S Series Helical-Worm Gear Reducer

cat-worm-gear-reducer

Combined helical first-stage and worm second-stage right-angle gear reducer, available in sizes S37 through S157. The helical pre-stage delivers 96 to 98% efficiency to the worm second stage, giving the S series significantly higher overall efficiency than a single-stage worm gearbox at the same ratio while retaining the compact right-angle geometry, self-locking at high ratios, and the wide ratio range that make worm gearboxes the standard choice for conveyor, gate, and agitator drives.

Sizes: S37 – S157
Ratios: 9.96 – 244.74
Output Torque: 200 – 4,000 N·m
Right-Angle Output
Self-Locking Above 35:1
IP55 Protection
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Helical Pre-Stage
Worm Right-Angle Stage
Higher Efficiency vs Worm
Self-Locking at High Ratios
Compact Right-Angle Body
ISO 9001 Certified

Best of Both: Helical Efficiency with Worm Self-Locking in One Package

The S series helical-worm reducer solves the fundamental compromise between efficiency and self-locking that limits the single-stage worm gearbox. In a single-stage worm gearbox at 50:1, the efficiency is approximately 52% because the worm gear must both change the shaft direction and provide the full 50:1 reduction in a single mesh where sliding contact losses are unavoidable. In the S series, the helical first stage provides 3:1 to 5:1 of the total ratio at 97% efficiency, reducing the speed delivered to the worm second stage. The worm second stage then provides 10:1 to 50:1 at lower input speed, which reduces the sliding velocity in the worm mesh and therefore the mesh friction losses, raising worm stage efficiency to 65 to 75%. The combined S series overall efficiency at 50:1 to 200:1 ratios is approximately 62 to 72%, versus 48 to 55% for a single-stage worm at the same ratio.

The self-locking characteristic is preserved in the S series because it is a property of the worm second stage, which operates at the same helix angle geometry as a standalone worm gearbox. At overall ratios above approximately 35:1, the S series is self-locking: the load cannot back-drive the gearbox when the motor is de-energised. This makes the S series suitable for all the applications where worm self-locking is a functional requirement — inclined conveyors, gate drives, positioning drives — while delivering meaningfully lower energy cost and housing temperature than a pure worm solution.

S Series Helical-Worm Gear Reducer Korea Ever-Power

Sizes S37 through S157 cover output torques from 200 N·m to 4,000 N·m, filling the gap between the NMRV150 worm (1,500 N·m maximum) and the K series bevel-helical range (starting at 200 N·m but fully back-driveable). Cast-iron housing, phosphor bronze worm wheel, and case-hardened gear and worm shaft throughout.

Explore matched motors at Three-Phase Induction Motors, or browse the gearbox range at Helical Gear Reducers.

S Series Size and Performance Data

Performance data at rated input speed 1440 rpm (4-pole motor). Overall efficiency includes both helical and worm stages. Self-locking applies at overall ratios above approximately 35:1.

Size Stages Ratio Range Max Output Torque (N·m) Overall Efficiency (%) IEC Motor Frames Max Input kW Weight (kg)
S37 Helical + Worm 9.96 – 244.74 200 62 – 72 80, 90, 100 2.2 12
S47 Helical + Worm 9.96 – 244.74 350 62 – 72 90, 100, 112 4.0 18
S57 Helical + Worm 9.96 – 244.74 600 62 – 72 100, 112, 132 7.5 28
S67 Helical + Worm 9.96 – 244.74 1,000 62 – 72 112, 132, 160 11 42
S77 Helical + Worm 9.96 – 244.74 1,500 62 – 72 132, 160, 180 18.5 65
S87 Helical + Worm 9.96 – 244.74 2,000 62 – 72 160, 180, 200 30 95
S97 Helical + Worm 9.96 – 244.74 2,800 62 – 72 180, 200, 225 45 138
S107 Helical + Worm 9.96 – 244.74 3,200 62 – 72 200, 225, 250 55 185
S157 Helical + Worm 9.96 – 244.74 4,000 62 – 72 225, 250, 280 75 285

Gearbox Specifications

Helical gear material 20CrMnTi case-hardened
Worm material 20CrMnTi case-hardened
Worm wheel Phosphor bronze (CC483K)
Housing material GJL-250 cast iron
Gear oil ISO VG 220 worm oil
Protection IP55
Self-locking ratio Above 35:1 overall
Mounting Any orientation

Input and Output Options

Input type IEC B5 flange direct
Shaft arrangement 90° right-angle
Output shaft Solid keyed (standard)
Hollow shaft Available S47 and above
Output flange Available S47 and above
Worm position Above or below (specify)
IEC frame range 80 – 280
Standards ISO 9001 / CE

Typical Applications for S Series Helical-Worm Reducers

S Series Helical Worm Reducer Inclined Conveyor Application

Inclined Conveyor Drives
Inclined belt conveyors for aggregate, grain, and recycled material handling use S series reducers where both right-angle geometry and load-holding self-locking are required simultaneously. The S series at 50:1 overall ratio holds the loaded inclined belt stationary when the motor trips, while consuming 20 to 25% less power than a single-stage worm at the same ratio during normal operation.
 S Series Helical Worm Reducer Food Processing Application

Food and Beverage Mixers
Bakery dough mixers, confectionery batch mixers, and dairy product blenders use S series reducers for right-angle agitator drives where the lower heat generation of the helical-worm versus a pure worm reduces the ambient temperature rise in temperature-sensitive production areas, and where self-locking prevents impeller reverse rotation during product loading.
 S Series Helical Worm Reducer Chemical Processing Application

