R/F/K/S Series Helical Gear Reducer
R/F/K/S Series Helical Gear Reducer Overview
The R, F, K, and S series gear reducers form a modular family of industrial speed reduction units designed for continuous-duty power transmission. Each series uses helical gearing as the primary reduction stage, providing higher efficiency, lower noise, and greater load capacity compared to spur gear or worm gear alternatives. The hardened and ground helical tooth profiles operate with a contact ratio above 1.5, distributing the load across multiple teeth simultaneously for smooth, quiet power transfer.
All four series share a common modular architecture: standardized IEC motor input flanges (B5 and B14), keyed hollow shaft or solid shaft output options, and multiple mounting positions including foot, flange, shaft, and torque arm configurations. This modular design allows the gearbox to be paired with any IEC standard three-phase motor without intermediate couplings or adapter plates.
Gear reducers are filled with synthetic polyalphaolefin (PAO) gear oil (equivalent to Mobil SHC 630 or Shell Omala S4 GX 220) for extended oil change intervals of up to 20,000 hours. Oil sight glasses, vent plugs, and drain plugs are fitted as standard for easy maintenance access. Operating temperature range is -20°C to +40°C ambient, with high-temperature seals available for environments up to +60°C.
Four Series Comparison
| Feature | R Series (Inline Helical) | F Series (Parallel Shaft) | K Series (Helical-Bevel) | S Series (Helical-Worm) |
|---|---|---|---|---|
| Output Shaft Direction | Coaxial (inline) | Parallel offset | 90° right angle | 90° right angle |
| Gear Type | Helical only | Helical only | Helical + spiral bevel | Helical + worm |
| Sizes Available | R07 – R167 | F37 – F157 | K37 – K187 | S37 – S97 |
| Ratio Range | 1.3 – 289 | 3.77 – 281 | 5.36 – 197 | 5.69 – 3,038 |
| Max Input Power | 160 kW | 160 kW | 200 kW | 22 kW |
| Efficiency (per stage) | 96 – 98% | 96 – 98% | 95 – 97% | 70 – 90% |
| Best Application | Conveyors, agitators, inline drives | Space-limited parallel offset | Right-angle high-torque drives | Very low speed, self-locking |
R Series Inline Helical Gear Reducer Specifications
| Model | Max Input (kW) | Output Shaft (mm) | Ratio Range | Max Torque (N·m) | Weight (kg) |
|---|---|---|---|---|---|
| R07 | 0.12 | 14 | 3.66 – 67 | 85 | 1.4 |
| R17 | 0.25 | 20 | 3.66 – 67 | 170 | 2.8 |
| R37 | 1.5 | 35 | 3.66 – 289 | 800 | 8.5 |
| R57 | 5.5 | 50 | 3.66 – 289 | 2,000 | 22 |
| R77 | 22 | 70 | 4.39 – 289 | 7,400 | 65 |
| R97 | 75 | 100 | 4.39 – 289 | 25,000 | 195 |
| R107 | 132 | 120 | 4.39 – 150 | 35,000 | 330 |
| R167 | 160 | 140 | 4.39 – 150 | 50,000 | 500+ |
Key Technical Parameters
| Parameter | Specification |
|---|---|
| Gear Material | 20CrMnTi alloy steel, carburized and hardened to HRC 58–62 |
| Gear Accuracy | DIN 6 (ISO 1328), ground tooth flanks |
| Housing Material | High-strength cast iron HT250 |
| Shaft Material | 42CrMo alloy steel, quenched and tempered |
| Bearing Type | Tapered roller bearings (output shaft), deep groove ball bearings (input shaft) |
| Sealing | Double-lip oil seals (NBR standard, FKM Viton available for high temperature) |
| Protection Class | IP65 (housing sealed against dust and low-pressure water jets) |
| Lubricant | Synthetic PAO gear oil VG220/VG320, filled at factory, oil change at 20,000 hours |
| Service Factor | SF ≥ 1.0 (standard), SF 1.25–2.0 for shock-load applications |
| Operating Temperature | -20°C to +40°C ambient (high-temp seals for up to +60°C) |
| Motor Interface | IEC B5/B14 input flange, standard for all IEC frame 63–315 motors |
| Output Options | Solid shaft with keyway (standard), hollow shaft with keyway, hollow shaft with shrink disc |
| Mounting Positions | M1–M6 (6 standard positions), foot, flange, shaft-mounted, torque arm |
| Noise Level | ≤ 75 dB(A) (R37–R57); ≤ 83 dB(A) (R77–R97) at rated load |
| Standards | DIN 3990 (gear strength), ISO 6336 (load capacity), DIN 3992 (profile shift) |
Features and Advantages
Hardened Ground Helical Gears
Gears are carburized from 20CrMnTi alloy steel with an effective case depth of 0.8–1.2 mm, achieving surface hardness of HRC 58–62 while maintaining a tough core (HRC 33–38). After heat treatment, tooth flanks are precision-ground to DIN 6 accuracy. This combination of surface hardness and core toughness provides high contact fatigue strength (≥ 1,500 MPa per ISO 6336) and resistance to pitting, spalling, and tooth breakage under sustained heavy loads.
