Parts & attachments
HOREY BMM Orbital Motors
The HOREY BMM is a compact orbital motor with shaft distribution and a 4/5-tooth integral rotor/stator. Six sizes run from BMM8 to BMM50, with actual displacement of 8.2 to 50.3 cm³/rev and a mass of 1.9 to 2.4 kg. HOREY's store offers it for lawn mowers and small hydraulic machines, listed against the OMM50. Below are the rated figures for each size, the catalogue's continuous, intermittent and peak limits, two curve points, the shaft, flange and port choices, and the details to send with a quote request.
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Build my procurement briefRated figures for each BMM size
HOREY's webpage gives one rated point per size. BMM50 has less rated torque than BMM40 (33 against 37 N·m) because its rated pressure drop is lower, 6 MPa against 8.5 MPa. Choose the size from the working point you need; the biggest displacement is not automatically the strongest. If no BMM size reaches your working point, compare the tables for HOREY's BMR and BMS orbital motors.
| Size / actual displacement | Webpage rated speed, torque, pressure drop, flow, mass |
|---|---|
| BMM8 / 8.2 cm³/rev | 1537 rpm; 8 N·m; 9 MPa pressure drop; 14 L/min; 1.9 kg. |
| BMM12.5 / 12.9 cm³/rev | 1256 rpm; 13 N·m; 9 MPa; 18 L/min; 2.0 kg. |
| BMM20 / 19.9 cm³/rev | 814 rpm; 19 N·m; 9 MPa; 18 L/min; 2.1 kg. |
| BMM32 / 31.6 cm³/rev | 513 rpm; 31 N·m; 9 MPa; 18 L/min; 2.2 kg. |
| BMM40 / 39.8 cm³/rev | 452 rpm; 37 N·m; 8.5 MPa; 18 L/min; 2.3 kg. |
| BMM50 / 50.3 cm³/rev | 358 rpm; 33 N·m; 6 MPa; 18 L/min; 2.4 kg. |
Sources [1]
Continuous, intermittent and peak duty
The catalogue rates the BMM in three duty bands. Intermittent means up to six seconds in any minute; peak means up to 0.6 seconds in any minute. The curves pair a torque with a speed at a stated flow and pressure, and shade the intermittent region.
| Catalogue point | How to use it |
|---|---|
| BMM40 at 20 L/min and 7 MPa | 37 N·m at 487 rpm, inside the continuous region. A good reference for steady work. |
| BMM40 at 25 L/min and 8.5 MPa | 37 N·m at 607 rpm, in the shaded intermittent region. For all-day running at that torque, plan below this speed. |
| Reading the curves | Take speed and torque from the same point. The top speed of one cell and the top torque of another never add up to one output. |
| Your work cycle | Send the speed and load cycle, supply and return conditions and any shock loads. For a mower, say whether the motor drives the blade or the wheels. |
Where the webpage and catalogue figures differ
Inlet pressure: the webpage gives 11 MPa rated and 14 MPa maximum for BMM8 to BMM50. The catalogue gives 14 MPa rated, 17.5 MPa continuous and 22.5 MPa intermittent.
Flow: BMM40 and BMM50 are rated at 18 L/min on the webpage and at 20 L/min in the catalogue. The webpage's maximum speed, torque and power figures broadly match the catalogue's continuous row, and the catalogue adds intermittent and peak rows.
Oil temperature: the webpage gives 80°C maximum. The catalogue's general guide gives 20–60°C for normal running and 90°C for limited periods.
The downloadable catalogue file is dated 2014/2017 and carries a different internal title. Size the motor from the current dated table for the build you order.
Published specifications
Read each value with its stated conditions, and ask the manufacturer for any limit not listed here.
