ZL35 Winch Drive Planetary Gearbox — 1-4 Stage

ROV Launch and Recovery Systems

Remotely operated vehicle (ROV) launch and recovery systems (LARS) must deploy the ROV through the splash zone as fast as possible to minimise wave-induced pendulum motion. At ratio 3.84 with the motor at moderate speed (1,500-2,500 rpm), the drum produces 60-120 m/min of umbilical cable speed — fast enough to transit the splash zone in under 5 seconds. Once below the wave influence, the motor slows to a controlled descent speed for the remaining depth. The single-stage ratio provides the speed; the VFD provides the control.

Fast Cargo Transfer Winches

Ship-to-ship and ship-to-shore light cargo transfer where cycle speed determines throughput. At ratio 3.84, the ZL35 paired with a 150-250 kW motor hoists 1-5 tonne loads at 40-80 m/min — 2-3 times faster than a conventional crane hoist gearbox at the same power input. The low gear ratio means low torque multiplication, so the motor must be large relative to the load — but for light-load, high-speed transfer operations, the speed advantage justifies the motor cost.

Emergency Recovery Winches

Man-overboard recovery winches, rescue basket hoists, and emergency evacuation cable systems where the speed of recovery directly affects survival. At ratio 3.84, the ZL35 can achieve the rapid cable recovery speeds that rescue protocols demand — 30-60 m/min — with moderate motor power. The 85,000 Nm peak absorbs the shock when the rescue basket contacts the water surface and the cable snaps taut.

ROV Launch and Recovery Systems

Complete LARS winch drives for work-class and observation-class ROVs on offshore support vessels, research vessels, and naval platforms. The ZL35 at ratio 4-15 provides the splash-zone transit speed (60-120 m/min), and the VFD reduces the motor speed for controlled descent at depth (5-30 m/min). A single ZL35 covers both speed regimes without a two-speed gearbox. The slewing drive positions the A-frame or over-boarding system on the same vessel.

Electric Crane Hoists (15-30 t SWL)

The ZL35 at ratio 40-120 paired with 150-350 kW electric motors provides the main hoist torque for new-generation all-electric cranes. At 34,000 Nm continuous, the ZL35 covers the same crane SWL range as the 4xxW models from 407AW (18,000 Nm) to 410W3 (37,500 Nm) — but with helical-gear quiet operation, regen braking compatibility, and the 85,000 Nm peak that absorbs shock loads the equivalent 4xxW models handle only with derating.

Scientific and Oceanographic Winches

CTD (conductivity-temperature-depth) profilers, sediment corers, and deep-ocean instrument packages deployed at sub-metre-per-minute cable speeds through 2,000-6,000 metres of water. The ZL35 at ratio 1,000-2,397 provides the ultra-slow drum speed, and the DIN 5-6 gear accuracy plus motor encoder resolution enables the research team to command depth to within centimetres at any point in the water column. The auxiliary drives handle the vessel A-frame and instrument handling systems.

How does the ZL35 achieve ratio 3.84 when the ZL30 minimum is 4?

The ZL35 uses a slightly different single-stage gear set with a larger sun gear relative to the ring gear, producing a lower per-stage ratio. The minimum theoretical ratio for a 3-planet helical stage depends on the tooth count combination and the minimum planet gear size that maintains adequate tooth bending strength. The ZL35 gear module is approximately 10% larger than the ZL30 (to carry the higher torque), which allows a minimum planet gear with enough teeth to achieve ratio 3.84 while maintaining DIN 5-6 accuracy and the 85,000 Nm peak capacity.

At ratio 3.84, does the ZL35 still produce 34,000 Nm of output torque?

Yes, the continuous torque rating is independent of the ratio — the output bearing, housing, and gear teeth are rated for 34,000 Nm regardless of which ratio is installed. However, the motor must provide 34,000 / 3.84 = 8,854 Nm of input torque to achieve full output at ratio 3.84. This requires a motor producing 8,854 Nm at 4,000 rpm — approximately 3,700 kW. In practice, low-ratio applications use a fraction of the rated torque: a fast cargo hoist at ratio 3.84 typically operates at 5,000-15,000 Nm output (2-6 tonne loads), not the full 34,000 Nm.

Is the ZL35 at ratio 2,397 suitable for a winch that must hold a load for hours?