High Mechanical Efficiency
Helical gear stages achieve 96–98% efficiency per stage, significantly higher than worm gear reducers (70–90%). For a typical two-stage R57 gearbox, the overall efficiency is approximately 94%. This means less energy wasted as heat, lower operating temperatures, longer lubricant life, and reduced electricity costs over the service life of the equipment. The efficiency advantage is most pronounced at higher loads and lower speed ratios.
Modular Combination Capability
All four series (R, F, K, S) can be combined with each other to achieve very high total ratios or unique shaft configurations. For example, an R37 can be mounted as a pre-stage on top of an R57 to achieve ratios up to 84,000:1. The K series can be paired with an R series to create a right-angle drive with an extended ratio range. This modular architecture reduces the need for custom gearbox designs and shortens delivery times.
Direct Cross-Reference to Major Brands
Our R/F/K/S gearboxes are dimensionally compatible with SEW Eurodrive R/F/K/S series, Nord SK series, Bonfiglioli C/A/S series, and Flender/Siemens MOTOX series. Output shaft diameter, center height, and mounting bolt patterns match the equivalent model from each brand, allowing our gearboxes to serve as direct replacements without modifying the existing machine base or driven equipment connection.
Industry Applications
Conveyors and Material HandlingBelt conveyors, screw conveyors, roller conveyors, and bucket elevators. The R series (inline) and K series (right-angle) are the most commonly specified for conveyor head drives. Typical sizes: R57–R97 with YE3 motors 2.2–55 kW. |
Mixers and AgitatorsTank agitators, paddle mixers, ribbon blenders, and reaction vessel stirrers. High output torque at low speed (typically 10–60 rpm) is achieved with two-stage or three-stage helical reduction. K series right-angle drives allow top-entry vertical agitator mounting. |
Packaging and Processing LinesCartoning machines, palletizers, stretch wrappers, and automated assembly lines. The F series parallel shaft design provides a compact drive for machines with limited space between the motor axis and the driven shaft. |
Cement and Building Materials
Kiln drives, clinker cooler drives, raw mill separators, and cement mill drives. Heavy-duty R97–R167 gearboxes with service factor 1.5 or higher are specified for these high-inertia, shock-load applications operating 24/7.
Wastewater Treatment
Sludge thickener drives, clarifier rake drives, screw press drives, and aerator rotation mechanisms. Low output speeds (0.5–5 rpm) with high torque are typical requirements, achievable with K or S series at extended ratios.
Sugar and Beverage Industry
Sugar mill roller drives, centrifuge drives, and bottling line conveyor drives. The food-grade lubricant option (NSF H1) is available for gearboxes installed in direct food contact zones within beverage and sugar processing plants.
Cross-Reference to Major Gearbox Brands
| Korea Ever-Power | SEW Eurodrive | Nord Drivesystems | Bonfiglioli |
|---|---|---|---|
| R Series (Inline) | R Series (R07–R167) | SK 0182–SK 12282 | C Series |
| F Series (Parallel) | F Series (F37–F157) | SK 3282–SK 9382 | A Series |
| K Series (Bevel) | K Series (K37–K187) | SK 9282–SK 12382 | A/HDO Series |
| S Series (Helical-Worm) | S Series (S37–S97) | SK 1282–SK 5282 | S Series |
Maintenance and Lubrication
All gear reducers are factory-filled with synthetic polyalphaolefin (PAO) gear oil for extended service intervals. Maintenance schedule:
First oil change: after 500 operating hours (to remove initial break-in particles)
Subsequent oil changes: every 20,000 hours or 3 years (whichever comes first) for synthetic oil; every 10,000 hours for mineral oil
Check oil level via sight glass monthly. Top up if level falls below the minimum mark.
Inspect output shaft seals annually for oil leakage. Replace seals if leakage is detected. Clean the housing surface and inspect for cracks or damage during each oil change. Record oil analysis results (particle count, water content, viscosity) to monitor internal wear trends and predict maintenance needs before failure occurs.
Frequently Asked Questions
What is the difference between a helical gear reducer and a worm gear reducer?
