ZR95 Winch Drive Planetary Gearbox — Right-Angle

At 2-Stage (Bevel + 1 Planetary)

The bevel gear pair carries the full input torque from the motor, and the single planetary stage carries the full output torque to the drum. The bevel tooth bending stress at 115,000 Nm output through a typical 2-stage ratio (15-50) is at approximately 85-90% of the 100,000-hour endurance limit. This is acceptable — but at 133,000 Nm (ZR120), the same 2-stage configuration would push the bevel tooth stress to 98-103% of the endurance limit, which is structurally marginal. The ZR95 is the last model where 2-stage stays below the 90% threshold.

At 3-Stage and Beyond (Bevel + 2+ Planetary)

Adding a second planetary stage (making 3 total) splits the torque path into a lower-ratio-per-stage cascade. The bevel stage now carries lower input torque (because the first planetary stage provides additional reduction before the bevel reaches its full load), and the bevel tooth stress drops to 70-75% of the endurance limit at ZR120 torque. For the ZR120, ZR150, and ZR200, 3-stage minimum (or 4-stage for ZR200) keeps all components within the 85% stress ceiling. The result: the compact 2-stage option disappears above 115,000 Nm, and the gearbox gets approximately 80-100 mm longer.

At 245,000 Nm peak through a 2-stage ratio of 30 (typical for heavy crane duty): the bevel input torque is approximately 8,167 Nm at 3,100 rpm. The bevel tooth contact stress reaches approximately 93% of the material endurance limit for a sub-10-second transient duration. The 20CrMnTi case-hardened bevel gears withstand this stress without surface pitting because the transient duration is shorter than the minimum stress-cycle count needed to initiate a fatigue crack. Between peaks, the stress returns to the continuous level (approximately 70%), and the gear surface recovers.

The bevel gear pair at 245,000 Nm generates approximately 8,000-12,000 N of axial thrust on the bevel shaft. The heavy-series tapered roller bearings in the ZR95 are rated for 15,000 N continuous axial load at 100,000 hours — providing a 25-88% margin above the peak thrust. The bearing design life is not reduced by peak events because the transient duration is negligible compared to the L10 fatigue cycle count. The bearings are the most conservatively loaded components in the ZR95 at peak torque.

The bevel tooth peripheral velocity at 3,100 rpm is at the upper limit for reliable hydrodynamic lubrication. At peak torque, the tooth contact zone heats locally by 5-10 deg C above the bulk oil temperature — reducing the oil viscosity and thinning the lubricant film. The DIN 5-6 surface finish (Ra less than 0.4 microns) ensures the film thickness remains above the surface roughness even at the peak temperature excursion. This is why DIN 5-6 accuracy is not optional for the ZR series — it is a lubrication engineering requirement.

Heavy Electric Cranes in Tight Machinery Rooms (60-100 t)

Electric cranes at 60-100 tonne SWL where the machinery room depth behind the drum is limited to 400-600 mm. The ZR95 at 2-stage delivers 115,000 Nm in approximately 350-400 mm of axial depth — the most torque from the shortest right-angle gearbox in the catalogue. The slewing drive Ve wheel drive complete the all-electric crane system.

Electric Marine AHTS and Towing Winches

Main towing and anchor handling winches on electric AHTS vessels and large tugs where the drum runs athwartship and the sustained towing load stays below 115,000 Nm. The 245,000 Nm peak absorbs the anchor chain snatch and towline snap loads that define AHTS operations. The 2-stage compact option minimises the winch footprint on the aft deck — critical on medium-sized AHTS vessels where deck space is shared with anchor racks and chain lockers.

Electric Mining Main Production Winders

Main production winders at mines with 400-700 metre shaft depths where the headframe winder house design requires perpendicular motor mounting. The ZR95 at ratio 150-400, 3-5 stage, with 500-800 kW motors provides the winding torque with regen recovery of 20-35%. The 2-stage option at ratio 15-50 serves fast-cycle auxiliary hoists where the hoist speed is the priority and the compact gearbox length is essential.

What is the actual axial length difference between ZR95 at 2-stage versus 3-stage?

Approximately 70-90 mm. The 2-stage ZR95 (bevel + 1 planetary) is approximately 350-400 mm behind the drum mounting face. The 3-stage (bevel + 2 planetary) is approximately 420-490 mm. The additional planetary stage adds the width of the gear set plus the carrier plus the bearing set. For installations where 400 mm is the available depth, 2-stage fits and 3-stage does not — making the 2-stage option critical for these constrained geometries.

