Every frame band has a hinge point - the size where the duties stop being auxiliary and start being process. In the right-angle industrial family that hinge sits at the third frame. The MC3RLHF03 bevel-helical gear unit is bought when a frame two would run warm under a real duty and a frame four would waste bedplate space the layout does not have, and it ends up on conveyors, mixers and feeders that the plant genuinely notices when they stop.
The architecture is the family's: bevel pair at the input turning the drive through ninety degrees, then two helical stages down to output speed. The output is the hollow bore that gives the H in the type string, mounted over the driven shaft from a foot-mounted case. Everything about the build is one careful step up from the small frames - more oil, wider bearings, a heavier foot plane - and that step is what this page is about.
One Step Up the Band, a Different Machine
Frame numbers look like a smooth scale and are not. Between two and three, the driven machines change character: where a frame two turns something that can stop for a shift without anyone calling, a frame three usually drives a step in a continuous line - the conveyor that feeds the next process, the mixer the batch depends on, the feeder the upstream plant is sized around. The duty cycle hardens accordingly, with more starts, longer runs and less forgiveness for an undersized service factor.
That is why the third frame is the smallest one that should be selected against measured duty rather than against a catalogue guess. The torque table will accept a frame two for many of the same ratings on paper. The difference appears in the second year of three-shift running, as a bevel mesh that has lost its pattern and a case that runs ten degrees warmer than the day it arrived.
The Third Frame Between Conveyor and Mixer
Walk through any mid-size process plant and the third frames sit in a recognisable set of places: head shafts of short belt conveyors, drag chains under the broke system, agitators on slaking and make-up services, feed pumps that start against pressure, and rotary screens that shake through the wet season. What the duties share is a load that varies with the material rather than with the schedule, which is why the selection has to survive the worst hour, not the average one.
The right-angle input earns its place in exactly these positions. Motors sit where there is floor space, not where the shaft points, and on a crowded conveyor gantry or beside a mixer bridge that freedom decides whether the installation is maintainable or merely installed. A drive that a fitter can reach without stripping a guard is a drive that gets greased, sampled and listened to.
Decoding the Type String on a Frame Three
The designation carries the whole arrangement, and each character maps to a choice made before the case is cast.
| MC | Industrial gear unit family built for continuous process duty |
| 3 | Three-stage train: bevel input pair and two helical reductions |
| R | Right-angle bevel-helical geometry, motor across the driven shaft |
| L | Horizontal arrangement, both shafts level in one case |
| H | Hollow output bore mounting directly over the driven shaft |
| F | Foot mounting onto a bedplate or fabricated support |
| 03 | Third frame of the band: continuous line duties where duty cycle, not torque, decides the size |
The string stays quiet about the details that cost weeks when missed. Which end the motor mounts on. Whether a second shaft end is wanted for a brake or an encoder. Where the breather must face to survive the washdown. None of these are option lists on a page; all of them are one line each on an order confirmation, which is where they belong.
Torque, Overhang and the Honest Duty Cycle
The classic selection error at this frame is not the ratio but the load history. A duty described as 'sixteen hours a day, gentle starts' and a duty that is in truth 'sixteen hours, eight starts, two of them against a stalled chain' fit the same line in a simplified table and different lines in reality. Starts per hour, breakaway torque and the worst material surge are the three numbers that separate a frame three from a hopeful frame two.
Overhang deserves the same honesty even on a hollow-shaft build. The bore carries the driven shaft, but anything else hung beyond it - a sprocket, a sheave, a bracket - acts on the bearings through a lever the rating was never given. Measuring the actual overhang and stating it on the enquiry costs nothing and removes the one assumption that most often turns out wrong.
Foot Bolts, Bedplates and Small-Frame Rigidity
A small case forgives more than a large one, but not infinitely. Foot pads that do not share load turn one bolt into a hinge, and at this size the symptom is subtle - a seal that weeps on one side, a bore that frets unevenly - rather than a dramatic failure. Levelling the mounting face, shimming until the pads take evenly and tightening in the diagonal sequence is fifteen minutes of work that protects the whole arrangement.
Fabricated supports deserve a second glance. On a conveyor gantry, the steelwork under the drive often moves more than the gear case does, and the unit is blamed for a vibration that belongs to a beam. Checking the support for resonance before the unit is bolted down is cheaper than two site visits later, and it is work the millwright can do with a hand on the steel and the motor running.
Oil Volume in a Small Case Runs Hot Fast
The small frames have the least thermal reserve in the family, and they spend it quickly when the ambient climbs. A case that sits beside a steam line, under a roof in summer or in a washdown corridor needs its thermal rating checked at the true corner temperature, not at the workshop average. Where the check fails, the answers are ordinary: a breather moved clear, a fan of air directed at the case, or one frame more with the oil to match.
Oil condition tells the story early. Small sumps contaminate fast because a few grams of wear metal or water is a large fraction of the volume, so the first sample at the first oil change sets the baseline and a yearly sample after that catches drift. A milky sample in a washdown corner is a breather problem wearing a bearing costume; catching it at sample stage is the whole point of taking one.
Standardising a Plant on the Low Frames
Plants that run many small duties have a choice: size each drive to its own exact optimum, or standardise the low band on one or two frames with a common oil, common seals and one disassembly sequence the crew knows by heart. The first looks efficient on paper; the second runs cheaper for decades, because the holding cost of six different spares pools dwarfs the few kilograms of iron saved by perfect sizing.
The hollow-bore foot build is a natural standard for this. The same frame mounts over shafts of one diameter across half a plant, the fitters learn one fitting sequence, and a breakdown anywhere borrows the spare kept for everywhere. When the next small drive is specified, the question worth asking first is not 'what is the minimum frame' but 'does the standard cover it'.
An Enquiry That Closes in One Pass
Everything a selection engineer needs fits in a short list. Motor power, speed and starting method. Driven machine and its load pattern, with starts per hour and breakaway stated. Output speed and tolerance. Hours per day and the worst duty hour described. True ambient at the corner, steam and washdown included. Driven shaft diameter, key and available length for the bore. Mounting position, motor orientation, rotation direction. Paint, nameplate and documentation requirements.
Supplied complete, that list returns a quotation and an outline drawing in one round, and the order confirmation becomes the commissioning checklist. Supplied incomplete, it returns a query sheet, and every exchange adds a week to a delivery the production plan already assumed. A third-frame unit is small money in a project; the week of delay it can cause is not.
Full Frame Range of 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 |
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
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.
Selection Example: Inclined drag chain conveyor at a rendering plant
Take a 7.5 kW motor at 1450 rpm driving the tail sprocket at 22 rpm. The ratio follows directly: 1450 / 22 = 65.9, so a ratio near i=66 is drawn, and the service factor is set by the restarts that follow a chain stalled under a surge of raw material rather than by the running load alone. In this case the third frame absorbs those restarts with margin to spare, and the foot-mounted case holds the conveyor line true without a torque arm to adjust. 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
How is the gear unit protected against dust and moisture?
Housings are gasket-sealed with labyrinth or lip seals at both shafts as standard. Dusty plants, washdown areas and outdoor installations are covered by coating and sealing options specified together with the order.
What inspection access does the housing provide?
The horizontally split housing opens along the shaft centreline, so gearing and bearings can be examined without removing the unit from its foundation. Covers give access to the oil galleries and bearing seats during service.
![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 motor for car wash system? Tell us the duty point and we will confirm the model in writing.
