ZR55 Winch Drive Planetary Gearbox — Right-Angle

A matched pair of helical bevel gears — one on the input shaft (motor side) and one on the intermediate shaft (planetary side) — mesh at 90 degrees. The bevel pair provides the first ratio reduction (typically 1.5-3.5:1) and the direction change simultaneously. The intermediate shaft then drives the first planetary stage in the same manner as the ZL series. The bevel gears are ground to DIN 5-6 accuracy and operate in the same oil bath as the planetary stages.

Bevel gears at the ZR55 pitch diameter produce tooth peripheral velocities that reach the lubrication film limit at approximately 3,300 rpm. Above this speed, the bevel tooth contact would risk scuffing — metal-to-metal contact through the oil film. The ZL coaxial series avoids this constraint because it has no bevel stage. The 3,300 rpm ZR limit matches standard 4-pole industrial motors at 50 Hz (3,000 rpm synchronous) and 6-pole motors at 60 Hz (3,600 rpm synchronous) — both common in industrial and marine applications.

The bevel stage adds one gear mesh (approximately 1-2% efficiency loss), the bevel gear pair weight, and the right-angle housing volume. The ZR55 at 2-stage (bevel + 1 planetary) is slightly less efficient than the ZL55 at 1-stage (planetary only): approximately 93-94% versus 96-97%. At 5-stage (bevel + 4 planetary), both converge at approximately 90-91% because the additional planetary mesh losses dominate. The right-angle geometry also generates a thrust load on the bevel shaft bearings that the coaxial ZL does not produce — handled by the heavy-series tapered roller bearings in the ZR housing.

The drum has axial depth for the motor behind the gearbox. The application needs single-stage low ratios (below the ZR minimum). Maximum efficiency matters (96% vs 93%). The motor speed exceeds 3,300 rpm (up to 5,000 rpm for later ZL models).

No axial space behind the drum — the motor must mount beside, below, or above. The bulkhead, hull frame, or headframe column is directly behind the drum cavity. The motor alignment is simpler with a perpendicular mount. The motor is a standard 4-pole or 6-pole industrial motor at 3,000-3,300 rpm.

Retrofit Crane Hoists in Existing Machinery Rooms

Crane hoist conversions where the existing machinery room layout places a bulkhead, hydraulic tank, or structural column directly behind the drum position. A coaxial ZL motor would project into the occupied space. The ZR55 redirects the motor 90 degrees — mounting it alongside the drum within the existing room footprint. For offshore platform crane conversions where the deck penetrations and structural layout are fixed, the right-angle geometry is often the only way to fit an electric winch drive without structural modification.

Marine Deck Winches Against Hull Frames

Mooring, towing, and cargo winches mounted against the hull shell plating where the drum axis runs athwartship (across the vessel) and the motor must mount fore-and-aft (along the vessel) to avoid projecting outboard through the hull. The ZR55 right-angle input turns the motor shaft parallel to the ship centreline while the drum operates athwartship — the standard geometric arrangement for deck winches on tankers, bulk carriers, and offshore support vessels. The slewing drive handles the fairlead positioning on the same vessel.

Mining Headframe Narrow-Profile Winders

Auxiliary winders on mine headframes where the winder house width is constrained by the headframe column spacing. A coaxial motor projecting axially behind the drum would exceed the available depth. The ZR55 mounts the motor perpendicular — reducing the total assembly depth by 30-40% compared to the coaxial equivalent. For mine electrification programmes converting hydraulic auxiliary hoists in existing headframes, the ZR geometry fits where the ZL cannot.

Does the bevel stage reduce the reliability compared to the coaxial ZL?

The bevel stage adds one gear mesh and one set of thrust bearings — increasing the theoretical failure modes by one pair compared to the ZL. However, the bevel gears in the ZR series are ground to DIN 5-6 accuracy from the same 20CrMnTi material as the planetary gears, and the heavy-series tapered roller bearings are rated for the full thrust load at 100,000 hours. In practice, the bevel stage is not the life-limiting component — the output bearings and seals, which are identical between ZR and ZL, determine the overhaul interval. The ZR55 reliability is within 5% of the ZL55 at equivalent duty.

Is the ZR55 noisier than the ZL55 due to the bevel stage?