At ratio 2,397, the gear train friction is high enough that back-driving (load turning the motor) is practically impossible — the system is mechanically self-locking. However, as with all planetary gearboxes, this friction-lock must not be relied upon as the sole load-holding mechanism. The motor electromagnetic brake or an external calliper brake must be engaged for static holding. The self-locking tendency at ultra-high ratios does provide a secondary safety margin — but it is a bonus, not a designed holding mechanism.

How does the thermal power rating (17-53 kW) vary across the stage count?

More stages means more internal gear meshes, each generating friction heat. The thermal power Pt is the maximum continuous power the gearbox can transmit without the oil temperature exceeding 85 deg C in still air at 20 deg C ambient. At 1-stage: Pt = approximately 53 kW. At 2-stage: approximately 40 kW. At 3-stage: approximately 25 kW. At 4-stage: approximately 17 kW. If the application demands more power than the stage-specific Pt value, add an external oil cooler to increase the effective thermal capacity. Contact Korea Ever-Power for the exact Pt value at your specific ratio and stage count.

How does the ZL35 compare to the ZL30 for electric crane hoists?

The ZL35 provides 26% more continuous torque (34,000 vs 27,000 Nm) and 13% more peak capacity (85,000 vs 75,500 Nm), at a slightly lower peak-to-continuous ratio (2.5 vs 2.8). For crane hoists in the 15-25 tonne SWL range, the ZL30 is adequate. For 20-30 tonne SWL or for cranes with high cycle rates that approach the continuous torque limit, the ZL35 provides the additional margin. The wider ratio range (3.84-2,397 vs 4-1,259) is irrelevant for crane duty — both models cover the crane hoist ratio range (40-200) with identical ratios at those mid-range points.

Can the ZL35 at different stage counts be changed in the field to adjust the ratio?

No. The stage count is set at manufacture and determines the housing length, the number of internal gear sets, and the output bearing arrangement. A 2-stage ZL35 cannot be converted to a 4-stage in the field. However, within a given stage count, the ratio can be changed at the factory by replacing the internal gear sets — a procedure that takes 3-5 working days and costs approximately 20-30% of the new unit price. For applications where ratio flexibility is needed over the product life, specify the stage count that covers the anticipated ratio range and plan for a factory gear set change if the requirement shifts.

Work-class ROV LARS winch on a DSV. ZL35 at ratio 8, single-stage, paired with a 200 kW PMSM motor. Splash-zone transit at 80 m/min — the ROV passes through the wave influence zone in 3.5 seconds, eliminating the pendulum-induced umbilical stress that was our number-one failure mode with the previous slow-speed winch. Controlled descent at 1,500 m depth at 15 m/min through VFD speed reduction. The 85,000 Nm peak handled the snatch load when the ROV entered the current shear layer at 800 m without any protection trip. Twelve months in service, 340 deployments, zero umbilical failures. The ROV availability rate improved from 91% to 98% — directly attributable to the fast splash-zone transit.

All-electric 25 t harbour crane, main hoist, ZL35 at ratio 80, 2-stage, 300 kW AC motor. The ZL35 replaced a 4xxW-family hydraulic winch drive and eliminated the hydraulic power unit, the oil cooler, and 200 metres of hydraulic hose. Weight saving: 380 kg on the crane head. Noise at the operator station: 58 dB(A) — 14 dB below the hydraulic baseline. Regen energy recovery across 3 months of harbour operations: 22% of the lowering energy returned to the grid. The 85,000 Nm peak handles the container snatch loads that occur when the spreader locks engage on a swinging container — previously the leading cause of hydraulic pressure spikes and hose bursts on the old crane.

Oceanographic CTD winch on a research vessel, ZL35 at ratio 1,800 (4-stage), 15 kW servo motor. The winch deploys a CTD rosette to 4,000 m depth at 0.8 m/min descent — exactly the speed our sampling protocol requires for the thermocline layer profiling. Depth accuracy measured by acoustic altimeter at the instrument package: within 0.3 metres at 4,000 m — exceptional for a cable-deployed system. The 4-star is a thermal observation: at 4-stage ratio 1,800, the thermal power limit is approximately 18 kW. Our 15 kW motor is within this limit during descent but marginally exceeds it during sustained recovery at full speed with a loaded rosette (22 bottles x 10 L = 220 kg). We added a small fin-tube oil cooler that resolved the issue. For scientific winch applications at high stage counts, publishing the Pt value for each stage-count variant on the product data sheet would help scientists size the cooling requirement during the specification phase.