The M3RHT80 shaft mounted bevel gear unit fills the gap between the medium frames used on plant conveyors and the very large drives reserved for overland systems. Its spiral-bevel first stage turns the drive through 90 degrees, a pair of helical stages multiplies the torque, and a hollow output bore carries the whole reaction onto the driven shaft through a torque arm rather than a bedplate. For a head pulley that has to move hundreds of tonnes per hour, all day, this is the most direct mechanical path available.
The Size 80 Shaft-Mounted Drive for Main-Line Tonnage
Frame growth inside one industrial family is not only a matter of a bigger casting. At size 80 the gear centres, shaft diameters and bearing sections are stepped up together, which is what allows the unit to absorb the shock of a loaded belt starting under material and to hold the overhung load of a pulley without an auxiliary bearing. Engineers comparing a size 80 against a size 70 usually find the decision turns on starting torque and bearing life rather than on nominal ratio, because both frames will turn the shaft - only one will still be turning it a decade later.
How the Type Code Maps the Mechanics
| M3 | Three-stage industrial gear unit family |
| R | Right-angle bevel-helical input; a P in this position would mean parallel shafts |
| H | Hollow output bore, keyed, bored to suit the pulley shaft |
| T | Torque-arm reaction; F in this slot denotes foot mounting |
| 80 | Frame size 80, second largest of the horizontal band |
Note what the letters do not say. Neither the code nor the catalogue page states a ratio, a power rating or an output speed, because those are decided by the selection calculation for the specific duty. Treat the designation as the mechanical envelope and the calculation as the content that fills it.
Service profiles this build is regularly chosen for:
- Head pulleys on main-line bulk conveyors in cement works
- Apron feeders under primary screening stations
- Slurry thickener rake mechanisms in mineral processing
- Rotary drum drives on aggregate washing plants
- Travelling stacker and reclaimer boom conveyors
- Dewatering screw press drives in tailings circuits
Fitting Without a Foundation
The practical argument for a shaft-mounted build is installation time. The unit slides onto a finished pulley shaft, the torque arm is pinned to a bracket on the conveyor frame, and the motor is carried on a swing base or a motor mount bolted to the housing. There is no grouting, no soleplate alignment and no coupling gap to set. When the drive eventually needs attention, it withdraws along the shaft, which matters on a conveyor gallery where lifting equipment is scarce and shutdown windows are measured in hours. Hollow-bore contact is made with a key and a shrink disc or ringfeder arrangement depending on the option chosen; either way the fit must be clean, dry and free of paint.
From Duty Point to Delivered Unit
Three inputs decide the selection: motor power and speed, required output speed at the pulley, and the character of the load - uniform, moderate shock or heavy shock. From these the service factor, thermal capacity and overhung load check follow. WGT supplies the catalogue and the size 80 outline drawing as PDF downloads so that bore, keyway and torque-arm geometry can be confirmed against the machine frame before ordering. The final selection is issued with a written quotation; units are assembled, run tested, crated for export and warranted for one year.
Selection Example: Primary apron feeder drive
Take a 160 kW motor at 1485 rpm driving an apron feeder head shaft at 11 rpm. The ratio follows directly: 1485 / 11 = 135, so a deep three-stage ratio is chosen and the frame is then checked against breakaway torque with a heavy-shock service factor. In this case the hollow bore takes the feeder head shaft with a shrink disc, and the torque arm pins to the feeder frame so no bedplate is fabricated. That is the whole calculation. If your duty involves heavy starting, frequent reversing or many stops per hour, tell us and we raise the service factor.
Which Frame Size Do You Need?
| 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 |
Foot-mounted frames are listed below; torque-arm (T), hollow-shaft (H) and vertical (V) variants are available across the size range. Ask for the outline drawing to check the interface before ordering.
Answers to Common Questions
What ratio range does an industrial gear unit cover?
The range spans from low single-digit reductions to very high ratios by combining stage counts: two-stage builds for the lower band and up to five-stage builds for the highest reductions, with intermediate ratios available between catalogue steps on request.
Which lubrication system does the unit use?
Small and medium frames run on splash lubrication with mineral or synthetic oil. Larger frames or high ambient temperatures can be ordered with forced-feed circulation and cooling coils; the lubricant grade is stated on the nameplate and in the manual.
How often should the oil be changed in heavy duty?
With mineral oil, plan an initial change after the running-in period and then roughly every 5,000 hours. Synthetic oil stretches the interval to around 10,000 hours. Hot environments, dust or frequent starts shorten the interval - we advise the schedule with the quotation.
![gearbox sizing steps for engineers]()
Four steps from your application data to a firm model number.
Case Notes from the Field
Asphalt plant aggregate feeder
An asphalt plant powers its aggregate feeders with reducers in outdoor, dusty conditions. The cast-iron housing and standard paint finish have come through several winters without refurbishment.
Fertiliser granulator drum
A fertiliser producer drives granulator drums with gear units. The slow, high-torque rotation needed to tumble the granules is a natural fit, and the torque-arm option avoids a heavy base frame.
![industrial gear unit application overview]()
A cross-section of the installations we supply every month.
Tell Us the Torque, We Confirm the Model
Not sure where to start? Try the WGT Motor & Gearbox Online Selection System, then send the result sheet - we return a complete datasheet, drawing and price the same day.
A photo of the nameplate, the motor power and the output speed you need are enough to start. We confirm the frame size, ratio and mounting style and return a written quotation the same day. Looking for a gearbox for belt conveyor? Tell us the duty point and we will confirm the model in writing.
