At the top of its size band, the M3RHT90 heavy duty bevel gear reducer is the frame specified when a shaft-mounted drive has to carry the full tonnage of a plant rather than a branch conveyor. The bevel input stage accepts a foot-mounted motor on a swing base, two helical stages build the torque, and the hollow output shaft is sized for the pulley or drum it rides. Everything about the frame is proportioned for continuous duty under shock - thick housing walls, wide bearing centres, and a torque arm rated for the starting reaction of a loaded belt.
Size 90: The Largest Frame in the Horizontal Shaft-Mounted Range
Frames in this industrial band run from 50 to 90 horizontally, and each step up brings a larger gear centre distance, heavier shafts and a bigger bearing envelope. At the top of the band the unit is no longer a convenient way to avoid a foundation - it is a primary drive. Overland conveyor head stations, run-of-mine feeder drives and thickener bridge centres are the classic duty points, and in each case the alternative is a much larger foot-mounted unit with a fluid coupling and a fabricated base. Choosing the size 90 shaft-mounted arrangement removes that entire sub-assembly from the layout.
Load Path Through a Bevel-Helical Train
Power enters through the spiral-bevel pinion, turns ninety degrees, and passes into the first helical stage; a second helical stage then brings the speed down to the shaft. Every stage uses case-hardened, ground gearing running in an oil bath, so contact stresses stay controlled at high torque and the mesh stays quiet at speed. The bevel stage carries the direction change, the helical stages carry the ratio, and neither relies on sliding friction the way a worm set would - which is why efficiency stays high even at the deep reductions a slow pulley needs. Heat generation is correspondingly modest for the torque transmitted, and the housing is ribbed to shed it.
Machine groups this unit is specified into:
- Long overland conveyor head stations at full plant tonnage
- SAG mill discharge and pebble handling conveyors
- Bucket wheel boom and transfer conveyor drives
- Heavy apron feeders beneath run-of-mine hoppers
- Clarifier and thickener bridge drive centres
- Kiln and dryer shell drive pinion stations
What Decides Suitability at This Size
| Starting duty | A loaded belt started against material draws several times running torque; the service factor must cover the breakaway, not the steady state |
| Overhung load | Pulley weight plus belt tension acts on the hollow-bore bearings; mounting close to the pulley reduces the moment arm |
| Thermal capacity | Sustained high torque in a hot gallery may call for a fan cowl or a cooling coil, decided at selection rather than after commissioning |
| Shaft fit | Bore, keyway and shrink-disc size must match the pulley shaft drawing exactly; this is verified before the order is released |
None of these four can be read off the type code. They come from the driven machine drawing and the operating profile, which is why the enquiry should carry the conveyor or drum drawing rather than the model number alone.
Specification Support
The catalogue and the size 90 outline drawing are available as PDF downloads for layout work - foot and torque-arm fixing points, bore and keyway dimensions, motor flange interface. Send the driven machine type, motor power and speed, required output speed and the operating regime; the selection is calculated with a rated-torque and thermal check and issued with a written quotation. Units are factory run tested, shipped in an export wooden crate, and covered by a one-year warranty.
Full Frame Range of the M3 Series
| Model | Centre distance | Output | Typical duty |
|---|
| M3RHT90 | size 90 | hollow shaft, torque arm, right-angle | heavy shaft-mounted drives |
| M3PSF50 | size 50 | solid shaft, foot | conveyors, feeders |
| M3PSF60 | size 60 | solid shaft, foot | crushers, mixers |
| M3PSF70 | size 70 | solid shaft, foot | ball mills, shredders |
| M3PSF80 | size 80 | solid shaft, foot | kilns, heavy conveyors |
| M3PSF90 | size 90 | solid shaft, foot | mill and kiln drives |
| M3RSF50 | size 50 | solid shaft, foot, right-angle | inclined conveyors, elevators |
| M3RSF60 | size 60 | solid shaft, foot, right-angle | screw classifiers, feeders |
| M3RHF70 | size 70 | hollow shaft, foot, right-angle | agitators, drum drives |
| M3PHT80 | size 80 | hollow shaft, torque arm, parallel | shaft-mounted conveyors |
Every frame in the table can be ordered with alternative shaft and mounting styles. If you are matching an existing installation, send the nameplate details and we confirm the equivalent frame in writing.
Installation Snapshots
Cold-store conveyor
A cold-store operator uses reducers on freezer-room conveyors. Low-temperature synthetic oil and moisture-resistant seals keep the units running below -20 deg C ambient.
Bakery spiral cooler
A bakery equipment builder fits units to spiral cooler drives. The compact right-angle layout fits under the spiral cage, and food-grade lubrication was specified for the hygienic area.
Selection Example: Overland conveyor head station drive
Take a 250 kW motor at 1490 rpm turning the head pulley shaft of a main-line conveyor at 8 rpm. The ratio follows directly: 1490 / 8 = 186, which sits in the deepest band of the three-stage range and is verified against the full-tension pulley torque. In this case at this size the unit becomes the primary drive, so the bore, keyway and torque-arm pin are matched to the pulley shaft drawing before release. Use the same method for any frame in the series, then confirm the service factor with us - it is the one number buyers most often get wrong.
![speed reducer selection process diagram]()
The selection path we follow when checking your enquiry.
Technical Q&A
Can the unit be rebuilt instead of replaced?
Yes. Bearings, seals and gear sets are available as spare internals, and the horizontally split housing allows inspection and reassembly on site. Many operators overhaul units during annual shutdowns instead of buying new.
What ambient and altitude limits apply?
The standard build suits -10 to +40 degrees C at altitudes below 1,000 m with the supplied oil grade. Colder sites get synthetic oil and heaters; high altitudes or hot climates may call for the next frame size or forced cooling.
![speed reducer use cases across sectors]()
Typical installation environments for this gearbox family.
Your Selection, Cross-Checked by an Engineer
Send the numbers, get the model. One screen in the WGT Motor & Gearbox Online Selection System is usually enough to pin down the frame size; we confirm the service factor afterwards.
Every enquiry is checked by an engineer against the rating tables before it is quoted, so the unit we recommend carries a real torque margin - not just a catalogue guess. Spare-unit and OEM volumes are both welcome. Looking for a gear reducer for screw conveyor? Tell us the duty point and we will confirm the model in writing.
