors and fans
- Medium-speed models (50-300 RPM): BM2, BM4, OMS series for winches and mixers
- Low-speed models (10-100 RPM): BM5, BM6, OMT series for high-torque, low-speed applications
Always verify that your hydraulic power source can deliver the required flow rate at the target speed.
4. Shaft Configuration
Choose the right shaft type for your coupling:
| Shaft Type | Best For | Available On |
|---|---|---|
| Parallel Key Shaft | Standard coupling with keyway | All BM/OM series |
| Spline Shaft | Direct gear engagement, compact installation | BMV, BMP, OMR, OMS |
| Tapered Shaft | Tight-fit pulleys and sheaves | BM4, BM5 |
| Hollow Shaft | Direct wheel mounting (wheel motors) | Special order |
5. Mounting Flange
Standard mounting options include 2-bolt SAE A/B/C flanges, 4-bolt square flanges, and wheel flanges for direct wheel mounting. Verify flange dimensions against your equipment specifications.
Seric Hydraulic Orbit Motor Series
BM1 Series (OMP Replacement)
- Displacement: 50-200 cm³/r
- Max Pressure: 20 MPa (continuous), 22.5 MPa (intermittent)
- Speed: 10-800 RPM
- Features: Compact and versatile, interchangeable with OMP and Danfoss OMP series
- Applications: Small augers, agricultural sprayers, conveyor drives, fishing equipment
BM2 Series (OMR Replacement)
- Displacement: 80-395 cm³/r
- Max Pressure: 20 MPa (continuous), 22.5 MPa (intermittent)
- Speed: 10-600 RPM
- Features: High distribution accuracy, compact structure, interchangeable with OMR series
- Applications: Mobile equipment, sweepers, mixers, recycling machinery
BM4 Series (OMH/OMS Replacement)
- Displacement: 200-500 cm³/r
- Max Pressure: 20.5 MPa (continuous), 24 MPa (intermittent)
- Speed: 10-400 RPM
- Features: Robust and compact design, pressure up to 27.5 bar in special configurations
- Applications: Heavy winches, crushers, forestry equipment, industrial mixers
BM5 Series (OMT Replacement)
- Displacement: 400-1250 cm³/r
- Max Pressure: 20 MPa (continuous), 25 MPa (intermittent)
- Speed: 10-200 RPM
- Features: High-pressure capability, tapered roller bearings for high axial/radial loads
- Applications: Mining equipment, marine winches, large augers, heavy construction
BMV Series (BMV Motor)
- Displacement: 80-315 cm³/r
- Max Pressure: 18 MPa (continuous), 22 MPa (intermittent)
- Features: Precision cycloid design with splined shaft for compact installations
- Applications: Precision machinery, robotics, compact drive systems
BMP Series
- Displacement: 50-400 cm³/r
- Max Pressure: 14-20 MPa
- Features: Custom configurations available, cost-effective for OEM applications
- Applications: Agricultural machinery, small construction equipment
BZZ Series (Steering Control Units)
- Displacement: 50-400 cm³/r
- Max Pressure: 16 MPa
- Features: Hydraulic steering control unit — combines orbit motor with directional control for vehicle steering
- Applications: Forklifts, tractors, loaders, construction vehicles, marine steering
OMM Series
- Displacement: 8-50 cm³/r
- Max Pressure: 5.5-14 MPa
- Speed: Up to 1950 RPM
- Features: Compact, high-torque, suited for light-duty applications
- Applications: Small machinery, medical equipment, conveyor rollers
Orbit Motor vs Other Hydraulic Motors
| Feature | Orbit Motor | Axial Piston Motor | Gear Motor |
|---|---|---|---|
| Torque at Low Speed | Excellent | Good | Poor |
| Cost | Low-Medium | High | Low |
| Efficiency | 75-85% | 90-95% | 70-80% |
| Noise Level | Low | Medium | High |
| Serviceability | Easy (cartridge replacement) | Complex | Easy (replace motor) |
| Speed Range | 10-800 RPM | 50-3000 RPM | 50-4000 RPM |
| Best For | High torque, low speed | High efficiency, variable speed | Low cost, simple applications |
Industry Applications
- Construction Machinery: Excavator attachments, drill rigs, concrete mixer drums — BM4, BM5 series
- Agricultural Equipment: Sprayer pumps, grain augers, fertilizer spreaders — BM1, BM2, BMP series
- Marine & Fishing: Winches, net haulers, anchor windlasses, steering systems — BM5, BZZ series
- Forestry Equipment: Log splitters, chippers, sawmill drives — BM4, BM5 series
- Mining & Tunneling: Conveyor drives, drilling equipment, crusher feeds — BM5, BM6, OMT series
- Material Handling: Conveyor belts, rotary tables, lift platforms — BM2, OMR, OMS series
- Recycling & Waste: Shredders, compactors, sorting conveyors — BM2, BM4 series
Why Choose Seric for Orbit Motors?
Guangzhou Seric Hydraulic Co., Ltd. has been a leading hydraulic orbit motor manufacturer since 2008. Our motors are:
- 100% Interchangeable with Danfoss, Eaton, Char-Lynn, Parker, and White Drive Products
- CE Certified and ISO 9001:2015 Compliant
- Factory Tested — every motor undergoes pressure, flow, and torque verification
- Competitively Priced — direct from the manufacturer, no middleman markup
- Shipped Worldwide — air freight in 3-5 days, sea freight in 15-30 days
We also manufacture complementary products including hydraulic vane pumps, gear pumps, piston pumps, solenoid valves, and modular valves — making Seric your one-stop hydraulic supplier.
Frequently Asked Questions
Q: What oil viscosity should I use with an orbit motor? A: ISO VG 32-68 hydraulic oil at 40°C. For cold environments, use ISO VG 22-32. For high-temperature applications, use ISO VG 68-100.
Q: How do I calculate the required flow rate for my motor? A: Flow (L/min) = (Displacement in cm³/r × RPM) ÷ 1000. Factor in 10-15% for volumetric efficiency loss.
Q: Can I use an orbit motor as a hydraulic pump? A: No. Orbit motors are designed for motor operation only. Using them as pumps can cause seal failure and internal damage.
Q: What is the expected service life of an orbit motor? A: 8,000-15,000 hours under normal operating conditions with clean oil and proper filtration (ISO 4406 18/16/13 recommended).
Q: Do you accept OEM orders with custom specifications? A: Yes. We can customize shaft configurations, port sizes, mounting flanges, and paint/label requirements for OEM orders of 100+ units.
Contact Seric Hydraulic today for a free quote on orbit motors and complete hydraulic solutions.