If I need more than 115,000 Nm in a right-angle 2-stage, is there any option?

Not from the standard catalogue. The ZR95 at 115,000 Nm is the 2-stage maximum. For applications needing 115,000-175,000 Nm in a right-angle configuration, the ZR120-ZR200 at 3+ stages is the catalogue answer — with the approximately 80 mm additional axial length. For extreme space constraints at torques above 115,000 Nm, contact Korea Ever-Power for a custom engineering assessment — in some cases, a wider-diameter bevel gear pair or a non-standard gear material can extend the 2-stage limit, but this is a custom-engineered solution, not a catalogue product.

Does the ZR95 share planetary spare parts with the ZL95?

Yes. The planetary stages are identical between the ZR95 and ZL95 at overlapping ratios. Only the bevel stage and input housing are ZR-specific. For fleets operating both ZR95 (deck winches, headframe winders) and ZL95 (crane hoists), the planetary spare parts inventory is fully shared — a significant logistics advantage for operators with mixed ZR/ZL installations.

How does the ZR95 compare to the ZR85 for mainstream applications?

The ZR95 provides 31% more continuous torque (115,000 vs 88,000 Nm) and 23% more peak (245,000 vs 200,000 Nm) at the same 3,100 rpm and the same 2-5 stage range. For cranes in the 60-80 t range, the ZR85 is adequate. For 80-100 t cranes, or for marine winches where the peak load regularly exceeds 200,000 Nm, the ZR95 is the necessary step up. The thermal power is identical (26-90 kW), so the choice is purely about torque headroom.

What overhaul interval applies to the ZR95 at heavy marine and mining duty?

Marine: first overhaul at 20,000-25,000 hours (salt-spray environment accelerates seal wear). Mining: first overhaul at 25,000-30,000 hours (dust environment, but less corrosion). Oil changes every 1,500 hours (marine) or 2,000 hours (mining/industrial). Bevel gear and planetary gear inspection at each overhaul. Oil sampling every 500-1,000 hours — monitoring iron particle counts for bevel tooth surface distress and planetary bearing wear. Contact Kore'nin Daimi Gücü for the environment-specific maintenance schedule.

80 t offshore platform crane, hydraulic-to-electric conversion. The machinery room survey showed 380 mm of clear depth behind the drum — well below the minimum for any coaxial gearbox at this torque. The ZR95 at 2-stage, ratio 40, with 600 kW motor delivered 115,000 Nm in 365 mm of axial depth. This was the only product in the catalogue that could deliver the required torque within the available space. The crane has completed its classification survey and 8 months of operation. The 245,000 Nm peak handled a 72-tonne proof-load test (80 t x 1.25 x 0.72 dynamic amplification factor) without any VFD protection event. We are now surveying 4 additional platform cranes — 2 will require ZR95 (tight spaces) and 2 will accept ZL95 (open spaces). Same torque, same performance, different geometry.

Main towing winch on an all-electric 80 m AHTS vessel, ZR95 at ratio 120, 3-stage, dual 350 kW AC motors (one per drum end, torque-sharing through the ZR95 bevel input). The 2-stage option was evaluated but rejected — at towing duty (sustained 80,000 Nm, 72% of continuous), the 2-stage thermal load exceeded the Pt without a cooler. The 3-stage at 65 kW Pt with cooler provides the thermal margin. The ZR95 245,000 Nm peak absorbed the towline snap-back during a heavy-weather emergency disconnect test — measured at 2.3x steady-state by the load cell. The vessel electrical system recovered 17% of the towing energy through regen during the trial.

Main production winder at a 600-metre platinum mine, ZR95 at ratio 250, 4-stage, 550 kW AC motor mounted vertically on the headframe column. The headframe winder house is a 1970s design with 450 mm between the drum and the back wall — the ZR95 2-stage would have fit, but the mine engineer selected 4-stage for the ratio requirement (250 exceeds the 2-stage maximum ratio). The 4-star is a commissioning observation: the vertical motor mount produces a gravitational pre-load on the bevel shaft thrust bearings that is not present in horizontal mounting. The pre-load is within the bearing capacity but changes the vibration baseline — the commissioning vibration survey should be performed with the motor running in the actual installed orientation, not extrapolated from horizontal test-bench data. The mine inspector initially flagged the elevated vibration as a concern; we resolved it by providing the vertical-mount vibration baseline from the Korea Ever-Power factory acceptance test.