Slightly. The helical bevel mesh produces a distinctive mid-frequency whine (800-1,600 Hz) that is not present in the coaxial ZL. The overall noise level is approximately 2-4 dB(A) higher than the ZL55 at equivalent speed and torque — noticeable in a quiet environment but masked in typical crane or marine machinery room ambient noise. For noise-critical installations (hospitals, residential areas), the ZL coaxial remains the quieter option. For industrial, marine, and mining environments, the ZR noise difference is imperceptible against the ambient background.

Can the ZR55 accept the same motor as the ZL55?

The motor shaft interface (spline or key coupling) may be identical between ZR and ZL at the same torque level — verify by serial number. However, the motor mounting flange is different: the ZR55 motor mounts perpendicular to the housing, while the ZL55 motor mounts coaxially. The motor itself (IEC frame, power rating, brake option) can be the same unit — only the mounting adapter and coupling orientation differ. For fleet commonality, specify the same motor model for both ZR and ZL installations and provide separate mounting adapters.

How much axial space does the ZR55 save compared to the ZL55?

The ZR55 gearbox housing behind the drum is approximately 30-40% shorter axially than the ZL55 because the motor does not project behind it. However, the ZR55 adds a lateral dimension — the bevel housing and motor extend perpendicular to the drum axis by approximately 300-500 mm (depending on motor frame size). The total volume envelope is similar; the shape is different. The ZR55 is compact behind the drum but wide beside it. The ZL55 is narrow beside the drum but deep behind it. Match the geometry to the available space.

Do the ZR and ZL share internal planetary gear components?

At the same model number (ZR55 vs ZL55), the planetary stages (stages 2-5 in ZR, stages 1-5 in ZL) share the same gear sets, bearings, carriers, and seals. The bevel stage (unique to ZR) and the input housing (different geometry) are ZR-specific. For fleet operators running both ZR55 and ZL55, the planetary spare parts kits are interchangeable — only the bevel gear pair and the input bearing set are additional ZR-specific items. Contact Корея Вечная Сила to confirm parts commonality at your specific serial numbers.

What overhaul interval applies to the ZR55?

The same 100,000-hour life rating as the ZL55. The bevel stage does not reduce the overhaul interval — it is designed for the same L10 bearing life and gear fatigue life as the planetary stages. Target first overhaul at 25,000-30,000 hours at 60-80% of continuous rating. Bevel gear inspection at 15,000 hours (included in the standard overhaul scope). Oil changes every 2,000 hours. The bevel gear oil must be the same specification as the planetary oil — both stages share the same oil bath. Contact Корея Вечная Сила for the maintenance schedule at your duty profile.

40 t offshore platform crane, hydraulic-to-electric conversion. The original machinery room has a structural bulkhead 400 mm behind the drum housing — impossible to fit a coaxial ZL motor. The ZR55 at ratio 80, 2-stage, with a 300 kW motor mounted perpendicular to the drum, fits within the existing room envelope with 50 mm clearance to the bulkhead. No structural modification required. The conversion eliminated the HPU, oil cooler, and 120 metres of hydraulic hose. The crane has completed 9 months of operation since conversion — the operators report no perceptible difference in hoisting performance compared to the hydraulic system, but the noise reduction is "dramatic" (their word).

Electric mooring winch on an LNG carrier, ZR55 at ratio 120, 3-stage, 150 kW AC motor mounted parallel to the ship centreline while the drum axis runs athwartship. This is the standard geometry for deck winches on large commercial vessels — the coaxial ZL would have projected the motor outboard through the hull strake. The ZR55 right-angle input is the geometrically correct solution for this installation. The IP67+ sealing has survived 14 months of deck wash and saltwater exposure without any seal degradation. Mooring line snatch loads measured at 2.1x steady-state during berthing in crosswind — absorbed within the 112,000 Nm peak without any VFD fault.

Auxiliary winder on a 1960s-era mine headframe, ZR55 at ratio 200, 4-stage, 100 kW AC motor. The headframe winder house is 1.2 metres deep between the drum and the back wall — no room for a coaxial motor. The ZR55 motor mounts vertically below the drum on a bracket welded to the existing headframe column, with the right-angle input turning the torque upward into the drum. Total installation footprint: 600 mm x 800 mm versus the 600 mm x 1,400 mm that the coaxial ZL55 would have required. The 4-star is a vibration observation: the bevel gear mesh produces a 1,200 Hz tonal component that was detectable on the headframe vibration monitor. The amplitude is well within structural limits but the monitoring system initially flagged it as an anomaly until we updated the baseline to include the bevel mesh frequency. For ZR installations on monitored structures, providing the expected bevel mesh frequency range in the commissioning documentation would prevent false alarm investigations.