| Specification | Published value | Meaning / limit |
|---|---|---|
| Family and internal form | BMM8 / 12.5 / 20 / 32 / 40 / 50; 4/5-tooth integral rotor/stator; shaft distribution [1] [2] | Six displacement sizes in one family. HOREY describes the motors as compact, efficient and long-lived. |
| Actual displacement and mass | 8.2 / 12.9 / 19.9 / 31.6 / 39.8 / 50.3 cm³/rev; 1.9–2.4 kg [1] [2] | Size the circuit on actual displacement; the code number is a rounded name. |
| Webpage rated and maximum speed | 1537–358 rpm rated; 1950–400 rpm maximum, by size [1] | Each size has its own row. HOREY rules out running at maximum speed and maximum pressure together. |
| Inlet pressure | Webpage 11/14 MPa rated/maximum; catalogue 14/17.5/22.5 MPa rated/continuous/intermittent [1] [2] | The two sources print different inlet figures. Inlet pressure is a separate value from working pressure drop. |
| Interfaces in the catalogue | Rear/side ports; M/U/F flange references; 16 / 15.875 mm keyed or B17x14 spline shaft [2] [3] | Each choice is part of the full order code and has its own dimension drawing. |
Shaft, flange and port choices
Catalogue pages 4–7 show rear-port and side-port versions with different flanges and lengths. Choose shaft, flange and ports as one set and check them against the drawing for the code you order. Other drive and hydraulic components for farm machines sit in our parts and attachments section.
| Catalogue option | What it means for the installation |
|---|---|
| BMM50 body length, rear or side ports | With M/U flanges, L is 122 mm (rear ports) or 123 mm (side ports); with F flanges, 125.5 or 126.5 mm. Add shaft, coupling and hose space for the installed length. |
| M/U or F mounting | M/U is a three-hole circular mount; F is a two-hole mount. Each has its own code. Ask for the flange, pilot and hole drawing for the version offered. |
| A and B keyed shafts | A: 16 mm with a 5×5×16 key. B: 15.875 mm with a 4.8×4.8×19.05 key. Check key, engagement, fixing thread and tolerance against your coupling. |
| C spline shaft | B17×14 to DIN5482. Match it to the mating spline on your machine and state the shaft load. |
| Ports and drain | The code table lists threaded main ports and an external drain, in metric/G and UNF versions. Specify drain and return pressure so HOREY can confirm the seal arrangement. |
Sources [2]
Drain, shaft seal and the OMM comparison
The catalogue includes a shaft-seal pressure graph that varies with speed. It treats drain-line pressure separately from main return pressure, and the webpage inlet figure is a different value again. Ask for the seal and drain arrangement fitted to your motor and the circuit conditions it suits.
Danfoss describes its own orbital motors for work and propel circuits in agricultural and lawn markets, which shows where motors of this type are used. HOREY's OMM comparison is its own listing, and Danfoss limits belong to Danfoss parts. Compare a BMM with an OMM drawing against drawing and duty against duty.
Keep the size, full option code, current instructions and test record together on the order. Tell HOREY about any side loads and any control valves your machine needs with the motor. Where the motor must also hold a load at rest, ask about the ZBMR brake motors instead. HOREY publishes no lifetime, efficiency percentage or service interval for the BMM.
Buyer questions
Does BMM50 give more rated torque than BMM40?
Not on the webpage. BMM50 is rated at 33 N·m at 6 MPa, BMM40 at 37 N·m at 8.5 MPa. Compare sizes at the working point you need. [1]
Can I use 22.5 MPa as a continuous inlet rating?
No. The catalogue labels 22.5 MPa as intermittent, and the webpage prints a lower inlet table of 11/14 MPa. Ask HOREY to confirm in writing which inlet and flow rating applies to your motor. [1] [2]
Is 607 rpm at 37 N·m a continuous BMM40 rating?
No. That point sits in the catalogue's intermittent region at 25 L/min and 8.5 MPa. At 20 L/min and 7 MPa the curve gives 37 N·m at 487 rpm, in the continuous region. [2]
Prepare a model-specific brief
Write your actual conditions below. This local worksheet is not sent, uploaded or saved after reload. Copy or print it before leaving.
Sources
Specifications come from the manufacturer's publications listed below, with the date each was checked.
- Official BMM compact-motor webpage
manufacturer · Checked 2026-10-12
Six-size table with rated and maximum figures, an inlet-pressure table and the oil-temperature limit.
- Original HOREY catalogue, BMM printed pages 2–7
manufacturer · Checked 2026-10-12
Six-size ratings with continuous, intermittent and peak definitions, curves, rear and side port drawings, shafts, seal-pressure graph and order codes.
- Company-linked store: BMM/OMM50 lawn/compact-use description
industry platform · Checked 2026-10-12
Offers the BMM against OMM50 for lawn mowers and compact hydraulic machines.
- Danfoss official orbital-motor portfolio context
official disclosure · Checked 2026-10-12
Danfoss's own orbital motors for work and propel functions in agricultural and lawn markets, as background on where this motor type is used.
Report a correction through our contact form, quoting HOREY BMM Orbital Motors and the relevant specification.