The RX77 helical gear unit moves the RX concept into medium-torque territory. Its 77 mm centre distance and generously sized output shaft make it a natural fit for existing RX77 installations on mixers, extruders, aeration blowers and heavy conveyors. For machine builders the attraction is simple: one compact coaxial gearbox that reaches ratios a two-stage worm unit cannot manage without losing efficiency.
A Mid-Range Frame That Stays on Axis
- 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
RX77 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 |
Proven in service across these industries:
- Extruders and plastics machinery
- Cranes, hoists and winches
- Cement, lime and aggregate plants
- Paper, textile and light industry
- Belt, screw and chain conveyors
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 RX77 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.
Field Applications
Grain terminal elevators
A grain terminal powers its bucket elevators with gear reducers. The anti-run-back option holds the loaded buckets during power cuts, and standard interface dimensions meant the old foundations were reused as they were.
Pallet lift in a warehouse
A logistics integrator selected units for pallet lifts. The hollow output bore carries the lift screw directly, and one year of three-shift operation has passed without a single seal replacement.
![where gear reducers are used in industry]()
Where these units are installed across industry.
Selection Example: Paddle mixer in a food plant
Take a 4 kW motor at 1440 rpm stirring a paddle mixer at 29 rpm. The ratio follows directly: 1440 / 29 = 50, so i=50 is chosen. In this case the 77 mm frame takes the start-up torque of a settled batch. Once the ratio is fixed, check the required output torque against the rating table with the service factor applied - that is what decides the frame, not the ratio alone.
![gearbox selection guide: speed, torque, service factor]()
How a ratio and a frame size are determined, step by step.
Frame Sizes and Typical Duties
| Model | Centre distance | Output | Typical duty |
|---|
| RX77 | 77 mm | solid shaft, foot | mixers, extruders |
| RX57 | 57 mm | solid shaft, foot | small conveyors, dosing screws |
| RX67 | 67 mm | solid shaft, foot | packaging, light mixers |
| RX87 | 87 mm | solid shaft, foot | screw conveyors, agitators |
| RX97 | 97 mm | solid shaft, foot | thickeners, blowers |
| RX107 | 107 mm | solid shaft, foot | aerators, heavy conveyors |
| RX127 | 127 mm | solid shaft, foot | mill drives, large hoists |
| RX157 | 157 mm | solid shaft, foot | heaviest inline drives |
Read the frame number as the centre distance in millimetres, from 57 mm up to 157 mm. Gearing, efficiency and backlash are unchanged across the range; only torque capacity and shaft size step up with the frame.
From Duty Point to Delivery in One Working Day
Stop guessing the ratio. Engineers can size the unit themselves in the WGT Motor & Gearbox Online Selection System - input speed, torque and duty, get the model instantly.
Tell us what the machine does and how hard it works; we calculate the ratio, apply the service factor and send back the drawing and quotation within one working day, including sea-freight and air-freight options. Looking for a gearbox for mixer and agitator? Tell us the duty point and we will confirm the model in writing.
Common Questions from Buyers
What ambient temperature range can the unit work in?
Standard units suit -10 to +40 deg C ambient with the supplied mineral oil. For lower temperatures we fill with synthetic oil; for higher ambient or frequent starting we advise the next larger frame or an oil cooler.
What are the delivery lead times and shipping terms?
Standard lead time is 5-10 weeks ex-works, with popular ratios often available sooner. We quote EXW, FOB NINGBO / SHANGHAI or CIF, and urgent units can be air-freighted within 72 hours of payment.
What materials are used for the gears and shafts?
Gears are 20CrMnTi alloy steel, case-carburised to HRC58-62 over a tough HRC33-40 core. Input and output shafts are 42CrMo, quenched and tempered to HRC25-30. The housing is cast iron at HBS190-240.
