The R77 inline gear reducer moves the R concept into medium-torque territory. Its 77 mm centre distance and generously sized output shaft make it a straightforward match for existing R77 installations on mixers, extruders, aeration blowers and heavy conveyors. For machine builders the attraction is simple: one compact coaxial gearbox that covers ratios a two-stage worm unit cannot reach without losing efficiency.
Engineering Notes on the R77
- Helical gearing throughout - rolling contact, so losses stay low at every ratio
- Cast-iron / ductile-iron housing, HBS190-240, resists impact and harsh site conditions
- Gears in case-hardened 20CrMnTi, ground to grade 6~5; noise stays between 60 and 68 dB
- Backlash 20 arcmin or less, vibration 20 μm or less - smooth under reversing loads
- Heat treatment: tempering, carburising and quenching on the critical gear faces
Data Sheet
| Housing material | Cast iron / ductile iron |
| Housing hardness | HBS190-240 |
| Gear material | 20CrMnTi alloy steel |
| Surface hardness of gears | HRC58~62 |
| Gear core hardness | HRC33~40 |
| Input / output shaft material | 42CrMo alloy steel |
| Input / output shaft hardness | HRC25~30 |
| Machining precision of gears | precision grinding, grade 6~5 (ISO 1328) |
| Lubricating oil | GB L-CKC220~460 / Shell Omala 220~460 |
| Heat treatment | tempering, carburising, quenching, etc. |
| Efficiency | 94%~96% (depends on the transmission stage) |
| Noise (max) | 60~68 dB |
| Temp. rise (max) | 40 C |
| Temp. rise (oil) (max) | 50 C |
| Vibration | ≤20 µm |
| Backlash | ≤20Arcmin |
| Brand of bearings | HRB/LYC/ZWZ/C&U (SKF, FAG, INA, NSK optional) |
| Brand of oil seal | NAK -- Taiwan or other brands requested |
Where customers install this frame:
- Wastewater treatment and water supply
- Extruders and plastics machinery
- Food processing and packaging lines
- Belt, screw and chain conveyors
- Cement, lime and aggregate plants
Packing and After-Sales
Units are rust-protected, boxed with an installation manual and packed in export-grade wooden crates for NINGBO or SHANGHAI shipment. WGT supports every R77 with a one-year warranty, spare seal and bearing kits, and engineering advice on oil change intervals and mounting position. Send your specification - drawings, torque curves and a firm quotation come back within 24 hours.
Questions We Hear Most Often
What is the difference between a keyed hollow shaft and a shrink-disc connection?
A keyed hollow shaft is the economical choice for normal torque and easy maintenance. A shrink-disc connection transmits higher torque with zero backlash and no keyway wear, and is preferred for reversing or high-torque duties.
Can I get a CAD drawing or 3D model for my design review?
Yes. Send us the model and ratio and we provide a 2D dimension drawing and a 3D STEP model for your review, usually the same working day. Drawings follow the layout of the original series so they drop into your existing assembly.
What is the recommended oil change interval?
The housing is lubricated for life under normal duty and normal ambient. In hot, humid or continuous service, change the oil after the first 400 running hours and then every 4000 hours, or once a year, whichever comes first.
Choosing the Right Frame Size
| Model | Centre distance | Output | Typical duty |
|---|
| R77 | 77 mm | solid shaft, foot | extruders, heavy conveyors |
| R17 | 17 mm | solid shaft, foot | small conveyors, dosing screws |
| R27 | 27 mm | solid shaft, foot | packaging, light agitators |
| R37 | 37 mm | solid shaft, foot | belt conveyors, small mixers |
| R47 | 47 mm | solid shaft, foot | screw conveyors, feeders |
| R57 | 57 mm | solid shaft, foot | mixers, aeration blowers |
| R67 | 67 mm | solid shaft, foot | mixers, extruders |
| R87 | 87 mm | solid shaft, foot | screw conveyors, agitators |
| R97 | 97 mm | solid shaft, foot | thickeners, blowers |
| R107 | 107 mm | solid shaft, foot | aerators, heavy conveyors |
| R137 | 137 mm | solid shaft, foot | mill drives, large hoists |
| R147 | 147 mm | solid shaft, foot | mill drives, heavy hoists |
| R167 | 167 mm | solid shaft, foot | heaviest inline drives |
One gear set, many mountings. Pick the frame size for the torque you need, then pick the mounting style - foot-mounted solid shaft, flanged or shaft-mounted - to suit your machine layout.
Selection Example: Sludge scraper in a clarifier
Take a 4 kW motor at 1450 rpm turning the scraper arms at 12 rpm. The ratio follows directly: 1450 / 12 = 121, so i=120 is selected. In this case the inline frame mounts flat on the clarifier bridge with no side clearance needed. It always comes down to those three figures. Send them over and we confirm the frame, ratio and service factor in writing.
![online gearbox selection system workflow]()
Selection workflow used by our engineers for every quotation.
Real-World Duty Points
Cement plant clinker belt
A cement plant drives its clinker transport belt with reducers in dusty, high-ambient conditions. Sealed housings and a 40 deg C maximum temperature rise let the units sit close to the kiln without extra cooling.
Paper mill pulp agitator
A paper mill uses reducers on pulp chest agitators. Continuous 24-hour duty is handled by lifetime lubrication, and the low backlash keeps the agitator steady when the stock consistency changes.
![right angle gearbox duty points overview]()
An overview of the duty points this series is built for.
Your Selection, Cross-Checked by an Engineer
Send the numbers, get the model. Use the WGT Motor & Gearbox Online Selection System to turn your motor data into a model number, and we will quote that exact unit within the day.
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 gearbox for wastewater treatment? Tell us the duty point and we will confirm the model in writing.
