The M3RHF50 hollow shaft bevel helical gearbox joins two ideas that solve different site problems at once: a bevel input stage that turns the motor line 90 degrees, and a hollow low-speed shaft that slides straight onto the driven machine shaft. The result is a compact size 50 industrial unit with no output coupling, no intermediate pedestal and no motor projecting along the conveyor axis - the shortest possible drive train for a machine shaft that is already in place.
Hollow Output Meets the Right-Angle Layout
In the standard R-family build the solid output shaft leaves the unit through a keyed coupling. In this H build the machine shaft enters the output bore instead, so alignment effort on site shrinks to the motor side and the gear unit is held by its feet on a bracket or base while the hollow bore takes the torque. Inside, the gearing philosophy is unchanged from the rest of the industrial range: a case-hardened ground bevel stage followed by helical stages, all running in one oil sump inside a horizontally split cast-iron housing that opens for inspection without moving the unit.
The R-H-F Combination Explained
| M3 | Industrial gear unit family, three gear stages |
| R | Bevel-helical right-angle layout (P marks the all-helical parallel build) |
| H | Hollow low-speed shaft, keyed fit or shrink-disc connection (S marks solid shaft) |
| F | Foot mounting; the T code would put the unit on a torque arm instead |
| 50 | Frame size 50, entry point of the horizontal range 50 to 90 |
Because the three letters and the size number are independent, a buyer can step across the family - solid to hollow, foot to torque arm, size 50 to 90 - while the maintenance routine, oil specification and inspection practice stay the same. That is the practical appeal of specifying the industrial range as a plant standard rather than buying drives one at a time.
Duties this industrial gear unit is built for:
- Inclined and pocket belt conveyors where the motor must sit alongside the belt line
- Bucket elevator head shafts driven straight through the hollow output bore
- Rotary airlocks and discharge gates on hoppers and silos
- Paddle and plough mixers in fertiliser and chemical plants
- Screw conveyor tail and intermediate drive points on long troughs
- Travel drives on gantry and portal crane structures
Where This Build Simplifies the Drive Train
Every component that is not there cannot fail: with the machine shaft inside the output bore, there is no coupling to re-centre after foundation settlement, no flexible element to age, and no pedestal bearing to grease. For elevators, airlocks and paddle mixers where the driven shaft is short and stiff, the arrangement is usually the cheapest to install and the easiest to keep aligned over years of duty. Where the machine shaft is long or lightly supported, WGT will advise whether the foot-mounted hollow build or a torque-arm variant suits better before the drawing is issued.
Drawings, Checks and Ordering
WGT provides the M-series catalogue and the size 50 outline drawing as PDF downloads, so the bore diameter, keyway or shrink-disc seat, foot pattern and motor interface can all be checked before ordering. Send the driven machine, the motor power and speed, the required output speed, the machine shaft diameter and the daily running hours; the selection is verified against those figures, quoted in writing, factory-tested and packed in an export wooden crate under a one-year warranty.
Selection Example: Rotary airlock drive
Take a 15 kW motor at 1455 rpm turning a rotary airlock under a silo discharge at 34 rpm. The ratio follows directly: 1455 / 34 = 42.8, so a ratio near i=43 is selected. In this case the hollow output slides straight onto the airlock shaft and the bevel input keeps the motor clear of the hopper wall. The same three numbers - motor speed, target output speed, required torque - are all you need; our engineers (or the online selector below) cross-check the service factor for your duty cycle.
![gear reducer selection flow chart - ratio and frame size]()
Figure: from motor data to a confirmed gearbox model in four steps.
Common Models in the M3 Series
| 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 table below shows the M3 industrial range: P builds are all-helical on parallel axes, R builds add a bevel input stage for a right-angle drive; S / H describe the low-speed shaft and F / T the mounting.
Application Cases
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.
![industrial gearbox applications - conveyor mixer crusher wastewater]()
Figure: typical industries that use the WGT S-series gear reducers.
Frequently Asked Questions
What is a service factor and which value should I use?
The service factor multiplies your required torque to cover shock and duty class: around 1.0 for uniform conveyors, 1.25 for moderate shocks and 1.5 or higher for crushers, shredders and reversing drives. Tell us the driven machine and we apply the correct value before quoting.
Can the gear unit hold a load on an inclined conveyor?
For inclined belts a backstop prevents the loaded belt from driving the unit backwards when power is cut. Specify the incline angle when ordering so the backstop and the oil level are matched to the actual mounting position.
What is the difference between foot and torque-arm mounting?
Foot mounting bolts the housing to a foundation and suits most fixed installations. A torque-arm lets the housing swing on the driven shaft, so no base frame is needed - common on shaft-mounted conveyors where the reaction rod absorbs the torque.
Send the Nameplate - Get the Equivalent Frame
Matching an existing installation? Not sure which model fits? Try our online WGT Motor & Gearbox Online Selection System to match motor power, ratio and mounting in one minute.
Photograph the nameplate or note the model and ratio. We identify the equivalent frame, confirm the torque margin and return a quotation with the outline drawing - usually within one working day. Looking for a gearbox for steel mill? Tell us the duty point and we will confirm the model in writing.
