The M3PHT90 torque arm gear unit is the top frame of the shaft-mounted industrial range. At size 90 the three-stage all-helical train on parallel axes reaches the torque class of crushing station feeders, kiln shells and long overland conveyor head drives, yet the unit still installs without a base frame: the hollow low-speed shaft slides onto the machine shaft and a torque arm reacts the drive torque back to the structure.
The Largest Torque-Arm Frame in the Industrial Range
It sounds counter-intuitive to hang the biggest unit in the family on a machine shaft, yet that is exactly what heavy plants ask for. Building a foundation at a conveyor head that will be shifted, or under a cooler shell that moves on its own supports, is impractical; the shaft-mounted arrangement turns an existing stiff shaft into the mounting. At size 90 the housing, shafts and bearings are dimensioned so the unit carries the overhung pull of a large head pulley without an auxiliary pedestal, while the horizontally split cast-iron case opens for tooth inspection without being lifted off the machine.
M3PHT90 Code in Full
| M3 | Industrial gear unit family with three helical stages |
| P | All-helical gearing on parallel axes (R would add a bevel right-angle input) |
| H | Hollow low-speed shaft, keyed fit or shrink-disc clamping (S marks a solid shaft) |
| T | Torque-arm mounting - the unit hangs on the machine shaft (F marks foot mounting) |
| 90 | Frame size 90, the top of the horizontal industrial band |
The three letters and the size number are independent, so the same size 90 housing is also ordered as a solid-shaft foot-mounted drive or a hollow-shaft foot build. A plant already running smaller frames of this range steps up the ladder without changing oils, spares or inspection practice - one system across the whole site.
The service conditions this frame is selected for:
- Heavy overland and shiftable conveyor head drives in open-pit mining
- Primary and secondary crushing station feeder and discharge drives
- Large rotary dryer, cooler and conditioning drum shells
- High-capacity thickener and clarifier rake mechanisms on centre columns
- Bulk terminal stacker, reclaimer and shiploader travel drives
- Long trough screw and chain reclaimer drives in stockyards
Why Big Plants Still Prefer Shaft Mounting Here
Every component removed from the drive train is a component that cannot fail or drift out of alignment. Omitting the output coupling, the pedestal bearing and the foundation removes three recurring maintenance items, and the torque arm doubles as the swing point for belt tensioning on conveyor duty. The condition to confirm is the machine shaft itself: it must be short and stiff enough to carry the gear unit and its reaction. WGT checks the shaft geometry against the outline drawing on every enquiry, and advises a foot-mounted build when the shaft is long or lightly supported.
Selection, Drawings and Delivery
WGT supplies the M-series catalogue and the size 90 outline drawing as PDF downloads, so the bore, keyway or shrink-disc seat and the torque-arm bracket can be verified before any commitment. Send the driven machine, the motor power and speed, the required output speed, the machine shaft diameter and the running hours per day; the rated torque is verified against those inputs and a written quotation follows. Each unit leaves the factory tested, crated for export and covered by a one-year warranty.
Available Frames and Their Typical Duty
| 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 |
Note that PSF and RSF frames of the same size share the mounting footprint; the R build simply inserts a bevel stage, so switching layout rarely forces a foundation change.
Questions and Answers
What happens if my duty changes after installation?
Send us the new duty point. A revised torque and service-factor calculation is free of charge, and the answer is usually one of three: the unit is fine, add an oil change interval, or plan a frame change at the next shutdown.
Can this unit mount on my existing installation without redesign?
Yes - the series is manufactured to the same centre distances, shafts and flange dimensions of the common industry frames, so couplings, guards and foundations stay untouched.
Which lubricating oil should be used?
GB L-CKC220~460 or Shell Omala 220~460 as supplied. Under normal duty the housing is lubricated for life; in hot or continuous-duty environments an oil change after the first 400 hours and then every 4000 hours is recommended.
Installation Examples
Wood chipper line
A board mill drives its drum chipper with a heavy-duty gear unit. Knife engagement shocks arrive several times a second, and the case-hardened gearing with generous bearing spans has shown no measurable wear.
Fertiliser plant drag chain
A fertiliser complex runs drag-chain conveyors on industrial gear units in a corrosive atmosphere. The heavy-duty epoxy coating and FKM seals have kept the units presentable and leak-free through several campaign cycles.
![gear box application map for industry]()
From quarries to food plants - one right-angle drive concept.
Selection Example: Overland conveyor head drive
Take a 160 kW motor at 1485 rpm driving a shiftable overland conveyor head shaft at 11 rpm. The ratio follows directly: 1485 / 11 = 135, so the three-stage band with a raised service factor covers the head-end torque. In this case the largest torque-arm frame rides the head shaft, so the drive relocates with the conveyor as the face advances. The ratio is the easy part. The service factor for the shock level is what makes the selection safe, and we check that for you at no charge.
![how to choose a speed reducer model]()
Ratio first, then torque, then frame size: the standard selection route.
From RFQ to Dispatch - One Account Manager
Tired of chasing suppliers? The WGT Motor & Gearbox Online Selection System covers motor power, ratio and mounting on one screen - enter your numbers and see the model immediately.
One account manager follows your enquiry from selection to dispatch, with lead times and test dates confirmed in writing. Urgent unit needs and project volumes are handled on the same route. Looking for a gearbox for mixer and agitator? Tell us the duty point and we will confirm the model in writing.
