The M3RHF90 bevel helical gear unit sits at the top of the size 50 to 90 band, combining a spiral-bevel first stage that turns the motor through a right angle with two helical stages on parallel axes behind it. The size 90 low-speed shaft is hollow, so the driven machine shaft slides straight into the output bore; the foot-mounted housing carries the reaction into the foundation without a torque arm.
The End of the Size Ladder and Why It Matters
Every frame number in this family marks a torque step, and the 90 frame is the largest step available. Plants buy it where driven equipment is an inertia load that must be started and kept running for whole shifts - long overland conveyors, heavy mill shells, thickener rakes. The split cast-iron housing opens along a horizontal joint, so tooth contact and bearing condition can be inspected without disturbing the shaft alignment, and the ground helical wheels share one oil sump designed to stay thermally stable at continuous duty.
M3RHF90 Designation, Letter by Letter
| M3 | Industrial gear unit family, three geared stages |
| R | Spiral-bevel right-angle input stage ahead of the helical train (P would be all-parallel) |
| H | Hollow low-speed shaft, keyed or shrink-disc seated (S would be a solid output shaft) |
| F | Foot mounting bolted to a prepared foundation (T would give a torque-arm reaction) |
| 90 | Frame size 90, the top of the horizontal band |
The code reads like a contract: input direction, output connection, mounting and capacity are all fixed by five characters. A millwright can order a spare, a draughtsman can draw the bedplate and a stores clerk can shelve the kit, all from the same string, with no interpretation needed between departments.
Installations that call for exactly this arrangement:
- Sinter plant cooler and machine drives in steelworks
- Heavy apron feeders under primary crusher output
- Ball and rod mill circuits in mineral processing
- Tower-mounted bucket elevator head shafts
- Sludge and industrial wastewater thickeners and rakes
- Ship unloader and bulk terminal conveyor drives
Drive Points at the Top of the Torque Band
A hollow output at this frame size is chosen when the machine shaft is short, stiff and carried by its own bearings - the classic case is an elevator head or a conveyor head pulley inside a head station. The bevel input then earns its place whenever the motor must sit beside the machine rather than in line with it: inside a tower, along a wall, or under a gantry where axial space is priced by the metre. Where the driven shaft is long or lightly supported, WGT reviews the overhung load and shaft stiffness with the customer before the hollow build is confirmed, because the output bore carries both the gear unit weight share and the working pull.
Ordering, Drawings and Factory Test
The industrial range catalogue and the size 90 outline drawing are issued as PDF downloads, so bore diameter, keyway or shrink-disc seat, foot pattern and motor interface can be checked against the installation drawing before an order is placed. Send the driven machine, motor power and speed, target output speed, machine shaft diameter and the shift profile; the selection is verified with a rated-torque check against the duty service factor and confirmed in a written quotation. Every unit is run at the factory before packing in an export wooden crate and carries a one-year warranty.
Field Applications
Dust-extraction fan bank
An environmental-equipment plant uses reducers on the rotary valve feeders of its dust-extraction systems. Compact size, quiet running and food-grade oil options made the approval easy.
Steel mill run-out table
On the run-out table of a small steel mill, units handle the repeated starts and stops of hot billet handling. The 42CrMo output shafts tolerate the thermal cycling, and torque-arm mounting keeps the drive clear of the roller frames.
![where gear reducers are used in industry]()
Where these units are installed across industry.
Selection Example: Sinter cooler head drive
Take a 250 kW motor at 1490 rpm turning a sinter cooler drive shaft at 10 rpm. The ratio follows directly: 1490 / 10 = 149, so the three-stage band with a raised service factor covers the slow heavy torque. In this case the top frame and hollow bore ride the machine shaft directly, so no bedplate or output coupling is built. Once the ratio is fixed, check the required output torque against the rating table with the service factor applied - that is what decides the frame, not the ratio alone.
![gearbox selection guide: speed, torque, service factor]()
How a ratio and a frame size are determined, step by step.
Frame Sizes and Typical Duties
| Model | Centre distance | Output | Typical duty |
|---|
| 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 |
| M3RHT90 | size 90 | hollow shaft, torque arm, right-angle | heavy shaft-mounted drives |
The size number is the key dimension that steps up torque capacity through the range: 50 to 90 in horizontal builds, 10 to 90 in vertical builds. Gearing philosophy is shared across the family.
Talk to the Factory, Not a Catalogue
Questions before ordering? Engineers can size the unit themselves in the WGT Motor & Gearbox Online Selection System - input speed, torque and duty, get the model instantly.
Our technical team works beside the assembly line. Describe the application in your own words and you get a straight answer - including when a different frame or series would serve you better. Looking for a gearbox for packaging machine? Tell us the duty point and we will confirm the model in writing.
Common Questions from Buyers
How is each unit tested before shipment?
Every unit is run in on the bench before packing. Noise, temperature rise and backlash are recorded and the test sheet travels with the shipment, so you can file it with your incoming-inspection records.
What payment terms do you accept?
We normally work on 30% deposit and 70% against the bill-of-lading copy for sea freight, or 100% before dispatch for small orders. Other terms can be discussed for framework or repeat business.
Can you manufacture a custom ratio or a special shaft?
Beyond the catalogue ratios we can quote special ratios and custom output shafts - splined, extended, special keyways or drilled - for OEM volumes. Tooling is amortised across the order, so unit cost falls as quantity rises.