Helical gear reducers (R/F/K series) use meshing helical gears for speed reduction, achieving 96–98% efficiency per stage. Worm gear reducers use a worm and wheel mechanism, which is simpler and more compact but significantly less efficient (70–90% per stage). Helical gearboxes are preferred for applications requiring high efficiency, continuous heavy-duty operation, and back-drivability. Worm gear reducers are preferred when self-locking (non-back-drivable) capability, very high ratio in a single stage, and lower cost are priorities.
How do I select the correct gearbox size?
Start by determining the required output torque (N·m) and output speed (rpm). Calculate the required ratio by dividing the motor speed by the desired output speed. Then select a gearbox model with a rated torque equal to or greater than the required output torque multiplied by the service factor for your application type. The service factor accounts for shock loads, operating hours per day, and the number of starts per hour. Typical service factors are 1.0 for uniform loads, 1.25 for moderate shock, and 1.5–2.0 for heavy shock loads.
Can your gearboxes replace SEW Eurodrive models directly?
Yes. Our R, F, K, and S series gearboxes use the same designation system and are dimensionally compatible with the corresponding SEW Eurodrive models. For example, our R57 matches the SEW R57 in output shaft diameter, center height, mounting bolt pattern, and overall envelope dimensions. We provide detailed dimensional comparison drawings upon request to verify compatibility for your specific installation.
What type of oil should be used?
We recommend synthetic polyalphaolefin (PAO) gear oil at ISO VG220 viscosity for standard operating conditions (-20°C to +40°C ambient). Equivalent products include Mobil SHC 630, Shell Omala S4 GX 220, Castrol Optigear Synthetic X 220, and Fuchs Renolin Unisyn CLP 220. For operating temperatures above +40°C, use VG320 grade. All gearboxes are factory-filled with synthetic oil at the correct level for the specified mounting position.
What is the expected service life of the gears?
When operated within rated torque and speed limits with proper lubrication, the gear set is designed for a minimum L10 calculated life of 50,000 hours per DIN 3990 / ISO 6336. Actual service life depends on applied load, operating temperature, contamination level of the lubricant, and the consistency of the maintenance schedule. Many gearboxes in properly maintained installations exceed 100,000 hours before requiring gear replacement.
Can a gearbox be mounted in any orientation?
Our gearboxes support 6 standard mounting positions (M1 through M6), including horizontal foot-mount, wall-mount, ceiling-mount, and flange-mount orientations. The oil fill level, vent plug position, and drain plug location vary by mounting position. When ordering, specify the mounting position code to ensure the gearbox is assembled and filled correctly for your installation orientation.
What is the lead time for helical gear reducers?
Standard R and F series gearboxes in sizes R37 through R97 with common ratios ship within 12–20 business days. K and S series and larger sizes (R107, R167) typically require 20–30 days. Contact our team for current stock availability and exact delivery dates for your configuration.
Customer Experiences
We replaced 14 SEW R77 gearboxes on our aggregate conveyor system with Korea Ever-Power R77 units. The dimensional match was exact — output shaft, mounting holes, and flange all lined up without any modification to our existing conveyor structure. After 12 months of three-shift operation, oil analysis shows clean results with no abnormal wear particle counts. The cost savings of 40% compared to the original SEW units made the business case straightforward.
Steve R., Plant Maintenance Manager
Aggregate Processing Plant, Perth, Australia
We specified K57 helical-bevel gearboxes combined with YE3 5.5 kW motors for 8 tank agitator drives in our chemical plant. The right-angle output shaft configuration was essential for our top-entry vertical agitator design. Noise measurements at the gearbox surface were consistently below 72 dB(A) at full load, meeting our workplace noise regulation requirements without additional acoustic enclosures.
Dr. Anita M., Process Engineer
Specialty Chemical Manufacturer, Mumbai, India
Our packaging line needed 22 gearmotor units consisting of F47 gearboxes with 2.2 kW YE3 motors, all pre-assembled and tested. Korea Ever-Power delivered the complete units ready to bolt on, which saved our electricians approximately 3 hours per unit compared to sourcing the motor and gearbox separately and assembling them on site. The parallel shaft configuration fits perfectly within our machine frame width constraints.
Thomas K., Engineering Manager
Packaging Line Integrator, Hamburg, Germany
Important Technical Note
Torque and power ratings listed in this document are based on continuous duty (S1) at the rated input speed with standard ambient temperature (40°C maximum). For applications with frequent starts, reversals, shock loads, or elevated ambient temperatures, a higher service factor must be applied, which may require selecting a larger gearbox frame size. Thermal power limits may also restrict the usable torque for certain ratio and speed combinations. Contact our engineering team with your complete application data for a verified selection recommendation. All specifications conform to DIN 3990, ISO 6336, and DIN 3992 standards.
Need a Gear Reducer Quotation?
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Additional information
| Editor | Cxm |
|---|