Chemical Process Agitators
Reactor vessel agitators and blending tank drives in chemical plants use S series reducers where the output torque exceeds the 1,500 N·m ceiling of NMRV worm gearboxes but the application still requires right-angle geometry, self-locking at ratio, and the lower running noise of a worm-bronze worm stage output.
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Positioning and Gate Drives
Large industrial gate drives, dam sluice mechanisms, and valve actuator drives use S series reducers at high ratios (100:1 to 244:1) where the self-locking characteristic is a primary safety requirement and the gate or valve must hold position against hydraulic or pneumatic load without a separate brake when the motor is de-energised.
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Packaging Machine Turntables
Rotary indexing tables and turntable drives on packaging and palletising machines use S series reducers for their right-angle compact geometry, indexing position hold (self-locking), and the smooth output motion produced by the combined helical-worm mesh which has lower output torque ripple than a single-stage worm at the same ratio.
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Textile Winding Drives
Yarn package winding and thread-guide traverse drives use S series reducers for the combination of precise low output speed, quiet worm-bronze mesh output, and self-locking at high ratios that prevents the winding spindle from releasing tension when the motor is stopped between packages.

The Four Gearbox Families: Choosing the Right Type for Your Application

RV / NMRV Worm — Compact Right-Angle, Low Power

Best choice below 3 kW input and below 1,500 N·m output torque where compact dimensions, low purchase price, and self-locking above 30:1 are the priorities and energy efficiency is secondary. Applications: small conveyor drives, gate motors, packaging machine auxiliary drives, small agitators. Not suitable for high-duty continuous operation above 5 kW due to thermal limitations of worm mesh at higher power.

S Series Helical-Worm — Right-Angle, Self-Locking, Mid-Power

Best choice from 2 kW to 75 kW where right-angle geometry and self-locking are both required, output torque exceeds 1,500 N·m, and better efficiency than a pure worm is needed. Applications: inclined conveyors, large gate and sluice drives, food and chemical agitators, positioning turntables. The S series fills the gap between the NMRV worm and the K series bevel-helical for right-angle drives with load-holding requirements.

K Series Bevel-Helical — Right-Angle, High Efficiency, Heavy Duty

Best choice above 10 kW where right-angle geometry is required but self-locking is not needed (or a motor brake provides load holding), and where high output torque and high efficiency are the primary drivers. Applications: heavy conveyor head and tail drives, crane travel drives, side-entry agitators, extruder main gearboxes, kiln pinion drives. Maximum output torque 50,000 N·m substantially exceeds any worm or helical-worm alternative.

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Frequently Asked Questions — S Series Helical-Worm Reducer

Why is the S series minimum ratio 9.96:1 rather than 5:1 like the worm gearbox?
The S series minimum ratio is set by the combination of the minimum helical first stage ratio (approximately 1.5:1 to 2:1) and the minimum worm second stage ratio (5:1 to 7:1). Below approximately 10:1 overall, the worm second stage would need to run at only 5:1 reduction from an already-reduced helical input, producing a worm geometry that is back-driveable and no longer self-locking. For overall ratios below 10:1, the K series bevel-helical or the R series inline helical (which achieves down to 3.77:1) is the appropriate choice. The S series is optimised for the 10:1 to 250:1 range where the combination of helical pre-stage and worm stage delivers maximum benefit.
Does the S series worm wheel use the same phosphor bronze as the NMRV series?
Yes. The S series worm wheel is centrifugally cast phosphor bronze (CC483K grade), identical to the material used in the NMRV series. This material provides the same hardness differential against the case-hardened worm shaft that gives worm gearboxes their characteristic quiet operation and the long wear life of the bronze wheel relative to the steel worm. The larger S series worm wheel diameters (compared to the NMRV for the same worm shaft centre distance) provide a larger contact area and therefore lower contact stress at higher output torque, which is the mechanism by which the S series achieves higher output torque than the NMRV at the same worm shaft size.
How is the oil lubrication managed between the helical and worm stages?
The S series uses a single shared oil sump that lubricates both the helical first stage and the worm second stage. The oil grade must therefore be compatible with both gear types. ISO VG 220 worm gear oil with extreme pressure (EP) additives suitable for worm-bronze contact is the correct specification for all S series sizes. Standard mineral gear oil without worm-specific additives is not recommended for the worm stage. Both stages share the same oil change interval: 500 hours for the initial flush, then 5,000-hour intervals (or 2 years) for mineral oil, and 10,000-hour intervals (or 5 years) for synthetic worm oil.
At what overall ratio does the S series become self-locking?
Self-locking in the S series is a property of the worm second stage and depends on the worm helix angle. At overall ratios of approximately 35:1 and above, the worm second stage helix angle is below the friction angle of the bronze-steel interface, and the gearbox is self-locking under static load. At overall ratios between 10:1 and 35:1, the gearbox may or may not be self-locking depending on the specific ratio split between the helical and worm stages; Korea Ever-Power can verify the self-locking status for any specific ratio in this range on request. For safety-critical load-holding applications, self-locking alone should not be the sole retention method; a motor brake or external mechanical lock provides the necessary fail-safe backup.
How does the S series compare in size and weight to the equivalent K series at the same output torque?
At the same output torque level, the S series is generally slightly heavier than the K series equivalent because the worm stage housing must be larger to provide the structural support for the worm shaft bearings and the worm wheel diameter needed for the bronze-steel worm mesh. For example, S77 (1,500 N·m) weighs approximately 65 kg versus K77 (1,500 N·m) at approximately 55 kg. The overall housing footprint of the S series is also slightly larger in the worm shaft axis direction than the K series. However, the S series provides self-locking which the K series does not, and for applications where this is a functional requirement the weight difference is the accepted trade-off for the self-locking capability.
S Series Helical Worm Gear CNC Machining

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